(New?) Composite Panel Construction Technique

[redbicycle]

What is the largest panel size you think you can produce like this on your garage setting? This is awesome stuff.


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[StrongFeather]

What is the largest panel size you think you can produce like this on your garage setting? This is awesome stuff.

Thank you. There are a couple of factors that will limit panel size...

First is the size of the mold surface, which could be glass, marble, granite or any smooth flat surface. I plan on using reclaimed patio door glass for my full-scale panels. Just remember that the largest panel that you can produce on any mold surface will be around 6" smaller in both dimensions because of the flange area needed around the panel to attach the vacuum bagging film.

The second limiting factor is that carbon fiber fabric comes on 50" wide rolls and the fabric has to wrap up and around the wood frame and back onto itself. That's 1" up on the outside of the frame + 1/2" on top of the frame + another 1" down the inside of the frame + at least 1" back onto itself. That comes out to 3.5" per side, or 7" total, making 43" the widest carbon fiber panel width.

With that said, you could potentially push it to 48". If I were to go that wide, here's what I would do... the edge of the 50" fabric would end at the top of the outside of the 1" tall wood frame - a narrow strip (~5") would have to be placed on the outside of the frame to overlap the end of the 50" fabric and wrap around the rest of the wood frame. I hope that makes sense. It would be a challenging layup, but I think it could be done.

Fiberglass, which also comes in rolls like carbon fiber would not have the same width limitation because any seams created by overlapping fabric would be hidden by the gelcoat.


Steve

[StrongFeather]

Allow me to quote... myself.

With Panel #2, I used one layer of really thick, heavy 18oz fiberglass cloth instead of two 7oz. layers. I thought I could get away with not using flow media on this one because the 18oz cloth has such an open weave - wrong! It did infuse, but it was extremely slow and needed some help from a plastic spatula to get the resin to the edges. Lesson learned. I also brushed in a gel coat on the top half of the panel prior to laying the fabric just to see how it comes out. I also used a fiberglass veil on the left half. The weave pattern of a course fabric, like the 18oz., may show (print) through the finished surface - a veil is a thin matting that is supposed to prevent this "print through".

Panel 2 is out of the mold, so I thought I would share some notes...
The finished surface came out somewhat cloudy because the glass was somewhat cloudy when I started. The cloudiness came from the Frekote 770NC Industrial Mold Release, which is supposed to be "the best", but clearly something went wrong. Although the glass was cloudy looking, I did buff it with a cloth beforehand, so it was smooth. I wanted to see if it the cloudiness would still imprint onto the part, and if so, how much. The answer is completely. Now I have to figure out what I did wrong.

Also, the 18oz cloth pattern did not print through any part of the panel, either with or without the veil. This is significant because now I know I can use 1 layer of 18oz fiberglass ($5 / yard) instead of 2 layers of 7oz ($7 / yard). I was also worried about the 18oz cloth adding weight due to extra material and resin, which turned out to be a non-factor. Panel #2 is only 10 grams heavier than Panel #1, and considering that #2 is 12 square inches larger, I would say the weight is a wash.

Finally, the gelcoat that I brushed on seemed to work just fine, other than the cloudiness mentioned above from the mold. It covered well and looks like brushing it in will work, but I'll make the final determination when I fix the cloudiness and see how it turns out.


Steve

[Esteban]

Up above one of the limitations for a panel size was the lack of available carbon fiber cloth wider than 50". uscomposites.com sells Discounted Carbon Fiber Fabrics that are 60" or 63-1/2" wide. As well as narrower widths.

5.7 oz x 60" wide plain weave carbon fiber fabric sells for $18.50 (full roll of100 yards) up to $23.50 (1 yard) per linear yard.
5.7 oz x 63-1/2" wide plain weave carbon fabric sells for for $19.50 up to $25 per linear yard.
Larger orders sell for the lowest price per yard.

I bought 10 yards of 5.7 oz x 60" carbon fiber cloth from USComposites to build a teardrop. At current prices that would cost $215.00 ($21.50/yd).

