birch blades

jany77

Member
Joined
Jul 13, 2008
Messages
573
Location
central california
Aircraft
cessna 150,172,182,trikes,ul
Total Flight Time
over 2000
hi guys i know this was here before but still there is something more about the wooden blades,as i was reading a lot about different kind of rotor blades either composite,aluminum or wood ,i think the wood is the best choice ,thats just my personal opinion ,id like to make or at least try make wooden rotor blades ,since i did not find any manufacturers whos offering 20' dia blades,as i was reading about structural analysis of blades my idea is as folows,leading edge the first 2,5" out of laminated yellow birch or maple ,the rest will be either 2lb hot wired foam core or pvc foam ,with fwe layers of fiberglass,at root 5 ply total at 45 degrre ,as for balance id like to use 5/16 diameter brass rod and at tip extra 12" for beter autorotation as birch has 15100 psi they should hold up load of 12000lbs with pretty good safety factor ,does anyone here has any experience with blades such as this thank you
 
I'll say this once.

Wood is not the right choice. Your opinion won't change that fact. Also, making your own blades is sketchy at best.

If you want a 20' rotor system, call us at Sport Copter and we'll discuss your exact requirements.

Sport Copter: 503-543-7000 ask for Jim or Jon
 
Bell-47 rotorblade. Similar blades were used on Hiller UH12 and A&S 18A.

These blades had unlimited life but had to be rebuilt as condition warranted; namely, abrasion of fiberglass cover.
 

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My five and Dime opinion....
<Yes, even Newbies have one>:

I have only ONE life to live...the best blades I can get are my ONLY <mechanical> insurance when flying
<...since they are act as a defacto Parachute>.

While the designs for Wood blades served a purpose years ago...THEY HAVE NO STANDING today (safety wise) since far SUPERIOR materials and designs NOW EXIST making those Old Sticks OBSOLETE.

I'd just HATE TO SEE ANYONE DIE A HORRIBLE HEIGHT INDUCED DEATH just because they think older is better than newer.
<YES...veiled message there-in>.

I make no apologies here: Agreement with the "Experts" on this very important point is a no brainer..!
 
The multiple world record holder and one of the oldest and most experienced gyro pilots ever exclusively uses his own wooden blades (and as far as I know, has always used them). I'm speaking of Ken Wallace, of course. Ken Wallace flew "little Nellie" in the James Bond movie Dr. No. I just hope he fully discloses and shares the design for them before he passes on.

If I were to make my own wooden blades today, I would get a copy of the original Bensen plans for wooden blades and start there. Any changes to the design would be run by Chuck Beaty and tested carefully in a build up strategy, keeping weight and speed to a minimum while exploring their flying characteristics. There was also a guy named Monte Hoskins about 20 years ago that was building and flying wood blades. He sold a booklet that described their design and construction. As far as I know they were very similar to Bensen types.
 
I guess I'd have to ask...what became of wood blades? Were they unsafe? Was it just harder to achieve efficient airfoils? Does today's crummy lumber quality make them more difficult to build or balance?

Termites?

I don't recall wood blade horror stories, and if you have to inspect for condition, abraded fiberglass can be spotted without a borescope or penetrant dye. The so-called wood blades used metal spars to carry loads, with the wood acting as filler to maintain the airfoil shape, right?
 
Ken Wallace flew "little Nellie" in the James Bond movie Dr. No. I just hope he fully discloses and shares the design for them before he passes on.
as I devote Bond fan I must correct you, it was in the movie you only live twice, not Dr No.

Lil Nellie is a Wallace WA-117.
 
High quality wood is fairly expensive these days, they are labor intensive to make, and wood blades don't tolerate wet weather (during flight or just being stored outside) very well.

They also aren't as sturdy as composite or metal ones if you happen to hit something.

I've flown them on Bell 47's - they were popular with schools because of no life limit, but they disappeared from most utility operators years earlier. Schools could usually hangar the ships when not in use, but even then you spent more time tracking & balancing wood blades more than the others.
 
Ok I have also been very curious about the whole wood blade matter. I also would agree we do have the tech no how to make a better blade today and I most certainly would love to have a set of MasterRotor blades on my bee, but in having said that, what is the b id deal with the wood blade issue.

1. Is it that they are just not made any more?

2. That the wood blades were inherently unsafe but all there was at the time

3. Are of better or equal quality and performance as the newer blades today and pose to much competition.

4. Very difficult to make and maintain a true airfoil shape.

There are just 4 questions I am sure there are more. Regardless of what most of us think about the wood blade question they do deserve some real development and testing. There is someone out there that will find out how to make a great quality wood blade will long life and good performance.

So let’s discuss it openly. Should the blade be hollow, should it be solid, what type of materials should be used and so on and so on? I would find this topic most intriguing indeed.

Dan
 
One way of rating aircraft structural materials is by specific strength, the ratio of strength to density.

The ratio yields a number that would equal the length of a rod supported by one end at the point of breaking from its own weight.

For 6061 T-6 aluminum, this would be 7.25 miles.

For normalized 4130 steel, it is 5 miles.

For birch, it is 10.5 miles and for spruce, it is 9.9 miles.

For Kevlar 49, it is 26 miles.

Bensen plywood blades were designed for ease of construction rather than efficiency and as Brett says, tracking was a nuisance; especially here in Florida with its high humidity.

