Roof Sagging On Our Bigfoot TT ????

[Kurt & Ann K.]

Good questions Linda, and I'm no expert. It's been many, many years since I've had my hands-on experience.
The tubes on my boat were simple cardboard mailing tubes.It's actually the cured fiberglass which provides the strength, The cardboard is simply a form used to create the shape with the cloth draped over it.
Use a "T" brace with the vertical part a little too long to fit. To protect your floor use a piece of plywood. The "T" goes against the ceiling and as you straighten the brace the ceiling will be forced to return to the original shape.
Details about how many layers of cloth and/or roving are needed should be researched at a boat repair yard. They can also advise about how temperature affects
cure rate.
Heating the fiberglass seems like a good way to start a fire.
Concentrated points of impact are what cause too much stress, I doubt if cracking will occur as long as the "T" is long enough to spread the stress. You are only trying to return the roof to it's original shape (and possibly a little more), not trying to gain inches more head room than was there originally. Wrapping the "T" with some rags should protect the ceiling then slide the bottom to apply the vertical pressure. A second person would be a big help if only as an observer. A long straight stick across the roof will provide evidence when it's been raised enough.
Anything permanent against the ceiling will eventually come in contact with someone's head!
The more info you gain, the better your chances of success,

Kurt & Ann K.

[Andrew Gibbens]

I'm 99% sure the 'half-tubes' in Frederick's photos are part of the mould that the body came from, so they are completely integral to the shell, not added on. So you can't copy those directly.

The idea of bolting or screwing anything thrugh the roof doesn't appeal to me - the stiffeners you add on the outside are bound to make rainwater pool up against the stiffener, so having bolt or screw holes just near that pool of water is asking for trouble, however good the sealing is.

So I like exactly what Kurt has descrbed which is external-only bonded-on stiffeners. It sounds like he's talking about whole mailing tubes, which would look really awful, but I'm guessing he meant tubes cut carefully down the middle to make half-tubes.

So here's a repair scheme. Sorry if it's long, but the detail may avoid potential problems.

1) Mark off where the half-tubes will go. They will stop 3" short of the sides of your roof bulge - I'm assuming that's what you're trying to straighten. If it's the whole roof, centre bulge and sides, then that's a much bigger job. I would guess that you'll need stiffeners spaced at 2 to 3 feet intervals - that may be just one or as many as three or four.

2) Mark off 3" all around the half-tube and really, really sand this area. Ideally you should sand through the (unreinforced) gel coat and just (just) start to see reinforcement fibres. This step is the single most important by far - skimp on it and everything else is a waste of time. Less than an hour of sanding per half-tube is skimping, unless you do the easy thing which is to put a 60 grit sanding pad in a small angle grinder and carefully (carefully) sand with that. When done, re-mark the half-tube positions that you've rubbed away.

3) Prop the roof exactly as Kurt described. The props will stay in until after the whole job is done (and then some). You might want to apply masking paper around each site, staying 1" beyond the sanded area, to save dripping resin on the rest of the roof.

4) Cut the half-tubes to length, chamfer the ends and stick them to the roof. This is so they stay in place while you're working, and so strength isn't critical. You could use a little resin and hold the tubes in place with masking tape till the resin goes off. I would do the same but using car filler (Bondo) as the adhesive. Remove all masking tape before continuing. Fill the chamfered ends of the half-tubes with Bondo so they smoothly taper down to the roof - square ends are not good.

5) I'm assuming you know how to mix and apply resin and glass - if not there are lots of guides, so I won't repeat it here. I suggest you apply four layers of 1-1/2 oz/ft2 (ounce per square foot) chopped strand mat in regular (clear) polyester resin - three is strong enough, and the fourth is for luck! Make the first layer nearly out to the 3" mark and then make subsequent layers a little smaller so you don't get a sharp step where they end. Apply two layers, let it cure and then apply the final two layers - four layers in one go is fine for a pro, but a bit much for an amateur. You could use the more expensive epoxy resin, in which case three layers is plenty, but it's a bit overkill for this job.

6) The next day, sand any bumps or spikes smooth - you won't get a smooth surface, all you're doing is knocking off the high spots. Now apply a generous coat (as thick as you can) of 'flow coat', overlapping the edge of the repair and covering any sanded area - 'flow coat' is gel coat resin, tinted about the right shade of white to match the existing roof, but it has a small amount of wax pre-mixed in it. This will provide the very best protection and watertightness - paint is definitely second-best to this. Without the wax, gel coat resin will never set, so if you can't get gel coat with wax in it (ie, flow coat), which you'd have to get from a fiberglass supply store, you'll have to use paint - a marine paint would be best.

