Wooden Rotor Blades

[joe nelson]

Has anyone used a molding machine to produces wooden blades? Knives could be made to produce any airfoil you would need uniformly and efficiently.

joe

[joe nelson]

Yesterday, I glued together three pieces of 3/4 inch a-c exterior grade ply. After drying, I formed an airfoil, shaped by planing by hand and machine, into a 2x8x48 inch blade. I cut lightening hole aft of the 25 percent station and about an inch forward of the trailing edge. The moisture content was measured and it was given a coat of three pound shelac.

A flexible bending plywood has been ordered and will be laminated to the blade upon its arrival. The blade then will get a cover of unidirectional fiber-glass cloth.

This process will give me some data as to weight per foot of the blade, torsional flexibility and moisture up-take.

I will up-date everyone when finish.

joe

[C. Beaty]

Here’s a cutaway of the Bell-47 blade construction, Joe.

Balance about the ¼ chord point is quite critical if the blades aren’t absolutely rigid in torsion. Otherwise, they’re likely to flutter, ending up as a shower of toothpicks.

[joe nelson]

Chuck,

Is the Bell blade beech and balsa wood? I've flown the TH-13 but must have been asleep during that lecture. I do recall how easy it was to fly after the TH-55's.

Do you know of any info on test stands. I would like to "try it before I fly it." I have a few ideas I would like to research with it. One is the application of a Kman type servo flap control system to large diameter rotors for gyros. As you might guess the interest in wooden blade for their torsionally flexible properties. Another is hinges...both standard and elasomeric.

I am sure this will be an up hill climb because I have only been blessed with high school level physics... did I spell that right.

Many thanks,

joe
joe

[joe nelson]

Sorry Chuck,

I should have looked a little closer and I would answered my first question! I'm getting old having CRS...can't remember s**t and now I can't see either.

Again many thanks,
joe

[C. Beaty]

Joe, the easiest test stand can be made from a junk car; one that was rear wheel drive with standard rear axle.

Stand the axle on end, weld the differential gears together (locks the differential) and attach teeter towers to the wheel hub. The ring and pinion doesn’t get any oil but you can remove the cover and slosh oil on it from time to time. It lasts longer than you might think.

[joe nelson]

Chuck,

that sounds easy enough. what kind of powerplant would I need to drive a 30 plus foot rotor on the stand at 200% NR?

Has plywood been used as a blade material? If so what were the results?

joe

[C. Beaty]

“what kind of powerplant would I need to drive a 30 plus foot rotor on the stand at 200% NR?”

A big one. Ernie’s junk automobile test stand used a 6 cylinder Chevy engine and was huffing and puffing in taking a 23’ foot set of blades to 600 rpm. Admittedly, the old stove bolt engine was pretty well clapped out but a lot of power is required to drive rotor blades above 700 fps tip speed. I would start with a V-8.

[joe nelson]

chuck,

This sounds like a lot of fun to me.... just slap some NO2 to it! It appears the testing may be as much fun as flying.

A 283 or 350 cid would be the ticket. Just mount the engine mounts directly to two "I" beams as if they were still in the power train...directly to the rear end. Would the rear end have to be braced for "out of balance" events?

This keeps getting better as we go... now I also have an excuse to buy more tools(toys). Could be like Xmas!!!!

joe

[a1frankie]

Have you ever seen the Bensen wooden blade plans? Vortech has some also but I don't know if they have been flown.

[C. Beaty]

Yes, I’ve seen a few Bensen wood blades; even built and flown several.

The Bensen plywood blades suffered from an external noseweight and an airfoil made from flat plywood skins so performance wasn’t the greatest. But they did fly; hand starting was a breeze and if the plans were faithfully followed, were quite safe. Marine plywood is available in 3-mm (0.118”) thickness and 5’ x 10’ sheets.

I imagine plans sold by Vortech are copies of Bensen plans.

[joe nelson]

Thanks Chuck,

I'll get on their websit and order the a set of plans. I'll keep everyone updated on my progress.

I did check some junkyards yesterday for parts for my test stand. Also, I'm going to order a maintenance manual, off line, for the Kaman H-43. Hopefully, this will give me some additional insite on wooden blades and servo flaps.

joe

[arka]

try two links (my vortech doc,s copy):

1) http://www.gyroblade.times.lv/

scroll down till english text appears;

2)http://www.gyroblade.times.lv/drawings.htm

here thumbnails for drawings.

If not sucseed,try upper left second button(of main page)

[joe nelson]

Howdy,

I have ordered plans for the b-19/20 and it does include plans for wooden blades. Now, I'm looking for different airfoils for my main project. It's my intent to have knives cut for my moulding machine so I can replicate them as I use them up on a test stand.

I have completed my work on a super simple swash plate that will allow me to try a set of servo flaps on wooden blades.

If successful the flaps will allow me to fly larger diameter rotors (30+ feet). If all that I've read can be accomplished we can have reduced control pressure and maybe even jump t.o. or at least very short ones.

joe

[arka]

you can download free copy of B-19 doc-s,sold by V. few years ago.
Link -above:

http://aviamaster.sla.ru/zipfiles/B19.zip

Near zero useful information about airfoil and its machining:(

[joe nelson]

Thanks Arka,

I recently bought a set of plan for the B-19/20 from Vortech. I am finding that there is so many types of wooden blades plans it is almost confusing as to which would be best for my gyro design.

I like the old 1940's style gyros with larger diameter rotors. The bad part is they are not available anywhere so I will have to build them. Many ideas have long since been forgotten like jump T.O. technologies and rotor head constructon. I guess all that is new is not always better.

I'll keep everyone on the forum updated on my progress with my blades.


respectfully,

Joe

[joe nelson]

Update,

I've finally answered one of my first questions; can a moulding machine be use to cut the airfoil shape in wooden blades? Answer; Yes, but not without several other steps... possible but not practical.

Next I'm going to try a router with X and Y axis movement to hog out my blades. Would anyone have suggestions as to the type of bits to use?

Joe

[C. Beaty]

Joe, I can see why you might not be able to shape the leading edge in a single pass through a single spindle molder but I imagine a multiple spindle machine could be built to do it. But it’s not worth the investment, considering the market potential.

I’ve shaped metal spars in a vertical milling machine but it took 3 passes.