But I’ve never heard of a set coming apart without first hitting a tree or something.
 
blades

blades

thank you for reply guys,yes i get that idea when i saw ken wallis flyies his gyro,wallis blades have chord balance as bensen blades,iwant my have it at nose of leading edge , i think that wood blades will have the best performance ,most of blades today are too heavy and most does not have the right 8-h-12 airfoil most of them are modified to be less dificult to made ,as cabinet maker with 20 years of experience im not scare take the chalange ,i saw bensen and monte hoskins wood blades even have drawings for both ,but just looking at them they look and i believe they are too dragy ,laminated solid birch or maple leading edge of 2.5" deep will be strong enough as i did allready some structural analysis on 20' blades for 12000 lbs max load
 
Here is a cross section of the laminated birch spar that I used on one of the 3-blade gyros.

There was a lead bar at the leading edge for chordwise balance and the after section used balsa with the grain running vertically; pieces sawn from 2 x 4 balsa planks.
 

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If I'm not mistaken, many Gyro world records are on wood blades. Aren't all Wing Commander Wallis's gyros flying wood blades?
 
I don't think the airfoil on wooden blades would necessarily be hard to make and make accurately - at least in comparison to the difficulty and expense one must go through to get a typical aluminum extrusion made in addition to the layup and bonding work required with both metal and composite blades. A high speed cutter blade could be made that is very similar to a typical router blade that's used to cut wooden molding type shapes. That way almost all of the hand and guess work would be removed from the airfoil part, leaving a much more uniform and quality controlled final shape. If I recall, Monte Hoskins used to hand carve the airfoil and was still quite successful. The grain of the plywood laminations give you contour gradiations to follow as you sand and file the airfoil. Here's an image of what I recall the basic design to be:

wood-blade.jpg


As far as vulnernability to moisture, it'd be interesting to hear from Wallace on that. He lives in the UK so I'm sure him and his blades have been dealing with humidity for a very long time. I saw him on the History channel taxiing out of his hangar through the woods and to a grassy airfield. I assume all his machines are under roof all the time. But they still have to be exposed to that English humidity and over the years to precip in flight at times, I'm sure. As long as you have some form of shelter, I doubt the problems are insurmountable.
 
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blades

blades

i started yesterday grinding knife for shaper ,first im going to run the leading edge top part on shaper than join together with 2lbs hot wired foam still with flat bottom for better accuracy when aplyieng top layers of fiberglass,the trailing edge will have roving runing at full span just for more strenght when hand starting,then the bottom leading edge will go thrue shaper with different knive,the rear portion of foam will be shaped by hand,then rest of layers of fiberglass will be applied ,1 uni full span then one bid 75% one bid 50% one bid 25% and two at root total 5 plies top and 5 plyies bottom then drilled for tension straps and joined to hub bar
 
If I had to make a choice today to bet my life on wood rotor blades or modern metal bonded blades I would choose wood in a split second.

But If I was a manufacturer trying to save ounces on a flying machine I would choose lightweight bonded metal and honeycomb rotor blades.

Also If I was an engineer or designer trying to manufacture a consistent quality blade in large volumes , that were all balanced at the factory , and could be interchanged in the field , I would vote for metal bonded blades as seen today in most modern rotorcraft. That would apply to composite blades as well.

But if I had to make a personal choice of the type of blade I could depend on for thousands of hours , a blade that could chop down a few small trees , a blade that could hit a Canadian Goose or two , and still get me to the ground , a blade that could take several bullets and keep flying .... a blade that will give me 2 years notice when it is getting tired .... I will fly under wood thank you. Now I am repeating myself.

I love modern rotor blade design , just don't knock wood , that is unless you are knocking on wood to bring good luck. That is ok.

The whole helicopter industry started flying under wood rotors. A lot of them are still flying today. Some Gyro's too.

Modern day designers are still trying to duplicate this dependability with metal and composite materials.

Wood is old school technology. This we know. Modern technology gives us the opportunity to search in flight rotor blade failures. Add up all the in flight blade failures of wood , and metal blades per 100,000 hours of use and see what you come up with.

Before you know it you will be an old fart like me who would not knock wood , that is unless it is to bring good luck. Now I repeat myself for the third time.

Here is hoping that modern day brilliant designers and experimenters can come up with something as good as .........
 
blades

blades

thank you
the reason why im choosing wood over other material is simple im working with wood every day ,im very familiar with all kinds hardwoods and soft woods ,im not trying save any money ,i just didnot find any blades for my aplication, smalest dragon wings i can get are 10.5' each blade ,the fly nice but need prespin so im talking about not saving any weight here ,there is no realy any small rotors on market these days ,and besides they are heavy ,im not saying they are bed they just dont fit m needs all im doing is makeing blades for my self ,my goal is simple hand startable weight less than 30 lbs ,good performance
 
One way of rating aircraft structural materials is by specific strength...

Chuck, the other half of the question, though, is what strength is needed?

If the wood in wood blades is there mainly to provide aerodynamic properties, and a steel spar carries the real loads in most designs, why not some plastic extruded in the shape needed, instead of wood, with a steel spar and whatever noseweighting was required?

Extrusion might rule out taper or twist, but the upside would be the availability of any custom length you wanted, and very low costs. It's already moisture resistant. Treat/coat it for UV resistance, paint to taste, and voila - inexpensive blades.
 
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