Exact cutting skin before applying

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Exact cutting skin before applying

Postby ryan112ryan » Sun Jun 11, 2017 12:13 pm

So I'm going to be using a CNC to cut all the part of my build then going right into the build full time until it's done. Part of my plan was to get all the wood parts assembled and then, seal with "the mix" then float the aluminum skin.

Since I'm using a CNC I was going to have it trim the metal to the 1/4" narrower than the body width ahead of time, plus put holes that would be tiny ovals for the trim screws to go through so if it expands it had room to move. Use some flexible sealant.

Wanted to float (see what I did there) this concept out there to see if it would be ill advised or if I'm missing something? Is 1/4" narrower not enough for expansion, I assume the trim could cover up 1/2" each side? I know many oversized and then trim. Also wanted to know if there is other things I could do to prevent oil canning?


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Re: Exact cutting skin before applying

Postby tony.latham » Sun Jun 11, 2017 4:33 pm

I was going to have it trim the metal to the 1/4"


I think that's a lot... if I were going to do that, I'd be leaning towards somewhere short of 1/8". It also depends on whether you put it on when it's hot or cold.

1/2"? It depends on what trim you might use. Here's a sampling of commonly used pieces: http://teardroptrailerparts.com/Hinges_ ... _Trim.html

And BTW, having sheeted three of these beasts... I'd cut the walls 3/16" proud, clamp it at the doors and hatch and trim it flush with a router. It'd drive me nutts to get a wall sheet set perfectly in place.

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Re: Exact cutting skin before applying

Postby greygoos » Sun Jun 11, 2017 7:55 pm

How about laminating the aluminum to the ply and then cutting it out. I have cut out windows that way, then fastened the aluminum with screws. It has been my experience and not speaking for everyone that the aluminum will eventually delaminate and the screws keep it in place.
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Re: Exact cutting skin before applying

Postby ryan112ryan » Sun Jun 11, 2017 9:21 pm

greygoos wrote:How about laminating the aluminum to the ply and then cutting it out. I have cut out windows that way, then fastened the aluminum with screws. It has been my experience and not speaking for everyone that the aluminum will eventually delaminate and the screws keep it in place.


That was my initial thought have it adhered to the side walls and on the outer sheet of 1/8" ply on the roof panel but a few things things:

1. Wasn't sure how that would effect ease of bending

2. I wasn't sure how to seal the wood shell, I thought a single application might be better and then I'd have to figure what to adhere the metal to either "the mix" Or epoxy.

3. The oil canning might be an issue when compared to floating.

Thoughts?


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Re: Exact cutting skin before applying

Postby ryan112ryan » Sun Jun 11, 2017 9:35 pm

tony.latham wrote:
I was going to have it trim the metal to the 1/4"


I think that's a lot... if I were going to do that, I'd be leaning towards somewhere short of 1/8". It also depends on whether you put it on when it's hot or cold.

1/2"? It depends on what trim you might use. Here's a sampling of commonly used pieces: http://teardroptrailerparts.com/Hinges_ ... _Trim.html

And BTW, having sheeted three of these beasts... I'd cut the walls 3/16" proud, clamp it at the doors and hatch and trim it flush with a router. It'd drive me nutts to get a wall sheet set perfectly in place.

Tony


I should have been clearer, 1/4" total so it would be 1/8" on each side for the roof panel. I was going to cut the wall metal skin to be a 1/8" shy too. Looks like most of those trims you linked to give me plenty of room unless I'm looking at the wrong one or am missing something?

Alternatively I could glue the whole metal to the wall and also to the outer 1/8th roof skin, then lay it? That would be easier for me if there aren't issues with that approach and I could figure out how to seal the wood underneath. Thoughts?


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Re: Exact cutting skin before applying

Postby tony.latham » Sun Jun 11, 2017 9:37 pm

so it would be 1/8" on each side for the roof panel.


:thumbsup:


The oil canning might be an issue when compared to floating.


Ryan: I'm fairly sure the only one that notices my oil canning is me. It isn't a problem.

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Re: Exact cutting skin before applying

Postby greygoos » Mon Jun 12, 2017 12:45 pm

I dont think my suggestion would work for the roof. I agree with Tony, a 1/4 inch sounds like a lot. I dont think your aluminum will expand 1/2 inch. I went right to the edge on my current build. I also laid down FRP as the base for the roof with aluminum over that, it is only about a 20 pound difference from plywood, yes it is twice the price but it is extremely flexible and certainly water proof. I figure my time is worth more than the 40 bucks.
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Re: Exact cutting skin before applying

Postby dmdc411 » Tue Jun 13, 2017 3:33 pm

I to think 1/4" is to much. Half that the most. But, I used a router to trim my sheets. Then drilled all holes possible. Took it all off, oversized all the holes a bit. Deburred, cleaned up everything. Then, sealant, screws, rags, tape to keep the mess to a minimum. Like said above, only I notice any oil canning. Standing still, or 70mph, you don't notice it if it's there!

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Re: Exact cutting skin before applying

Postby tony.latham » Tue Jun 13, 2017 6:52 pm

plus put holes that would be tiny ovals for the trim screws


I'd suggest just drilling bigger holes. The metal is going to move in both directions.

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