Transom surgery

Topics primarily or specifically about the DS2. Many topics are of general interest, so please use forum sections on Rigging, Sails, etc. where appropriate.

Moderator: GreenLake

Transom surgery

Postby Champlaner » Mon Aug 13, 2018 6:33 pm

Hello from the summer of repairs! After 4 great seasons of sailing my '77 DSII out of St. Albans bay on lake Champlain, I decided to tackle some repairs, including fixing the jib tracks, barrier coating and painting the bottom (not blistered), a few gunwale dings, and reducing wobble in the CB. Oh yeah, and there were a couple little leaks from previously plugged holes near the lower gudgeon on the transom. Not having a garage or barn, this project had to wait through the coldest, snowiest April we've had in a long time. Since then, work has been very sporadic. I decided not to mess with the CB too much but did my second replacement of the downhaul (posted that story in the recent-ish thread.) I will be happy to answer questions and post more detail about my barrier coating experience, done with West 105 and 422 additive. Later.
So I started poking around and drilling out the failed plugs in the transom and then removed the gudgeon to find about 7 old holes plus the 2 currently used ones! In hopes of making a small repair in just that area, I cut out a small section of the transom skin(s) around the gudgeon, which revealed that my transom is a double plywood sandwich on 3 slices of fiberglass! See pictures. I cut out one more section since that direction had obvious rot The other direction (right side) actually is hollow about 2 inches past where I cut. So there is a lot going on in there that I don't understand. Maybe the left side has more plywood for motor support, because I've drilled pretty far to the left and am still hitting rotten plywood.
So my next (and what maybe should have been my first) step might be to cut most of the transom skin off and attack the whole thing. Yes, I know most people do this from the inside, but too late for that now, and access is much nicer on the outside. I guess I would cut following the lower profile of the bottom about an inch higher like I already started. Not sure if I would go all the way to the top corners of the transom, or how close under the transom cap I would cut. The cap seems very beefy. I do NOT plan on grinding a 12:1 bevel ratio for the skin replacement. I just want the boat to be sound and don't care if the repair is obvious.
Has anyone else seen or worked on a triple-skin transom like mine? I don't see how one layer of both ply and glass could have been added after production, but it's possible. Any ideas on how much should be removed side to side? And I'm really not sure about the cap. If I cut below the cap, I suppose replacement plywood/epoxy will be more difficult if I have dug out the last inch, like at the bottom. Maybe I should just cut the cap off first. Ouch.
The other option is to leave some of the rot and patch what I've done, but it wouldn't be easy since I have to maintain the draining ability of the bilge. I can't just pour thickened epoxy in between the inner and middle skins or it will plug the area in front of the drain. Fitting pieces of epoxy coated plywood in there won't be easy either unless I can grind out some squarer angles. Between the middle and outer skins is less of an issue since the middle skin ends flush with the front of the drain tube.
Any suggestions or information are very welcome, and commiseration helps a little too.
Thanks and enjoy the water!
Attachments
drain tube.jpg
drain tube.jpg (84.1 KiB) Viewed 2008 times
Transom 2nd cut.jpg
Transom 2nd cut.jpg (81.34 KiB) Viewed 2008 times
Transom first cut.jpg
Transom first cut.jpg (116.32 KiB) Viewed 2008 times
'77 DSII #8420
Champlaner
 
Posts: 8
Joined: Fri Aug 01, 2014 9:14 am

Re: Transom surgery

Postby GreenLake » Mon Aug 13, 2018 7:28 pm

There are three issues.

1) provide support for the gudgeons

2) limit further rot

3) restore appearance

I would tackle #1 by replacing the plywood backing (in the gudgeon area) by something that cannot rot, even if moisture wicks in there. For example you can get pre-laminated fiberglass sheets in various dimensions, product called G10. With that, it should be possible to build up a solid backing plate for your gudegeons. You may not need to fill the whole space to the inner hull, that may be overkill, but you would need at least some "spacers" so that the bolts could be pulled tight.

For #2, I would treat all plywood that may have gotten wet, but is neither fully rotted nor fully removed with a borax solution to make it less susceptible to any further moisture. System Three Board Defense would be a product for that. They also sell borax rods ("impel rods") that you can insert into a hole drilled into the wood and it will help saturate the wood with borax if it wicks moisture. All this is applicable only if they used marine plywood in the first place, otherwise delamination and not rot is your main issue. (This suggested "repair" tries to strike a balance between effectiveness and effort. If you are happy to remove more skin and can remove more plywood, then that would be the more permanent option).

