Composite or Built up which is best???

[Flyfalcons]

	Quote: Originally Posted by Mithrandir
	and vastly easier to build repeatability and interchangeability...

Mold-built composite ARF or jig-built wood/foam ARF, they're all interchangable and straight.

[snap a saurus]

I have both but had much better luck with the wooden ones, I have a wooden plane with around 700 + very abusive flights with hundreds of harrier landings, minimum maintenance was required while my composite airframes have needed beaucoup maintenance with a lot less flights.

[Ando]

	Quote: Originally Posted by Yakster
	Me too Dennis, but I think I need to get my hip waders, the bull**** is getting a little thick (talking about the mile high full throttle blender).

I don't care if you believe me or not, but I will still see what I can do about the vid, If Dennis would have came to our funfly at Mt. Pleasant he would have personally seen it. Like I said, I will see about getting a video of it. I don't know why DR doesn't since they have other video's of their other airplanes.

Is there no other DR Hobbies guys on this forum?

[gstjohn]

I have a 2.3M comp-arf extra 330 and love it. I also just recently bought a 3.1m Super Xtra. and our local club is slowly getting more and more comp-arfs. I have flown wood planes as well as composite planes and the wood planes feel great but I personally like the crisp responsiveness I get with my comp-arfs over the wood planes, just my opinion. this opinion could change though as I am looking at getting a Robert Godfrey 40% Extra this spring.

[Yak Attack]

Thanks for the input. It has been interesting to here everyone’s point of view. I have been modelling for 28 yrs, and have built both composite arf and built up models, but have not yet built any 150cc planes. I am in two minds as to build composite or built up in this size. In Australia we are limited to kits in this size except for composite arf. I love reading reviews on the Dalton extras, Carden aircraft and Aerotech. It would be good to try something different in Aust. In either of these large scale models. It is good to here pro’s and con’s from other builders.

[forgues research]

	Quote: Originally Posted by Aerotech
	Hello, Thats easy. Wood...... Later John

I have to agree with you John,
I have composite and wood, and wood will not fatigue as other materials.
My opinion only.

Roger

[Mithrandir]

	Quote: Originally Posted by OnTheEdge
	So you're saying all the composite airplanes out there with brocken gear plates and canopy stress cracks are not properly constructed?

No... I am saying it was not properly ENGINEERED!!!! The construction is likely exactly as their "Drawing" says it should be....
Check this out... http://www.uav.com
See that plane on the first page??? I designed and engineered a good portion of that plane. 66 foot wingspan, 10,000 pounds, 300 kt dive speed, 40 hour endurance above 40,000 feet carrying 800 pounds of payload and 4000 pounds of fuel.
(We chose composites rather then wood)

The way to design a plane is to start off with requirements. Having a landing gear that does not rip out IS a requirement. Having a canopy frame that does NOT crack apart IS a requirement. It is my (Professional) opinion that many of the Composite airframe manufacturers could benefit from the services of a Professional Aerospace Engineer. The experiance of the manufacturer is important, but I have seen fundamental mistakes made by many of these planes.
Example... Why does Comp Arf make the landing gear strut out of carbon?? (Don't get me wrong.. I LOVE MY SX!!! I am working on acquiring another!!!)...
But.....Making the strut stiff in bending is stupid. That is a decision made by the marketing dept. (To use carbon which is very stiff)...The strut can and should have the bidiectional material on a plus-n-minus 45 degree bias for TORSIONAL Stiffness... but the Uni's should be FIBERGLASS!!! The whole point of a landing gear strut is to limit the accelerations on the airframe... it does this by yielding.. by bending... by absorbing energy!!! Fiber glass is less stiff then carbon... it will deflect and reduce the loads on the fuselage... (Energy absorption is basically the "Area under the force vs deflection curve"...Comp-Arf... are you listening?!?!!?)

I have see molded fuselages with the cloth direction at a "zero-ninety" bias... this is wrong! The fuselage is a torsion tube with very LOW bending loads. The cloth should be bias'd plus-n-minus 45 degrees with very light carbon longerons... like under the canopy rail and down the middle on the bottom.. This scheme is stronger, stiffer and lighter.
Wood is better... at the smaller sizes.. (Lower loads) the thickness of composite materials for skins and spars becomes so thin that either the materials are not available in those guages, or it becomes vulnerable to handling and hanger rash.... but at the larger scales, the loads require the thicker skins, and it makes sense. (But even in the smaller sizes, a hybrid of Balsa and composites make a better structure... I think some of the tow-line free flight gliders are using kevlar "D" tube leading edges on the wings.. but often this requires non traditional manufacturing methods)

Wood is good...
.......but

MOLD'n is Golden!!!

[OnTheEdge]

	Quote: Originally Posted by Mithrandir
	No... I am saying it was not properly ENGINEERED!!!! >>The way to design a plane is to start off with requirements. Having a landing gear that does not rip out IS a requirement. Having a canopy frame that does NOT crack apart IS a requirement. It is my (Professional) opinion that many of the Composite airframe manufacturers could benefit from the services of a Professional Aerospace Engineer. The experiance of the manufacturer is important, but I have seen fundamental mistakes made by many of these planes. >>Example... Why does Comp Arf make the landing gear strut out of carbon??.....Making the strut stiff in bending is stupid. That is a decision made by the marketing dept. >>I have see molded fuselages with the cloth direction at a "zero-ninety" bias... this is wrong! The fuselage is a torsion tube with very LOW bending loads. The cloth should be bias'd plus-n-minus 45 degrees with very light carbon longerons... like under the canopy rail and down the middle on the bottom.. This scheme is stronger, stiffer and lighter.

