Transom Rotted

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Transom Rotted

Postby nickc » Sat Jan 07, 2023 1:38 pm

https://photos.app.goo.gl/HojLKRxQ7Dtko87b8

The above link is a video of what I am describing. I went to roll my DSII out of the garage to pressure wash it before completing some gelcoat repairs and I noticed some water dripping out of a crack near the top of the transom. I drilled a few inspection holes and sure enough the wood inside is wet and mushy, but the transom doesn’t feel week or soft from the outside. Is this something I need to address right now or is this something I can leave for the moment and deal with next season? Or, is this something that means the boat is dead? I really hope that’s not the case.
Thanks,
Nick
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Re: Transom Rotted

Postby tomodda » Sat Jan 07, 2023 2:25 pm

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Last edited by tomodda on Sat Jan 07, 2023 2:32 pm, edited 1 time in total.
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Re: Transom Rotted

Postby tomodda » Sat Jan 07, 2023 2:31 pm

In my humble not-altogether-informed opinion, this is something that can wait for another season. Should be addressed in the medium future, but get some sailing done first. Now, GreenLake has a lot more fiber experience than me, especially when it comes to restoration, so you definitely want his opinion. However, I'll dissect my own (humble, blah-blah) opinion for you:

-Top consideration - What does the transom actually do, besides being a place to hang your rudder and paint the boat's name? It keeps water from entering the boat and keeps the two sides of the hull in place. So it needs to be watertight and structurally sound. With that in mind....

-If the transom isn't flexing and the joint (corner) between transom and hull looks ok, you'll be fine. Is it watertight? Then you're good here.
-I'd beef up the structure aft. Maybe put a 2x4 across the very back of the cockpit, on top of the seats, up against the transom. You'll need to screw and glue it in place, so think about how you'll remove it later. Also screw/glue it to the front of the transom, and make sure to beef up the area behind (actually forward of) the Rudder Gudgeons. Maybe an extra 2x4 vertically for the gudgeon area? Anyway, that's your structural issue sorted (for now).
-Fix that crack though, do it properly.. grinding it out, building layers of tape, etc, etc. GreenLake has pointers on how that's done (Search for grind or fiberglass repair on this forum). And cover up your test holes.
-I'm surprised that the entire core rotted out.. I'm assuming the rot is due to the crack you mentioned, and not surprised that the core would rot around the crack. But whole transom? Wow. Well, you said the boat was sitting out for a long time.
-If it were me, I'd eventually replace the entire transom, SawZAll it off and build a new one from 3mm Okoume (or Luan if you really wanna go cheap), fiberglass cloth, and Epoxy. Cost guestimate? $300-$500ish, depends on shipping for the Okoume and how much epoxy you'll need. You're greatly helped by the fact that the transom is flat. FWIW, I replaced the transom on my old 1/4 tonner after it got ripped off in a collision, so it's doable. Anyway, once you've beefed up the structure, you can worry about replacing the transom later.

As you can see, this will be as much a thought exercise as it will be boatbuilding work. You need to think of what your "permanent fix" will be, and then do a "temporary fix" that is compatible with that. A temp fix that doesn't get you drowned, of course. I think my approach works (brace the transom with 2-bys, replace it next year), but I'm sure GL can shed some light. A whole other question is if it's all worth doing? Which is why I'd get in a season of sailing before major repairs. Get a feeling for what works for you.

I believe that you wrote that your DS is just a stepping stone to getting a boat to cruise in. So, on the one hand it may not be worth doing REAL repairs (give this boat away after a year or two). On the other hand, replacing the transom is a great learning experience. One well worth having before picking up a used cruiser and fixing it up. You'll figure it out, good luck!
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Re: Transom Rotted

Postby nickc » Sat Jan 07, 2023 3:37 pm

I appreciate the insight! The crack that the water was coming out of is actually a crack in the adhesive between the hill and the deck, not a crack in the glass. The boat has a lot of gelcoat scratches and cracks but so far I haven’t found any cracks in the glass. I have a can of total boat gelcoat with wax that arrived in the mail yesterday, I have already ground out the bad gelcoat spots with a dremel tool. Now i’m just waiting for it to get warm enough to apply the gelcoat.

As far as structural integrity goes, it’s solid to the touch i’ve pushed and pulled on it and it doesn’t move around. If i put weight on the motor mount the motor mount will flex up and down some, so i believe it is sunk into rotten wood as well so i definitely won’t be putting a motor on that until after i get her repaired.

A user on here, Wylie, documented himself doing the exact repair i am considering. He and greenlake discussed it extensively on that thread and Wylie posted videos of the entire process on the daysailer facebook group. So I have a pretty good general idea of how to go about doing it, but I have never done fiberglass work before so this would be a learning experience when it comes to cutting the glass and then putting it all back together haha. I’m not sure how to link to another thread in here but if you go to the advanced search and put “wylie” into the author search box his only posts are regarding this type of transom repair.

I appreciate the ideas for a temporary fix I will start racking my brain about how I can beat go about that with my needs and goals for the boat and the future.
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Re: Transom Rotted

Postby GreenLake » Sun Jan 08, 2023 2:41 am

What I like about Tom's answer is the focus on goals to help in decision making.

The maximal repair for this problem has been performed recently by a DSII owner who cut off the entire rear of his boat, rebuilt the transom and then glued it back together. For someone who is organized, reasonably skillful in a workshop and persistent in seeing this through, it's doable that way. The result would be "good as new". I personally might shy away from something that big, mainly because it seems daunting. It's probably true that the fiberglass work required is way less demanding in terms of skills and practice than doing equivalent work on a wooden boat. Anyway, that approach is written up somewhere.