[StrongFeather]

Thanks for the info, Esteban!

That’s the first time I’ve seen 2x2 Twill 1st quality in 60” width - although I wasn’t really looking for it before just now. Typically, the only wider fabrics I’ve noticed are either commercial grade or plain weaves, which aren’t typically used for cosmetic applications.

FWIW, I get most of my stuff from Composite Envisions or Express Composites. CE has a pretty cool stabilization process called WebLock that I think I’m going to use on this build.

Cheers!

Steve


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[Esteban]

Steve,
Thanks for sharing the two suppliers you use. I added them to my teardrop favorites. I like the helpful product descriptions, and the good values of the products sold by compositeenvisions.com. Some of their epoxy & hardener bundles seem to be very competitive to products I purchased from raka.com.

I plan to buy their composite-workshop-solutions-fabricators-essentials instructional CD for $29.99 to learn more good/best practices. And to learn how to avoid making boo boos.

[StrongFeather]

I remember looking at Raka epoxy some time ago, but I honestly don’t remember having an opinion one way or another about it. I know a lot of people use it, so I’m sure it’s good stuff.

After comparing cost and physical properties of several different brands, I decided to go with Adtech Marine 820. It’s reasonably priced, has great physical properties and is UV stable.
Here’s a link to Soller’s web site that explains why they use it.
https://www.sollercomposites.com/Epoxy.html
And a link to the mfg. site...
http://www.axson-technologies.com/find- ... cts/Resins

I buy mine from Express Composites.

Steve


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[StrongFeather]

Finally time for another update. It's been a while because I was waiting on some supplies that were in the "large" order with all of the material needed to make all of the panels for the trailer. Unfortunately, instead of coming on Friday, like I hoped, it didn't arrive until Monday and Tuesday. That's a great way to kill a nice long weekend of testing. Nevertheless, I didn't exactly expect the prototyping process to go smoothly, and to be honest with you, I'm relatively pleased with the progress thus far.

So, after finally getting everything together, I was able to strip the old mold release out of the mold (which is what caused the matte finish on panel #2) and reapply a much thinner coating. It looked great, which meant I was ready to test apply the in-mold clear coating (another part of the large order that was delivered late). I set up my new HVLP spray gun - a mid-level gun from Amazon - and was not happy. The spray was pulsating in a bad way, rather than a nice continuous spray that you'd expect from a spray gun. I proceeded with the test anyway because the clear coat was catalyzed and in the gun anyway. The result was not a smooth continuous layer, but a bunch of tiny droplets that beaded-up on the mold surface. Failure! Since I couldn't rule out that the gun's pulsating spray caused this, and since I needed another new gun anyhow, I went to Harbor Freight and picked up a $15 gun. After removing the first layer of clear from the mold, and setting up the new-new gun, I sprayed the second test... same result. Here's a picture. There is actually zero clear coat between the individual droplets.

DSC00012.JPG (219.61 KiB) Viewed 2047 times

Shot off an e-mail to Hawkeye Industries tech support, which meant another delay, but it looks like the problem was the mold release. I tried hard to use the very best products in nearly every aspect of building these panels, and as a result, I selected a semi-permanent release agent Frekote 770NC rather than a traditional paste wax. As it turns out, 770NC is just too good. So, I stripped the mold again, waxed it with Partall Paste #2 wax and resprayed the mold with clear coat.

Here's a picture of the culprit and the savior; new-age vs. old-school...

DSC00017.JPG (132.4 KiB) Viewed 2047 times

And a picture of the (hopefully) successful clear coat application. There is a quite a bit of orange-peel, but I don't think it's bad enough to print through or disturb the carbon fiber pattern. We'll see tomorrow when panel #3 gets pulled from the mold.

DSC00021.JPG (167.09 KiB) Viewed 2047 times

Steve

[StrongFeather]

I pulled Panel #3 from the mold today and I really like what I see. The clear coat worked great! It's smooth, flat and shiny as I hoped. This is significant because the clear coat protects the epoxy from UV breakdown, adds shine, is more scratch-resistant than epoxy, and can also be wet-sanded and buffed.

