Thread: Newbie Fibreglassing Questions

Interesting thread on the camping site - you seem to have most of it down pat!

I liked the initial testing of the ply, and the pic of the worn out jigsaw blade from cutting out your tailgate mistake!

If you haven't already, read the butt join how-to guide at West Epoxy.

Basically, for butt joins, apply the fabric, epoxy it all up, let it get to that 'tacky and rubbery but not hard' stage (a couple of hours after initial mixing), trim the fabric edge with a straight edge and a stanley knife, pull off the offcut (gentle persuasion with a chisel can be used if it is a bit too hard...), and voilà! there is your neat butt edge, ready for the next piece (which you overlap and trim with the stanley knife when that pieces epoxy is rubbery).

If you are going to be doing it over a few sessions (rather than spending a day doing epoxy - letting it firm up, turn over, prep butt edge and put on the next piece of fabric), a strip or two of el-cheapo duct tape can be used to keep epoxy off the timber so that when you rip the duct tape off you have clean unglued timber for the next piece (use the duct tape as your 'cut on this line' guide).

The joy of Bote-Coat is the nice feature of not getting amine blush (so no cleaning required if gluing to fully cured epoxy) - good feature if you are doing the job over a number of weekends.

When doing the fabric, aim to fill the weave over two or even three epoxying sessions - first one just gets the cloth on without wrinkles, then while it gells up you get the next batch of epoxy (thickened) to fill the weave - you really don't want to be sanding the actual fiberglass fabric to get it smooth!

I think I'd glass each corner first say about 2" either side, cut strips with the weave at 45 deg to the edge wet out go back and fill the weave when it's tacky then when cured grind/sand back to a feather edge. Next step glass each side while horizontal (much easier to avoid runs). After the weave is filled and cured sand back the slight overlap at the the edge glass.

One thing if you haven't already run a router 19mm roundover bit along each corner that will make laying the glass over the corner and wetting out go well and avoid bubbles that are a problem around a sharp edge.

Boat Coat is less blush reactive, but it will and can blush. There's no such thing as a true blush free epoxy (okay there is, but generally not available to the public). For this reason, all back yard users should consider their epoxy blush prone and clean each coating, before subsequent coatings. Unless you have environmental control over the work space, this is just good insurance you don't have a delamination issue down the road.

Do the sides of the camper first, starting at the bottom and work your way around with a full width of fabric (usually around 50"). If you need to continue up the sides with more fabric (camper sides are taller then the fabric is wide) put on a second wrap of fabric, cut flush to the top. Over lap the first layer with this second side wrapping by an inch or two.

Now, with all of the sides sheathed, you can move onto the top. Cut a piece to drape over the top with 4" to 6" over hang. If the fabric isn't wide enough to cover the whole top, make a seam down the center line (a few inches of over lap).

The rule is work from the bottom up, so successive layers of fabric over lap the previous ones and can shed water off. If done the other way, you can catch water in a bad spot or incidental damage area.

Light weight cloth will not give you any real strength increase, but it will improve water proofness and abrasion resistance. If you want water proof, then you need to overlap, not butt join. Butt joints are for people afraid to smooth out a finish after they've applied 'glass.

Log onto www.westsystem.com and wwwsystemthree.com and download their user's guides. These will cover the basics. Also log onto Mik's site Michael Storer Boat Design - Wooden Boat Plans - Australia USA UK South Africa and check out his excellent epoxy use, application and technique section.

Thanks PAR!

This link drops you in the epoxy and glassing section.
FAQ - Boat Building and Repair Methods - Plywood Epoxy Fibreglass Cedar Strip - Michael Storer Wooden Boat Plans

MIK

Well this must just about be a record for asking a question and then not responding to the great replies. I beg your humble apologies for not thanking you all for getting back me so fast. I have loads of excuses but none of them really matter.

@Master Splinter
Thanks for all the comments and glad you are enjoying the build thread. I've read the West’s Guides and have the BoteCote book too. I'm kind of ok on the techniques and the joints but was more interested in thoughts on how to actually lay-up the cloth. Either wrap the full width cloth around the box covering as much as possible in one go or cut it up into panels for each side? Or cut strips for the corners and then fill in the panels afterwards?

@m2c1Iw
Doing the edges first was one of the ways I was thinking of doing it as it would ensure that the joints are definitely strong. You say to feather the edge and then overlap with a panel infill and sand the joint flat. However, every thing I have read says not to sand the glass itself as it weakens it. Only sand the resin. Would a butt joint as Master Splinter describes be better or does it still retain strength ok if the edge is feathered and overlapped?

@PAR
Thanks for a detailed response as always. You are saying wrap full cloth pieces and overlap the joints. If you read my thread you will see it's not a tradition USA-style slide-on truck camper but is a significantly smaller camper box. I have 1.5m wide cloth so one layer will cover each side but I don't like the idea of having an overlap cloth joint on every edge. How do you finish this overlap off smooth? Are you talking about fairing? Why are butt joints bad? Why are butt joints not waterproof? Wouldn't the resin provide the waterproofness and not the cloth? As said before, it's just a small box so I wasn’t planning on fairing the whole thing just to transition an overlapped joint and the finish is definitely not going to be 'boat' quality.

@Boatmik
I have spent a lot of time on your site. Cheers.

Pleasure to help.

