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Roof construction

PostPosted: Tue Jan 16, 2018 9:39 am
by Twalt87
Just a quick question, my trailer is 5x8 and I want to do the roof out of 1/8" maple. Due to the size, I will have to flip my roof panels sideways and cut them, how to you guys hide the seams where each sheet meets? I'm going to clear fiberglass the whole trailer.

All I can find are builds using sheet metal for the roof skin. Is using plywood for the roof skin not advisable? Being in a small area in Canada, metal supply stores are far away and expensive.
Which is why I decided wood skin for the roof, plus I like the look more.

Re: Roof construction

PostPosted: Tue Jan 16, 2018 10:30 am
by linuxmanxxx
Twalt87 wrote:Just a quick question, my trailer is 5x8 and I want to do the roof out of 1/8" maple. Due to the size, I will have to flip my roof panels sideways and cut them, how to you guys hide the seams where each sheet meets? I'm going to clear fiberglass the whole trailer.

All I can find are builds using sheet metal for the roof skin. Is using plywood for the roof skin not advisable? Being in a small area in Canada, metal supply stores are far away and expensive.
Which is why I decided wood skin for the roof, plus I like the look more.
Frp would be your best bet to not worry and less to deal with and should be easily available. Unless you love fiberglass layup.

Sent from my Pixel 2 XL using Tapatalk

Re: Roof construction

PostPosted: Tue Jan 16, 2018 11:22 am
by Socal Tom
Twalt87 wrote:Just a quick question, my trailer is 5x8 and I want to do the roof out of 1/8" maple. Due to the size, I will have to flip my roof panels sideways and cut them, how to you guys hide the seams where each sheet meets? I'm going to clear fiberglass the whole trailer.

All I can find are builds using sheet metal for the roof skin. Is using plywood for the roof skin not advisable? Being in a small area in Canada, metal supply stores are far away and expensive.
Which is why I decided wood skin for the roof, plus I like the look more.
If your roof is curved, plywood will be tough to bend, you may want to use multiple sheets of luann. A lot of folks use just paint, or PMF ( poor mans fiberglass). Real fiberglass should be fine if done properly.
Tom

Re: Roof construction

PostPosted: Tue Jan 16, 2018 1:09 pm
by tony.latham
Is using plywood for the roof skin not advisable?


1/8" plywood is fine for your roof. Especially if it is sandwiched over hard foam and fiberglassed. There's been many a fine "woody" done this way.

As far as hiding the seam... all I can suggest is to make sure you get a tight butt joint and live with it. The joint should be high enough up on your 'drop that it shouldn't jump out. I think people seem to focus on a teardrop's profile. Not so much the roof.

The roof on this little 4x8' was built using 5'x5' Baltic birch (over hard foam, 12" OC spars and another layer of birch forming the ceiling) ––so the seam is a foot higher than on your build. (And it was sheathed in aluminum). I just don't think it'll be a big deal.

Image

Tony

Re: Roof construction

PostPosted: Tue Jan 16, 2018 2:40 pm
by Twalt87
Thanks for the replies everyone. We will be doing a proper fiberglass setup. My gfs dad has made several canoes and even a 24" boat with a cabin all finished with fiberglass. He is more then happy to help us apply the stuff and let us use his heated shop for that part.

So as far as building goes, do I just fallow the same tutorials as the metal roof builds? Is it the same process? I was thinking of doing 1/8 shell, 3/4 foam and frame and 1/8 interior shell.

Re: Roof construction

PostPosted: Tue Jan 16, 2018 8:03 pm
by azgreg
You could use a small strip of decorative wood like Bryan (ratrod71) used on his build.
http://tnttt.com/viewtopic.php?f=50&t=61738&start=30

Re: Roof construction

PostPosted: Tue Jan 16, 2018 8:45 pm
by Xanthoman
As a trim carpenter I have found 35 degrees for the best continuity of surface. It is enough to widen the joint a bit more than the butt joint but not so sharp it leaves a near nothing tip as a 45 angle would produce. I prefer installing the upper sharp panel first and then tucking the next panel underneath it until the joint is flushed tight. I will often only secure the preceding panel up to about 1” away from the joint so it’s not deathly right to fiddle with while installing second panel and then secure once the second goes in.. This goes for all baseboards, deck fascia, soffit and fascia; pretty much anywhere a continuous seam is needed. As you may know with strip boats, the angle is sometimes easier to achieve with a pass of a hand plane rather than a floppy material on a table saw. Butt joints would probably be sufficient, but if it was me I would do a quick hand bevel.

Re: Roof construction

PostPosted: Wed Jan 17, 2018 3:06 pm
by tony.latham
For my ceilings, I butt the two pieces of Baltic, and glue a 4" strip on the back side with TB2.

Image

Image

It's a strong joint and I think it looks fine on the ceiling ––especially if placed where the fan will break it up.

I haven't done it that way on the roof pieces since I can work it out to place the joint over a spar.

Tony

Re: Roof construction

PostPosted: Tue Jan 23, 2018 8:57 am
by earl84
Technique from Steve Frederick’s build book: Clamp the two sheets together butted one to the other. Run a very small straight cut router bit right down the butt joint. When placed together, the two pieces will be the absolute tightest joint you can make. I used this technique and it works great. I then did like Tony and glued a 4” strip on the back with TB2 for strength. Works great, almost invisible if your adjoining sheets color and grain are very similar.