| Author | Message | ||
| Erston Reisch (Erston)
Registered Member Username: Erston Post Number: 5 Registered: 10-2006 Posted From: 70.89.134.94 Rating: N/A |
Hello all! Our '48 GM 4151 has a ill-planned and ill-conceived vent in the roof, directly at the top of the bus and about half way between the front and rear. The vent is rectangular, about 4" by 18" and isn't near a support rib. The cover is missing, but even without that the vent is leaking around the flashing (installed with 2" sheet metal screws!) and letting water in the bus. We want to remove it and patch the panel. I've done some searching in the archives and wasn't able to find any advice on what would be the best route to fix this. My original thought was making an aluminum panel of a similar type and thickness to the original skin (which would be...?) and then riveting it with aluminum rivets... and should I use "buytl tape" as mentioned in one of the archived posts? Thanks in advance for helping the newbies! ~ Erston and Blue | ||
| Busfool (Chuck)
Registered Member Username: Chuck Post Number: 71 Registered: 12-2004 Posted From: 216.209.123.11 Rating: N/A |
do you have access from the inside?If you do make two identical pieces and make a sandwitch use a buytl tube of caulking to seal it. Before you rivet put some screws into the piece to make sure that the new piece is completely tight then drill between the screws and put in rivets every inch or so then remove the screws you put in and replace them with rivets be sure the rivets you use are going to fit the screw holes or you may have to ream them out.This process works better than tape you can use this process with a piece on the outside only or with a piece on both sides the key is to make sure you put lots of buytle caulk all over the surfaces to be joined . Home depot has a fifty year caulk in the paint department.Chuck | ||
| Erston Reisch (Erston)
Registered Member Username: Erston Post Number: 6 Registered: 10-2006 Posted From: 70.89.134.94 Rating: N/A |
Chuck - yep, we have access from the inside (we will be finishing the gutting job on the bus). There are screwholes allready (the vent was installed with screws!) and I was planning on using the existing holes in the bus as a template and using a marker to transfer the hole pattern to the new panel. I guess I'll make two when I make them and make a sandwitch - makes sense that it will be stronger and more waterproof. Good tip on the screw hole size and rivet size... I hadn't thought through that far to realize that I may have to drill out the holes to round them out then go with slightly larger rivets. Now, anyone have any advice on what kind of aluminum I should use? Thanks! ~ Erston and Blue | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 349 Registered: 10-2003 Posted From: 71.58.126.56 Rating: N/A |
From the decription on the dimension,it sounds like a refrigerator vent like the one on mine. The vents are still available if you need to retain it. | ||
| Bob greenwood (Bob_greenwood)
Registered Member Username: Bob_greenwood Post Number: 387 Registered: 7-2006 Posted From: 4.90.5.117 Rating: N/A |
I'd use 16 guage & I'd make it 4 inches longer & 4 inches wider & either buytle or pure silacone | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 127 Registered: 7-2006 Posted From: 66.217.105.148 Rating: N/A |
Why use rivets on the roof at all? Sheet metal screws are the choice of most all RV shops, and screws allow for future tightening (or removal of the panel) if/when needed or desired.... (and screws don't have nasty holes through the center that eventually leak) | ||
| Busfool (Chuck)
Registered Member Username: Chuck Post Number: 72 Registered: 12-2004 Posted From: 206.172.106.74 Rating: N/A |
caution with the silicone you can't really paint over silicone too well that is why the buytle was suggested.The sheet metal screws is a good idea as well.Find some nice stainless screws.On my patches I used 16ga. material.On my roof caps I used 1/4" stainless bolts with locks and lock tight but made sure there was lots of buytle in all the screw holes. No leaks yet Chuck | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 36 Registered: 7-2006 Posted From: 4.240.213.186 Rating: N/A |
Sikaflex, PL and others work very well. We have three skylights.....no problems for several years.... far as I know. Stainless metal screws into the Aluminum with at least a 1/4 inch bead at the screw line...another around the cut. As FF says....works for me///  FWIW RCB '64 Crown Supercoach (HWC) | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 243 Registered: 11-2005 Posted From: 63.97.117.27 Rating: N/A |
Your roof is probably 0.060" Al alloy like my 4104 so I would recommend using the same thing for a patch. Go to the library and get a book on aircraft sheet metal repair or ask your friendly airport mechanic. Make a ring around the underside of the hole so it sticks out into the opening about 1.5-2.0". Use SS or Al industrial 1/8 or 3/16" pop rivets to rivet this ring to the bus roof then rivet the patch to the ring. Industrial rivets have solid centers. This makes the patch flush to the roof, stronger and better looking. Using this method all you need do with the old holes is fill them with sealer. Don't bother with aircraft driven rivets unless you already know how to use them or have a lot of time to learn. Forget the silicone, use the same silastic type sealer as used on RV roofs. Rivets are better than screws because they fill the hole and restore the metal to its original strength. GMC buses are monocoque construction just like airplanes, which means the sheet metal is a major part of the structure of the bus since it has no frame. | ||
| Brian Elfert (Belfert)
Registered Member Username: Belfert Post Number: 24 Registered: 7-2006 Posted From: 132.148.80.215 Rating: N/A |
What I did to patch two holes in my roof from vents I removed was to use aluminum from cutting other holes. I put a lot of poly caulk underneath before I started and then riveted the aluminum down. (Bulb-tite rivets, not pop rivets.) I then put another bead of poly caulk around the edge when done. Brian Elfert | ||
| Skip N (Skip)
Registered Member Username: Skip Post Number: 3 Registered: 11-2006 Posted From: 65.19.219.101 Rating: N/A |
I have a similar situation. The solution I came up with is to make a vent cover matching the interior. That way during cold or hot times I can open it for venting purposes instead of cracking a window open. For you I guess that would include a new exterior roof vent with proper screws or rivets. Skip | ||
| Erston Reisch (Erston)
Registered Member Username: Erston Post Number: 7 Registered: 10-2006 Posted From: 70.89.134.94 Rating: N/A |
Thanks for the replies, all! I'm in Seattle, so I'm going to go down to the Boeing Surplus store and see if I can score some 0.060 aluminum for patching it. I'll try to find some solid rivets of the right size (Aluminum, hopefully) and then make a patch sandwitch with butyl compound to seal the areas. Hopefully my rivet tool will work the solid type as well. John, now that I look at it, our fridge does indeed have the same kind of vent... but it still has it's cover. We don't want to keep it, as it is ugly, leaking and useless... and since my head brushes the roof in the center, we're trying to keep the center isle ceiling clear of additional things to whack my head on. Thanks again for the advice, y'all! Between this hole and the windshield gaskets that Luke @ US Coach has that sound like they'll fit, I will have a watertight bus... so now I can start rewiring the dash. Cheers, ~ Erston |