My own experience with one off blades is that a body grinder with 00 discs will shape an airfoil in almost no time, finishing with a belt sander. You need an accurate template.

[Mayfield]

I suspect that you could find a shop in most large cities that has a long table 5 axis router.

www.cncmotion.com/multiaxis.htm

I built several sets of Bensen blades in the early 70s. I was not qualified at the time to evaluate performance, but I do remember they were very easy to start.

It would be interesting to compute the weight advantage (or disavantage) of laying up blanks like those of the Bell 47 or 18A, routing a good profile, like the VR7, and finishing the blade with a coat of glass.

Jim

[joe nelson]

Thanks Chuck and Jim,

What I experienced was moulders knives only cut about 4.5 inches. This would only give me a nice profile on the leading edge above the cord line. A 1/2 inch round-over router bit was used for the lower radius. The 8H12 airfoil being made has a 7 inch cord which leaves me with approx 4" to taper to the trailing edge. I used my router to shape the remander of the airfoil which seemed to be labor intensive!

I do'nt intend to make "one of" blades! These blades are test blades which will tested to destruction on my test stand. They need to be uniform to yield similar performance when tested. I'm interested in different construction techiques, materials, flutter and blade control.

My comment about the moulding machine was one of disappointment rather than function. I thought construction could be accomplished in less time and effort because of my shop being well equipped... no brag just fact! My game plan was just faulty:wacko: However, the blades did turn out nicely.

Rumbling, bumbling and stumbling,

joe

[joe nelson]

Jim,
If you have a VR-7 airfoil profile that you can post I'll copy it and cut it out for testing. How many layers of glass and what kind would be needed on each blade.

Thanks,

Joe

[C. Beaty]

Jim, I attempted some quantitative measurements on rotors back in the '70s but errors creep in when you don’t know the actual rotor disc angle of attack.

I mounted a hydraulic pressure transmitter to measure force along the roll pivot axis and mounted a machinist’s bubble protractor on a lever connected the rotor head via a push-pull cable so as to enable me to eliminate the component due to the machine sliding down the inclined axis; but not knowing the rotor thrust angle introduces error. And if you know the angle of the rotor’s thrust line, you already have lift/drag without the other complications.

Anyhow, the numbers I got were:

Bensen wood blades had the worst L/D

Bensen metal blades were significantly better.

Hughes-269 blades with NACA-0015 airfoil were better yet.

And the best were home built, bonded metal blades with a cambered NACA-0006 airfoil.

But Joe is correct. The easiest way to measure rotor L/D is with an instrumented test stand that provides numbers for rpm, torque and thrust. To eliminate ground effect, the blades should be mounted upside-down. Keeps the poor guy sitting in the middle of all this plunder out of the wind.

[Mayfield]

Sounds neat Chuck. Did you have any structural challenges with a 6% thick blade?

Joe,

I don't have the coordinates handy. I know Chuck, and others, have the url for a web site that has the coordinates of a bunch of airfoils.

As for the fiberglass: The only blade I'm really familiar with is the 18A blade. It has a single layer of very light (6 ounce?) cloth as weather/abrasion protection.

Jim

[C. Beaty]

Joe, here are some scans of some wood spar blades I’ve made.

The upper scan is the spar section of a VR-7 airfoil I used in one of the 3-blade rotors you might have seen elsewhere. The leading edge was lead, nailed to the spar with hardened wire brads and covered with a couple of layers of fiberglass.

The lower scan was a sample section of a NACA 23012 airfoil that was used as a test section to ascertain the CG but was never flown.

Straight grained birch has a tensile strength not far from 6061 aluminum and on a weight/strength basis, is stronger.

It is important that rotorblades be balanced about their ¼ chord.

To machine the balsa afterbody, I made a profiler using a sanding belt. Balsa is available in nominal 2x4 planks but the stuff I bought ran ~2¼ x 5.

[joe nelson]

Many thanks guys!

joe

[C. Beaty]

Jim, the NACA 0006 rotorblades I made used a spar milled from lengths of 3/8” x 2” 2024 bar stock. Tensile strength was more than adequate but they were pretty floppy in a flapwise direction. But that’s not necessarily objectionable; when Cierva first went to 3-blade cantilevered rotors, he had a vertical shake problem that was cured by fitting an additional flap hinge at midspan. The problem was eventually solved by softening the blades in the flapwise direction.

Ordinates for the VR-7 airfoil can be found at the UIUC web site:

http://www.ae.uiuc.edu/m-selig/ads.html

[StanFoster]

I used to own a Williams & Hussey WH7 planer/moulder machine. It had knives that could take up to a 7 inch wide profile and up to 3/4 of an inch deep.

It had a power feed and you could mill crown moulding and the like with it.

If the top profile of the rotor blade fits within the 7 in. x .75 inch limits...this machine could do a beautiful job milling them out. The bottom of the front nosing could be removed with a table mounted router.


Stan

[joe nelson]

Stan,

I have a shop fox moulder with a 4.5 inch detent for the knives. This has been the limiting feature of my machine to date. I will look into the WH7 but my tool account is running a little low right now! I have just acquired parts for my test stand/tower.

The use of a router table has been the way I've made the lower radius with no problems. I have also made a PVC pipe jig (copied from an old Bell video) that allows me to use my small router with a follower to route the upper surface of the blades by by way of a airfoil template on each side of the jig. This has worked but I have only used MDO in it so far.... very dusty!! I'm experimenting with different bits to improve the end product and reduce the finishing time. If you have any suggestions please feel free to make'm.

I haven't made templates with a reflex yet... hope it works! I will probably divide the airfoil along the cord line and run them on both sides.

Thanks,

joe

[StanFoster]

Joe: Putting a router on rails would be an excellent way to do this. I built a civil war cannon carriage years ago and acquired some U.S. government blueprints for the carriage. It had to have a tapered trail for the tongue of the carriage. I made some rails that had the correct taper...and made a sled for my router to ride these rails. The router then just milled off what wasnt a cannon carriage.:yo: It worked real slick.

Though I have never attempted an airfoil shape...I dont see any reason a sled could be made for a router to follow the airfoil profiled guide rails.

By the way...tomorrow is Memorial day and every year on this date I shoot this 6 pound civil war cannon at the ceremonies held here in Paxton. I will post some pictures, and if I am lucky someone will be able to catch the cannon when it fires.

