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Ready to skin... I think

PostPosted: Sun Apr 09, 2017 2:03 pm
by Rasmateo
My trailer isn't exactly tiny (16 '), but I think I'm ready to skin. My plan is to use sheets of aluminum from the local mill. I thought about ordering continuous rolled aluminum, but the thought of trying to attach it to the sides was intimidating. My thinking is to overlap the sheets, use butyl tape at the seams, and use stainless steel screws to attach to the frame/ply exterior. Is this a good idea, or am I way off?

Re: Ready to skin... I think

PostPosted: Sun Apr 09, 2017 3:50 pm
by aggie79
I would not recommend butyl tape. I lapped my aluminum and used 3M 4200 sealant on the overlaps. Another good sealant available at most box stores is OSI Quad.


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Re: Ready to skin... I think

PostPosted: Sun Apr 09, 2017 4:01 pm
by Rasmateo
That's a marine sealant right? What are the advantages of using this type of sealant to putty tape? This is my first rodeo, I'm just curious.

Re: Ready to skin... I think

PostPosted: Sun Apr 09, 2017 9:10 pm
by aggie79
The 3M sealant is a marine sealant. The OSI is a sealant for gutters and downspouts. Both are polyurethanes.

The butyl tape is not bad. It deals fairly well but will crack and dry out over time.

The biggest issue with butyl tape is its thickness. It is hard to compress less than 1/16". In overlapping aluminum sheets, that offset would lend itself to leaks.

A polyurethane sealant can be easily compressed and can seal at very small thicknesses.


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Re: Ready to skin... I think

PostPosted: Sun Apr 09, 2017 11:43 pm
by Andrew Herrick
You can also use EternaBond Double-Stick or similar tape to waterproof overlapping sheet metal joints. It's more expensive than most sealants, but much less messy to apply.

Re: Ready to skin... I think

PostPosted: Mon Apr 10, 2017 12:54 pm
by Gunguy05
+1 for the osi.... It will quite literally stick to anything, and it stays flexible. I've had mine sealed for 2 years now without an issue. I overlapped the seams about 4 inches with 2 or 3 beads of the OSI underneath. I used #8 pan head stainless steel screws and washers about 4 inches apart. It's as tight as a boat.

I wouldn't use butyl or putty tape for the reasons mentioned above. I'm using that now on a shasta restoration, and it's a completely different beast.

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Re: Ready to skin... I think

PostPosted: Mon Apr 10, 2017 7:27 pm
by Rasmateo
I appreciate the info guys, I'll stay away from the tape. Should I use the osi for windows and doors as well? What is the minimum you would overlap? Once again, I appreciate your help.

Re: Ready to skin... I think

PostPosted: Tue Apr 11, 2017 8:05 am
by aggie79
Rasmateo wrote:I appreciate the info guys, I'll stay away from the tape. Should I use the osi for windows and doors as well? What is the minimum you would overlap? Once again, I appreciate your help.


I used sealant to seal the overlap seams of my aluminum sheeting, trim and attached hardware...but for the windows I used butyl tape. Sealant alone will make it almost impossible to remove or separate the aluminum. Butyl tape will allow the windows to be removed in the future.

For the windows, I applied butyl tape and tightened the screws so that there was some squeeze-out of the tape. Be careful not to over-tighten or you will distort the window and door frames. After about a month in hot weather, the butyl tape "oozed" slightly, so I re-tightened the screws. Then I used an Exacto knife to cut off the squeeze-out and sealed around the edge of the butyl tape with sealant to keep the butyl tape from drying out and cracking over time.

Re: Ready to skin... I think

PostPosted: Tue Apr 11, 2017 6:42 pm
by Rasmateo
I was thinking of overlapping 2-4 in, is that enough?

Re: Ready to skin... I think

PostPosted: Wed Apr 12, 2017 5:45 am
by aggie79
I used a 2" overlap. That put the fasteners 1" from the edge of each sheet.



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Re: Ready to skin... I think

PostPosted: Wed Apr 12, 2017 8:38 am
by Rasmateo
Thanks,I appreciate all your help. By the way, your trailer looks awesome!

Re: Ready to skin... I think

PostPosted: Wed Apr 19, 2017 5:10 pm
by Rasmateo
I'm planning to run stainless panheads where the sheets will meet. What about the edges of the trailer (sides, top, and bottom)? I'm planning on running some trim. It seems like I wouldn't want screws getting in the way of the trim, right? On that subject, where did you guys get trim for your trailers?

Re: Ready to skin... I think

PostPosted: Wed Apr 19, 2017 10:31 pm
by Andrew Herrick
Nothing wrong using stainless steel pan head screws to secure the lap joint. Personally, I prefer aluminum rivets, but both work well! Don't space them too far apart. I think the rule of thumb with rivets/shear screws is not to space them more than eight diameters from each other. You can play a little loose with that number. I use 1- or 1.5-inch spacing. And I think a 2-inch overlap is PLENTY. Anything more than that sounds wasteful.

Most teardrop builders use extruded aluminum RV trim. Dimensions vary, but most roof-to-wall joints use a trim with a 5/8-inch leg and a 1-1/4-inch width. Don't get the trim with the 1-inch leg unless A) you can anneal it with a propane torch or B) you want to kerf it or C) you have a sweet pipe bender. It won't bend without severely crimping the sides. Depending on how you built your walls, you can either use the same 5/8x1-1/4-inch trim for the bottom edge, or use flat trim. All trim has predrilled holes for screws. And you purchase a 3/4-inch or 1-inch vinyl insert that folds into the trim channel once installed.

This trim is sold by many teardrop builders (Vintage Technologies, Oregon Trail'r, etc.). Expect $12 - $15 per 8-ft length + shipping costs. I think you can find other threads on this issue.

Lastly, do yourself a giant favor, and before you install the roof edge trim, tape the corner butt joint with your choice of permanent waterproofing tape. Then seal and add the aluminum trim over that. It's the easiest, foolproof method to prevent leaks. Again, search other threads for things like EternaBond or Tite-Seal.

Is your head spinning yet? :p

Re: Ready to skin... I think

PostPosted: Thu Apr 20, 2017 8:03 pm
by Rasmateo
Thanks for the info, head spinning a little. 8 cm apart for screws correct? I'll check the other threads for sealing, thanks again!

Re: Ready to skin... I think

PostPosted: Thu Apr 20, 2017 10:07 pm
by Andrew Herrick
Rasmateo wrote:Thanks for the info, head spinning a little. 8 cm apart for screws correct? I'll check the other threads for sealing, thanks again!


I'm about to do the unforgivable: math.

If you use #8 screws, which are 5/32-inch in diameter, then eight diameters would be 40/32 inches or 1.25 inches.

So if you follow the old truism to space rivets/shear screws no more than eight diameters apart, then you'd want to space your screws 1.25 inches apart. That's about 3.2 centimeters.

With that said, we aren't building airplanes. I usually go with 1.5 inch spacing, because A) I like how it looks B) it's easier to measure and C) I know it'll clamp the overlapping metal. If you want to go with 8 cm spacing (that's about 3.2 inches), then that'll probably work just fine. The only downside is there's a little more possibility for future leaks. How much, I don't know ...

I guess that's the long way of saying, "Full steam ahead!"