Where & What composites.

[Joe Patterson]

I couldn't find a good place to ask this question.hence the new thread.

 

having read as much as possible, It seems it would be OK to use , Kevlar on the Engine Cowlings a bonus for holding down noise, and vibrations.

 

It also seems to me that using it on the fuselage, would create no problems. Is expense the only reason not to use it???? At least on bulkheads.......and maybe for fire protection.

 

I understand it is important for the "Glass to Give" on wings, strakes and Verticle Sabalizors, and flying surfaces.

 

Any thoughts.........<ducking behind large embankment>

[dust]

It's not the "giving" it is the system. the bulkheads are structural, even the seat back and the instrument panel, they transfer loads to and from the fuse sides, stiffen the bulkheads and you may have to stifen the fuse sides.

 

Kevlar is not like eglass. eglass has about the same strength in compression as tension, kevlar does not.

 

it is strong in one or the other, i forget which, and NOT the other.

 

The other problem with kevlar is it's workability, it just doesn't. Special cutting tools to cut it and it doesn't sand, it balls up, i hear it is a real pain in the arse to deal with.

 

Now if you are planning to fly over south america or africa where they test thier guns out on GA planes, then maybe try using the balistic kevlar to build the plane out of.

 

enjoy the prebuild

 

Dust

[No4]

Hallo Joe,

I'm guessing you've already read this, seeing how you have a post just two lines up. But just incase you missed it.

 

http://www.homebuiltairplanes.com/forums/showthread.php?threadid=580

[Steve Davies]

Well here's something I do know a little about... Its a cost versus properties issue. At the company where I work, almost everything is glass laminate. Hulls, decks, chairs... If we started using Kevlar, those 40,000 dollar boats would most likely double at least. Graphite is ok as long as stiffness and weight saving is what you want.

 

Ease of use is also an issue. From what I've seen, E-glass is alot easier to use. Kevlar is hard to cut, needs special shears. E-glass I can cut with Gramma's old tailoring shears.

 

I might maybe consider some ceramic fiber laminate to the inside of the engine compartment, but I havent heard any problems with E-glass in that area, so maybe ceramic is overkill.

 

Of course, keep in mind I build boats right now, not airplanes. When the plane begins, I'll be messing with some structural properties of different laminate fibers. Research continues...

[dust]

Research = reason not to build

 

been there, done that for over a year, talked to variouse suppliers, got samples of carbon fiber, kevlar, diferent core materials, etc., etc

 

Then read a book on composite construction, explaining all of the properties and materials, wisper foam, boron, eglass, then realized.

 

new materials = reengineering

 

enjoy the build

 

dust

[cncdoc]

I have to admit, when I got into the build, I was predisposed to finding an improvement for every aspect of it.

The one improvement I thought would give me an edge, would be the use of carbon fiber in the airframe and Kevlar in certain other strategic places. After talking to builders who have tried it, it is not worth the trouble unless you want to increase the build/experiment/teardown/rebuild time expotentially. Kevlar and carbon fiber fabric doesn't want to lay down in epoxy, so vacuum bagging becomes a necessity. Mistakes become costly and time flies just as fast when rebuilding a boo - boo as it does doing it the recommended way.

This brings me to the other point of this post. A wise man (with an English accent) once said (in so many words) "The perfect airplane being built sits in a hangar, while the other [imperfect] planes fly over it". (brackets mine)

 

So basically, anything is possible, but as Dust put it so succinctly : New materials = re-engineering

I will add: re-engineering = time lost not flying.

 

So, do you want to build a perfect Cozy? (just in time to watch your grandchildren finish the sanding?)or do want to fly in one with minor mods?

 

But, to each his own. It may be worth waiting for.

It's good to visit a builder and talk to him (or her) about the time it took to build it according to plans and then about whether or not they would have spent the months or years making changes .

From what I have seen and from the general knowledge base here and elsewhere, there is very little to be gained in making changes in the "plans build". Engines, retractable gear, constant speed props, heavy epoxy loading notwithstanding, even upper end speed can be limited by other factors (see post on Mach Stall).