Stan


Stan

[joe nelson]

Stan,

I'm not good at catching cannon shells! I tried it once and was'nt very good at it.

Did you make the wheels for your gun carriage? Wheels are more difficult than even making chairs! They both have too many angles. I found it out the hard way by building my daughter an 8 foot dinner table with chairs.


gitter done!

joe

[joe nelson]

Stan,

Had a couple of thoughts. What about the use of sizing before the blades are covered with glass? It would stop some of the uptake of the resin into the wood keeping the blades lighter. I don't think would affect the resin adhesion when the fiberglass is applied. It would aid in preventing moisture damage. A three pound cut of selac would be a good starting point.

I'm going to start with polyester glass and bi-directional cloth in a single layer for my first try. Moisture content and weight will be monitored....leave'm on the patio... wife willing. Me think a trip to the aviation department of
Auto Zone and Home Depot is in order.:peace:

joe

[Timchick]

Stan,

......Me think a trip to the aviation department of
Auto Zone and Home Depot is in order.:peace:

joe

You mean AutoGYRO Zone? :D

[joe nelson]

Good one, Tim.

[RHGraham]

Stan,

Had a couple of thoughts. What about the use of sizing before the blades are covered with glass? It would stop some of the uptake of the resin into the wood keeping the blades lighter. I don't think would affect the resin adhesion when the fiberglass is applied. It would aid in preventing moisture damage. A three pound cut of selac would be a good starting point.

I'm going to start with polyester glass and bi-directional cloth in a single layer for my first try. Moisture content and weight will be monitored....leave'm on the patio... wife willing. Me think a trip to the aviation department of
Auto Zone and Home Depot is in order.:peace:

joe

I wouldn't do that myself Joe, particularly with polyester resin, you want all of the "soak-in" you can get to make a good bond, especially with something that's going to flex alot. It won't "soak" very deep anyway.
A common problem in boat-building is folks glassing thier wood boats for the first time and not doing a good enough job of getting all the previous paint or varnish off before they do the lay-up, with polyester espeically, when it kicks-off and starts it's shrinking phase the glass layer de-laminates from the surface underneath. Sometimes not right away, sometimes after some stress has been put on it... like flexing.

You'll need a lot of resin for a blade too, if you are using polyester, use something that'll let the resin spread out nice and thin so it won't get so hot... a small diameter can for instance that has the polyester resin "deep" instead of "shallow" will cause it to get screamin hot and it'll kick-off really fast, and might be a fire hazard also. Use a nice wide tray or large diameter container so it's shallow and it'll be a lot easier to deal with.

If you end up going ahead and get to the point where you are making blades in earnest, I'd suggest looking a lot harder at either Vinylester resins for economy, but even more strongly at true epoxy, West System is what I'd reccomend, far stronger, very little shrinkage issues, much longer open ( working) time, and long-set epoxies are generally FAR more flexible and resistant to cracking over the long run. West System is industry standard in marine where I'm familiar with it, and they set-up thier cans and pumps to be very easy to deal with.

Cool project Joe!

[joe nelson]

Thanks for the info,

Do you have any experience with vacuum bagging? This was another step I was going to research. That ole adage about those who start with wooden boats always end up with a fiberglass one must apply to rotor blades as well.

What would you recommend as far as cloth? I was going to use uni-directional or something in that order. Eariler in this thread Jim said that 6 ounce cloth was used on the AS-18... that will be a good starting point as to weight of the cloth.

Another idea that I've been considering was to use fiberglass honeycomb on the rear 60% of the blade and cover that with glass. It would make the CG issue less of a problem.

[RHGraham]

Thanks for the info,

Do you have any experience with vacuum bagging? This was another step I was going to research. That ole adage about those who start with wooden boats always end up with a fiberglass one must apply to rotor blades as well.

What would you recommend as far as cloth? I was going to use uni-directional or something in that order. Eariler in this thread Jim said that 6 ounce cloth was used on the AS-18... that will be a good starting point as to weight of the cloth.

Another idea that I've been considering was to use fiberglass honeycomb on the rear 60% of the blade and cover that with glass. It would make the CG issue less of a problem.

Yeah, I've done resin infusion alot, but, it's a lot of extra gear and the consummables are pricey, and it's something best done on very small things to start with, it's a finicky thing that isn't really hard to do, but one of those deals where practice helps alot in reducing waste and figuring everything out.

6 ounce standard E-glass would be fine for initial work I think.

Lots of choices for core material on a job like this, but to start, if you we're going to do something for testing I'd suggest structural foam instead as a proof-of-concept material.

Here, let me ramble for a bit and give you my thinking on it;

Composites are wonderfull, and one of the wonderfull things about them is that they can be applied on many levels and at many price-points also.
And they are reletively easy to use as well, BUT, it's a total learning curve thing, so I think it's best to start very simply and with very basic materials and hand-lay-up, and that will teach a lot that you won't wanna miss if you want to upgrade later on.

So, to begin, I'd personally recomend standard bi-directional "standard" glass cloth, ( also called "e-glass") in the 4-6 ounce range, and polyester resin, and structural foam. Wood, E-glass, and structural foam composites are really quite suprising in strength, toughness, and flexibility, and are still the mainstay of the boat industry. And all these materials are cheap enough that initially, as you throw some of the bugger-ups away, it won't break ya.

Then the first change I'd reccomend looking at is a change in resin from polyester to vinylester or epoxy and figure those out. OR, go right to epoxy, but it is expensive in comparison. It's also easier to work with and structurally better pretty much across the board... so it's your call on that one.

Then, when you can lay up by hand over a core and it's starting to come together nice, I'd suggest that that would be the time to look into vacuum infusion and start doing some trial runs on some small-scale models of whatever it is you want to do with it. It's not quite like vacuum-clamping stuff as is done alot in wood-working, but it's similar, if you've done that it would be a bit of a head-start. But in any case, you want to have a good feel for getting stuff together by hand first before you commit to the vacuum infusing gig, cause when it goes bad, it can ruin a lot of expensive material, and if it goes REALLY bad, you can bugger-up your vacuum pots and stuff too.

