Vent Fan Rough Opening & Options

[jeff]

My 1983 34V has two of three vent fans not working. One of them even has the motor and fan blade component removed. Appears to be a 13 x 13 inch rough opening, but everything on the market is 14 x 14.

I saw one other thread about someone modifying the opening an inch to accommodate the new size, but wanted to query the group for other "new" options.

Thanks for any input!

[silverloaf]

My 1983 34V has two of three vent fans not working. One of them even has the motor and fan blade component removed. Appears to be a 13 x 13 inch rough opening, but everything on the market is 14 x 14.

I saw one other thread about someone modifying the opening an inch to accommodate the new size, but wanted to query the group for other "new" options.

Thanks for any input!

We had a 13 x 13 fan opening in our '88 30P. The corners were radiused. Is this similar to yours?

I was able to install a new 14 x 14 MaxxAir ventilator with a little surgery around the existing opening in the roof.

[jeff]

Yep - the corners are rounded on mine too. As part of your surgery did you just have to shave the "lip" - I have about 1/4 inch of edge, and if removed would give me about 13.5 x 13.5 squared....or did you have to create a 90 degree angle on the corners?

Thanks for replying.

[silverloaf]

Yep - the corners are rounded on mine too. As part of your surgery did you just have to shave the "lip" - I have about 1/4 inch of edge, and if removed would give me about 13.5 x 13.5 squared....or did you have to create a 90 degree angle on the corners?

Thanks for replying.

Jeff-
Unfortunately, my picture file is not available for immediate access. If I recall, the aluminum extrusions that form the rounded opening in the roof are not structural to the roof. The extrusions are actually riveted to the sides of a square box formed by 2 structural roof supports. If you pull down the interior roof skin slightly, you might be able to see the structure beyond the rounded extrusions. When I cut out the rounded extrusions, I found adequate rough-in space for a 14 x 14 ventilator. An angle grinder and vibrating saw worked well for this.

If I recall, I did not cut the roof skin to the edges of the box. The opening would have been too wide for the ventilator's sealing flanges. Instead, I cut the skin just wide enough for the fan housing to drop in. I took necessary precautions to protect the wiring and connections. There's lot's of places for metal to rub against wiring.

Lastly, a previous owner had already replaced the other two ventilators with Fantastic brand; neither of them worked. I installed 3 MaxxAir ventilators, model 00-04500K. I am very pleased with their performance.
https://www.airxcel.com/maxxair/products/fans

[jeff]

Bob,

Really appreciate the detailed reply. I am trying a couple bootleg options before I go the surgical route, and will report back to the group if I found anything workable. Otherwise I will probably do what you did here.

Glad to hear that you didnt have to suffer any removal of external skin or structural items to make this work...

[silverloaf]

Jeff,

You will quickly learn the roof around the fan opening is not flat, making sealing a challenge with the newer ventilators. I built up layers of butyl tape around the opening to create a uniform surface for the fan's flange. I then snugged the fan down with sheet metal screws.

I followed up with a sealing tape over the flange. "Eternabond" seems to be the go-to material among the Avion crowd for sealing seams on the roof. I used a 3M product designed for shipping containers and trailers. Either one works well to keep things dry.

Good luck, my friend!

[Overdrive]

I just installed two fans replacing the old original ones. The roof is framed for a 14x14 opening. They just cut the opening smaller and radius it because the fan body is radiused itself. Once you remove the fan housing you’ll see the aluminum ribs and cross bracing. It took me about 4 hours to do both fans.
I dint take any pics but it’s really a straight forward addition.

Your hardest part is cutting the roof. I used a metal cutoff wheel but a pair of shears will work. You’ll also need to cut the same square inside the trailer. I’ll go up there this weekend take ad post some pics.

[silverloaf]

Glad everything worked out for you!

[Overdrive]

I’ll put up some pics this weekend of roof and inside