Thanks Mithrandir! You are making my (and other's) point! Yak Attack's original question was of comparisons of giant scale model airplanes, not 60ft UAV's!! If he was asking about 5 ton UAV's then I would have said composite is the way to go and not wood. However he's asking about model airplanes that are currently out there in the hobby market place.

Look at your quotes, you admit that the compostite airplanes are not engineered properly (gear blocks, gear materials, directional weave etc). We're just giving him (Yak Attack) an overview of our (and apparently your's as well) experiences to help aid him in his giant scale airplane selection.

I have no doubt that a composite plane can be designed to the utmost in strength, but apparently it can't be done at this point where it is cost effective in the hobby.

.........Mark

[Mithrandir]

	Quote: Originally Posted by OnTheEdge
	...... ............... apparently it can't be done at this point where it is cost effective in the hobby. .........Mark

I disagree....first off.. it has never been tried...
Many changes have no impact on manufacturing... changing the ply orientation adds no cost... using fiberglass as opposed to carbon is less expensive...
The difference in cost/effort is up front.. in the design work.
There are enuff model airplane dorks in the world who are ALSO engineers... that most of these manufacturers could just about get the engineering work done FREE!!!
If the question is "Will the best commercially available composite airplane outlast the best commercially available wood arf?"
I would have to say yes! Likely there are some areas of the best composite models that could stand some adjustment... ( ex. I will NOT harrier land my Compy... )... but there have been wooden planes with issues as well... wooden planes being marketed by rather well known pilots.....
The 3 big killers of planes are....
Striking the earth, vibration and oil soaking....
No plane will survive an earth strike.... Composite (As utilized today) will survive the oil contamination and vibration better then wood.
I have a friend who typically flies his planes very aggressively... more aggressively then anyone I know.... he recently sold a 3 year old compy-arf with hundreds of mind numbing, aggressive hard fought flights.... the only indication of age was from the dings he put on it putting it in and out of his trailer!!!
I have very little time myself.. I NEED a low maintanence airframe... I bought an SX...(Comp-Arf) and since I bought it... I have done NO maintanence.. I routinely inspect.. but no broken stringers...no wrinkled covering... nothing... I suspect the 3W composites are similarly robust.... perhaps the Krill as well???
Would I like a wooden Dalton... sure, you bet... I would wax it and pull a mold!!!!

A bigger decision maker for most modelers is what position are they in to repair this airframe if it breaks... everyone can work with balsa and aircraft ply... that alone is a compelling reason to choose wood.

[Flyfalcons]

	Quote: Originally Posted by Mithrandir
	No plane will survive an earth strike....

There are different levels of striking the Earth though. Have you seen the video of Jesky botching a Parachute maneuver and pancaking his Carden onto the desert brush? That move, which would have destroyed my composite plane, didn't seem to do anything to the Carden. I have also seen two Cardens lose radio contact, go in pretty hard, and fly another day after repairs. I know it won't take much to destroy my composite plane, and if/when that happens it'll be replaced with a wood/foam plane. Foam/wood has the compression properties to allow it to survive many years of abuse, composite not so much. Fly what you want though, they can all handle the air loads just fine, the question is which one will last through years of handling and incidents.

[Dr. Yankem]

Last week I had my engine flame out in a hover; almost made the recovery..just needed the ground deeper by 10 to 20 feet. Smacked the nose on my37% Godfrey Extra. Broke the airframe from the cowl forward (including the engine box). Punched some holes in the wings. If that was a Compy then it would have been a total loss. This is a repair on the engine box, new cowl and some rebuild of a built up wing. Don't even need to recover the fuse, except on the bottom where a few stringers got zapped.
Maybe for the pros the compys are the answer, but for the rest of us: Compys look nice, but wood is good.
Jerry

[excelpoint]

I personally prefer Composite planes. They are not hard to fix if you know the basics of fiberglassing. remember they are only a couple of layers of 2OZ cloth with a foam mid layer. That being said I agree the landing gear mounting has been a real issue, but this is more to do with design rather the material. I personally hate covering and cant do it to save myself so for me I can get a better finish out of composite.

[Wayne]

Definately good and bad with both.
Fly what you like and dont poop on the guy next to you cause he isnt doing the same thing you are..

[Mithrandir]

	Quote: Originally Posted by excelpoint
	I personally prefer Composite planes. They are not hard to fix if you know the basics of fiberglassing. remember they are only a couple of layers of 2OZ cloth with a foam mid layer. That being said I agree the landing gear mounting has been a real issue, but this is more to do with design rather the material. I personally hate covering and cant do it to save myself so for me I can get a better finish out of composite.

I can repair most composite structures...
It is the paint job on a compy I could never reproduce!!

[excelpoint]

Yes the paint job is an issue unless you have a white one that you have painted yourself.

	Quote: Originally Posted by Mithrandir
	I can repair most composite structures... It is the paint job on a compy I could never reproduce!!