AS far as material goes, after you can vacuum infuse e-glass in simple layups, you can start looking at the more high-zoot stuff like S-glass, kevlar, and carbon fibre... although, as cool as kev and CF are, they are WAY, WAY over-represented as far as qualities go. For flexibility and strength/toughness in that mode, S-glass rocks.
Kevlar comes next, and gets lighter, and has incredibe puncture/abrasion resistance, but it's expensive, and will not flex as far before a de-lam or breakage. Lightest and "strongest" in specific directions and loadings is Carbon Fibre, BUT, It's missleading and over-stressed in many discussions, CF composites are very stiff, and have very little flexibility, and can be extremely brittle outside of loads that happen in a straight line, or outside the laminate's designed directional strength... which all means, it ain't no good if you need something to be flexible.
In fact, a lot of the CF you see on race cars has S-glass or kevlar underneath it, or other high-strength cores so it isn't forced to carry a load all on it's own.

There are a myriad of core materials too, two I've used alot are nomex (kevlar) honeycomb, and aluminum honeycomb. PITA to work with, but make very strong structures.
Although, for what you are doing, I honestly would have to say your idea with high-grade ply and glass covering is going to be hard to beat, and maybe structural foam would be a real boon to balance issues, as you mentioned.
To go outside of that, it's probably better to go ALL composite, like the Dragon Wings. Glass, foam, and wood, just happen to work together well with similar properties, Kevlar and CF are in a bit different place and will likley work better with cores and structures that match them better.
I've seen some stuff with CF over wood, but I have to be honest and say the reasoning behind that always struck me as being a bit weak, other than the fact that CF cloth LOOKS really cool, and an awfull lot of products are made and sold with that in mind.
I like CF, don't get me wrong, I'd just rather see it used with materials that match it and make sense, like nomex or aluminum honeycomb or solid structural foams, because otherwise it's kinda a waste of material and money.

The very best book to get to start with, IMO, is "Fiberglass and Composite Materials", by Forbes Aird ( awesome guy), ISBN 1-55788-239-8

Another great one is "competition car composites", by Simon McBeath, ISBN 1-85960-624-5

I've read a few books on composites that were supposely geared towards aviation but I was extremely dissapointed in them, and thought alot of what I read was poorly explained and not very clear. So Ireccomend those other two books as I think they are far more consise and informative and will get you up to speed far quicker and with a better knowledge base to work from.

You figure it all out, and test them, I'll be wanting a set.

[RHGraham]

Here are some links to places I've dealt with;

Fibreglast... good place for resources, as well as supplies, take a look through the learning section, it's great.
http://www.fibreglast.com/

Aerosleeves; I've used a lot of thier product, small outfit, great to deal with. The glass sleeves are totally appropriate for what you are intending and will take a lot of pain out of the lay-up... and if you just HAD to do carbon fibre, they got it.
http://www.aerosleeves.com/tut.php
I've used the sleeves to cover wings on cars with great results, and made tubular structures over cardboard cores, as well as odd shaped stuff carved from foam. Damn handy.

Only thing I'd do is get my Epoxy from West System, at this point, I won't use anybody elses resins or catalysts, it's industry standard.

[PW_Plack]

I've only ever seen one set of homebuilt glass-over-wood blades, and the glass separated from the wood in the heat at El Mirage. Is this just incorrect choice of materials, an error in construction technique, or a common issue?

[RHGraham]

Could be all of those things... all the "standard" resins can be heat-sensitive to one degree or another, especially if they are dark-coloured and in direct sunlight. And epoxy can be UV sensitive also, so in molded lay-ups this is taken care of by some kind of gel-coat to address the possible problem.

In a hand lay-up, where glass or whatever is applied over a core, it's best to paint the piece afterwards. On boats it'll usually be some kind of urethane or spar varnish, you sand out the item as you would with any orther surface and paint it. Have to test on the resin though because some paints or clear-coats won't play nice with the resins and make it soft, and the paint will never harden.

If the blades were light-coloured and the lay up was done with good materials and good prep, they "shouldn't" de-laminate unless the temps were REALLY high. Any of the common resins should be ok up to 200F or so.

[joe nelson]

RH and Paul,

I think the heat/de-lam issues are one more check item on the test list. Sounds like a very good excuse to go to El Mirage next year with some test blades! :whoo:

I remember early in the home-built foam airplane industry this was an issue but I haven't heard of any problems lately. Burt Rutan has put a sub-orbital foam and glass aircraft into space without problems. He also used carbon fiber as a heat abative material for reentry.

RH, what grit abrasive is best for wood prep prior to applying the glass?

[RHGraham]

I'd suggest 120 at the finest, it's good to have a fair amount of "roughness" for the resin to "key" into. As long as it's otherwise smooth and straight, even 80 would be fine. It's hard to not think of resins as "glues", but they are not very good glues in the traditional sense, it's best to have a good mechanical bond between the resin and whatever it's being used on.

[RHGraham]

Hey Joe, two things I thought of, before I log-off and go git some work done...

First, the more I think about it, the more strongly I wanna reccomend those aerosleeves, they will make your life a lot easier than trying to apply straight fabric to those aerofoil shapes.... but, if you use it, there are two tricks to it;

A= to size it for your blades, measure around the blades to get a circumference, then divide that figure by 3.141, to get the approximate "diameter", and use that figure to order the right diameter sleeve. They are listed in ranges, you wan't ideally to get a sleeve diameter that has your measurement falling right in the middle of the upper/lower end of the ranges.

B= if you try to slide the sleeves over the blades, it'll make you insane... the trick is to take 4 or 5 inches of the sleeves and turn it in on itsself, put that section on the end of the blade, and then roll it on over itsself.
IF you try to just pull it on over the rough sanded blades, it'll just turn into a gigantic chinese-fingerpuzzle and it'll make you crazy... trust me...
:0)

( friends have remarked while I've covered tubes that it's like a gigantic fiberglass condom....)

[joe nelson]

RH,

Thanks for the info. I've for the last few hours I've been in my shop hogging out another blade for testing. I have 80 grit on my belt sander so I leave the surface on blade at that finish. I'm using exterior grade A/C ply until my skill level get where I'm consistent in blade quality...cheap education!

I've looked a the website that you recommended and I'll will certainly use their services in the near future. There's a lot of information to digest here.

MANY THANKS,

[RHGraham]

Well I hope it helps, composites are not my primary area but I've done quite a bit with them, they have thier place. Just don't get carbon fibre fever... the marketing and fans will say things like "stronger than steel" over and over but it needs a serious dose of context... for what you're doing, carbon fibre I don't think is the ticket, go with the glass at least to get it all worked out.

