GRP kayaks - joining up the halves.^

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OGB
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GRP kayaks - joining up the halves.^

Post by OGB » Mon May 30, 2005 9:17 pm

I've just become the owner of a secondhand fibreglass boat, and took it on the water for the first time today - and it leaks. The seam between the upper and lower halves had been tarted up with black tape, and removing this revealed a lot of holes in the silicone that had been used as a waterproof filler. I'm in the (laborious) process of scraping off the tape - it's like gaffa tape, and leaves a very sticky residue - and peeling out the old silicone.
The question is - how do I put it back together again in a way that will keep the water out and look smart? I don't have any local paddling mates that I can turn to for a first-hand inspection of their boats, and catalogue pics etc don't have the detail I need. Can anyone help?

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NickB
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Post by NickB » Tue May 31, 2005 7:18 am

Assuming you only want to work on and repair the outside seam, continue with your 'labour of love' to remove all traces of the existing seam and repair work. You may find that Acetone helps with the removal of the gaffa tape. Fill any holes or cracks with a resin, powder and catalyst mix.

Once this prep is finished use masking tape to mark out the area (about a 1" strip equally spaced either side of the join) for the new seam and rough up this area using sand or wet and dry paper. Then, if your rubbing down has damaged the masking tape replace it with new ready for the application of the new seam.

It is easiest to work with the boat supported on its side so it is one side at a time I'm afraid.

Make up a mix of Gelcoat and MW Solution (I think this is the right name but it is the additive required to ensure the Gelcoat cures in air), add your preferred pigment and catalyst. Follow manufacturer guidelines for quantities and give it a reasonably slow cure time to give you time to finish the seam.

Brush a generous quantity onto the seam area, apply the 1" diolin/polyester bandage down the length of the seam and stipple more resin into the bandage to thoroughly wet it out. Tidy up the bandage at the ends and ensure that it is stuck to the boat for its entire length. Remove the masking tape now before the resin has cured. Go away and have a cup of tea or a beer, or depending on cure time leave it overnight before repeating the whole process for the other side.
Cheers
Nick Benny

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mharrall
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Post by mharrall » Tue May 31, 2005 9:17 am

Spot the bloke who's been around canoes/kayaks since the dawn of time!

Martin

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NickB
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Post by NickB » Tue May 31, 2005 9:28 am

Aww, back in the good old days all boats were made this way (wobbling along on walking stick)!
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Nick Benny

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MikeB
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Post by MikeB » Tue May 31, 2005 6:12 pm

Nick Benny wrote: Make up a mix of Gelcoat and MW Solution etc etc

Brush a generous quantity onto the seam area, apply the 1" diolin/polyester bandage down the length of the seam and stipple more resin into the bandage to thoroughly wet it out.
When I had the great joy of doing this job to a fleet of glass boats some many years ago, having first masked the area, I just used a thickened and colored mix of resin to give the same "thick / smooth" external seam that modern glass boats have. The mix was thickened with some form of powder stuff sold specifically for the purpose, a bit like talc as I recall. (No tape was used).

The end result was good though.

I should add that the hull and deck had been joined internally with a glass tape strip - if your boat doesnt have this then splitting the craft and remaking it may be worthwhile????

Ah, the joys of working with glass boats - - - - - - - -



Mike.

OGB
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Post by OGB » Tue May 31, 2005 9:18 pm

Thanks, Nick & Mike, for the advice. I've got the tape off now, and most of the glue. Luckily, it was sunny this afternoon (usually is, after a Bank Holiday) and putting the boat outside for an hour was enough to soften the tape enough to scrape most of it off (tape was black "duck tape"). Petrol is getting rid of the gunk left behind.

Have uncovered what were obviously designed to be toggle attachments (holes), a lot of crumbling gel coat with air underneath and quite a lip where the 2 halves join....this is going to be a longer job than I thought.

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NickB
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Post by NickB » Wed Jun 01, 2005 6:54 am

MikeB wrote:
I just used a thickened and colored mix of resin to give the same "thick / smooth" external seam that modern glass boats have. The mix was thickened with some form of powder stuff sold specifically for the purpose, a bit like talc as I recall. (No tape was used).
The French Chalk and Resin solution was the standard approach for seams where bandage was not being used, using this mix with bandage would not thoroughly 'wet out' the bandage, IMHO the best solution for a more durable or an external seam is the bandage and Gel one.
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Nick Benny

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Jim
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Post by Jim » Sun Jun 05, 2005 11:29 am

For my 2p worth, it will be easier to do the filling with epoxy putty, it's amazing stuff and all composite boat paddlers should carry it for doing repairs.

As for all the other details, it's all based on using polyester resin the same as the boat, personally I prefer to work in Epoxy these days and would probably choose an epoxy resin and 1" glass tape to actually join the seam, and then possibly cover it over with a mix of epoxy and microballons (type of filler powder) if it looked pretty rough. Always sand epoxy well if you let it go hard before applying the next layer.

Not sure what additive Nick refers to for making gel coat set in air, we used to just add liquid wax to get it to do that (2% I think).

JIM

OGB
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Post by OGB » Sun Jun 05, 2005 8:00 pm

The wax referred to is "wax in styrene" - called M/W for some reason, in the trade. It allows the final finish to be glossy without being tacky. All this discovered in the last week, while becoming an "instant expert" in this.
AAMOF, I've gone the "marine filler" route for plugging the gap, and now waiting for the necessary to arrive to sort the outside of the seam (2" f'glass tape, M/W, polyester resin - this seems to be the right stuff as epoxy is too brittle, apparently). One of the problems of living too close to the Arctic Circle - everything by mail order and it costs both arms!

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