Rot repair

[J. Dillon]

On another thread Jim asked about repairing rot on his Thistle.

I also have rot on the transom stb side just below the stern knee.

A small crack under the paint allowd sweet water to enter and do some rot damage

http://img152.imageshack.us/img152/6991/rotrepairfix1yi1.jpg

Image 1


Here's how I intend to repair the transom.

As can be seen the rot went almost thru to the opposite side of the 1/2" plywood transom.

Repair Phase 1

http://img512.imageshack.us/img512/7563/rotrepairfix11ew9.jpg

Image 2

The plywood has been cut back past the rot using the dremel tool shown in the image. Notice the inside side of the fiberlass sheathing is exposed.

I have ripped 1/32 ' fir strips which will be cut to fit in the dished surface. across first then 45o , 90o another 45o and across again till it all is flush with the surface. Each piece will be custom fit with the back side beveled to fit in the dish better or creating a scarf. Epoxy will be used on each layer and held in place by whetever means I can devise. When cured (when warm weather is dominant) I'll attack the rot from the outside of the transom in the same maner. This will get at the rotted portion behind the transom's framing. When finished I expect it will hold together quite nicely and probably be stronger than surrounding ply. Paint will finish the inside and fiberglass and paint on the outside of the transom.

Susequent repair images will follow as weather and temp. permit.

Any critique /suggestion welcome pro or con

Thanks

JD

[Ian McColgin]

Given how extensive it is, I'd have thought it easier to assault the problem from the outside. Easier to work, new stuff against the frame and very simple surface to scarf against. A little new glass and Voila. The job you're looking at here, even if you square up the edges for simpler fitting, looks really hard.

[J. Dillon]

Not really. From the inside it is easier to get at being the angle of the transom. I'm looking down on the work .:) From the outside I'd be looking up and at a very awkward angle with the debris falling on my face.:( If I cut the pieces square I'd induce stresses in the corners , scooped out dishes as shown distributes them. I will have to tackle the project from the outside but time spent there and at a backward angle will be minimal.

I consider each problem has different solutions and there are many ways to solve them .. some better than others.;)

JD

[Bob Cleek]

Looks like it will work fine. I'd soak the hell out of the original wood with CPES and hope what spores you might have missed aren't going to take off again if the moisture gets to them. A good dose of CPES should prevent that and also provide a good bonding surface for your epoxy adhesive repair... but you knew I'd say that, didn't you?

[Yeadon]

My gut says you're on the right track. I also think it's smart to hit it with the CPES after each new layup. Can't hurt.

Love the photo with the dremel. Reminds me of photos that I take during projects.

[jim binnings]

Hello guys, thanks for the good advice on the rot repair. I was suspicious of GitRot because the is no cure all for anything! I have just gotten back from my friends house(boat is in his garage) and have cut out most of the rot. It looks to be a patch about 2 by 4 inches. And unfortunately it has gone all the way though in one small spot. I am going to take everyones advice and step scarf the patch. I have found a source for 1/16" mahgony veneer and am going to order a foot or two.

Afew questions.........should I treat the wood with an epoxy sealant before I get started with the patches to keep the rot from spreading if I miss any of it? When I put the patches in should I put the patches in so that the grains of each patch cross instead of going in the same direction?

If I can find a digital camera I will post a picture or two as the work goes.

[Cuyahoga Chuck]

It's normal practice when gluing any kind of plywood scarf to paint straight epoxy mix on the scarf sufaces because the end gran of the exposed veneers will suck up some epoxy. Then come back with your thickened epoxy and do the glue up.
Upon occassion thirsty wood has sucked enough epoxy out of the glue mix that a "dry" joint resulted and the joint was no good.
I don't think the orientation of the veneers makes much difference (other than looks) as long as the patch isn't too big.

[Wooden Boat Fittings]

.
I'd do as Bob suggested too, Jack. Once you've cut out all the rotted wood (and then some more, to be quite sure,) well and truly soak the surrounding timber in CPES before further work.

I had Aileen Louisa's burden boards stored on end out of the boat in what I thought was a safe location, only to find that water had wicked into the end grain, and about six boards forming one segment had developed rot. So after removing the bad timber I soaked the adjacent wood in CPES for as long as it would accept it, and that was that -- doggone rotgone.

