Pros & Cons-Composite frame vs. wood airframe

[selfportrait]

Here is my solution. Buy an ARF, strip-off the covering. Cover the Fuse and Wings with balsa sheeting, fiberglass with 3/4 oz. cloth, Prime, Paint and Fly. If you use smoke, fuel-proof the interior of the Fuse before you install the electronics. You save $1,500.00 and give your sanding arm a good workout. You get the good-looks, nice paint scheme and impress your buddies who have the same ARF still in the stock covering.

www.RedAeroRC.com

[Tired Old Man]

IMO there is only one thing that places a wood plane over a composite one, and that is the up front price. Comps cost more and you won't get away from that. Frequenly you can purchase them in white, clean up the fuselage seam, and do your own paint. Then again, Comp Arf provides a colored set of tapes to cover the seam and adding a little heat sticks it nicely.

Composite airframes can be noisey due to resonance. When that happes applying some inside glass or carbon stffeners in the fuselage will cancel it out. It's neither difficult or heavy.

Composite repairs are easy to do once you learn the methodology. The work is not done in a manner anything similar to wood. Generally a repair properly performed on a composite airframe will be lighter than one performed on a wood airframe that has the same damage. It's all in knowing the correct way to do so.

Paint repairs will be more difficult to match that a wood airframe with covering. Then again, a painted film covered wood plane will be more expensive and difficult as well, so you might say it comes out a "bump" in that area. A composite airframe will never have the covering bubble once it comes out of the box or after sitting in the sun for a period of time..

A super light framed wood plane may come in lighter than a composite airframe, but it will start falling apart years before a composite airframe will. A well built wood plane will genrally weigh in pretty close to the composite one. Wood framed planes are higher in general maintenance than composite. That's just the way it is if you want to keep a plane.

So price is the one major item keeping people away from composite airframes. A couple smaller things are learning new ways of mounting and new ways of performing repairs. In general, people resist change and moving to something different takes a lot of mental effort.

You do need to know who the composite manufacturer is and learn who makes the best and the lightest. There are some composite manufacturers out there that pay little attention to weight and quality. Purchasing one of their airframes can leave you with a very heavy plane with a lot of cosmetic and/or parts fit issues.

[DKnippen]

I like composites, but that seam turns me off . Even though you can't see it at twenty feet away I still know it's there. The other thing is the noise they seem to generate. The sound of the hatch rattling and the servo wires vibrating inside the wing gives me a headache. . You have a set of cannisters and then you hear all that racket. It just doesn't do justice for the plane IMO. If I ever have one I would surly do something about that.

[pepatrick]

I have a solution for the rattling canopy...the screws will vibrate out and the canopy flies off...NO more canopy to vibrate

[DKnippen]

LOL. I did see that happen a couple of years ago at our Imac contest. The whole a** of the plane filled up with air exploded and blew off.

[crhammond]

You do have to take care of rattles for sure... use guide tubes/cable wrap and tie everything down good. And yes... your canpoy screws need locktite from time to time LOL - ouch! I use those rubber backed Aztec washers - or I counter sink the hole like recommended - and line it with a little goop to keep the screw head tight and in-place. Once the goop hardens it is a little rubbery and the screw will be nice and snug in there but still easy to get out.

I used 24 nylon 4-40 screws to hold the cowl on on my 2.6 260. Everything is tied down and it is VERY quiet with no rattles at all.

I have heard some Comp-Arf planes with regular mufflers and wires all flopping around... in a composite frame the noise is crazy as it tends to resonate or amplify or something... I agree it is annoying.

[jaguar bone]

Good points to consider - Thanks guys.
Resonance- maybe fill with expandable foam or use thin sponge tape between rattaling parts- like I'm doing with my EF YAK canopy.


Do you think vynyl graphics would look any worse on a painted composite surface as opposed to a monocoated surface? Be gentile please with your opinions on this one!

[Flyinhigh]

I have seen many Comp's with vinyl, and they look fanatastic when the graphics come from quality production, like Bad Brad or Kirby's.

[Mithrandir]

OK... in a 50 cc size.. there are not really any suitable composite airframes. Composite does not make sense until you get to 35% or larger... even 35% is a push... allow me to explain

With a composite structure, there is what is refferred to a "Minimum Gage". That is basically what is the thinnest skin that you can use. This is frequently driven by resistance to hanger rash and handling. Quite frequently, the amount of composite needed for a structure to handle air loads and even ground loads is very low... needing only a few thousandths of an inch. But just picking a plane up, or tying it down in a trailer can cause skin damage. When you get to the size of a 40%, the skin thickness needed for airloads approaches minimum gage...
Repairs are easy.. but different... 'cept for the paint. Re-Painting a model painted in the mold is hard to do. (For me)

If you are willing to have a plane that is more of a egg shell, even a 2 meter pattern plane can be all composite.