[Dean_Dolph]

Joe, I've posted this info several times before so I hope the veterans forgive me for doing it one more time! Hopefully you will find it of value.

There is a guy in Houston TX. that is a former Shell Answer Man on composites. His name is Gary Hunter and he has been retired from Shell for several years now. He owns Gary Hunter Composites and the following is his contact info.

Email - glueguru@earthlink.net
Home phone - 281-277-7767

If you google him, you will find some interesting info! Please let me know if the contact info doesn't work and I'll try to get an update.

Gary loves to help people with composite questions and while he is very nice about it, he is brutally honest and candid in his evaluation of projects. I've known him for years and have had the experience of suffering through his explanations of why my 'great' idea wasn't so great. I've learned to email him rather than call so that he won't hear the sobs when I hear what he has to say!

[RHGraham]

Joe, I've posted this info several times before so I hope the veterans forgive me for doing it one more time! Hopefully you will find it of value.

There is a guy in Houston TX. that is a former Shell Answer Man on composites. His name is Gary Hunter and he has been retired from Shell for several years now. He owns Gary Hunter Composites and the following is his contact info.

Email - glueguru@earthlink.net
Home phone - 281-277-7767

If you google him, you will find some interesting info! Please let me know if the contact info doesn't work and I'll try to get an update.

Gary loves to help people with composite questions and while he is very nice about it, he is brutally honest and candid in his evaluation of projects. I've known him for years and have had the experience of suffering through his explanations of why my 'great' idea wasn't so great. I've learned to email him rather than call so that he won't hear the sobs when I hear what he has to say!

I'd second that wholeheartedly... I've never met him, but he has a well-known reputation in the composite circles.

[joe nelson]

Thanks Dean and Randall,

I'm a few weeks from getting a hard start on glassing my blades. I had some trouble yesterday in hogging out a couple of additional blades. They're not as uniform as I wanted. I think my jig has died or something! This will give me some time to digest the info on the glassing techiques and gather supplies.

Many thanks,

[joe nelson]

Dean,

I e-mailed Gary Hunter the day that you posted your message and I haven't heard from him yet. I'll give him a call on Monday if I haven't heard from him by then.

Many thanks,

[Dean_Dolph]

Joe, he may be tied up with getting ready for Oshkosh or involved with the Exxon Flying Tiger for which he is the crew chief.

[joe nelson]

Hey Dean,

Just received a flyer from the EAA on their construction workshops. There's a composite class offered and I strongly considering attending! It might not help and it sure won't hunt!

Maybe I'll invite one of my buds from PRA40 to go as well. You know it hard being the only rotorhead in a bunch of "fixed wingers" for a whole weekend!:bored:

[Dean_Dolph]

Joe, it may be that Gary Hunter is giving the class. I know he presents seminars at most of the major EAA events. However, like I said in a previous post, Gary is the crew chief for Bohannon's Flying Tiger and may be involved with it at that time.

[Kewlwill]

any updates here?

Thanks!

WILL

[joe nelson]

Will,

Sorry about the delay in the update, I was on vacation.

I have not done anything new at this point. I have enrolled in a local vocational school for metal shop and welding classes to improve my skill level... it's starts tomorrow! In about three weeks, I'll be taking a weekend composite course, given by the EAA, to get some hands-on experience in covering my blades with glass. So, it's looks like about the middle of October before I'm back working on the wooden blades.

One thing that I have done since my last posting was to brazed up some 12 foot long 3/8 inch drill bits for the control rods, for the servo flaps, on my blades.

[joe nelson]

Paul stated that he had seen delamination of the fiberglasses wooden blades at the El Mirage event. It is my oppinion that these blade were not cured correctly. To my understanding, if the glass is allowed to cure at an ambient temperature...say 75 degrees in Cincinnati then taken to El Mirage at 100, the blades will soften at 76 and surely delaminated by 100 degrees not including solar gain temperature.

The large airplane manufacturers routinely bake composite structures in huge ovens/autoclaves. This is were we are in error, I think. We'll need to oven cure our parts to gain higher tollerence to temperature variations. As you may have guessed, the length of time in the ovens is directly related to the type and thinkness of composite to be cured. I do have the forumla but I can't find it in my notes at this time... will post it later!

The Rutan/composite plane builders make their own ovens per conversations I had over the weekend with EAAers. It is a simple plywood box insulated with foam, some source of heat(heat lamps or heating coils) and an accurate thermometer. It sounds very doable.

[Kewlwill]

Thank you very much joe! Ill do some research too.

WILL

[joe nelson]

I've strung control cables, yesterday and used uhmw plastic as cables guides. It seems to have smooth action under normal "G" ... 0 rrpm. I have also built set of blades with a 3/16 stainless rod as servo tab control. When I finish my test tower we'll see which works best under normal rrpm. Both sets of blades will be covered in 8 ounce cloth and given a single coat of glass and autoclaved. I watched an old video of a Sikorsky R-4 and it stated that it's blades were tubular sparred with wooden leading edge and ribs covered with aircraft fabric... I might just try that down the road when I get the other projects under better control.

What was a real bummer was I broke my vice trying to bend cold metal with a BFH.

[Kewlwill]

Joe can I see some pictures of your blades?

WILL

[Edvin Tjernlund]

Interesting ideas.
I will start to produce my own rotor wings using old Oak and plastics but not homogen material. I think it is possible to make a shell construction with different materials up on metallic or aluminium bones.

As I understand from old gyro movies it is most important to find a good balance with weight and lenght to get the best flying feeling in a gyro?

Is there some calculations with weight of the gyro, Horsepower of engine that say this is the best lenght of a rotor balde?

Also the propellor for the engine maybe will be on the drawing table later.

Edvin - iMedvind

[Damocles]

You could shape your propeller with a shaper with a head with 2 blade.
Like this guy sell on Ebay (120215598114).
You could shape your blade in2 to 4 pass (depending how fast you move).
To do that with a router is not precise enough and very time consuming.
I would make the blade in 4 pass. 2 pass on each side.
It would require 4 different set of knife that would be custom made to the airfoil you decide to make. Very little finishing would be required (depending if you want to cover with fiberglass or sheet metal). By the way, I happen to work at Goodfellow and we have engineers that design gluelam all day long and I had a conversation with them about that.

