birch blades

If I was a manufacturer trying to save ounces on a flying machine I would choose lightweight bonded metal and honeycomb rotor blades...
To obtain the angle of the cone you want, you need a sufficient weight. The density of the materials used does not change this value. For a diameter and a lift, this weight is just proportional to the chord of the blade.
Jean Claude
 
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.
The steel bar in Bell-47 rotorblades played no structural role; its only purpose was chordwise balance. Its only structural connection to the rotorblade was at the root end.

Arless Riggs, an old California desert rat, carved his blades from spruce planks and embedded a concrete rebar at the leading edge for chordwise balance.
 
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To obtain the angle of the cone you want, you need a sufficient weight. The density of the materials used does not change this value. For a diameter and a lift, this weight is just proportional to the chord of the blade.
Jean Claude
If the blades weighed nothing, tip weights could be used to achieve whatever centrifugal force and moment of inertia was needed.

The weight saving vs. MOI is 3:1; the weight saving vs. CF is 2:1 for a weightless blade compared to one with uniformly distributed mass.
 
Sorry, Chuck, my Google translator did not understand. I think blades built with a infinitely light material (and infinitely resistant) would only be 30% lower compared to one with uniformly distributed mass. Vrai?
 
Please excuse, slightly off topic but regarding the relevance of wood as a suitable aviation construction material. It was certainly up to the manufacture of the 'Timber Terror' or 'Wooden Wonder' Mosquito twin engine bomber of WW11.

Mosquito's were made of custom plywood. The fuselage, a frameless monocoque shell made of ⅜ in (9.5 mm) sheets of Ecuadorean balsawood sandwiched between sheets of Canadian birch. In areas needing extra strength—such as along cut-outs—stronger woods replaced the balsa filler. Plys were formed to shape by band clamps over large concrete moulds, each holding one half of the fuselage, split vertically. As Casein-based glue in the plywood dried, carpenters cut a sawtooth joint into their edges while other workers installed the controls and cabling on the inside wall. When the glue was completely dried, the two halves were glued and screwed together. A covering of doped Madapolam (a fine plain woven cotton) fabric completed the unit.

Wings were similar construction but used different materials and techniques. The main wing was built as a single unit. To form the basic shape, two birch plywood box spars were connected by plywood ribs, and stringers spanned the ribs. The skinning was also birch plywood, one layer thick on the bottom and doubled up on the top; between the two top layers was another layer of fir stringers. Brass screws, 30,000 per wing were used. The wing was completed with wooden flaps and aluminium ailerons.

With both fuselage parts complete it was lowered onto the wing, and once again glued and screwed together. The remainder consisted of wooden horizontal and vertical tail surfaces, with aluminium control surfaces. Engine mounts of welded steel tube were added, along with simple landing gear oleos filled with rubber blocks. Wood was used to carry only in-plane loads, with metal fittings used for all triaxially loaded components such as landing gear, engine mounts, control surface mounting brackets, and the wing-to-fuselage junction. Total weight of metal castings and forgings used was only 280 lb (130 kg).

Glue initially used was casein-based. After some unexplained crashes of aircraft operating in tropical climates, this was changed to "Aerolite", a synthetic urea-formaldehyde adhesive developed by Dr. Norman de Bruyne, better able to resist deterioration in high humidity conditions. De Havilland also pioneered the use of radio frequency (RF) heating to accelerate curing of the adhesive.

In England, fuselage shells were mainly made by furniture companies, Ronson, E. Gomme, Parker Knoll and Styles & Mealing. The specialized wood veneer used in the construction of the Mosquito was made by Roddis Manufacturing in Marshfield, Wisconsin, United States. Hamilton Roddis had teams of women ironing the (unusually thin) strong wood veneer product before shipping to the UK. Wing spars were made by J.B. Heath and Dancer & Hearne. Many other parts, including flaps, flap shrouds, fins, leading edge assemblies and bomb doors were produced in High Wycombe, Buckinghamshire, well suited to these tasks due to a well established furniture-manufacturing industry. Dancer & Hearne processed much of the wood from start to finish, receiving timber and transforming it into finished wing spars at their High Wycombe factory.

About 5,000 of 7,781 Mosquitos made contained parts made in High Wycombe. In Canada, fuselages were built in the Oshawa, Ontario plant of General Motors of Canada Limited and shipped to De Havilland of Canada in Toronto for mating to fuselages and completion. De Havilland Australia started construction in Sydney. These production lines added 1,134 from Canada and 212 from Australia. It could carry 1,000 lb (454 kg) of bombs for 1,500 mi (2,414 km) at a speed of almost 400 mph (644 km/h), almost twice that of contemporary bombers, and the prototype in testing exceeding the speed of the current Spitfire of the time.
 
