alternative building material

[dhaulk]

Hello everyone I am new and I am in the process of deciding if I can actually build a cozy. I saw somewhere that someone said they new someone that built a plane with honeycomb and saved a wopping ten pounds. My question is this 10 pounds may not be alot but is it stronger then the foam? Also what about paint I no your not supposed to paint a cozy anything other then white because the foam cant take the heat. But wouldn't the honeycomb be able to stand up to the heat? Cause I think a black cozy would be dead sexy.

[dpaton]

Two short answers-

 

Honeycomb for a Cozy requires such a significant departure from the plans I'd STRONGLY discourage it, and yes, I've done a little honeycomb work. It's hard to get right. Very hard.

 

Stay away from dark colors unless you hanger your plane and only ever fly at night, honeycomb or not. It's the epoxy that matters too, and without a giant autoclave and industrial epoxies and processes, you won't change the temperature limits.

 

Building a Cozy isn't hard. Major mods like that are.

 

My $0.02.

 

-dave

[dhaulk]

Ok well thanks for the info. I am still just thinking about this whole project. I also saw a ceramic paint aditive somewhere that is supposed to block heat transfer and uv rays. So naturally I was thinking with this stuff add to the black paint wouldn't the epoxy and foam stay nice and cool?

[dpaton]

You could probably make the ceramic stuff work, but you'd end up applying so much of it you'd make your plane heeeeeeeavy. Weight for these kinds of planes is the enemy. Make it only as heavy as is required...anything else compromises strength, range, and performance. Remember, there's more than 25 years of experimentation and mistakes for the Rutan derrived canard designs. There's a reason people build them the way they do. Small changes (longer noses, widened, lengthened, retracts, big engines, etc) sure, but radical departures in the structure and finish are discouraged by history and common sense. I'd suggest you read this article before thinking about changing the structure of a plane that much.

 

UV is blocked nicely by modern finishes...no special tricks needed for that.

 

-dave

[karoliina]

dpaton,

 

one does not need to be a structural engineer to understand that

this yardstick example is preaching and not based on any engineering, otherwise everybody would be building their wings from gum. The fact that something is less flexible does not make it less strong since it is about static load and not static flexing that is measured. In other words, one could build a wing out of carbon fiber and it would fail with lesser amount of flexing than a e-glass wing. However, it would require lot of more force to flex the carbon wing enough to make it fail. And the more the wing flexes, the more at risk is the foam inside to either break or separate from the skin. If that happens, the strength of the sandwitch is lost immediately "bam" and the wing will fail. The blue foam can flex to certain extent without failure, but after that, the failure happens immediately without warning.

I have my doubts if Burt have ever said this thing which appears in the "Howdy Burt, I Fixed Your Puny Spar", the real story is propably something else and the reasoning is propably something else than presented in the story. I had some structural engineering in my engineering studies, but I have largely forgotten the equations etc. we were using about everyday. However, the one thing that has remained (as common sense) since reformatting my brains with C/C++/etc., is that with thinking it even a little, the claim represented in the article you are referring to, can not be correct. If you do not believe, you can do a test laminate and test with static loading which part fails earlier. The strenghtened part fails later despite its flexture at failure may be less, especially if the material is carbon fiber.

 

If somebody strengthtens some component, he or she needs to take account also does it require some other reinforcements. Fixing wing in one place can make it fail from another - it needs to be strenghtened equally and of course the core material is one important thing that contributes to the strength of the resulting sandwitch. There are better structural foams than blue styrofoam out there in that sense, but for the construction method (hot wiring etc.), the blue foam is irreplaceable.

 

Karoliina

[dhaulk]

Ok you said I could prolly use the ceramic paint additive but that it would add weight. I agree that it would add weight but I have to question whether this is going to be much of a problem. I mean we're talking about 15-20 lbs over the entire aircraft. And this plane will normally just have me and some light bagage on short trips, and maybe on rare occations me and 3 others on a short joy ride with bagage consisting of a camera and film.

[dpaton]

dhaulk-

 

The real question is if it can maintain a potentialy 100F temperature gradient across it's application thickness for an entire day. I have my doubts about that, especially since it would need to be completely rigid ceramic to achieve that kind of isolation over time, and your plane is flexible. You'd need to know a lot more about the material and its mechanical and thermodynamic properties before it'd enter into the realm of fesable. I think everyone here will agree that it's a much better idea to paint the top of your bird white.

 

Karolina-

 

I know better than that. I should have couched that link with my own views on it: The ruler example is not good engineering, I agree, but the gist of the article is that by changing the plane from something flexible to something rigid, without the required engineering knowledge, will make it weaker and potentially less safe. There are too many interdependentcies in these planes to make radical changes to the structure (carbon fiber applied randomly) or construction (honeycomb) without following through with careful engineering analysis and risk assessment first. There is apparently a safe envelope we can modify our planes within, but things like that put us far outside that envelope, and invite disaster.