[joe nelson]

Luc,

I tried to use a shaper early on in my experiments and the shapers could only make a blade 4 to 7 inches in cord. However, it makes a beautiful leading edges on the blades.

You're correct that it is slower but the jig that I built can change airfoils in the middle of the blade without additional set-up. I can change the airfoil and the washout without removing the wood from the jig.

[Damocles]

Humm, I wonder how long your jig is! Is it, by any chance, the entire leigh of the blade?
Are you thinking of multi layers with a different density core?
You mention glass covering, will it resist particle sand ect... Or are you thinking of puting a kevlar strip or similar to protect it?
How will you join the wood and metal?

[Damocles]

About the shaper thing, it can go much higher than 7" in cord, but the price is a lot more after 7". This is why when I said earlyer that I would make the blade in 4 pass. Using 4 different set of knifes you can make a 14" cord.
Are you using marrine plywood or the more expensive birch select plywood?

[joe nelson]

Luc,

I think your idea of using a shaper is a good one. I have a small Shopfox shaper in my workshop but it's too small to do molding work on rotor blades. If you have a larger industrial size shaper, I'm sure it would work as you said.

My blade jig is my version of a machine that I saw on a video produced by Bell Helicopters in the 1940's. It is a simple router set-up on a tram arm that follows a pattern airfoil cut from medium density overlay board. The patterns can be alligned to cut a twist in the blade or even change the type of airfoil altogether.

The jig is approx. 24 inches wide and 48 inches long with out-feed rollers on each end to accomodate any length of blade stock. It can be adjusted to cut a cord of 18 inches but it can be modified to any width. There are small in-feed rollers(horizontally and vertically) to insure the blade stock is prevented from moving while the router is running.

You asked about the types of wood to be used. For my test blades I used CDX exterior grade plywood. This type of plywood has voids in the laminations and is unsuitable for "man-rated" blades. A good grade of marine or aviation grade plywood is my choice of building material. You may need to laminate your blade stock to an inch to a inch and a half in thickness so a good exterior grade of glue is required, if not T-88 epoxy aviation grade glue. I use vacuum bagging as my preferred method of clamping the laminates. You may want to talk with the engineers at work to see what they think before you try this.

I will be building a rotor test stand soon to test my blades and I'll keep all informed on my progress.

[joe nelson]

43231

43232

Luc,

Here are a couple of pictures you may find interesting. It is the first prototype of my blade cutting jig. I have made several improvements since the photos were taken but it will give you some ideas I'm sure.

[StanFoster]

Thanks for posting the router sled jig pictures! I use similar methods when using a router to cut compound curves on stairway components.


Your techniques make me drool. I never plan on making rotorblades but its nice seeing ingenuity at work. STAN

[Damocles]

Thank's for the pix. It's a good idea but I was wondering what do you do when it's time to flip the blade to do the other side? What glue did you decided to use? What thickness of ply have you decided? I tough 1/4" could be good. I was also wondering if it would be possible to use thick aluminum foil bonded with epoxy. I wonder ........

[joe nelson]

Luc,

When you're making symetrical airfoils all that needs to be done is to flip the blade stock over and put it back in the jig. A blade trailing edge shim is placed in the jig to bring the 25% cord line on the blade stock in line with the airfoil template's 25% cord reference line in the jig. After routing, the end product should be a symetrical blade.

I like to use 3/4 inch thick plywood in my laminations because it is easier to make scarf joints of 16/1 inches when joining the wood butt to butt. Also when I place another lamination over top of the scarf joint it is important to separate the joints as much as possible.... in other words, don't put the joints close to each other!

I use Titebond III glue for my blade stock and use a vacuum bag for clamping.

One interesting thing about plywood is after it has been machined the lamination form lines indicating if you have taken equal amount of wood off the blade. If your lines are not straight then you'll need to do additional shaping....neet!:wave:

[joe nelson]

Thanks Stan,

I have sawdust in my veins, in my hair, on my clothes and up my nose. lol

I'm building an armoir for my sister-in-law right now but it's not as much fun as rotor blades.

[joe nelson]

Luc,

I have just discovered a major error in the jig set-up for my rotor blades. I said the index line is on the 25% cord line....this is incorrect! It should be located on the 30% line on the blade cord where the symmetrical blade is the thickest (NACA 0012).:der:

[Bumperdog]

Hey Joe,
If you build that test stand with an 8 cyl engine and 30' rotor you could be launching the biggest wherly gig in history.
Bruce

[joe nelson]

It would be something to see wouldn't it? There was a video on the forum of a rotor being tested on a trailer. It was picking up trailer and all.

I've been told the target tip speed is 700 fps and that would take a V-8 to do the job, I think.

[tyc]

Joe, the easiest test stand can be made from a junk car; one that was rear wheel drive with standard rear axle.


Have you considered a sturdy tripod frame and use a large electric motor? When testing main or for that matter, tail rotors, that's what many aeronautical design teams do.

tyc

[joe nelson]

Tyc,

Early on in the design process I'd considered an electric motor. There was two major problems that I had to deal with. An electrical motor of the size needed was very heavy and expensive. The other consideration was that they are three phase and high voltage... not available in residential areas.

I have several pictures pilfered from the net of test stands that do what I want. The first design was mounted on a trailer which in my situation was very interesting. It could transported to a place like Mentone or Wachula for demostrations and rotor balancing. The tower was a four leg truss type welded directly to the trailer with what appears to be an automobile engine attached by a 90* gearbox to the head.

At this point, I'm interested in what instrumentation that needs to mounted to the stand. I want an oscilloscope to measure the vibration and their frequency in the rotorblades. Of course, rrpm and lift will need to be measured. Any thoughts would be appreciated.

[tyc]

Tyc,

... I'd considered an electric motor. ... two major problems ...
... An electrical motor of the size needed was very heavy and expensive.
... The other ... they are three phase and high voltage... not available in residential areas.


Used electric motors can be had very cheaply relative to the almost insane cost of purchase of a new unit - and will perform just as well.

As for two problems you listed, there may be a third you haven't considered until now - litigation. If when testing those blades - in a residential area and probably in violation of the local zoning code - should one of those blades fail in a catastropic manner; it might amaze you as to just how far some of those parts and pieces will sail after they detach when spinning at only two or three hundred RPM. As one who has attained his majority and as a home owner, know that you can expect to be held liable for any and all damages; and should the damage(s) be only to your own home, your own home owners insurance may not even protect you.

