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trevork
3949 Posts |
 Posted - 27 Apr 2020 : 23:28:55
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This from Vince via email. So you wise heads on here see what you can offer. Vince has a norman 18 project boat, I bought it about 4 years ago knowing that it needed a transom replacement and at the time didn't even think about stringers or other structural aspects of the boat iv started working on it recently since the pandemic started and have done some investigating and I think I'm going to have to re-do most of the timber structure it's a shame really I think my boat is lovely given it was built probably early 70s the hull looks in brilliant condition but I think this boat has been neglected for atleast 20 years or more and I would really like to get it fixed up to its former glory but I think I might need some advice and was wondering if there might be any structural drawings in existence that I might be able to use or copy also would like advice on what wood to use ... I will send you some pictures if you would like to see them.
I would be grateful to hear any advice you might have to offer |
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cliveshep
Thailand
1324 Posts |
Posted - 28 Apr 2020 : 01:40:43
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It's an 18 - you cannot do much to the design except follow what was there before. If as is normal the bottom of the bulkhead has rotted away use the old one as a pattern or else scribe in new sections. Clean off the hull with a mini grinder and flap disc or, and this is what I used to do pre-retirement and emigration - use a painters shavehook and hot air gun, soften the surface and scrape it off where you need to glass timbers in.
Buy materials from East Coast Glassfibre supplies, reasonable prices, sell everything and in these times importantly do mail order.
Use Far Eastern or Malayan WBP plywood - it will be brown wood all the way through, almost as good as marine plywood but about 15% of the price. You'll need to shop around because there is a lot of red veneered white cored Chinese stuff about last time I bought and the Malayan was hard to find. Travis Perkins or Jewson might have some.
Glass in with woven cloth - not CSM (chopped strand mat) as ity drapes around corners far better and "wets in" easily. You can brush the resin on and then stipple it, try that with CSM and you'll have a clump of fibres on the brush.
Whole gallery of one I did some years back here:
https://postimg.cc/gallery/jSrTH0C
Not in any particular order but the pics show the different stages of a complete rebuild excluding transom.
Finally living the dream!
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cliveshep
Thailand
1324 Posts |
Posted - 28 Apr 2020 : 02:06:01
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For a transom replacement you'll probably find it easier to cut away the outer skin, dig out the rotten core from the outside, and bond in new plywood using the same Malayan WBP in 2 or 3 thicknesses. Bond 1 layer to the old glass-fibre with an epoxy paste.
Cut the transom outer skin away leaving a 2 inch/50mm piece all round both sides, top under side decks only and bottom. Chamfer that down with a mini-grinder and flap disc over the entire 2 inches, chamfer the piece you cut out the same way - both sides tops and bottom - set it aside for later re-fit.
Bond ply layers for infil core together with a casein glue from Travis or bought on-line, used to be called Cascamite, now sold as Ultramite powdered resin glue - water proof and perfect for boats, sold by Travis Perkins or Jewson, DON'T use PVA glues - not waterproof. That includes Evostik wood glues no matter what the salesman tells you.
Once the core is properly bonded in, prime the ply core with (POLYESTER not Epoxy) resin, when it dries off apply a further coat and apply a layer of CSM with resin stippled in properly, then coat the saved piece of transom grp in resin and push it into place. Temporarily screw with dry-wall screws to make sure it makes a good contact until the resin hardens. Take them out after and fill holes with epoxy filler.
Then glass in the prepared transom piece to the 2 inch surround you left and tapered before. Use a small strip say 2 inches wide first, then a 2.5 inch inch wide then 3.5 inch and finally when it is all hard you can fair-in with epoxy filler and sand it down before painting. Refit the ali trims around the motor well with a good squirt of marine sealant under because THAT is where the water got in before - the joint between motor-well moulding and hull moulding which the builders never closed properly on any of their boats. Drill out the drains and bond in small bits of pvc conduit and seal them in on both ends.
The strength of the replacement transom relies on the original GRP hull and glassing in and motor-well mouldings which you have left intact, all the outer skin does is keep the water out - theoretically!
Finally - paint the transom and go boating!
Finally living the dream!
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Edited by - cliveshep on 28 Apr 2020 02:16:04 |
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Norman 18 project boat - advice needed
