(New?) Composite Panel Construction Technique

[StrongFeather]

I love learning, so even though it’s another delay and a $50 sheet of plywood that I didn’t want to buy, I’m still smiling and enjoying the journey.

I can’t recall the reason at this point, but I either ruled PVA out for some reason or just decided to not use it. Not sure. Nevertheless, the part did demold really easy with the Frekote770 and Partall 2 wax. The problem was that some epoxy made its way into the corner between the aluminum frame pieces mechanically locking the part to the frame. And since the frame was essentially glued to the glass (because I didn’t use mold release there) when I lifted on one end, it twisted the frame (and the glass) until the glass couldn’t take it. If this happens with in the future, with mold release between the glass and frame, the frame should just pivot up along the outer edge where it’s being held down with gum tape and not break the glass.

The new table is built, so now I have to clean and polish the glass and redo the frame.

Cheers!
Steve


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[aggie79]

The panel does look fantastic!

Thank you for the pictures and documentation.

[Atomic77]

I stopped using mold release and wax years ago. We PVA everything. Saves a lot of steps during prep and if you get a leak its no worries at all

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[Pmullen503]

The panel looks great. What does it weigh?

[StrongFeather]

Thanks Tom (& Linda) and Michael.

Pmullen, the panel, which is 60" x 30.5" x 1" weighs 7lbs 3oz.

Doing some quick math... that's 0.57lbs/sq.ft..

My trailer will have ~231 sq.ft. of skin surface, so the weight of the panels will be around 130 pounds - keeping in mind that smaller panels will be heavier per sq.ft. and larger ones will be lighter psf. This also does not account for the foam or the inner skin. My rolling trailer frame (frame, axle, brakes, floor, hardware, coupler, jacks, wheels, tires, chains, etc...) is around 230lbs (if I remember correctly), which should get me under my dry weight goal of 1,000 lbs. with room to spare.


Steve

[OP827]

..
I wasn't able to find any examples here on TNTTT of builders stating that they experienced XPS delamination due to heat - probably because the search function isn't very good. The only statement that did pop up was GPW saying he didn't have an issue after 4 years in Florida, and I believe he also said his foamie is black. I'm wondering what the circumstance were for the ones that you've read about or experienced yourself. Perhaps there are other factors involved other than heat. No matter what, I still plan on looking further into this in the coming days and I'm hoping that you'll share some more with us. Thanks again


Steve

There is a bubble delamination mentioned in pods8 truck camper build on Expedition portal. The fiberglass surface was initially painted in grey bedliner. Link: https://www.expeditionportal.com/forum/threads/pod-homebuilt-foam-core-fiberglass-skin-pop-up-camper-build-thread.58926/page-24#post-1756461

I remember that Atahoekid with Road Foamie build on this site mentioned that he needed to repair/re-inject bubble under the FG surface that appeared after some time. His trailer was painted grey metallic paint. Atahoekid did not say why the de-lamination occurred, could be other reasons than heat.

Another delamination example I remember mentioned on this site I could not locate anymore unfortunately. It was with a deep purple/blue mirror like car quality painted teardrop. It was extremely well made out of XPS foam covered with epoxy fiberglass with compound curves. I am not sure if the build was documented here, the author just mentioned delamination during paint finish discussion. Could be in general forum somewhere...

I feel that many people generally may not be eager to widely publicise failures with their build, although having such information shared brings great value to our knowledge base. We learn by failure and make it work by figuring out what needs to change to address that, not so much by succeeding with something and not knowing why it did not fail.

Have you heard of aircraft engineer Burt Rutan and his composite designs with some of them sold for building at home? I heard him mention at least once https://youtu.be/hDc0d2AZbs8?t=204 that composite planes are naturally white to stay cool due to their composite structure. He would have a reason to say that and I share the same opinion while having structural engineering background. I am taking it from long term durability point of view and not a one time temperature tests data.

But as they say, there could be two engineers and three opinions and it is ok . That is why prototypes and testing are done to figure out what works and what does not.

Cheers,
Oleg

[Atomic77]

Nothing to add to that other than this...

