Drilling vent holes - scary stuff!!! - Fiberglass RV

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Old 09-05-2013, 11:06 PM   #1
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Name: Tom
Trailer: 32' 2007 Keystone Cougar TT
New Hampshire
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Unhappy Drilling vent holes - scary stuff!!!

I need to drill two 4" vent holes in the sidewall of my 2007 Keystone Cougar. I have bought a 4" hole saw for this purpose but I am stuck at this point. How can I determine proper placement of these holes so that I don't cut through any studs, thus weakening the units integrity? Is the 4" hole saw the way to go, or is there a better approach? Do I cut from the outside in? How do I determine and avoid stud locations? Will a standard carpentry type stud finder work on fiberglass? I would greatly appreciate any thoughts or suggestions on this problem.

This project is to install a portable A/C in the bedroom. The unit on the roof works great until the temps hit the 90's, and then the bedroom becomes like a suana. The vent holes are to install intake and exhaust vents. Also, any thought on how far apart these vents should be to avoid sucking warm exhaust back into the intake vent? I had considered a second roof unit but decided that my roof would not support it.

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Old 09-06-2013, 05:51 AM   #2
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Name: bob
Trailer: 1984 u-haul ct13; 1996 Casita 17 Spirit Deluxe; 1946 Modernistic teardrop
New York
Posts: 3,704
Try a stud finder. Also consider the possibility of any wiring in the wall. Can you make a small opening on the interior wall to see what's in there first, then cover it with some kind of trim piece if necessary.

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Old 09-06-2013, 06:53 AM   #3
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Name: Bob
Trailer: 1973 Hunter Compact II
Posts: 7,914
As they "might" have said in The Treasure of the Sierra Madre; "Studs, we ain't got no stinkin' studs".

About 99% of the trailer owners on this site have molded fiberglass trailers, all built without studs, and none big enough to have to worry about needing a second a/c for the bedroom (LOL)

The technique I have used is to cut a 1" hole in the area I wanted to explore and then use that to look around inside. If it proved to not work out I could always stick a small 4" diameter vent cover over my boo-boo.

You might get better information and help on a site for your make trailer and/or on sites for what we refer to as "stick-built" trailers.

That said, I once tried to use a stud finder and it just kept pointing at moi! (LOL)
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Old 09-06-2013, 07:30 AM   #4
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Name: Steven
Trailer: Currently Shopping
NW Wisconsin
Posts: 1,933
Drill a small hole in the location you desire the 4" hole . Stick a small piece of stiff wire bent in the middle through the small hole and try to rotate the wire in the hole , If there is something in the way the wire will hit it. It is a lot easier to patch a 1/4" screw hole than a 4" screw up .
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