Sorry, Chuck, my Google translator did not understand. I think blades built with a infinitely light material (and infinitely resistant) would only be 30% lower compared to one with uniformly distributed mass. Vrai?
Jean Claude, I imagine your physics book and my physics book say the same thing.
 

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My last 2 cents worth:
I'm not interested in ruffling anyone's feathers here.
And yes...I'm fully aware of the history and use of Wood...of the characteristics and benefits they can afford.

HOWEVER...it is damn irresponsible <with all the preaching that goes on in this forum> to advocate building Wood blades when FAR SUPERIOR alternatives exist. I do not care how accomplished one may or may not be, THIS SPORT NEEDS NO MORE BLACK EYES from anyone thinking they can "do it".
There exist items on these machines that should NEVER be created by the back yard hobbyist...THIS IS HOW THIS SPORT GAINED IT'S DESERVED BAD REPUTATION. Further..to merely advocate on a public forum...even slightly giving credence to "Building Your Own" is BEYOND irresponsible.
Many in this field have worked tirelessly to REVERSE our collective image....the errors of JUST ONE mistake are magnified a million fold upon all of us.

To advocate making Wood Blades by any Home builder is just plain stupidity.
Sorry folks....I'm not here to be your best buddy....I care what this WILL DO to our Sport's reputation should ANYTHING dire occur.
End of rant.
 
My last 2 cents worth:
I'm not interested in ruffling anyone's feathers here.
And yes...I'm fully aware of the history and use of Wood...of the characteristics and benefits they can afford.

HOWEVER...it is damn irresponsible <with all the preaching that goes on in this forum> to advocate building Wood blades when FAR SUPERIOR alternatives exist. I do not care how accomplished one may or may not be, THIS SPORT NEEDS NO MORE BLACK EYES from anyone thinking they can "do it".
There exist items on these machines that should NEVER be created by the back yard hobbyist...THIS IS HOW THIS SPORT GAINED IT'S DESERVED BAD REPUTATION. Further..to merely advocate on a public forum...even slightly giving credence to "Building Your Own" is BEYOND irresponsible.
Many in this field have worked tirelessly to REVERSE our collective image....the errors of JUST ONE mistake are magnified a million fold upon all of us.

To advocate making Wood Blades by any Home builder is just plain stupidity.
Sorry folks....I'm not here to be your best buddy....I care what this WILL DO to our Sport's reputation should ANYTHING dire occur.
End of rant.

I agree with you.
 
The well deserved reputation of gyroplanes came from incompetent “designers” scaling Bensens without understanding how and from gullible customers believing that something built in a “factory” was beyond reproach.
 
My last 2 cents worth:
(snip snip)
End of rant.

God forbid anyone should actually experiment with building components for their experimental aircraft. And to actually speak about it on a public forum!

Are you going to go onto other aircraft forums and chastise builders there for building wooden wings and wooden fuselages? Some people even carve out their own wooden props. :eek:
 
There exist items on these machines that should NEVER be created by the back yard hobbyist...THIS IS HOW THIS SPORT GAINED IT'S DESERVED BAD REPUTATION. Further..to merely advocate on a public forum...even slightly giving credence to "Building Your Own" is BEYOND irresponsible...

Mike, there are those who would use your premise to end all homebuilt aircraft. Until you explain what's irresponsible in using one of the most thoroughly proven of all aviation materials, it's hard to embrace your position.

I could agree with you if there was a history of accidents caused by wood blades. But I can't find it. Properly selected wood appears to have the necessary strength, and some very desirable properties. Plywood was just an early composite. It has been used successfully for decades.

I've only ever read two reports of in-flight failure of gyroplane rotorblades (that didn't first hit some part of the airframe due to other causes.) Neither case involved wood blades. One involved improperly modified/assembled extruded aluminum blades, the other abuse of the flight envelope. I'm sure there are cases which have gone unreported, but I doubt wood is to blame.

I've heard anecdotal reports of a set of large-chord blades which didn't hold their shape and folded the trailing edge up in flight. They were bonded aluminum.

This sport earned its reputation mainly through stupid pilot tricks and poor design stability, falling into spinning props and rotors, poor maintenance, inadequate preflight inspections. I'll ask again - where are the accidents caused by homemade wood blades?
 
I have thousands of hours of crop dusting with bell helicpters and both wooden blades with various models from the mark 5 tomcat the the g5 metal bladed versions... at fist start up even the best wooden blades have some issues with one blade up or down and the dew getting in one end or the other but after start up and they spin any water or uneven condensation out... they are great. One can pick up much more with the wooden blades than metal. they cone more and can pick up more with less rotor width.
the metal ones cone only to a point and then damage.. also one can repair the wooden blades much easier ... with metal one bent or damaged in most cases oreder a new set.

wood may be old but so an I and sometimes new is not always better.
 
