Crack in stern

We have been working on restoring a 16 ft wood lapstrake cat boat and have run into an issue with a crack in the stern.

The previous owner had filled the crack and added some boards on the inside to strengthen the stern.

He had also applied fibreglass cloth over the outside of the entire stern.

We had a moisture problem and ended up with the cloth delaminating.

Because of this and much of the paint needing to be stripped, we decided to redo the entire boat.

The rest of the boat is solid, but on the stern where the previous repairs had been made, one side of the crack separated.

We ground out the initial filler and after letting the boat sit in our garage for 2 years we filled the crack with west system epoxy mixed with the silicone filler.

Everything looked great so we proceeded with the refinishing.

We filled any other gouges in the hull with the West fairing compound, then applied a layer of epoxy over all.

2 coats of epoxy primer and left it until this summer.

When we checked the stern we noticed that a small crack had opened over the previous repair.

We have ground it out and noticed that the filler seems to have separated from the wood in several spots.

We have put in many hours to get to this point and don't want to give up on the old girl.

Would you have suggestions?

Comments for Crack in stern

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Aug 10, 2014
How to deal with old wood (for stem people)
by: Anonymous

1. Oak turned black is done for. Epoxy will not adhere - basically no matter what. You will have to cut any part of the stem out that has bad wood / fit in new piece / use long scarf joints to extent possible.

2. Epoxy doesn't work with moisture - as we all know. Getting moisture out can be a matter of applying gentle heat - from heat guns to putting the boat in drying/solar buildings - sometimes gentle dry warmoth over a long time. (Yes, two years is a long time - but how dry was the garage?)

3. Acetone is the 'chemical friend' of epoxy. sorta. In some circumstances, wood can be helpfully prepped by saoking with acetone.

4. Serious repairs often begin by forcing liquid epoxy into the fault, then coating (soaking) the sides, then building up from there.

5. Filler design in epoxy repairs is a serious matter. For what it sounds like you are doing, you want some cabosil and some fibers. No microbaloons, no 'lite' mixes.

6. You didn't use the word "glass". The great majority of repairs of a serious problem in a wood/epoxy structures involve at least the use of a couple of layers of glass. Using carbon or kevlar fibers or weaves is not uncommon either.

7. In the end, don't think 'goo' (as in putting chewing gum into a crack) think 'structure.'

Jul 31, 2014
Epoxy repairs
by: Gene

Certainly epoxy would work and all of the major manufacturers publish detailed manuals covering the use of their products.

If you look in the west system site, they have an online manual which may prove helpful.

Not knowing the size or depth of the crack makes it difficult to recommend a specific product but there are plenty available.

Just remember to clean the edges of the carck to present a smooth surface and to work in small (golfball-sized) batches.

If the crack is large enough to require a filler try to select one that matches the hardness of the oak to avoid sanding irregularities.

Jul 30, 2014
Adhesive suggestion
by: Anonymous

Thanks for your suggestions.

What type of adhesive would you recommend using.

Would epoxy work?

Jul 30, 2014
Adhesive reccommended
by: Anonymous

Thanks for your helpful comments.

We were wondering what marine adhesive would you recommend-would it be something other than epoxy?

Jul 30, 2014
Blackened oak
by: Anonymous

Two things come to mind with oak turning black.

If steel wool had been used in preparing the stern small iron splinters might have embedded themselves into the wood, reacted with the tannins in the oak and caused black spots wherever they occur.

This is the basis for oak gall ink used in the past.

The other is a fungus having taken hold in the wood.

In that case the best thing I can recommend is carving out the black and using household bleach before trying to refill it.

The bleach should get rid of any fungus remaining.

If the crack is very deep or goes all the way through the stern, I would look to a marine adhesive rather than fairing compound which really doesn't have the strength to hold two pieces together.

I also have to wonder how much the wood dried and shrank during its two years in the garage.

If it's within your capabilites a new stern would not be a bad thing to consider.

Best of luck.

Jul 30, 2014
Type of wood
by: Anonymous

The stern appears to be oak.

Although it seems to be solid, it is quite black and we are wondering if we need to remove the blackened wood to carry on with the fix.

There were a couple of screws that bulged the epoxy.

They were quite rusty and have now been drilled out-it looks like they were added to hold the inside and outside boards together.

Jul 29, 2014
by: Gene

Any idea what kind of wood it is?

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