With the above said, have you considered renting a rural tract and setting up shop there? In most instances 220 and 440 power is readily available. With gasoline and diesel costs where they are today, such a move just may prove to be an economically attractive alternative to what you currently propose.

As for the instrumentation, basic aeronautical engineering texts should answer most of those questions you pose. Want to see just how many cycles/hours those blades can take before failure? It shouldn't prove difficult to come up with a rapidly operating "Collective Stick". Once the blade shows signs of failure (dye testing/ non-destructive testing looking for fractures at the leadng edges as well as at the root), one simply divides the total number of hours by two (a safety factor of 2) and there's your reasonable limited life rating.

Hope this was of some help.

tyc

[joe nelson]

Tyc,

I ran across a three legged test stand with an electic motor today. Students at Purdue U. had built it for testing the rotor for a man-powered helo. I'll need to study their design for a bit before making any judgement. In looking at it, I did see some interesting features. The rotor mounted onto a circular component which would be good for measuring the rotor authority.

One advantage to using an electric motor would be its' nearly vibration free operation. This would be a definate plus when measuring the frequency of vibrations in the rotor. The down side is I've already collected most of the parts for my test stand. I only need to finalize the design and put it together.

As far as litigation, I'm extremely well versed in dealing with this subject and well protected! My father, my oldest daughter and my youngest brother all attorneys....no worries mate.:hippie:

[joe nelson]

I've come across a new airfoil type on a website that I would like to get your input. It's called a bi-camber blade. It looks a though it might work in theory. However, it may be weak in structure.:help:

[karlbamforth]

The Bi camber blade is quite efficient, not sure how it autorotates tho so that needs trying.

It does look as though it might be a bit weak but it has already flown as a prop so reasonably strong.

[Arnie Madsen]

You found another Interesting idea Joe. It may work on helicopter blades because of the high tip speeds they encounter.

The little bit I know is that the supersonic aircraft builders often use this design on the fuselage to keep airflow smooth at high speed.

It is loosely called the "coke bottle effect" because it mimics part of the shape of the bottle. The indented portion creates a vacuum to keep the boundary layer from breaking up into turbulance .... something like that.

Thanks Joe , I always enjoy your posts with your ideas and experiments.

Arnie

Here are a couple of pictures. The Coke bottle is for the youngsters who have never seen one ...... :confused: .. so they know what we are talking about...:)
.

[StanFoster]

Arnie: I like those airfoil drawings you just posted.....Its interesting all the aerodynamics that are hard to visualize.



Stan

[Arnie Madsen]

Arnie: I like those airfoil drawings you just posted.....Its interesting all the aerodynamics that are hard to visualize.



Stan

Same with me Stan , some of the advanced aerodynamics can be understood (even by me) with good visuals. My favorites are videos of wind tunnel tests when they use smoke streams and you can see exactly what the air is doing. A 5 minute video can teach more than 5 days of higher mathematics and aerodynamics which I never completely understand anyway.

While I am thinking about it Stan , a while ago you asked about elasomeric bearings as used in your helicycle. Also Joe was asking about bearingless rotor heads.

I won't answer those questions directly but shortly I will do a thread on how the Hughes 500 system works. It is my favorite , very simple and strong etc. It will give a good understanding of these rotor systems .

I have some good pictures and diagrams prepared but will probably post them later this evening when dial-up is best.

Cheers......Arnie

[StanFoster]

Arnie- Looking forward to what you have to post! Stan

[joe nelson]

Arnie, Karl and Stan,

Thanks for your replies. I think that this airfoil looks as if it would be good for high angle of attack (pitch) with it's boundry layer control. This airfoil would certainly be a candidate for carbon fiber construction, I think. It just looks weak in the middle.

Karl had a good point about its' autorotative ability. If it doesn't autorotate well it surely wouldn't work on a gyro sans collective. With higher lift the corresponding drag could also be an issue. Higher approach speeds and a more restrictive H/V curve wouldn't be "user friendly" either.

Arnie, I am indeed interested in bearingless rotor systems. The simpler, the better! Hughes system or EC's starflex systems...they're all so interesting, kinda like the proverbial "Timex". "Takes a lickin' and keeps on tickin'".

[joe nelson]

Arnie,

Thank for the great bit of information on the Hughes rotor system you posted. I've been looking on line to see what thicknesses were available in 440c stainless and 4130 chromoly sheet. So far I've found .025" in both materials but none even close to the .0009 " used by Hughes. Maybe I could reduce the number of laminae by 30% to have the same strength but my concern is the flexability due to the thicker material.

I'm ordering some aluminum rod today to make some parts for my swash plate experiment. I'll include some 4130 sheet stock with that also.

The Hughes laminations were coated with teflon which I'm sure was for ease of movement between the laminations. For my experiment, I have UHMW plastic tape that I use for making jig in my shop. This might do the trick for a teflon substitute.

One recent discovery, Damocles (Luc) had asked about Gluelam. I thought gluelam was plywood which I'd routinely used... I was wrong! Translated into my native hillbilly vernacular, gluelam is LVL ( laminated verneer lumber) which is lighter and stronger than ply...good show Luc! I will look at gluelam closely. Sorry about being SOS...stuck on stupid or my coefficient of stupid was high..your choice.:sad:

[Arnie Madsen]

Hi Joe
I still have a bit more to post on my Hughes 500 strap pack thread . Will also give you some good links to stress tests they did. I will try to do it in the next day or so. Most of the material is ready. Dial up is a bit slow and sometimes I am really slow. :)

Some of the information shows where failure starts on the stainless strap as Hughes designed it. Will help you on your experiments.

Bottom line , we shouldnt even be using the word failure , The Hughes method is super strong and will stay together with half the straps broken. It is simple and easy to inspect .

The little bit I know about modern elastomeric bearings is that instead of seperating them with teflon like Hughes did , they encase all the metal components in rubber material and call it something new. To me Hughes had it figured out in 1960.

Once Stan is working on his Helicycle hub I hope he can show us BJ's way of incorporating elastomerics to his design.