7) Personally, I would leave the props in for several days, but 24 hours after step 5 is the minimum.

This won't give you a smooth glossy finish like theret of the roof - it will be white, it will be watertight and how often do you crawl around on the roof?

If you want to get real fancy, you could fair (smooth out) the glass after you've sanded it in step 6 with some Bondo and then sand that smooth before appyling the flow coat.

If you haven't used fiberglass before, I suggest you practice the whole of this scheme on a piece of cardboard or plywood first, to get some experience. Either throw it away afterwards, or mount it on your living room wall as proof of your new-found skills.

Any questions?

Andrew

[Frederick L. Simson]

I'm 99% sure the 'half-tubes' in Frederick's photos are part of the mould that the body came from, so they are completely integral to the shell, not added on. So you can't copy those directly.

Thanks, Andrew!
Close inspection of the interior surface would seem to confirm this. It looks like part of the manufacturing process added flat "patches" enclosing the underside of the ridges in the roofline. The exterior surface is completely smooth.

[Andrew Gibbens]

My guess is, Frederick, that most/all of the fiberglass layers go around the half-tube, then they filled in the hollow centre with some pre-cut pieces foam and a bit of filler, and finally slapped a layer or two of glass on the underside (inside). The foam never fits perfectly, so that's why you can see the slight bump on the underside. Actually quite good workmanship as the extra layers on the inside replace the front-to-back strength that is lost in the half-tubes.

What I don't like about it is the negative aerodynamic effect of those transverse ribs, but in truth I'm being picky.......

Andrew

[Kurt & Ann K.]

Good advice Andrew. Thanks for contributing to the info.
I was under the opinion that a layer of woven cloth would increase the strength considerably when added to several layers of the chopped strand mat (roving). My memory is that the first layer was woven cloth. Please correct me if I'm wrong.
It would be nice to have a body of info for the "tutorials".
Linda, please try to get step by step pictures of the process if at all possible. Probably best to leave photos to someone else though, because you'll be busy!
Use some TP or paper towel rolls to practice shaping the ends.
Once the process is over, you'll realize the project is actually relatively easy and kind of fun being creative with a different medium.

Mitch,
Are you soaking this up?

Kurt & Ann K.

[Andrew Gibbens]

Woven cloth is better (ie, stronger weight-for-weight) than chopped strand mat by quite a margin, but it's also more difficult to use - wetting cloth out is easier to get wrong, and mostly it doesn't conform to shapes as well as mat does.

If you are going to restrict yourself to buying only one reinforcement, then chopped strand mat is the cheapest, most universally available and most universally usable. If you are willing to buy products to start up a small fiberglass repair shop at home, then for sure other reinforcements would appear on the list! Having worked in a professional fiberglass shop, I see the biggest problem facing the amateur as locating and buying the materials in sensible quantities (and at sensible prices) - using the stuff is fairly easy by comparison!

Taking this one step further, the first place I found by Googling "fiberglass supplies san diego" is Fiberglass Warehouse - who seem to stock all that Linda might need. However even they don't sell pre-mixed 'flow coat' or 'topcoat' resin. They do sell white gel coat resin, so at least that avoids the expense and complication of buying white pigment to mix into clear gel coat resin - though their white certainly won't be a good match for old Boler white. So Linda will (would?) have to make her own flow coat resin by mixing in 2% by weight of what Fiberglass Warehouse call 'Surfacing Agent' into standard white gel coat resin.

Sadly Fiberglas Warehouse don't seem to provide much online assitance. The only place I know is a British supplier CFS Fibreglass Supplies and anyone wanting basic info might want to read their 'methods' and 'projects' articles. I don't doubt there is better information available online within the US - if anyone knows of it, I hope they post a link.

Andrew

PS All techniques recommended for fibreglass work just as well on fiberglass.....

[Kurt & Ann K.]

