Composite or Built up which is best???

[rdgood]

Ok I'm gonna stick my foot in it here.

One thing I have never liked about Comp-Arfs IS the landing gear design. The Compy landing gear saddle block affair. I had one of the first generation Giles 202's that had to be built (the saddle block was not installed nor was the internal structure wing hold down points through tube etc.. the whole sha bang). So I became extremely intimate/familiar with just how the saddle blocks were installed. In fact - you only have 2 - 3/16" ply bulkheads holding the landing gear plate on. On a 40%er it just wont take alot of abuse especially if your doing alot of grass field landings. On my G202 I added vertical grain block balsa to the underneath side of the gear plate deck area. This increased the gluing area to roughly 4 times that of the original plates. Mine never pulled out and that was after several harrier Aunt Jamima's and bent aluminum gear also.

I have seen the best pilots all unlimited ones (I might add) and all of them have had to either replace one or both of the gear legs, either replace or rebuild the gear saddle area. This is a very REAL weak point in the aircraft. Whether its a the Super Extra 330 or the Extra 300 or a G202 they have this weak feature IMHO!


It will fatigue at some point.

Now with all that said - if you do have to repair it, I recommend very strongly that you learn your ABC's about dealing with epoxys... Everyone should remember these comp Arfs are bult in molds and they all come from the factory with mold release all over the place - you need to remove the mold release before rough sanding and epoxying new structure in place.

I still love the Compy's - I dont currently own one now but I might own one in the future if the price is right. I must admit that the G202 was the best tracking rolling airplane I have ever owned at least for IMAC stuff - I would not recommend it for 3D - though. FWIW I lost the G202 because of my own stupidity - I had a small dent in the lower aft part of the fuse about a 1/8 inch ding. Didnt think much about flew it for about 60 flights that way - One hot afternoon was doing a series of snap rolls on 45 down line and the fuse seperated right at the dinged point behind the canopy. Remember the skin IS the structure!!! So lesson is if this is your first Compy just be aware of the structure - if gets dinged repair it imediately - I wish someone would have kicked me in the head about this.

Hopefully my hard lesson wont get repeated !!

I'm off my soapbox now..


Ronster

[Flyfalcons]

	Quote: Originally Posted by Ando
	I am all for the carbon buildups. I have personally seen composits go through manuvers that will destroy wood built airplanes and the composite comes out without a stress mark...

Uh, like what?

[as722]

ando,

What manuver have you seen a comp plane do that would destroy a wood plane ? I know you don't mean a bad landing !
I guess you've never seen Mark L. flying his wooden airplanes.

Albert

[Ando]

take a DR 33% with a Kroma 180 on it, put it in a full throttle dive from a very small speck till it gets about 200 foot high, then put it in a blender manuver, I have seen more wood airplanes that I know was built go just snap into pieces. I was not saing that wood airplanes are bad and are not strong, I agree that their are great kits out there, just I have seen the DR Extra's and my Krill do high speed and high G manuvering, then watched someone else do it and fold their wings...

[shannah]

Well,
I can only speak from my direct experience. (Dalton 260 compared to comp arf 3m 330s and stick time on the superx 3.1 and yak 3.3). The Dalton flies fantastic but the composites are much more durable and soak up the vibes so you'll get longer equipment life. When you get right down to it, it comes to airframe design and weight. The lightest airframes out there are wood, and they also have some of the best airframe designs. The lighter wood airframes are not going to hold up as well in the long run, but in the short run they fly outstanding. That being said, there are some real pigs out there that are wood, so it's really buyer beware. There is no slam dunk answer on this. Now, if comp arf had a 37 lb 150 size Yak 55sp, it would be game over.

[Mithrandir]

At about 30% scale or so, a properly engineered composite airframe can be built lighter (To a given structural specification) then a wood plane.
A composite airframe does not degrade from a gooey slimy smoke system and does not fatigue like a wooden airframe. (Wood can be oil proofed, but it is another process, not to mention iron on films are vulnerable )
Wood is certainly better for prototyping an airframe that is likely to go thru design
iterations, but once the configuration is stable, composites result (When properly implemented) in a lighter and more robust airframe.
Another thing to consider is that in the event of damage, a wooden plane can be repaired... unless you own or have access to the molds, you are forced to order replacement parts and pay a premium price....

