Fiberglass spacer

[Rick kl]

I am installing a new roof vent, it is made for a roof 1 1/4" - 2" thick, my roof is 3/4" thick , I was thinking of making a 3/4" spacer to go under the new vent out on the roof.If I make it out of wood and then coat it with resin,

would I have to use the fiberglass flock?
would this make it waterproof ?
anybody have any other suggestions?

[Donna D.]

Rick, that's also one of the main problems we hear about from members installing Fantastic Fans, etc. Here's a topic to check out, there's even a link to a helpful video:
Need Help With Installation of Fantastic Fan in Scamp

Hope it helps

[Rick kl]

The vidio talks about putting the spacer on the inside of the trailer I would like to put outside on top of the roof so the fan will be flush with inside roof. I have a few tall friends that just make in the raised section, if the fan was to extend down it would be a hazard.

[Raya]

Rick,

You could purchase pre-made fiberglass (FRP), which you can buy from a source such as McMaster-Carr in sheets, angles, tubes.... you name it. I use this quite a bit on boats where people might also use resin-coated plywood. It's heavyish, but you probably wouldn't be using enough to matter as compared to resin-coated exterior plywood.

The FRP is a bit harder to work (in terms of tools), but less prone to water ingress problems. It's also quite strong and uncrushable, and you can tap it for fasteners (for this we usually use GP03, the red colored one).

Anyone can order from MC (no need to be a business), and they often deliver the next day (on a normal shipping charge).

If you can get one of their paper catalogs, well, that's on my "Ten Books to Take to a Desert Island" list (they're hard to get though). On the other hand, they're one of the few companies I've seen who have a really good online catalog, and they're also quite helpful on the phone. (There's lots of materials information in the paper and online catalogs.)

Here's the red FRP board, for example, in a 1/2"x12"x12" sheet for about $19:

http://tinyurl.com/68fmb9

And their main page:

www.mcmaster.com

You can paint the FRP with whatever you usually use outside: Two-part LPU, one-part "poly" such as Brightsides, etc.

Raya

PS: Oops, I didn't address one of your questions: If you do use resin-coated plywood, you don't need to wrap it in cloth, in my opinion. You're going to have holes into it anyway, and if water were going to get in, it would do so at the holes much sooner than through the resin coating. You could over-drill, fill the holes with thickened epoxy, and then re-drill your smaller holes, but then you might as well just use FRP board.

[kconley]

If you go to a boat shop or West Marine they sell a white composit thet is used in marine applacations & can be cut & shaped. I think it comes in different thickness.. It will last forever & could be sealed & screwed tight from inside... I did a frame on the inside out of wood, It looks great. I got a fan that has a light around it, so we have a overhead light...

[Rick kl]

The fan I bought has a light and a power lift gizmo, The composit materials from West marine would work great except I am far inland and the cost would be prohibitive, I was hoping for a quick remedy like fiberglass covered wood with some paint to match the trailer, I was going to use butyl tape on the mating surfaces, I could use cedar so if any water does seep through the screw holes if would still last a long time.

[Raya]

Personally, I would advise against the "white composite," assuming you meant "Starboard" or "marine lumber," as it's sometimes known. The problem with this material is that caulk and adhesives do not like to stick to it. It's also subject to "creep" under load, although this wouldn't be as much of a concern with something light like a fan. You also cannot paint it, although that doesn't always matter. It tends to get dirty and can become unsightly. Not that it does not have its uses, but I would advise against it when sealant is going to be involved.

If you're looking for something "quick," resin-coated plywood is probably your best bet. Just be sure to pre-drill the holes and coat the insides with resin.

Or, you could just go with "plain" exterior plywood, if even the aforementioned is impracticable considering your time frame. Painted, it will last quite a while as long as water isn't sitting on it.

Whatever you use, the paint will stay on better if you radius the edges.

Not to sound prissy here, but I find that when I try to do something like this with an "I'll get this done quickly" mindset, it usually doesn't work out that well (especially in the long run). I've had to learn to tell myself that I'm just going to work away on it until it's done, and try not to think about trying to get it done fast. It is so tempting to just want a project done though


Raya

[Rick kl]

I am not trying to get anything done quick, I live in Saskatchewan and we are blessed with a thing called winter so the trailer is not being used for the next 4 months, however I am a bit of a cheapskate if I can get away with a $2 fix I will go that way.

Most of the plastics and other composite materials are subject to thermal expansion, the temperture here in the summer can be 40 above and 40 below in the winter if you use two types of material eg. aluminum and poly board they will expand and contract at different rates, this will loosen fastners such as screws and pop rivets causing leaks.

I will use solid wood (fir) instead of plywood, predrill the holes with a fortsner bit then fill the holes with resin (good idea Raya), I was just wondering if I had to use the fuzzy stuff with the resin.

[Raya]

Rick,

I misunderstood and thought you were looking for something quick - sorry about that.

[drdoyle]

Rick, There is a wood called Ipe ("E-Pay") sometimes called peyalopey (sp) - it is indestructable. It will not rot, bugs will not eat it even underwater. It is dense (does not float - will sink in water). It is easy to work with a router (carbide tipped) and will take a beautiful varnish finish which looks like Mohagany. You can tap treads into it or drill through, the drilled holes will not rot out. If left outside uncoated it will turn grey like teak, but will not deteriorate. Ipe is commonly used for decking material and wood pathways in state parks. The only disadvantage that may be an advantage is the fact that it will not bend and if you build decks with it all of the holes for nails of screws (decks are usually screwed with SS deck screws) must be drilled for a lead hole. I use this wood for all kinds of trim projects. You can find references with an internet search, but your local specialty lumber store should know where to get it. --Dan--

[Frederick L. Simson]

My Fiber Stream had a frame built up out of 2" x 4" lumber (laid flat) around the cutout. I covered all of the wood with Eternabond Roof Tape and installed the vent on top of that.




I also made a 1" x 2" trim piece of wood for the inside, between the ceiling and the "garnish" that comes with the fan.

[Bigsky1]

Originally Posted by Frederick L. Simson

My Fiber Stream had a frame built up out of 2" x 4" lumber (laid flat) around the cutout. I covered all of the wood with Eternabond Roof Tape and installed the vent on top of that.

Attachment 17312


I also made a 1" x 2" trim piece of wood for the inside, between the ceiling and the "garnish" that comes with the fan.

Attachment 17313

Thanks for this post - you just solved my problem with my after market fan and the garnish on the inside of the trailer. I am going to do the same fix you did - thanks Frederick!! Todd