new roof and rafters,ceiling on a 1997 sunline saturn t-17-a

[davesmary]

i need some help . everyone talking about bowed rafters .my rafters are 2x3 flat but at the ac it has like osb wood that's about 3/4 to 1 inch and the rubber roof material just ran over the osb wood i'm wanting use 3/8 decking on the roof . so do i have to make bow rafters to make the ac higher off the roof because it looks like the ac would touch the roof membrane it's 1997 saturn t-17-a any help would be great thank you

[JohnB]

Hi davesmary,

We may be learning/realizing something about Sunline's evolution in construction. The rubber roof started on the longer campers, and by 1996, all the travel trailers had the rubber roof. Yours is a 1997 T-17-A Saturn at 18' 4" (ball to rear bumper), 7 ft width, and has a rubber roof. The Saturn and Solaris models, having non-ducted AC of this shorter length, had 2 x 3 rafters. When they were 26 feet and longer, they had 2 x 4 rafters; I'm not sure if the 2 x 4 rafters were arched yet.

Which direction are the rafters placed? Is the 2" side laying flat, giving a 3" tall rafter, or is the 3" side laying flat, giving a 2" tall rafter?

You asked whether the roof should be arched or flat. Like many others, your camper was made with a flat roof, which you can reproduce if wanted.

By the time the 2000 models came, radiused arched rafters came standard on all campers regardless of length. This allowed rain runoff and helped prevent ponding water on the roof.

If you are going to reproduce the entire roof and ceiling, you have a choice to go flat or go with an arched roof. The flat is easier to build but not as good in water runoff. Ponding water can be a real issue over time, especially near roof openings. The arched roof offers good water runoff and no ponding water if you properly blend the roof deck into the front wall. The trussed arched rafter is more complex to build than a flat 2 x 3 roof. The truss rafters can allow you to vent the attic; I have done it, but I'm not sure you can do it very well on the flat roof. Venting the attic helps let hot air get out of the camper and not build up so hot in the high summer heat. Venting also lets moisture out from people being in the camper when the furnace runs while you are camping in cooler weather.

See this post on the 2004 T-1950, which is a little longer camper than yours and, in this case, 8 feet wide. It shows the roof structure in detail. While I used 1/4" plywood to save weight, I have also done them with 3/8" plywood, which can be directly walked on. There is a lot in this post, but you can skim the roof area later in the post if you want. https://www.sunlineclub.com/forums/f...avy-17684.html

If you want to go with the radiused truss rafter, let's talk about this. I am working towards gearing up to make the new radiused rafters different from the ones in the post above. The rafters will still look the same, but the wood-bending process to make them will be different.

Please post a few pics of your roof system once it is opened up. I'm curious about how they did the structure on the flat roofs.

If you need help posting pics, here are the basics.

There are 3 ways to add pics.

1. Upload pics to a specific post, attaching them at the end of the post.

2. Link them in from a publicly viewable web photo hosting service you have.

See here for 1 and 2 https://www.sunlineclub.com/forums/f...html#post86041

3. You can upload pics to the forum in your own personal photo album. Then, link them anywhere in the text of a post. See here for how to create an album. https://www.sunlineclub.com/forums/f...html#post87945

If you still get stuck, let us know. Pic's go a long way in helping show things you are working on, and we really like seeing Sunline pics!

I hope this helps.

John

[davesmary]

hey john got the roof all off i'm going to made bow rafter i need to know the height of a raft of a camper roof the center height . is 4 1/4 or 4 1/2 i know i can made any height i just need to know a starting point i think your right about the water run off i've got every thing tore off ceiling the rafter everything. i'm waiting on ceiling material. i'm using pvc roof membrane. starting on rafter in a few days i know the last rafter is lower than the other rafter i'm thinking about 1 inch 3 1/2 inch this is my first camper rebuild wow It's going fun but i got it thank you for your great help

[JohnB]

Hi Dave,

The Sunline main arched truss rafters are 4 1/8" tall, as measured from the bottom of the rafter to the top at the center, not including any ceiling board or roof decking.

That said, since you are creating an entirely new roof, you do not have to precisely adhere to the 4 1/8. You can pick 4 1/4 or 4 1/2" since you are creating all new ones.

A fellow club member asked about this last fall. This post may help https://www.sunlineclub.com/forums/f...uss-20878.html

Are you creating truss-style rafters or sawing them out of solid 2 x 6' or 2 x 10 or 12"s? I ask because if you are making truss rafters, let's talk about the process of the top arched chord. I found out the hard way the top arched chord has to be pre-stress relieved in an arched manner "before" you assemble it into a truss. If you force the top chord down, unstress relieved, over time (overnight, actually), it will bend up the bottom chord, which was dead straight when you assembled it into the shape of a curve, and the rafter becomes unusable. The stress trapped in kiln-dried wood is real!

When I create my next rafter set for a camper I'm restoring (maybe this winter), I'm researching a wood steam box to heat up the sawn straight top chord and then pre-bending it in a jig to hold it while it cools and dries. Then, I'll assemble it into a truss. It will be an experiment on how long the wood has to be held in the steam box. Bending wood is an art unless you are doing it commercially with automation or you learned from a master woodworker who made furniture, etc.

Here is a truss option. About a year ago, it was cheap, but I now see the price has doubled. https://www.rvsurplusparts.net/truss...-_7zG2iNrEr0FX

They could work for you. You would have to trim the overall length, but since I do not think you have roof AC ducts, these might work. If you have AC ducts in your attic, however, this will not work, as the opening in the truss is in the wrong place and too small, as they are using thicker chords.

If you happen to have pictures of the way Sunline made the flat roof structure in 1997, it would be interesting to see them and greatly appreciated.

Oh, and using PVC membrane, I have nothing wrong with using the PVC. I'm assuming yours might be the LaSalle Bristol PVC, right? These guys. https://www.lasallebristol.com/

A few tips to know on PVC or even TPO or EPDM.

1. Do not staple the decking down. Yes, it's fast, but the staples will back out and lift the membrane over time from towing down the road. Go with flat-head screws and get a countersink with a depth stop on it. Pre-countersink, then screw down the head dead flush. Do not go deep as there will be poke holes, and too high will create a stress cut in the membrane over time. Use a sharp edge putty knife to feel for high screws and hand screw them down.

2. Sand every sharp edge of the decking at the perimeter and the deck sheet joints. Make a 1/16" to 1/8" radius on the decking edge where the membrane goes over that edge. If that sharp 90-degree edge is left, it can crack the PVC or tear TPO; even EPDM is not found on these sharp edges.

3. Do not walk on wet PVC roofing. It is like walking on ice water; it is so slippery it is close to instant pain when you slip. For sure, make sure it is dry before climbing on the roof.

Good luck, and for sure, ask away any questions.

John