On reflection,

He's not building these by himself, he's getting help from the forum. He's collected info from other wood blade builders. Maybe he'll have no problem. I just won't condone it.

Good luck to you!
 
Do not attempt building of any blades

Do not attempt building of any blades

Look folks I have over 15 thousand hours in rotorcraft.... I have done everything in a rotorcraft one can do to make a living.. I have given tours, cropdusted, vetor controll mosquito control in florida, f/lew as a military warrant officer medevac pilot, civilian ems, executive 135 transport, just about everything ... Let this be known now ...though wood blades are good should you hae a qualified manufacturer. of which I do not know of anyone any longer that does this ..I used to get my wood bell 47 blades from tulsa helicpter... it took him ten years witht he faa to get his wooden blades certified.. since then Ihave herd he passed on... but please blades are your life blood. have you ever seen the video on blades that bell helicpgter put out depicting the twist turns and stress a blade has just in straight and level flight.. if you did you would go with a reputable in business for a long time blade company. It wouldd sort of be like trying to perform your own apendectimy... sure you could do it if you had to but why........... for the cost of your life why would you ... ask yourself this how much experience do you have building blades and as far as that go the secret is in the setting and balnceing and tracking as well.. just because you can build a blade does not mean you can set them up track them ,mast them etc.. why do you think they are built in pairs.... leave the blade building to the professionals .. ie like sport copter, rotordyne , redhawk vortex... if you want a mission research these companies and pick whats best for your flyig ... Out of 15k hours I have no time in blades that I built myself.... take that for what it's worth... of course that and 50 cents will get you a cup of coffee at mcdonalds but trust me after flying ems for over 18 years I don't want to pick up anyone with a blade loss at 1000 feet it's not pretty and it bloodies up the helicpter. It makes the mechanic mad when we bring them back all bloody from some one who thinks they can build a space shuttle just because they want to save a few buck and are board with the old lady.
 
Doc,

I may be missing your point. Regarding FAA certification, none of the factory-built aluminum or composite blades currently available commercially to gyroplane builders are FAA certificated.

As for bringing back bloody helicopters, please. Find one case of a wood gyroplane rotor that has failed. We have plenty of emotional reasons for being afraid of homebuilt wood blades. Does no one have any fact, history or engineering in support of this fear?
 
My piont being not necesarily FAA certified but to have somone makeing blades especially out of wood needs tried and true specifications and or proceedures ... Idon't think you want to bbe building blades out of elmers glue and birch. My oint is I have had wood blade failures two as a matter of fact ... one a whole chunk fell off the tip and was only held on by the fiberglass and was repaired by steve pond of tulsa helicopters... While crop dusting in stock bridge Michiagan although they were repaired one could not see the rot under the fiverglass cover and hid the damage. My whole point is that one can make many things to put on these elsa and experimental machines but leave the heart of the machine the blades to professionals is all that I am saying.. and yes I own 3 gyro and have left the helicopters behind at present. but building blades is far more than a weekend project and when it's somones life on the line ...Go bye sportcopter blades and save your wife some funeral expences.... although her boyfriend may thank you for it and help you pick out your wood.
 
My last 2 cents worth:...it is damn irresponsible <with all the preaching that goes on in this forum> to advocate building Wood blades when FAR SUPERIOR alternatives exist. I do not care how accomplished one may or may not be, THIS SPORT NEEDS NO MORE BLACK EYES from anyone thinking they can "do it". THIS IS HOW THIS SPORT GAINED IT'S DESERVED BAD REPUTATION. Further..to merely advocate on a public forum...even slightly giving credence to "Building Your Own" is BEYOND irresponsible...To advocate making Wood Blades by any Home builder is just plain stupidity.

Firstly, it's incorrect to say that everyone here who's discussing the possibility/feasibility of building and using wooden blades is necessarily advocating it. Secondly, wooden blades can be plenty safe as long as the builder/pilot knows what they are doing. Believe it or not, there are some people here who are intelligent, safety-minded, and know what they're doing. Not everyone is a stupid, irresponsible child that needs to be protected from themselves. Thirdly, since you're so fervently convinced wooden blades are harbingers of some kind of splintery apocalypse, obviously you can point to a wide variety of gyro crashes that have occurred as a result of flying wooden blades - so please, do list them so everyone can see what's behind your intense fear of wooden blades!
 
The first metal blade I saw was when the first HU1's arrived….all the other helicopters used wooden blades. Never saw or heard of a chopper going down because of a blade failure. But that was then, when woods like spruce had dense straight grain. Good luck finding blade quality woods now days.

There are better and easier materials to work with now, and they don't required exacting humidity control (warp-control). If you know what you're doing and plan it out well, I see no reason blades cannot be safely made.

But I will add, that if one is financially able and some company's blades will suit ones need, by all means….buy them. I need to build.
 
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