[Dennis C]

	Quote: Originally Posted by Ando
	take a DR 33% with a Kroma 180 on it, put it in a full throttle dive from a very small speck till it gets about 200 foot high, then put it in a blender manuver, I have seen more wood airplanes that I know was built go just snap into pieces. I was not saing that wood airplanes are bad and are not strong, I agree that their are great kits out there, just I have seen the DR Extra's and my Krill do high speed and high G manuvering, then watched someone else do it and fold their wings...

Holy Shizzzz i'd like to see that one.

[OnTheEdge]

	Quote: Originally Posted by Ando
	take a DR 33% with a Kroma 180 on it...

If the composite airframes weren't so heavy, you could put a 100cc motor on it like we put on 33% built-up frames.

Yep, take a video of this plane. A set up like that (on any plane) and full power dives (on any plane) is sure to eventually result in a video headed for YouTube.

[Ando]

The Kroma 100's are what they normally fly on the 33%'s, but DR put the Kroma 180 on one just to test its strength. Flying for quite a while now of heavy abuse and still no stress marks. I will ask this weekend if they have taken any videos on it, I checked YouTube and didn't find anything.

[Flyfalcons]

	Quote: Originally Posted by Ando
	The Kroma 100's are what they normally fly on the 33%'s, but DR put the Kroma 180 on one just to test its strength. Flying for quite a while now of heavy abuse and still no stress marks. I will ask this weekend if they have taken any videos on it, I checked YouTube and didn't find anything.

Just because the plane survives a few maneuvers doesn't mean you aren't doing damage to it. One Comp-ARF rep that I have spoken to had a wing delaminate after too many wall maneuvers. I have a Comp-ARF and enjoy it but it will be my last, simply because it doesn't handle the every-day use of flying off a grass field. In the air I have no complaints about it but a properly built wood plane will absorb vibration better and last much longer than a composite, which will wear out and stress crack over time.

[Yakster]

	Quote: Originally Posted by Dennis C
	Holy Shizzzz i'd like to see that one.

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).

[as722]

	Quote: Originally Posted by shannah
	Well, I can only speak from my direct experience. (Dalton 260 compared to comp arf 3m 330s and stick time on the superx 3.1 and yak 3.3). The Dalton flies fantastic but the composites are much more durable and soak up the vibes so you'll get longer equipment life. When you get right down to it, it comes to airframe design and weight. The lightest airframes out there are wood, and they also have some of the best airframe designs. The lighter wood airframes are not going to hold up as well in the long run, but in the short run they fly outstanding. That being said, there are some real pigs out there that are wood, so it's really buyer beware. There is no slam dunk answer on this. Now, if comp arf had a 37 lb 150 size Yak 55sp, it would be game over.

I don't see how a composite airframe vibrates less, I find it to be the oposite. On a wood airplanes specially one having a lot of foam will soak up vibration a lot better.

Albert

[Mithrandir]

	Quote: Originally Posted by Flyfalcons
	......... but a properly built wood plane will absorb vibration better and last much longer than a composite, which will wear out and stress crack over time.

Wood will only outlast a poorly built composite airframe....

A properly constructed and engineered composite plane is better then a wood airframe by every measure used to evaluate a structure... Lighter, stronger, stiffer, fatigue resistant, not vulnerable to oil soaking.... and vastly easier to build repeatability and interchangeability...

the only advantage wood has over composite is the ability to repair by the end user with modest tools and modest skills....

[Wayne]

	Quote: Originally Posted by as722
	I don't see how a composite airframe vibrates less, I find it to be the oposite. On a wood airplanes specially one having a lot of foam will soak up vibration a lot better. Albert

Albert,

Thank you for posting that. I was just about to say the EXACT same thing.

[OnTheEdge]

	Quote: Originally Posted by Mithrandir
	Wood will only outlast a poorly built composite airframe.... A properly constructed and engineered composite plane is better then a wood airframe by every measure used to evaluate a structure... Lighter, stronger, stiffer, fatigue resistant, not vulnerable to oil soaking.... ...

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