[jaguar bone]

	Quote: Originally Posted by Mithrandir
	OK... in a 50 cc size.. there are not really any suitable composite airframes. Composite does not make sense until you get to 35% or larger... even 35% is a push... allow me to explain With a composite structure, there is what is refferred to a "Minimum Gage". That is basically what is the thinnest skin that you can use. This is frequently driven by resistance to hanger rash and handling. Quite frequently, the amount of composite needed for a structure to handle air loads and even ground loads is very low... needing only a few thousandths of an inch. But just picking a plane up, or tying it down in a trailer can cause skin damage. When you get to the size of a 40%, the skin thickness needed for airloads approaches minimum gage... Repairs are easy.. but different... 'cept for the paint. Re-Painting a model painted in the mold is hard to do. (For me) If you are willing to have a plane that is more of a egg shell, even a 2 meter pattern plane can be all composite.

Thanks Mithrandir for your post!! Interesting concern you bring up (wall and skin gauge ).
True, I don't want an egg shell!!
For discussion sake ( not an attack -okay?), I'm curious how one would conclude all composites are made equally - regarding the wall thicknesses? Have you compared a couple of different 50cc. or asked about the gauge of a particular crafts to draw this conclusion? Again - not attacking ya, just asking for more supporting background for your statement ;. as I have ZERO background to draw from !

I don't know - I see the weight range of the Comp-ARF is similar to typical 50 cc. sized craft. I'm not sold yet on any particular manuf- the Extra 2.12m is just an easy one to pick on. Frankly I haven't seen many composite 50 cc size - and it may be because of the issue you have brought to light!

Plus I haven't been looking that long or hard. Figured I'd start a thread and git sum edju-macations first! This is the fun of growing beyond yo' comfort zone!

[pepatrick]

Here are my thoughts...First of all...I have owned a few compys in all sizes...
2x2 Extra red/yellow (sold and expired)
2.6 Extra Shulman Scheme (sold ???)
2.6 Yak Fantasy Scheme (sold before I built it)???
2.6 Yak custom scheme (sold but still wish I had it - still flying)
3.0 Yak JR Scheme (hopefully will keep for ever or until its expiration date)
eyeing a 3.0 Extra 260 in yellow or red kiwi scheme...

In the 50cc class...The compys dont do as well...They are too small for the 50cc engines (DA-50 or ZDZ-50). My 2x2 had a ZDZ 50 and I am pretty convinced you could hand launch it. I much prefer my Extreme Flight 50cc extra and 50cc Yak over the compys in the size range. Much lighter wing loading and EF 50cc planes are not much smaller than the Compy 100cc planes. A 50cc plane being much smaller even the Extreme Flight planes are easier to haul and less prone to hanger rash (at least from my perspective)...

My 2.6 Extra was a great flying plane. I just was not ready for a plane that size when I bought it...so I really did not know how great it was until I flew another one later on. The 2.6 Yak...cant be beat for a 100cc plane. It flies as well as the 3.0 Yak...but with more power to weight..DA-100 on stock mufflers pulls the 2.6 yak like a freight train.

In the 35% to 40% range...The compys rule. That wont keep me from buying one Extreme Flight 100cc or 150cc planes when they are out...but the Compys rule...They have very light wing loading and just look incredible in the air and on the ground. They all fly straight...I miss my 2.6 Compy Yak because it was fun to toss around and I may even buy another one at some point and time. My 3.0 Yak is incredible...Maiden flight needed 0 trim and uplines are perfect. There is no mixing for knife edge and better yet...no wrinkles to iron out. If I can get these Compy guys to improve customer service...I will be a compy fan for life...but right now I question if that will happen.

[Flyfalcons]

If you have composite fever then you might as well buy a composite plane. I still have my 2.6 after four years of ownership and it is still a nice flying airplane. I bought mine in all white and cut my own vinyl trim for another 20 dollars. Having said that, the plane flies well because of its design and not its construction methoed. There are many planes of wood and/or foam as well as composite construction that fly well. The secret to happiness in this hobby is getting something that you really want, and if you really want a composite then go for it.