 

-dave

[Nathan Gifford]

... I think a black cozy would be dead sexy...

If you succeed there will be a lot of questions how you did it. By succeed, I mean one that flies without the airframe failing or the paint flaking off.

[Wayne Hicks]

Per the Cozy plans, room temperature cure epoxies start to soften at 160F, foams begin to go at 240. It's the epoxy that leads to prohibition of dark colors on structural surfaces.

 

BTW, honeycomb prepregs are not immune either! Even Lancair, whose planes are mostly honeycomb prepregs, PROHIBITS dark colors. I paraphrase from the Legacy Assembly Manual, Chapter 28, Item G:

(1) Limit color choices to light pastels only.

(2) Lancair prohibits dark base colors.

(3) The vinylester/low temp foam cores can ONLY be painted WHITE.

(4) As will all resin systems, a temporary strength drop will occur as temperature rises. This temporary drop reduces the effective safety margin until the composite cools.

[Wayne Hicks]

Take a fiberglass fishing rod. Catch a really big fish. What happens? The rod bends along its ENTIRE length. Now slide a tight-fitting steel tube over the rod from the reel to the second to last eyelet. Catch a really big fish. What happens? The rod breaks where the steel tube begins.

[dpaton]

BTW, honeycomb prepregs are not immune either! Even Lancair, whose planes are mostly honeycomb prepregs, PROHIBITS dark colors. I paraphrase from the Legacy Assembly Manual

Stay away from dark colors unless you hanger your plane and only ever fly at night, honeycomb or not. It's the epoxy that matters too, and without a giant autoclave and industrial epoxies and processes, you won't change the temperature limits.

Thanks for the Lancair backup Wayne. Good to know.

 

So, all, have we successfully put this one to rest yet? Homebuilt composite planes should all be light colors on top. Agreed?

 

-dave

[dhaulk]

Ok well I sent an email to the manufacture and asked if this additive could be mixed with automotive paints. And if it would be a very effective heat barrier for use on blue foam/ fiberglass composites. So maybe they will get back to me on that and I post what they say. I have also thought about makeing up a small piece with a couple thermal sensors between the fiberglass and the foam, painting one half of it black with the ceramic and the other white without ceramic and monitoring the temps thoughout the day.

[Jon Matcho]

I am posting this on behalf of Wayne Hicks:

 

Jon:

 

I cannot find the recent posts about the puny spar. Please post this as a reply.

 

So I wrote to Burt and asked him: "Any truth to the puny spar story?"

 

He answered (unedited):

"As for as the story goes.......might be true but I do not remember telling anyone adding plies will weaken it. It could screw up the stiffness and mess with flutter though."

burt

So maybe Bill is embellishing a bit. I am reminded that the VariEze wing does not have a complete, root-to-tip spar like the Long-EZs and the Cozies. It's only a few feet long. The majority of the wing is supported by the cores and the outer skins. Right?

[dhaulk]

Ok well I emailed the company that makes the ceramic paint additive and ask a couple of questions. I asked if it could be added to automotive paint and more importantly if it would block any heat transfer to the epoxy under the paint? here is there reply.

 

Donnie Haulk,

Yes, the Ceramic beads will mix with any paint and give you an insulating

barrier. It does leave a slight texture. With a couple more coats of paint

over the beads, the texture will be gone, leaving a smooth finish.

 

The ceramic beads are the same technology used by NASA space shuttle to

protect the astronauts from the 2000 degree re-entry temperatures.

They use ceramic tiles made the same way as the beads.

 

Your project is interesting because I have my pilot's license, and I worked

for many years as an A&P and AI aircraft mechanic. I used to rebuild

aircraft as well as maintain them.

 

Good luck with your project.

 

 

Well this seems like good news maybe I can have my sexy black cozy!!!

[dpaton]

Holy cow that sounds like a lot of weight. 3-4 coats of finish paint? That could easily be over 100lbs of extra stuff on your bird, and VERY hard to offset. You still need to do the proof of concept test...build up a square yard of wing-like sandwich, thick foam, etc, with something like a spar cap layup underneath the skin, embed some thermocouples in strategic locations, and leave it outside, 4' above an asphalt (black) driveway on a hot day (90-100F air temp) without wind, to simulate worst case heat soak. A datalogged graph of the temperatures would be most valuable to calculate what those temperatures will do to the layups. Working from there, once the data is taken, should be relatively simple.