The only problem that I'm having now is kind of a minor post-mold issue that doesn't affect the final part. The "mold" - in this case - is a sheet of glass with a frame sitting on top. Here's a picture of the prototype mold so you have an idea of what I'm dealing with. The production mold will be glass from a sliding glass patio door and 1"x1.5" rectangular aluminum as the frame rather than wood as I used in prototyping.

DSC09969.JPG (168.4 KiB) Viewed 2005 times

The issue is that I'm using gum tape between the frame and the glass, and since the tape is about 1/16" thick, it creates a gap between the frame and glass. If the gum tape is too close the inside edge of the frame, it'll squish into the part. If it's too far away, the epoxy will cure under the mold frame, mechanically locking the part in the mold. I used modeling clay to fill the gap on Panel #3, which worked well, but it's soft and comes off on the part. Like I said, it's kind of minor, but the clay would have to be cleaned off of each part and that takes time.

If anyone has suggestions on other ways to seal the frame to the glass, I'm all ears. The gum tape, in spite of its thickness has several advantages - it creates an air-tight seal, it is not permanent and it does not contain silicone. One thing that I'm considering is sealing the mold frame to the glass on the outside perimeter (with the frame sitting on the glass) rather than underneath it. This would get rid of the gap, but it could end up being a PITA when trying to pull a vacuum. Something to ponder, I guess.



Steve

[Atomic77]

No bigger than this is, why not just lay up some glass and spray some gelcoat and make a reusable mold without the issues of the frame/glass

[StrongFeather]

Wish I could, Michael, but for this project I don’t think it would be faster or cheaper or easier.

There will be ~30 production panels of various sizes to make the camper, and at best I would be able to use each mold twice. The glass/frame will allow me to make whatever size I need - with limitations - and changing the mold should be really quick. I plan on making all panels that are wall height (60”) first. That way three sides of the frame remain fixed for all of those panels. Only the fourth side will move to change the width. After that I’ll use the same concept with the roof panels, and probably save the smaller, odd sizes for last.

What you’ve seen so far is just for figuring out the process and working out the kinks without risking too much in wasted material... and to prove the concept.

If I end up doing a teardrop later, I might try reusable molds, but then wit carbon fiber, I’d be limited to fabric width, so the wall height would be limited.

Cheers!
Steve


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[StrongFeather]

I’m not the best at ‘splainin’ things, so this might help explain how the mold will work. Below is a picture of the mold frame pieces laying on a 3’-wide heating blanket (I don’t have the glass yet).


And this is how I hope to make smaller pieces without having to cut the frame pieces shorter and shorter and shorter and oops no more frame to cut shorter.


I also hope to seal the bagging film to the top of the frame, but I realize that I might have to just go from the glass, up and over the frame. The key will be getting the frame sealed to the glass.

This is definitely a moving target and who knows where it will end up. I’m open to all ideas and suggestions to figure this out and improve the process or tell me when I’m messing up royally. Join me on the ride and we’ll see where it takes us. In many ways it’s about the challenge to do something different, solve some first-world problems and have fun doing it. If it turns into a new and innovative way to build a camper, great! If not I’ll still have fun doing it.

Cheers!
Steve


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[StrongFeather]

That last post made me realize that I need to get better at explaining... and showing my thoughts. I know that I can ramble on at times, so I usually try to keep things short (believe it or not) to maintain interest. I'm not a gifted writer, so I should probably rely on pictures more than words.

With that said, I decided to use a couple of the prototype panels to mock-up a small wall to show those that may actually read this, how this concept is supposed to work.

After the individual panels are made, they will get glued together (with epoxy) to form a wall. The glue in the case of this picture is the clamp. Once the wall is assembled, XPS foam will be glued (also with epoxy) into the interior cavities. Note that the picture only shows a partial foam because it was a piece I had laying around.

