Transom Replacement - Any help gratefully received

[duncan_ellison]

Usual story, bought an old 15ft speedboat hull for $200 and I'm now up to $5,000 including s/h engine, new floor, instruments etc. etc. etc....... nothing new here then <br /><br />I was getting very excited about getting nearer the water until I took the precaution of cutting away a small area of glass INSIDE the transom and found that one side of the transom is completely shot. Probably the hull had been lying on one side in the water for a while as the port side is reasonably sound.<br /><br />Having already mounted the motor and resprayed the hull, my 1st choice was to use a product like Sealcast, but I spoke to them and they don;t have any distribution in Europe (yet).<br /><br />So... I've ordered up some marine ply and epoxy and intend to demount the motor and cut away the outside skin 2" away from the edge and replace the entire transom, then glass the cut section back in.<br /><br />I'm pretty handy with glass and I can always respray this section of the hull, because it's painted, I don't have to worry too much about gelcoat matching. But a post from JasonJ a few down now has me worried. He says - don't do it under any circumstances.<br /><br />I have restricted access from the inside, but I'm worried that going that route will be like "trying to paint my lounge through the letter box" and I'll not acheive the structural integrity I want.<br /><br />Does anyone have any experience of literally cutting away the rear section of the hull and glassing it back in ? How was it for you ? What technique did you use to stitch the section back in (woven glass tape ? / Mat ? / or what ?) How did you manage getting an oversize piece of plywood into the hole ?<br /><br />Has anyone ever tried a substitute for Sealcast ? From what I can see it's simply thin polyester resin with a bulking agent to reduce the weight. <br /><br />I realise that this is well trod ground, but having got this far, I don't want to make a major mistake now and I'm hoping you good folks can help out.

 

[lark2004]

Re: Transom Replacement - Any help gratefully received

had to remove top of hull above the transom, usually stapled or screwed together under the gunwale rubber. This made it possible to drop the new timber core into the back. laid double bias glass around inside edge and glassed in. Used a bed of epoxy mixed with filler all around the edge for new timber to sit into. It's all fairly easy, just time consuming.

 

[ThomWV]

Re: Transom Replacement - Any help gratefully received

Don't cut off the back of the boat - if you try to do it that way you may as well go ahead and junk the boat now, save yourself some time.<br /><br />Remove the liner and then remove the inside skin of the transom. After that comes the work. Dig out every single bit of the wood coreing in the transom, but leave the outside skin alone. Once you have all of the wood out and the remaining glass skin clean you will then cut plywood to fit the transom and start laying it up using epoxy and one layer of matter between layers of plywood. Use 1/4" Luan plywood and slow set hardner for your epoxy. Use your motor boat holes to pull the first sheet of plywood tight to the transom skin. For the first layer of epoxy, which you will apply to the skin, mix cabosil with the epoxy to thicken it and basically plaster it to the skin so that the plywood will have a continous bedding to pull into. After that succeeding layers of the 1/4" plywood can be pulled tight with screws (which will be removed as succeeding layers are applied). Once you have it built to the desired thickness finish up with a layer of glass matt (biaxle of around 10 oz.) to finish. Also, make sure that you wrap your glass (between the layers of plywood) around to the inside sides an forward about a foot and a half (1/2 meter). Of course you also have to tie into the stringers as they come back to the transom. That is simple glass work though.<br /><br />Basically what you are doing is building a sandwich with the outer layer being the existing skin of the transom and then succeeding layers of glass and impregnated plywood. By using the thin luan, which soaks up epoxy like a sponge, you end up with an almost solid transom.<br /><br />Thom

 

[jim dozier]

Re: Transom Replacement - Any help gratefully received

While not a BAD thing, multiple layers of 1/4" plywood seems excessive to me. However, I have never built a transom either. But based upon what I have read, seen on TV, and seen in my boat, 1 to 3 layers of plywood to equal the original thickness, saturated and bonded with epoxy and covered by a layer of glass inside would be stronger than what most boats come with from the factory. I would think that a couple of layers of 3/4" marine plywood (no gaps) would be pretty strong for most runabouts. What's the consensus?<br /><br />Remember the reason the transom or whatever got rotten in the first place is that:<br />1. Polyester resin is not completely waterproof.<br />2. The factory probably did not attempt to seal the entire piece from access to water.<br />3. The quality control may have been spotty.<br /><br />Epoxy is more waterproof than polyester. Good quality plywood has already done the laminating for you, why repeat it. Pay attention to completely sealing the entire piece from water.<br /><br />The multiple layers of 1/4" would be a good idea for curved areas. This is basically the idea behind cold molded boat construction. The more curves the thinner the layer. With veneers you can make a very sexy cold molded shape in wood.

 

[duncan_ellison]

Re: Transom Replacement - Any help gratefully received

OK - so the consensus it NOT to cut the back off the boat, then. Good job I took advice as that was probably my next move <br /><br />Thanks for all the advice guys. <br /><br />I guess I won't really know until I start into this but I'm still not sure how I'm going to get the new plywood pieces in as they are going to be bigger than any hole I can make from the top or inside. I'll try to post a pic if I can figure out how. <br /><br />But the problem is that the inside skin is underneath a deep splashwell and quite hard to get to. I've managed already to remove some with a 4" hole saw, which is how I found the problem in the first place.<br /><br />So my plan would be to cut a section out of the splashwell just above the transom to gain better access. I guess if it all turns ugly, I can at least put some ali trim over this.<br /><br /><br />Good tip from ThomWv about using the motor holes to pull the first layer up tight to the outside glass - Thanks.<br /><br />BTW I've found (tip from me this time) that a diamond blade meant for cutting stonework in an angle grinder does a really neat job of cutting out f/glass with minimum mess rather than a grit wheel.<br /><br />One thing still puzzling me though (ref post from me further down). Why would the manufacturer have put a drain home at the bottom of the transom? This seems to be just inviting trouble and I think I'm just going to glass it up, or could it have been an attempt to provide some way of draining out any water that did get in ?<br /><br />Perhaps I might stop up the outer skin, but leave a bung hole on the inner skin in the bilge to allow occasional draining and prevent recurrence of the dreaded transom rot. Any thoughts ???

 

[robpoe]

Re: Transom Replacement - Any help gratefully received

I'm replacing the transom on a 16' runabout. The top of the boat (sides, splashwell, windshield mount, steering mount, etc) separates from the hull, giving full access to the transom.

 

[G DANE]

Re: Transom Replacement - Any help gratefully received

Hi Dunacan take a look at this side:<br /> http://www.fiberglass-repair.com/

 

[BillP]

Re: Transom Replacement - Any help gratefully received

Duncan,<br />I've replaced several transoms but never cut the outer skin away...the only reason is I didn't want to spend time jigging the hull to keep it true. However, if you visit boat repair shops here in Florida the practice is standard where liners and decks won't let the ply slip in from inside. There must be access for glassing though. <br /><br />Two layers of 3/4" ply glassed in are standard for up to 150hp motors on 99% of the production boats here...even bigger rigs use the same and don't have structural problems.