 

The line about the ceramic tiles on the shuttle sounds a little optimistic to me. The tiles, as I recall, are so soft as to be destroyed if you bump into them very hard. Their insulating ability comes from their low density, and the high amount of termal isolation that provides. Aerogel insulators work on the same principle. I wonder about the durability of the ceramic spheres...will the ones on the strakes get smashed and deformed when someone hops up there to get in? What about the 50th time?

 

A black composite plane still sounds like a really bad idea to me. Really bad. But if you can make this work, it'll be really astounding.

 

-dave

[CFernandez]

Well this seems like good news maybe I can have my sexy black cozy!!!

Bright red with racing stripes sounds good to me.

 

If it works you would turn a lot of heads.

[dhaulk]

Ok well here is kinda the look that I had in mind.

 

 

 

Credit for the plane I think goes to curt boyl I think hes the one that made it I did repaint it and added the retractable main gear. I would definately do a couple sample layups with temp probes. thought about putting a probe under the glass and one on top the glass but under the paint. And I really dont think a couple coats of clearcoat to smoth the texture would add that much weight.

[Jon Matcho]

Black... yuck. Take a look at the Rocket Racing League's concept vehicles for ideas: http://www.rocketracingleague.com/x-racers_gallery.html

 

Even if those magic black beads reflected major heat, I'll still bet that you won't be able to put your hand on the wing for longer than 5 seconds after the plane has been sitting in the lunchtime sun for an hour.

 

It's still a good idea...

[dhaulk]

Even if those magic black beads reflected major heat, I'll still bet that you won't be able to put your hand on the wing for longer than 5 seconds after the plane has been sitting in the lunchtime sun for an hour.

 

It's still a good idea...

As long as the heat is just on the surface and not radiating down to the glass then all is good. I think I can manage to remember not to touch after all my car is black and I dont touch it when its setting in the sun.

[Wayne Hicks]

How many night hours do you have?

[dhaulk]

How many night hours do you have?

# of night hours = 0

# of day hours = 0

# of x-plane hours = about 50+

 

scale of one to ten on my desire to learn to fly = 11+

[Richard Riley]

As long as the heat is just on the surface and not radiating down to the glass then all is good. I think I can manage to remember not to touch after all my car is black and I dont touch it when its setting in the sun.

It WILL radiate down into your structure. Ceramic additives are insulation. They slow down heat transfer, they don't prevent it. The surface will heat up - just a little slower than if you didn't have the insulative paint. There's nowhere for the heat to go on the underside. The 6" thick foam inside the wing is insulation, too.

 

You can get some pigments that are made to reflect more IR than carbon black (the standard black color). If you want to see if it's good enough, paint a sample panel, put it in the sun in July at 10 am, and take temperature measurements every half hour or so.

 

However...

 

If you're worried about what color to make it before you've started building, get another hobby. You won't ever finish an airplane. You'll spend several thousand dollars, and a couple of hundred hours building, and you'll decide it's not for you and sell it at a loss.

 

If a someone signs up for piano lessons that's never even sat at the keyboard, and his first question is what color his tux should be when he makes his debut with the NY Phil, you know he never will. He shouldn't buy that concert grand piano.

 

If you want to work with computer graphics, there's nothing wrong with that. It's not building an airplane. Sorry to be blunt, but I've seen it too many times.

[dhaulk]

If you're worried about what color to make it before you've started building, get another hobby. You won't ever finish an airplane. You'll spend several thousand dollars, and a couple of hundred hours building, and you'll decide it's not for you and sell it at a loss.

 

If a someone signs up for piano lessons that's never even sat at the keyboard, and his first question is what color his tux should be when he makes his debut with the NY Phil, you know he never will. He shouldn't buy that concert grand piano.

 

If you want to work with computer graphics, there's nothing wrong with that. It's not building an airplane. Sorry to be blunt, but I've seen it too many times.

Well first off I am not the type of person that gets discouraged from looking ahead at the big picture. I am the type that get encouraged. 2nd like I said I haven't commited myself to building anything yet. I am in the process of experimenting to see if I can build a cozy and if I can have it my way. 3rd if I do decide to build a cozy those computer graphics will be printed out poster sized and hung in my shop for encouragement. And last but not least I appreatiate you being so blunt because if I do decide to build I am going to print out your post as encouragement also.

[dhaulk]

You can get some pigments that are made to reflect more IR than carbon black (the standard black color). If you want to see if it's good enough, paint a sample panel, put it in the sun in July at 10 am, and take temperature measurements every half hour or so.

 

Hey I checked out the link you gave and when I went to products overview it says that they are ceramic pigments. Now I may be way off but isnt that kinda the same thing as ceramic paint additives?

[dpaton]

The short answer is no. Ceramic describes a radically diverse class of materials, and the ones used as paint pigments are manufactured in a very different way than your insulation material. They may have a teeny amount of insulation ability, but it's effectively useless for your purposes.

 

-dave