Restoring 20+ year old fibreglass kayak, need help..

Thanks Sam and PAR, great info, still just trying to decide the best way to repair it. Ive got the entire seam fully sanded and ready.

For an amateur such as myself, which option would be the hardest to screw up:

(Keep in mind that i had to sand a fair bit off the side, so boat will require repair to provide at least some structural reinforcement.)

1. Apply tape as per Sam's suggestion

2. Fill in gaps with epoxy (what is the fairing compound?) as per PAR

3. I have sitting here a fibreglass repair kit that I bought before i found boatdesign.net, which has .5 sq metres of fibreglass sheet, plus 500g of resin and catalyst. What are your thoughts on using that?

Again thank you very much, i am very grateful that you are all taking the time to introduce me to fibreglass ship building.

 

LOL "Fiberglass ship building." Something must have changed in the translation of "kayak". ; )

Well, the lip where the upper hull overhung the lower hull at the front of the boat seemed about as thick as the hull should be, more or less, so if you've ground it all flush it seems it's probably getting pretty thin there.
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PLEASE take out the one picture that is so wide. It makes the whole thread extra wide so you have to scroll. I had a bigger reply done but lost it scrolling around.


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If you want to add structure, you should use cloth and epoxy, preferably biax. The fabric you have and the resin are likely mat and polyester respectively. Mat will not offer any real strength to the area, just bulk it up and the polyester will not be particularity effective, in the thicknesses you plan of applying, so save these for something else.

To reinforce the seam, wetout the area with unthickened epoxy, then apply a structural filler mixture (silica and milled fibers is the best choice here). Smooth this out as best as you can with a plastic applicator and let it just lose it's tackiness (a few hours, depending on temperature and hardener used). Next apply a 2" or 3" tape of biax or 10 - 12 ounce cloth (not mat) on the seam. Wet this out with more unthickened epoxy, until it's transparent. Again wait until the epoxy is just barely tacky or just lost it's tackiness, then apply a fairing compound, which can be a pre-mixed, like that from System Three or home made from micro balloons or Q-cells and a touch of silica to stiffen it. Smear this on, again trying to make a smooth transition around the seam. Let this sit for a couple of days and sand until read for paint.

 

The places where the grinder didnt touch need to hand sand and or wire brush hard to get the years of gung and surface residue off and give the new resins something to stick to . I would also put glass cloth over the join double bias about 400 gram ideally and then the join is really water tight and stronger that ever before . a small rubber belting like i said before would hep and stop the edge damage again !!.

 

Thanks again for the great advice, and sorry for the stupid questions, just a couple more though, hope their not too annoying.

I found everything i need thus far at http://www.boatcraft.com.au/ looks like a great site.

Still not quite sure on a couple of things though.

1. Im having trouble finding structural filler mix, and also the necessary fairing compound. What would be some brands that I can search for that make such a product?

2. In relation to applying the tape, i assume its fine to do multiple layers in parts that require more reinforcement? Also is it ok to slightly overlap the gelled (but still slightly sanded) areas on each side of the seam or will the tape just not stick?

thanks

 

Structural filler mixes are self made, depending on the requirements. Again, download the user's guides from the major formulators (West System and System Three) so you can get a handle on the processes. For your needs, you'll want to use (in order of preference) milled (not chopped) fibers or cotton flock (West 403) and enough silica to stiffen the mixtures, so it doesn't sag or run out of the areas you're working on. You could probably use "Epox-E-Glue as your structural filler, though I'm not sure if the viscosity is stiff enough for vertical surfaces (you can always add some silica to stiffen it up).

Yes, you can do multiple layers of tape, though if using 12 or 17 ounce biax, you really don't need more then one for you project. Yes, you can overlay the gel coat slightly, but the bond isn't as good as it is when the gel coat is ground off and you're bonding to the mat or roving. This is an area that takes a lot of abuse, so maybe not the best to try this technique. The edges of the repair will be the first places to "lift", so you want a good bond there.

Lastly, you could cover the whole area (after repairs) with a wooden, aluminum or PVC/vinyl strip. This would serve to keep things from bashing into the seam and testing your bonds. You can buy extrusions or just make a strip of hardwood bend around as required.

 

OK, finally ready to start the repair.

I got some West Systems stuff, including 403, epoxy and hardener, and some west systems fairing powder.

My plan is to clean the sanded area with acetone, apply some unthickened epoxy to the entire area, then apply epoxy + 403 (as my filler) to the holes and seam groove. I will apply it all around the seam. Is it OK to do this, wait for it to dry, and then sand it, and apply the tape etc at a later date?

Also, is unthickened epoxy just epoxy without the hardener?

Thanks

 

Unthickened epoxy is epoxy without the filler (West 403 in your case). It's runnier and so harder to fill holes with, but soaks into cloth well. Thickened epoxy will have a consistency like paste or putty and will fill gaps without running. If it were me doing it I would use thickened epoxy or fairing compound to fill in the holes and then sand smooth, and once it was fair and smooth go over it with cloth and un-thickened epoxy. If you use the thin stuff on the holes you're likely to get voids.

Think of unthickened epoxy like paint and thickened as being like putty. Use the putty to fill the holes, sand them smooth and then paint them with the unthickened.

 

West 403 alone will make a very difficult to sand end result and may also need to be thickened a bit with silica, to remain on vertical surfaces, without running off or sagging.

Wetting out the surface with straight epoxy is a surface primer, which insures the next layer (what ever it is) bonds well.

Fillers added to epoxy (403, etc.) thicken it up, offering gap filling properties. The right combination of filler materials makes the job much easier. On preexisting 'glass work, the preferred filler is milled fibers, though 403 is cotton flock, it's nearly as good. In most cases, you'll use two or more filler materials, in a thickened epoxy mixture. Silica is commonly used to control viscosity. For example, you can add a whole bunch of micro balloons to a batch, but it'll still sag and run on vertical surfaces, so a touch of silica is added, to stiffen the mixture enough to prevent this.

Lastly, you probably don't want to wait and do the job in stages, but all at once. The result will be stronger and you'll have less likelihood of issues later.

Again, the process is wet it out, then apply a thin coat of structural filler, to get any cracks and other damage filled solid, then while still wet or in the "green stage", apply the tape, further wetting this out (more straight epoxy). At this point you can stop and let it dry, but if I was doing it, I'd continue and smear on a fairing compound of Q-cells or micro balloons and silica, trying to make the result as smooth as possible to ease sanding when it does cure. Sanding epoxy is something you want to minimize as best as you can, because the task sucks. The tape and filler will address any structural concerns and the fairing compound will offer you something to smooth out.