I seem to recall reading about someone just slicing off the fiberglass skin to get access and then rebonding that after digging out the rotted wood. If you can get the rear face off in one piece, you can probably reuse it, and the extent of fiberglass work might be limited to "curing" the cuts you made.

In contrast to the DSII, on a DS1 the transom is a single layer of laminate, with a strip of wood backing only where the rudder is attached. Because the DS1 has about 18" of rear deck (also single layer of laminate), the transom is effectively an L shape, which makes it a bit stronger and doesn't allow the actual transom to flex. For the DSII this design was changed to a sandwich, using wood as core. The wood being incompressible (when not rotted) makes it ideal for mounting rudder, motor brackets, swim ladders and all the other kinds of attachments you'll find at the rear of these boats.

Purely for stiffness (and to keep the sides of the hull in position) a foam core would have worked just as well, presumably. Panel stiffness is determined by the strength of the skins and their separation (core thickness). That's why foam cores, or balsa cores work. And for narrow panels the side walls provide the separation, that's why you see things like stringers that are simply hollow with rectangular profiles.

Even with rot, the transom "sandwich" will likely be strong enough to keep the water out and the hull sides in place (in moderate conditions).

But your rudder mounts won't be as strong and you certainly won't want to mount new hardware. And by drilling holes, you've committed to doing something - if only to close these against further water ingress. :oops:

In conclusion, the issue is fixable with a bit of mostly sweat equity. However, any decision to do something like go for trial sail before you commit to fixing this more permanently would be entirely up to your own judgement and you would be well advised to consider how you could temporarily shore up transom and rudder mounts to reduce the risk of any adverse outcomes.
~ green ~ lake ~ ~
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Re: Transom Rotted

Postby GreenLake » Sun Jan 08, 2023 2:50 am

PS: oh good, you found the discussion with Wylie. By the way, fiberglass repair with epoxy resin is not actually difficult. Get some instructions like the EpoxyBook from System Three or similar materials from West System or others.

The keys to success:
  1. Make a wide scarf (1:12) with rough sanded surface, avoid sharp corners
  2. Measure accurately!
  3. Mix well!
  4. Wet out thoroughly, but avoid excess resin
  5. Practice a bit as wet fiberglass is awkward to handle

Some repairs benefit from laying up the entire strip of laminate on a sheet of plastic on your workbench and then transferring that like a tape to your repair. Using stiff plastic means you'll also get a smooth surface. Advance skill would mean learning to vacuum bag. I think the latter is overkill for a simple join, but essential if you try to build larger panels (really keeps the resin ratio low).

Much easier skill to master than woodworking.
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Re: Transom Rotted

Postby nickc » Sun Jan 08, 2023 11:24 am

I already have gelcoat repairs to do, so I was planning on just filling the drilled holes with gelcoat for now. I have also seen the youtube video where the guy cuts off the back fiberglass panel of the transom and scraps out the bad wood. I feel like my transom is entirely gone, much like Wylie’s was. The guy who scraped the bad wood out and sealed it up still had quite a bit of good wood left.
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Re: Transom Rotted

Postby GreenLake » Sun Jan 08, 2023 5:30 pm

Gelcoat isn't structural. Think of it like thick paint. You can't use it to seal holes.

Using clear Gorilla tape would be a better short-term fix than using gelcoat. :roll:

Actually, old gelcoat can be rough or chalky, making it hard for anything to adhere. But other than that, a small patch clear Gorilla tape would have been strong enough to seal the hole you drilled. I've used it to repair swim toys and it works well for that. Not only watertight, but with enough adhesion to hold air pressure.
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Re: Transom Rotted

Postby nickc » Sun Jan 08, 2023 5:48 pm

I know gelcoat isn’t structural. I just didn’t think the 1/8th of an inch hole i drilled would require structural reinforcement. What is the proper way to fix such a small hole above the waterline?
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Re: Transom Rotted

Postby nickc » Sun Jan 08, 2023 5:56 pm

Did some googling. Would total boat polyester structural repair putty suffice?
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Re: Transom Rotted

Postby GreenLake » Sun Jan 08, 2023 6:01 pm

Looked larger than 1/8th in the video.

I found a place on my boat where somebody used caulk to fill a 1/4 - 1/2" hole below the waterline. Hidden underneath paint. Held "fine" until I poked at it; at which point it gave with no resistance. Any contact with anything other than water could have pushed it out with dire consequences.

For a small hole, an epoxy paste like Marine Tex would be what many people would use. Or you can use 3M High Strength Filler, which is vinylester-based, but has chopped strands of fiberglass mixed in. That's very durable, and even works to restore nicks in edges (that is, where the repair isn't level with a surface, but stands proud). Both are as easy to apply as gelcoat.

Once it gets large enough where some fiberglass reinforcement is desirable, you wont get around grinding a shallow depression and filling that with layers of cloth and resin.

PS: compare to the 3M product, I think they may be similar, just different manufacturers
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Re: Transom Rotted

Postby nickc » Sun Jan 08, 2023 6:34 pm

I drilled two holes, one is probably smaller than 1/8, the other is the one I had the pick in. That one is prolly 3/8-1/2. I will look into the repair resins.
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Re: Transom Rotted

Postby GreenLake » Sun Jan 08, 2023 10:50 pm

Yeah, those should be good, even if you keep that part after your permanent repair.
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