DSC00026.JPG (166.07 KiB) Viewed 1988 times

It's not a great picture, but the outside will look something like this.

DSC00025.JPG (172.28 KiB) Viewed 1988 times

And finally, the interior will be skinned with whatever. I'll probably go with 1/8" baltic birch if I can find it locally.

DSC00027.JPG (127.29 KiB) Viewed 1988 times

The end result should be an incredibly strong and lightweight structure that (hopefully) looks pretty cool too.

I'll take some time in a follow-up post to cover a few things that haven't been mentioned yet. Things like:
Windows
Doors
Wall-to-frame attachment
Wiring
Skinning the interior, and
anything else that comes to mind.


Steve

[StrongFeather]

As promised... some issues that haven't been covered yet. Just keep in mind that most of these would be personal preference for the builder and there's probably several ways to skin any of these cats. There are just my thoughts.

Windows
For my first build, I plan on simply creating wood frames that I'll epoxy in place on the inside of the panel, then cut out the opening in the skin with a router and flush cutting bit.

Doors
Doors could be done just like windows if using commercially built units. My doors will be custom panels (because I'm crazy) with 180° hinges and square windows. One door on each side.

Wall-to-frame attachment
My plan is VHB tape between the bottom of the wall and top of the frame. I'll also use 1/4-20 bolts up through the frame into the bottom of the wall panels using special T-nuts made for fiberglass/composites. Each wall panel will have one bolt.

Interior Skinning
I'm still on the fence with this. One option would be to skin the interior after the entire shell is assembled. Plenty of people do this on their traditionally made TD's and it works great, however it means working inside, on a vertical (or overhead) surface and could require mechanical fasteners to hold the skin on the wall (even if using epoxy). As of today, I'm leaning towards vacuum bagging the skins onto the walls (and roof) before assembling them on the trailer frame, i.e. skinning a hole wall laying on the floor. This means all of the wiring has to be installed, and windows, etc... have to be thought of and planned for before the skins are done. Doing it this way will create the ultimate sandwich panel and have a clean, smooth finish without mechanical fasteners.

For those that don't understand what I mean by vacuum bagging, I'll try to explain. An entire outside part of the wall would be assembled; the individual panels would be glued together, XPS would be glued into the cavities, wiring would be ran and window frames would be installed. Once that is done, it would be laid on a long sheet of plastic (at least twice the length of the wall). Then epoxy would be spread on the entire surface of the wall and the inside skin (luan, baltic birch, or whatever) would be laid on top. Then the plastic sheet would be pulled over the entire wall and a vacuum would pull all of the air out. The result is that atmospheric pressure becomes a very large clamp that acts equally across all surfaces of the part inside the "bag".

Wiring
My trailer will have a V-nose section that will house all of the electronics, batteries, wiring terminals and so on. I will home-run wires to all lights, switches, outlets, etc... No daisy chaining because chances are it will be a lot of work to open the walls up to fix something like a loose connection later on. I will drill small holes in the wall panel frames, similar to studs in a house, and run the wires along the top and bottom of the walls. I will also notch the foam for the wires to sit in with a router. The notching in the foam will be on the interior side, not the outside, mostly to avoid the higher surface temperatures from the sun beating down on a black surface. It will be a little tricky getting the wires from the side walls into the V-nose, but I have that mapped out in my head. The rear storage area and ceiling should be pretty straight forward.

Ceiling
I didn't mention this earlier, so here are a couple of comments. This trailer will be black (because I'm crazy), so I'll probably double-up on the insulation to stave off mother sun a little bit. The roof will be sloped to each side (higher in the middle), but the ceiling will be flat. This may create enough space for a pseudo attic that I'm thinking about using as an air conditioner plenum to distribute cold air evenly throughout the cabin vs one air outlet blasting cold air onto the lucky or unlucky person sleeping in the bunk next to the air conditioner.

Sorry for the long post. Thanks for hanging on.


Steve

[tony.latham]

Screened windows for ventilation?


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