Linda,
Since you are in San Diego, Calif. you should have a number of choices for locating materials. Many paint stores sell fiberglass supplies, possibly even Home Depot or Lowe's. Automotive paint stores, boat supply stores and even boat dealers who sell supplies are other choices. For small quantities of cloth, a boat repair shop might be able to help. It appears as if a minor quest is in the offing.
The half-tubes on my boat were not filled with anything. In fact the ends were not even closed since they were on the underside of the bow deck and not visible unless one crawled in there. For your purpose, sealing the ends makes sense.
Again please keep us posted about progress, your ultimate sources for supplies, etc.
Andrew, thanks for sharing your expertise.

Kurt & Ann K.

[mitch]

Mitch,
Are you soaking this up?

Kurt and Ann !!
!!!!

Just checked out another BF last night and it had a sagging front roof too !!!

I'm heading to Florida for our winter break and will have my notes with me

I look forward to reading more when we're back .

Happy trails y'all !

[Linda of San Diego]

Kurt and Andrew,

Thanks for all the ideas. I am not quite ready to start this yet, but will soon. I have to do a lot more reading on fiberglass.

Linda

[Frederick L. Simson]

I have a sag in the front on my Hunter 1 (Compact II). It is right in front of the pop-up, but I don't have any cabinets inside to support. It is over the table in the middle. I do like the 1/2 tube ideal. But I also thought of a brace on both the inside and outside.

Linda

I just remembered this:

My Compact Jr. had a sagging roof along the left, or street side (Port side for you sailors ) This was because it was gutted when I bought it, and the wall between the galley and the bunk was removed.



I had never seen an intact Compact Jr. before I went about replacing the interior, so I did not realize that that wall would have supported the roof for the Compact Jr.'s full-length pop-top. I left it out.

The opening for the pop-top had a [b]4" high lip all the way around, to the outside of which I bolted a 2" x 2" x 8' angle iron along the two sides for strength. The fabric covered the angle iron on the outside.




I was thinking about you adding an angle iron stiffener around the lip of your pop-top...

[Andrew Gibbens]

I have a sag in the front on my Hunter 1 (Compact II).

Oh, shoot - Linda, I do apologize that I completely failed to pay attention to the 'Hunter' part - a short circuit sonewhere in my brain had me believing it was the roof of a Boler you were trying to fix! Pretty much everything I wrote is quite innapropriate for your trailer - with such a (relatively) low roof, this sort of repair would be too noticeable.

I should perhaps stop poking my nose in, but I'll leave with a question: is the sag actually in just the flat panel in front of the pop-up, or is the front of the pop-up opening sagging too? The cures would be different.

Andrew

[Roger H]

Bigfoot has a really interesting history of innovation and improvement in design. I haven't seen many trailers older than mine, and most that I've seen have been relatively new ones, but I wonder at what point they added the "double-hull" and foam insulation between? It sounds like their earlier construction was a simple single layer glass hull (standard construction) with large, flat areas that were essentially shored up with the inside structure and rafters covered by panelling. I think the two I have actually have inner and outer hulls (the inside may be fiberboard, but I think the core samples show fiberglass on both sides of the foam) filled with a rigid foam between. Since both of mine are new enough not to have issues yet, I haven't had to take them apart to see what's under the surface.

Roger

[mitch]

6) The next day, sand any bumps or spikes smooth - you won't get a smooth surface, all you're doing is knocking off the high spots. Now apply a generous coat (as thick as you can) of 'flow coat', overlapping the edge of the repair and covering any sanded area - 'flow coat' is gel coat resin, tinted about the right shade of white to match the existing roof, but it has a small amount of wax pre-mixed in it. This will provide the very best protection and watertightness - paint is definitely second-best to this. Without the wax, gel coat resin will never set, so if you can't get gel coat with wax in it (ie, flow coat), which you'd have to get from a fiberglass supply store, you'll have to use paint - a marine paint would be best.

Hello Andrew and all !! This is newbie , Mitch here. I have some fiberglass questions for you since you seemed to be the expert here.... We had to do some fiberglass repairs on the bottom of the fuselage where the awning brackets are bolted on. The holes where about the size of two golf balls side by side on each side.... We applied four layers of fiberglass mat and rezin stuff. It's been dry for quite a while now and we are ready to sand...Can we do this outdoors with sanding blocks or should we be using an electric sander ?? The largest section is a foot square. Should we wet sand it ??

We haven't searched for the flow coat or marine paint yet....Hopefully it won't be too hard to find here in Calgary...We don't have a lot of bodies of water here in the foothills of the Rockie Mountains...

Any advice would be great. Thanks all !! Mitch