We were racing in Coeur d'Alene and I had heard that Burt had a place on the lake there. On Friday after qualifying, he came down to our pits to check out the boat. I remember he was amazed with it, being basically a boat on the bottom and an air plane on top. He had a hundred questions about how we use the wings, etc. What a brilliant man and a fun afternoon hanging out with him. Great memories

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[Atomic77]

I came across a race shop picture recently when I was laying up a couple upright wings for the boat. PVA in the mold, 2 layers of boat cloth, 8 layers of carbon fiber and a foam core. Enka mat for distribution.



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[tony.latham]

I came across a race shop picture recently when I was laying up a couple upright wings for the boat. PVA in the mold, 2 layers of boat cloth, 8 layers of carbon fiber and a foam core. Enka mat for distribution.



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What’s boat cloth?

T


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[StrongFeather]

Pretty cool, Michael.

I’m curious if you have ever used MTI tubing. Its spendy, but for my application I believe it’s necessary and with my lack of experience, I feel like it makes the process a little more forgiving - idiot proof even.

BTW, I’ve been in full production mode for the last two weeks, which is why I’ve been radio silent. The panels are coming out good. Some of the panel edges have some minor issues due to the resin getting under the aluminum mold frame - causing an effect similar to bridging - but I believe I can fix it pretty easily when I put the wall together.

Steve


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[Xanthoman]

Just saw this thread and wanted to get in on the process. Well done. I’m excited to see how the panel assembly goes. Seams are always things I try to avoid so seeing your class A finish at risk by a composite bond makes me anxious on your behalf. Hope you can get the assembly as slick as the panels themselves; they are sweet. Good to see people using VRTM for teardrops. I just graduated in mechanical engineering with an emphasis in composites, but like Michael, it was always someone else’s dollar. I hope to start mine in a few weeks in a composite method (monocoque composite shell) but your panel/modular system is very neat. Keep up the good work!

[Atomic77]

I came across a race shop picture recently when I was laying up a couple upright wings for the boat. PVA in the mold, 2 layers of boat cloth, 8 layers of carbon fiber and a foam core. Enka mat for distribution.



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What’s boat cloth?

T


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Tony, that's just shop speak for tight weave fiberglass cloth. We use it as the outer layers (first in the molds) because it is innately smoother than carbon. We paint the parts, rather than doing the bare carbon look, so we use boat cloth to:
1. Be paintable, without "printing" or seeing the weave through the topcoat.
2. Makes repairs easier because CF doesn't sand as nice and leaves tiny "splinters" which makes repainting more difficult.

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[Atomic77]

Pretty cool, Michael.

I’m curious if you have ever used MTI tubing. Its spendy, but for my application I believe it’s necessary and with my lack of experience, I feel like it makes the process a little more forgiving - idiot proof even.

BTW, I’ve been in full production mode for the last two weeks, which is why I’ve been radio silent. The panels are coming out good. Some of the panel edges have some minor issues due to the resin getting under the aluminum mold frame - causing an effect similar to bridging - but I believe I can fix it pretty easily when I put the wall together.

Steve


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Yes on the MTI



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[tony.latham]

Tony, that's just shop speak for tight weave fiberglass cloth.

[StrongFeather]

Another panel in the mold today. I sprayed the in-mold clear coat last night, so it was ready to be laid-up and infused this morning. I started at around 9:30 and finished the infusion at 1:00, so 3 1/2 hours. I can cut that time by about 30 minutes if I cut/prep the layup while the clear is curing, but in this case it was bed time.

Here are some times that I jotted down on the second production panel. I'm sure they're a little better now.
Remove part from mold and cleanup 45 min.
Wax mold, prep, tape-off mold 30 min.
Spray clear coat and clean up 45 min.
Cutting layup materials 45 min. (hopefully done while clear coat is curing)
Layup and infuse 2 1/2 hours

I can pretty much plan on 1+ panel per day on a non-work day, or about 3 days per panel during the week.

I spent a lot of time searching for vacuum leaks on the first few panels and was never able to get a 100% seal. It was pretty frustrating, not to mention a time hog. Now I don't sweat it that much. As long as I can pull a good vacuum, I just go with it and keep the pump running for at least an hour after the infusion is done. I was reluctant to do this at first because I've read/seen that it can cause pin holes in the part from expanding air that is entrained in the resin (the vacuum expands the air). Luckily I haven't had any issues, which I believe is a result of the MTI tubing, which should pull any remaining air out without removing resin.

Blew a piston ring in my compressor last night, so time to go buy a new one before the next panel is ready for clear.


Steve