For #3 if you cut the skin out in a nice section, the repair may not need to involve new large-scale laminate, but rather gluing on what you cut out and then fixing the gaps.

PS: when they built the boat, they glued the first sheet of plywood in the outer hull, then glassed that over in an attempt to keep bilge water from it. Then they added another sheet of wood to make contact with the inner hull. Does that sound plausible to you?
~ green ~ lake ~ ~
GreenLake
 
Posts: 4976
Joined: Mon Jun 18, 2007 3:54 am

Re: Transom surgery

Postby Champlaner » Mon Aug 13, 2018 9:23 pm

Thanks for the ideas. I considered plastic but since HDPE and epoxy are not that friendly, the g10 sounds like a great way to go. The rot I dug out to the left was really mushy. I was able to move the drill bit side to side from even the first plunge. Probably beyond borax or liquid wood. I've never had a motor on the boat but am planning to get one someday, so I think I might go with the majority glass removal. In some ways, the repair might be easier with room to move. On the other hand, the 3 skins seem to form a pretty strong assembly on their own. I certainly don't feel like a light outboard would cause the whole thing to fail. Your explanation of the construction seems like the right way to build it, but I'm still confused about the hollow section to the right (outer section). Maybe the left side plywood was added as I suggested in my first post. I know most of the DSII's have at least the center plywood section in the transom, as shown elsewhere on this board. For me, it's hard tellin' --not knowin'. I wish I had the Boatfax report for my hull number! And for #3, yes, my plan if I do the big removal, is to just epoxy the skin back onto the new plywoood (or other filler). I don't think the 12:1 grinding is as important when you are gluing to a backing, except cosmetically. I hope getting the skin off after cutting isn't too painful.
I'll post more when it happens, along with some other posts about the other repairs.
'77 DSII #8420
Champlaner
 
Posts: 8
Joined: Fri Aug 01, 2014 9:14 am

Re: Transom surgery

Postby GreenLake » Tue Aug 14, 2018 6:41 am

The 12:1 would seem to be intended to restore/retain strength and if you use G10 as a backing then I would think there's no issue simply filling the gaps. You do want to bevel the sides a bit, but I would use either an epoxy filler or 3M High Strength Marine filler. It's a polyester product, but filled with short strands of fiber and is really strong. It should take gel-coat, if you like to finish your repair that way, or you can use an epoxy fairing compound like QuickFair for the final fairing and paint your transom. (Painting just the transom is a viable option in my view, as it has well-defined edges that allow a transition. You can even go wild and use some contrasting color.)
~ green ~ lake ~ ~
GreenLake
 
Posts: 4976
Joined: Mon Jun 18, 2007 3:54 am

Re: Transom surgery

Postby GreenLake » Tue Aug 14, 2018 6:45 am

Looks like your transom (or even the entire hull) has been painted already. I just went back to your photos and there seems to be white on red visible at the edges. In that case, no need to first restore the gelcoat.

I re-painted my transom at some point, forgot why just that needed retouching, and it didn't create too much of a Frankenboat look, even though I didn't match the correct shade of off-white compared to the remainder of the hull. It's kind of forgiving that way.
~ green ~ lake ~ ~
GreenLake
 
Posts: 4976
Joined: Mon Jun 18, 2007 3:54 am

Re: Transom surgery

Postby Champlaner » Fri Aug 17, 2018 11:30 am

I thought the same thing when I first saw the red underneath, but other dings in the hull reveal a very thick, soft white layer over the red. I'm pretty sure it's gelcoat, especially after dry sanding (with vacuum) the old ablative off the bottom into the gel. Maybe the red was sprayed first for the boot and upper stripes and the rest is all overspray? More mystery. When you sand into gelcoat, it feels like you are sculpting--very distinctive. Where the stripe is dinged through to glass, on the other hand, reveals a much thinner coat of red.
gelcoat scratch side hull.jpg
gelcoat scratch side hull.jpg (31.63 KiB) Viewed 1963 times

Boot stripe ding.jpg
Boot stripe ding.jpg (48.41 KiB) Viewed 1963 times


I was/am 99.3% decided on doing the minimalist repair, but since I hogged out material behind the remaining skin in 3 directions, I'm not sure if I can just push/pour some kind of filler into those areas, after I borax and acetone as much as possible. I would use thickened epoxy, but I'm nervous about having it exotherm too much if I try fill an area 8" x 4" x almost an inch thick. (Had a pan go smokin' hot on me first bottom coat. Used 2 pans after that.) I know I can put plywood or G10 covered with epoxy mud in those voids, but the variance of thickness and shapes will be challenging. Maybe I could stuff wads of impregnated cloth along with some structural pieces of ply/G10. Not a very sound strategy, but should give me some strength and adhesion to the skin. Once I get back to the exposed area, it will be much simpler fitting in a couple layers of structure. I'm hoping to avoid waiting 2 hours after each inch of progress in the hidden voids, but that might not be such a bad way to avoid exotherm issues.