MIK

Originally Posted by Heifer Boy

@m2c1Iw
Doing the edges first was one of the ways I was thinking of doing it as it would ensure that the joints are definitely strong. You say to feather the edge and then overlap with a panel infill and sand the joint flat. However, every thing I have read says not to sand the glass itself as it weakens it. Only sand the resin. Would a butt joint as Master Splinter describes be better or does it still retain strength ok if the edge is feathered and overlapped?

Hello again,
PAR describes the procedure far better than but I will say you will be surprised how easy it is to achieve a smooth finish using an overlap joint. If you build the epoxy coats sufficiently over the area of the overlap sanding back with a random orbital sander will give you a pleasing result. When working with epoxy horizontal is best where possible it saves a lot of sanding back of sag/runs that is why an overlap at the edges would be preferable to wrapping a length of glass over a corner, not to say you shouldn't just for a first attempt it may save some grief till you have worked with the pox a bit.
I reckon in this case strength is not a priority so an overlap is not imperative other than to ensure you achieve a good seal of the ply but I think you will find it a lot easier than a butt joint as they can be very fiddly in my experience and yes there are other methods to retain strength when feathering an overlap but again I don't think it necessary with this job.

The good thing about glass and epoxy is if you stuff up just grind and sand it back and have another go which means it is probably a good idea to break the job down into sections you will get the hang of it pretty quickly.

I had a good think about it last night and I agree that for me it would be easier to work in sections so I'll cut my cloth and do the edges first and them infill on the horizontal.

I'm still concerned about sanding the glass at the overlap though. I guess the final coat of epoxy will cover that. Would the process be like -

1. tape corners
2. fill weave wet on wet on corners then let dry
3. feather edges of tape and lightly sand the rest (this will expose weave in some places)
4. layout infill panel and wet out
5. fill weave wet on wet on panel then let dry
6. sand it flat (this may expose weave in high spots)
7. final expoxy coat to seal everything up

Or do I apply that final coat after step 5 wet on wet and then sand it back flat so I don't get through to the weave?

Well that is what I would do and should avoid things getting out of hand except shoot for one session of coatings on the panel. I think you will find 3 wet on wet coats will do it but leave plenty of time to keep adding coats as necessary better to be on the thick side than have the weave exposed and saves time not having to re coat.
After you have done one side and see how it works I'll bet you will be inclined to try PARs method to speed things up when working on the vertical don't be tempted to lather it on roll out coats well to stop sags.

Good luck

Instead of trying to fill the weave with more resin, it's often best (and more economical) to just let the previous wetout coat "go off" then come back with a light weight fairing compound. You'll fill the weave and start the fairing process all in one shot. It's still a chemical bond, just easier.

Fabric overlaps can be cut out if desired, but it's just as easy to "fair them in" with thickened filler then bother with a razor cut, peeling back the top layer, removing the overlapped layer, then rewetting the flap and hoping it will stay down. The only time I bother with this technique is when the weave is left to show, simulating a canvas covering. Other wise I just fair the overlaps in with thickened goo. A 12" drywall knife is a really good tool for this.

Two other possibilities to consider are using a cabinet scraper for feathering edges and removing bumps, and using peel ply to reduce or even eliminate the need for fill coats.
The cabinet scraper has the enormous advantage if doing a good job even if the resin is not fully cured. Sanding isn't possible until the resin is pretty hard.
Peel ply is easier to use where there are no compound curves, so it should work well on your job. It adds to the cost, but you use less resin, so there is a slight saving in materials there.

OK thanks for all the advice guys. I took a good look at my camper yesterday and thought about the lay out of the cloth. I'm thinking a mixture of everyones advice will get it done nicely.

Starting with the box upside down I'm going to do one big panel for the floor overlapping the edges by about 50mm. I'll to the underside of the overhangs at the same time with the same overlaps. Then I'll turn the box on one side, feather the edges of the cloth and then glass that side overlaping the previous edges. Then do the same on the other side. Then do a back panel overlapping the extra cloth from the bottom and sides. Then put the box the right way up and do a big panel covering the top and overlaping the front, back and sides panels. There will also be some smaller strips for around the doors.

This way I'm working on a horizontal surface for everything, I can apply wet on wet without having to wait for much to dry and sand and I get the correct overlaps as PAR described.

I'm pretty happy with this plan and should be starting in a day or too once I get the workshop cleaned up a bit. I'll let you all know how I get on. Thanks for your help.

Always overlap the fabric so that in it's normal position it will shed water. This means the last piece to go on is the one on top of the cap. If you do your 'glassing properly it shouldn't matter, but in reality, it does, so don't offer an easy path for moisture to get under a sheathing.

Originally Posted by PAR

Always overlap the fabric so that in it's normal position it will shed water. This means the last piece to go on is the one on top of the cap. If you do your 'glassing properly it shouldn't matter, but in reality, it does, so don't offer an easy path for moisture to get under a sheathing.

Done!!! Thanks again for all your advise. I was quite nervous starting out on this as I didn't want to stuff it all up after spending so much time on the box. But I took my time, thought about what everyone here told me and I'm very happy with the results. I'll be cleaning everything up and doing the final coats in the next few days and I'm confident it will come out nice an smooth and most importantly, waterproof. Not bad for a newbie

Check it out at New and Improved Camper Box Ver 2.0

Cheers,
HB