Arnie
Bell 47 G2

ps:
Joe I dug up some good drawings of detailed early wood rotors you will find interesting. They do not apply to what you are doing but I would like to put them here for others wanting wood blade info.

Also , along the way I came across info that said Stainless is one of the most flexible fatigue resistant steels to use .... you are on the right track. more later. arnie.

[CopterCenturian]

Arnie,

Fairly good explaination of the coke bottle effect- I'd like to add a bit for some clarification. In laymans terms... the protruding parts of the aircraft "see" the buildup of air resistance when aircraft or airfoils are operated at high speed. In aircraft that travel less than the speed of sound air can still move around an obstacle but at higher speeds the air builds and at high enough speeds even air which is normally considered incompressable is compressible. What this means is things like our wings, intakes ect. "see" a wall of air this is where those cool shockwaves appear in pictures of F-14's and so on breaking the sound barrier. In the late 50's the coke bottle theorey was tested, the idea being if the protrusion is ahead of an area we wish to keep subsonic the air behind the shockwave will be subsonic. the idea worked and "control" of airframe shockwaves was understood.

Practical application to rotorcraft- the cheyenne by Lockheed had a pusher propeller at the back of the tailboom. When I was in the Army I knew a then senior sergeant who had worked as a mechanic on the Cheyenne. According to him the noise comming off the prop was so bad it would literally make the ground crews sick, passout or nauseated. See the prop would occasionally venture into supersonic speeds and when the prop would break the sound barrier the noise would reflect right back off the tarmac. I was told it could be a very uncomfortable feeling and affected different people in different ways. It is believed by some of those mechs that that and other technology challanges is what did the Cheyenne in. The Cheyenne is still one of the most impressive rotary-wing achievements man has done and is still the sexiest helicopter built to date.

In summary, the coke bottle effect worked for fuselage design, thin - strong wings were found most useful for supesonic speeds. Supersonic speeds or spinning airfoils produces other unwanted effects for which there currently is no resolution to counter these effects.

Ken

[joe nelson]

Arnie,

I'll look forward to your next post! I'm always interested in anything about rotor blades that you can show me.

The UPS man came today but some of the things that I wanted was back ordered. They delivered my 6061 rod and tube but not the 4130 sheets. My strap experiment will have to wait for a week or so until the 4130 arrives.

Since my last post I've hogged out a 4' blade from MDO in anticipation of the strap material. I will need to devise some way of solidly attaching it to the wall so I can make some measurements on it's flexability. I'll post some pictures when it all comes together.

Ken,

I think what you were talking about is called "area rule". I guess this was just applied to rotorblades and called bi-camber. It looked doable to me but what do I know... I'm still taking baby steps here!:lol:

[tyc]

... Do you know of any info on test stands. I would like to "try it before I fly it." I have a few ideas I would like to research with it.
... One is the application of a Kman type servo flap control system to large diameter rotors for gyros. As you might guess the interest in wooden blade for their torsionally flexible properties. Another is hinges...both standard and elasomeric.


For what it's worth, there is another thread in the forum regarding this subject. I believe it's in the helicopter section and you may find it to be of some interest.

As for a test stand design, there is sufficient information (generally photographic) regarding the use of these but rather than using an old and possibly unreliable automotive engine (consider the cost of gasoline today) you might want to use of a suitable, used, electric motor instead. You should find used electric motors to be far more reliable for this purpose than a gasoline engine - and they're a lot quieter to.

To test the torsion limits, it shouldn't prove very difficult for you to design an "active" collective control, one which will enable you to test a given set of blades for hours on end and test them to destruction, examining them every x number of hours, keeping records as you go along, until the blades being tested are noticably no longer serviceable or until they actually come apart, destroy themselves, while being tested.

It will take time to do this - right - but in the end, it's your life that's on the line.

Hope this helps.

tyc

[tyc]

... You'll need a lot of resin for a blade too,
... I'd suggest looking a lot harder at either Vinylester resins for economy, but even more strongly at true epoxy, West System is what I'd reccomend, far stronger, very little shrinkage issues, much longer open ( working) time, ... West System is industry standard in marine where I'm familiar with it, and they set-up thier cans and pumps to be very easy to deal with.


As I understand it the West System, if it performs as well for blade making as it does in the marine field, it'll be hard to surpass it. I understand that the owners of the West System once bid on a DOE contract to build wooden blades for a wind generator and in the testing, while the system, including the blades were over stressed, the blades which were treated with the West System remained intact - but the test stand they were mounted on was destroyed.

tyc

[joe nelson]

Tyc,

Randall's suggestion didn't go unheeded! As of now, I'm still using the cheap stuff from Auto Zone until my skill set is better.

This week has been dedicated to an experiment with an idea that Arnie gave me. UPS delivered some 440 stainless steel sheet to my shop and I cut it into strips. Each was 6"x11/2"x.022" in dimension. Each strap was comprized of four laminae each with UHMW plastic tape between them to aid movement. One end was bolted to my work bench and the other end had a piece of wood to simulate a blade. Pitch was measured and it exceeded the 12 (-2 to +10) degrees that was wanted. Flapping was also good at 15+ degrees (+10 to -5).

The next test is to set up a small electric motor with a escentric cam attached to the blade. 800 cycles (400 rrpm x2) will be the desired frequency of my test.

[joe nelson]

45380 This is my new experiment. The strap can be seen at the end of the blade. I'll continue to work with it until I get one that works as advertized!

[WVLeTendre]

I thought this was interesting, the Kmax heavy lift ariel truck composite rotor blades have wood laminate spars! http://www.compositesworld.com/hpc/issues/2005/March/773/2
Charles Kaman, the founder of Kaman Aircraft is also the founder of Kaman Music Corporation and helped to create the Ovation guitar, which has a composite synthetic bowl instead of a traditional wooden back. http://en.wikipedia.org/wiki/Kaman_Aircraft
Wayne

[joe nelson]

Thanks Wayne!

The information was very interesting. I have always liked Kaman helicopters and their unique way of doing things. The servo flaps used on their blades seems to me as a better way of blade control.

PS I also own an Ovation guitar!

[joe nelson]

I was reading last night and found a few paragraphs on blade stress. This was of interest because it was talking about "blade cut-outs" used to relieve blade stress at the blade roots. If I remember correctly, that was the problem with the four bladed see-saw rotor system from a few years ago. Would this be a cure?