Mike

[J. Dillon]

It got warm enough to do stage 1 of my rot repair. I cut a 1/32 D.fir veneer with an ordinary aviation snips to fit against the fiberglass on the outside. It was a simple trial and error fit . Once satisfied it was close I back beveled to a feather edge with a sanding board. A right angle up and down piece was also cut to fit only it was 3/32" thick. It served two purposes

1. to receive the "stay in place prop" and a start for the second layer to be fit on stage 2. The prop or leg other end is clamped to a board spaning the width of the boat about 2' in fromt of the repair. It was held in place by a pair of clamps.

In successive stages it might be used again but maybe by that time I will have enough thickness of veneer to use staples to hold all in place while the epoxy sets up.


http://img84.imageshack.us/img84/6436/rrrotrepairstage1in6.jpg

Another small leg helps hold the longer leg in place in place while the epoxy cures.
JD

[J. Dillon]

http://img339.imageshack.us/img339/4431/rotrepair2ndlayerstarteze0.jpg

The start of the 2nd layer

http://img246.imageshack.us/img246/337/rotrepairupanddowntz8.jpg

2nd layer down and epoxied

In this image the second layer of veneer has been fitted , back beveled and epoxied in place in an up and down . I used a system of props to keep it in place while the epoxy cured. A heater with fan was positioned to apply heat to the repair area. Because the boat is still under winter cover the heat was contained. When cured I dressed up the surplus glue edges with my Dremel tool.

http://img412.imageshack.us/img412/367/rotrepair3layerjpgstaplau6.jpg

3rd layer stapled in place

I next fitted the next veneer layer in three across pieces as shown in the image back beveling as much as needed. When satisfied as to fit and before glueing up, I laid down the three pieces on a piece of cardboard to make a general pattern as to a guide for the next layer of veneer. It was cut with a little over sized to allow for the back bevel. The outer surface will need to be larger to extend to the sound portion of the transom.
The above image shows the third layer in place. At this point I had sufficient area and thickness to apply staples to hold on the veneers. I applied a little wood dough to the edges. After curing I removed the staples and sanded down the assembly thus far. I also laid down a straight edge across the repair, it’s edges resting on sound surfaces . This is to determine if the layered veneers are parallel to what will be the finished repair. I used two thicknesses of veneer as a kind of feeler gauge, under the straight edge and on the surface of the veneer layer.

http://img143.imageshack.us/img143/7966/rotrepair4thlayerstapleqr2.jpg

Forth layer stapled in place

The forth layer was cut , back beveled and fitted with the aid of the cardboard pattern.

Above we see the 4th veneer layer stapled in place with a little wood dough applied to the edges. When cured the edges will be dressed down to make a smooth surface for the final veneer layer

The last and final veneer layer will be across and made in three pieces and slightly thicker then needed. This will enable sanding down to be flush with the transom surface. A little fudging might be needed but since the entire repair will be painted I can bury and paint my mistakes.;)

JD

[CharlieCobra]

Nicely done JD.

[J. Dillon]

Thanks Charlie.

http://img524.imageshack.us/img524/3594/rotrepairdremeldressingxi6.jpg

I used the dremel tool to dress the scarfs in preparation for the last layer
Notice the across lay out lines for the fifth and last layer. It was cut from clear white pine just a hair thicker then needed. I fitted it in three pieces, the center one first. This gave me two straight lines to measure from in fitting in the upper and lower pieces.

http://img168.imageshack.us/img168/7807/rotrepairfthlayerstaplejh5.jpg

The final layer stapled in.

http://img404.imageshack.us/img404/8180/rotrepairfifthlayersandrl2.jpg

The last layer sanded and ready for paint

http://img514.imageshack.us/img514/4186/rotrepairpaintedfinus8.jpg

The finished repair after two coats of matching paint.

JD

[wbrent]

Great job. Simple , practical and very effective.

[Mrleft8]

Boy Jack...... You sure like making a simple fix a complicated matter don't you?! ;)

[J. Dillon]

Lefty :p
JD

[oakman]

Excellent solution for a nasty little project.

Oak

[SawmillBrook]

outstanding post. Very informative, thanks (not as good as "the story" though).

Andrew

[Lew Barrett]

He suckered us in and then showed the repair like a flip machine at a peep show! Not intuitively how I'd have thought it to be done, but an effective result. We finally know what a Dremel is good for! I thought they were only useful for trimming a dog's nails. Thanks JD.

[kulas44]

I think there is a lot more rot in the picture than was repaired.