Repairing belly seam, advice needed!! - Fiberglass RV
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Old 08-03-2020, 03:10 PM   #1
Junior Member
Name: Sonny
Trailer: 1975 Ventura
Posts: 28
Repairing belly seam, advice needed!!

I removed the belly band and I'm trying to figure out my next move. I plan on buying reinforced fibreglass filler and filling in the seam, although the gap is wide in some areas very small in others. There are screws running above the seam all the way around, should I take them all out? I'm worried about weakening the structure. Even though some are not grabbing anything anymore. There is also some give in certain areas above and below the seam, will this cause cracks in my fibreglass repair? I also need to do some filling work on the corners. Is reinforced filler the product I should be using or is this a job for cloth and resin? Thanks for any advice, I included photos. Sonny
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Old 08-04-2020, 05:50 PM   #2
Berthaduniverse's Avatar
Name: Paul
Trailer: Scamp
Posts: 62
I have a fair amount of experience in building fiberglass cars, and one thing I would never do is use a straight resin product (even if it is fiber reinforced) in a situation like this. Resin (and fiberglass as a whole), needs to have minimum contact areas and thicknesses to bond and not crack or tear away.

Additionally, I would never try to bond any resin product directly to gelcoat unless it was for cosmetic repairs. Gelcoat is essentially a resin based paint with no real structural (fibers) linking it to the fiberglass shot/layed over it. Also, by design, these seams need to flex, allowing a small amount of movement.

That said, barring any severe/structural cracks, I would clean, prep, and caulk the entire joint with proflex or zikaflex. Maybe trying a small section to learn how the products work and apply. If that works for you, then do the whole bead. Then re install the aluminum banding with a final upper bead of white (or almond) exterior silicone caulk. Don't caulk the bottom edge, as it allows moisture to escape.

That's my 2 cents.
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Old 08-04-2020, 07:52 PM   #3
Senior Member
Name: George
Trailer: Trillium
Posts: 197
There is a lot of info on this site on doing the band repair. I suggest you use the the F/G cloth tape as the final bonding material. I have used a aluminum tape with sealer on the inside when I wanted a quick temporary waterseal. Anyhow check out this site first for lots of advice.
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Old 08-05-2020, 12:32 PM   #4
Junior Member
Name: Sonny
Trailer: 1975 Ventura
Posts: 28
Any thoughts on putting butyl tape around the seam before reinstalling the band?
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Old 08-05-2020, 01:02 PM   #5
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John in Michigan's Avatar
Name: John
Trailer: 1978 Trillium 4500, 1979 Boler 1700
Posts: 1,715
Sonny, you could try searching "Ventura center seam repair" using the google box in the Search pull down link at the top of the page.

Many of us have repaired the center seam on a Trillium, and various techniques have been captured on numerous threads for that repair. However, I suspect the Ventura center seam construction is different than the Trillium, the Boler, and many other FGRVs.

The Trillium center seam has no wood, except that the Trillium 4500 center seam has a wood backing along the rear side. Other than this, the center seam is held together by a 4 inch wide strip of fiberglass applied around the inside of the trailer. To complicate matters, 40 or so small steel plates (about 1"x2" each) are sandwiched between the center seam and the 4 inch wide strip of fiberglass. The small steel plates rust out and then the aluminum trim that is riveted to the small steel plates pops out. Most owners grind out the steel plates, grind off the gel coat layers, taper the center seam edges and apply a fiberglass strip around the outside of the center seam.

Apparently the Ventura does not have a fiberglass strip applied on either the inside or the outside of the center seam, but instead, just wood inside and trim outside. Is this correct? If so, expansion and contraction may lead to leaks again if you use butyl tape. You may need a stronger bond, i.e., 3M 5200 adhesive or a fiberglass strip applied after grinding off the gel coat and tapering the center seam.
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Old 08-09-2020, 12:18 PM   #6
Name: Vanessa
Trailer: Ventura 73í
British Columbia
Posts: 31
I am nearly ready for primer after working thru this belly band task. ended up replacing inside wood/framing with 1x3 (with 2x2 PL glued - inside framing is all 2x2)... and whether itís right or wrong (maybe donít comment if Iím wrong lol). Put screws from outside, through fibreglass into wood. Then Sanded down to either thin gel coat or fibreglass (mostly in spots it was damaged or cracking). And then fibre bondo the seam. I did proper fibreglass patch work over other areas.. and added fibre bondo to smooth the surface... Iíve doubted this approach so much but now that itís done I feel better about the decision. Hereís a pic from early on in process.
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