And finally, if I change my mind again and go for the mostly total removal of the outer and maybe middle skins, will the inner be strong enough to hold everything while the boat is on it's side? Yikes. Cutting the very burly transom cap seems like asking for even more trouble in that respect.
rear view.jpg
rear view.jpg (67.72 KiB) Viewed 1963 times


Have a nice weekend all, and thanks GL!!
'77 DSII #8420
Champlaner
 
Posts: 8
Joined: Fri Aug 01, 2014 9:14 am

Re: Transom surgery

Postby GreenLake » Fri Aug 17, 2018 1:49 pm

Epoxy is not the right material for volume casting.

I did an accidental experiment the other day that resulted in a firm "epoxy foam" - very interesting.

I had left extra hardener stand for a while with minimal cover. It may have absorbed a bit of moisture that way. When I mixed it, the mixture simply had tons of little bubbles. I mixed it pretty hard.

I didn't use most of it in the end, it was perhaps as much as 1 or 2oz, so not very much, that was left in the pot. Anyway, left unattended it cooked and all the bubbles expanded and the epoxy rose like beer foam out of the container - at least 1" above the rim, but it only rose up, no flowing over the edge.

The result hardened into something that looks like one of the supersize marshmallows half way into their conversion to smores.

That kind of foam, if your could reproduce it, would definitely be structural enough to help fix some G10.

Generally, your best bet it to line the outer hull with a plate (or a stack of plates) of G10 to just about the thickness you need for strength. Then figure out some "spacers" at the places where the bolts go through, so you can tighten them. Also any place the motor clamps would squeeze.

The rest can probably remain a void.
~ green ~ lake ~ ~
GreenLake
 
Posts: 4976
Joined: Mon Jun 18, 2007 3:54 am

Re: Transom surgery

Postby Champlaner » Mon Sep 03, 2018 11:55 am

I completed a good portion of my transom repair through the existing hole I had cut. First, I epoxied a bar shaped piece of 3/4" plywood into the inner cavity, below my bottom cut line. I was super careful fitting and gluing that piece so as not to block the bilge drain in any way. After that, I ripped and cut 5 more bars of various shapes to slide into the hidden voids I had drilled in the outer cavity, as well as into the visible open part. Once the test fitting was complete, the neat+thickened epoxy coating and piece-stuffing was carried out in one fell swoop of panic. I still need to finish the outer skin replacement and patch, but what I've accomplished so far seems very strong.
If I ever add a motor or ladder or both, I would at least consider some similar local reinforcements at those installation points if needed.

Next up: Like many before, I had to cut my cuddy floor around the mast step (keel-stepped) since the screws for the step were stripped out. Will post that one soon.
'77 DSII #8420
Champlaner
 
Posts: 8
Joined: Fri Aug 01, 2014 9:14 am

Re: Transom surgery

Postby GreenLake » Mon Sep 03, 2018 3:41 pm

A post-scriptum on the red / white gel coat.

Likely production sequence: the boot stripe got masked off, all white gelcoat sprayed, the masking removed, and red gelcoat sprayed. That would make the inner red the overspray, which fits, as gelcoat is sprayed on the mould.
~ green ~ lake ~ ~
GreenLake
 
Posts: 4976
Joined: Mon Jun 18, 2007 3:54 am

Re: Transom surgery

Postby Champlaner » Tue Sep 04, 2018 9:14 pm

I'm not sure the red is gelcoat. It's very thin and appears to be glass just under the surface. And I think it came that way from the factory. Especially now that I've seen 109jb's identical stripe. Maybe it's just a thin coat, but I didn't think that was possible with gel. I can barely feel a difference between the stripe and the hull with my finger, so I'm still confused about the how. Anyway, it's a nice shade of red!
'77 DSII #8420
Champlaner
 
Posts: 8
Joined: Fri Aug 01, 2014 9:14 am


Return to Day Sailer II Only

Who is online

Users browsing this forum: Google [Bot] and 2 guests