 

With all of the same type (Rutan designs and knock-offs) you dont see that many with exotic modifications flying about. Maybe there's a reason for that.

 

Ok Jim, you can come out now..

[jperryfly]

I used a layer of heavy carbon fiber uni crosswise on the inside of my LEZ cowlings, made them stiff and light.

[Steve Davies]

new materials = reengineering

 

Totally agree.

 

That was rather the point I was trying to make, not so much that I'm researching materials, but that in general different airplane materials are being used in new applications.

 

I gets hot headed and sometimes my fingers are faster than my brain.

[Joe Patterson]

My biggest concern is Noise dampening.

 

If I can build in something now(while I am getting going) to dampen the noise, I would like to check into it.

 

I have no experience at all with these canard pushers, they may already be QUIET enough.

 

Does anyone here ,Have experience flying in one of these BIRDS, are they significantly quieter????????

 

It seems everywhere this question is posed, all are in agreement ......Do not mess with the building materials.

[dust]

Hey, this is STANDARD prodcedure, and it follows logic.

 

Eglass is old and there must be a better alternitive. It makes sense, then i read composite basics by andrew c marshall and he groups eglass with the exotics.

 

it is really great stuff, strong in compression and tension, forgiving if the fibers arn't perfectly straight, etc etc.

 

by forgiving i mean carbon fiber loses 2/3 or so of it's great strength if the fibers are not perfectly straight, eglass loses a few percent.

 

enjoy the build

 

Dust

[Jim Sower]

Originally posted by Joe Patterson

My biggest concern is Noise dampening ... I have no experience at all ... they may already be QUIET enough ... Does anyone here ,Have experience flying ... are they significantly quieter ...

For openers, it's a PUSHER. By definition, the engine noise is behind you, receding (instead of in front of you washing over you). It IS a good bit quieter than a spam can. You still need head sets (if for no other reason than to talk on the radio). My EZ (~200 hrs) and Velocity (~200 hrs) are significantly quieter than the Grumman I used to own (300 hrs) and any Cessna (30?) I've been in.

 

I'm not at all certain that it is possible to quiet the airplane enough to converse comfortably with no head set. If it were possible, I seriously doubt it would be affordable or light enough. I have 1/2" thick soft foam upholstery in my Velocity and I can't say it deadens sound much at all. When I tear up the roof to downdraft the engine, I might dispense with that foam unless I find that it's really REALLY easy to replace.

 

The Cozy is only very marginally a 4-place airplane anyway. 100# of sound deadening equipment would be a LOT more trouble than it's worth IMO.

 

The Cozy built to plans with the design materials is more than strong enough. Changing any structural materials would be an exercize in guilding the lilly, and would almost certainly get you INTO more trouble than it got you OUT OF. That said, I believe that there are some legitimate uses for "trick" materials (but in non structural areas). For example, my cowl has been off so many times that the holes are getting all wallowed out. I'm going to strip off the paint and lay up a strip of carbon fiber BID around the edges to stiffen them up and make the screw holes more robust. As for general structures, I've heard so many horror stories about trying to work with kevlar that I'm not going to touch it for anything, with the possible exception of a patch under the hockey puck on the nose so as to minimize damage in the event of a gear up landing - and I might find carbon fiber a better choice for that too.

[dust]

Mr. sower said

with the possible exception of a patch under the hockey puck on the nose so as to minimize damage in the event of a gear up landing

 

if i didn't buy the auto extend feature of wilhelmsons elec nose gear and if dave wouldn't have done such a great job of installing the manual backup extend system for the gear, I would have gone for a 10 or 20 layer of kevlar under the 1/2 hockey puck.

 

enjoy the build

 

Dust

[racingjeff]

Re-engineering ?

 

All you need to do is compare easily available data on each material, the biggest savings will be weight, very large difference between E or S glass and carbon. And hey what makes everyone think the fiberglass they are using is identical, like it all comes from the same place from the same manufaturer and same run of yarn.

 

As for Kevlar, correct it is difficult to work with, typically what is done when using it is to use a carbon tape over the edges, this provides the workability to finish the edges.

 

Weaves on any material depend on useage.

 

Best Regards,

Jeff Dimitry