Originally Posted by Rix
Sorry, blocks of wood for cabinet/framing stuff.
I put in a fair amount of blocking in my Sunrader. I did not put glass over it. You mix up some epoxy resin and thicken it, wood flour will be the least expensive. Make the mixture the consistency of stiff peanut butter so it does not run down the wall. Then spread it on the blocking and press it against the wall. To do a temporary hold here and there along the edge as a tack down while the epoxy sets I used urethane hot glue gun that set up within a minutes time. Not sure if the craft hot glue sticks would work for the job.
There is something you need to know about using blocking on a fiberglass shell. You don't put it out in the middle of the wall sections where there is a lot of flexing, you don't want to induce cracking of the shell or imprinting of the blocking into the shell shape. Keep your blocking towards the edges where bends happen or close to the join lines of the shell halves. It might not seem logical not to put it out there in the flexing center area but that is how it should be done.
On the Sunrader's they used an approach to the insulation and interior wall paneling that might seem to be insubstantial and illogical. However it does work and it allowed that light weight
shell to maintain some flexibility without inducing stress in it. It also substantially reduced labor cost because the walls floated over the join lines and other exterior details instead of each piece of blocking having to be a custom depth to account for the variations in the shape of the shell. The blocking they used was 5/8" thick. The foam was 1/2" thick which being applied with a thick construction adhesive make the insulation fit just inside of the blocking.
The shell is two angular halves but that interior wall gently curved to float over all the variations leaving a smooth inner surface. This method allowed them to fabricate the interior paneling,the blocking and the insulation on the walls on the factory floor using staplers and adhesive in caulking guns. So what they did was glue the blocking and the ridged foam insulation to the back side of the 1/8" wall panels, put some staples along the edges and where the 1/8" paneling met another section of it and then those prefabricated units were secured in place by being screwed to blocking that went into the plywood floor at the lower edge and then it was was clamped in position by the pressure of the window frames and the door frame. So all in all a very cost effective and efficient method of putting in the interior walls. Once you understand what the designers were doing and why you will realize it was actually a very practical system for handling the build up. When you start gluing blocking to the wall you will quickly learn about all those thickness variations in the shell and how it will take you a lot more time to level out to support the wall panels.
The roofs in the Sunraders were created as SIPS, structurally insulated panels. Before the upper shell was taken out of the mold a layer of urethane foam was added to what is the underside of the roof. Then adhesive and fiberglass skrim went over that and it was finished off by a sheet of plywood that had already been covered a vinyl wall paper. When you gut a Sunrader and take apart that SIP and toss it into the trash bit you have basically trashed the structural integrity of the roof. Now you are stuck trying to create a roof beam system to do the support work that was being done by that lightweight and strong SIP. Its strength having been created by those well bonded layers of materials. Unfortunately you can't get back to what was removed.
The strongest, smallest in size and lightest stiffener beams to strengthen the roof will be to create a hat section with foam covered with fiberglass. You could use wood as well, the strength is not from the inner filler, it is from the fiberglass over that substructure. But it must be done correctly with the layers applied in sequence as to width. This pdf file from West Systems will show you how to create them. http://www.westsystem.com/ss/assets/...aintenance.pdf
As to how you will get that curve of the roof back. You need to take a long board or piece of thick plywood and cut the bow shape into it. Then you will support it from underneath up against the roof pressing upwards until the roof is reshaped. You will likely need at least one pair of these spaced appropriate apart for building support beams. Then build your hat beams close to them and let those fully cure. Take out the pair of curved supports and move them then build the next set of hat beams in that position. Repeat until done.