Double Diagonal Mahogany River Thames Canoe - Hull sealing

[PatrickG]

I’m restoring a very nice 18ft ‘canadian’ rowing (or using two burr maple paddles) canoe, built by a River Thames boatbuilder in 1948. Construction is 4mm double diagonal mahogany strips with thin (no doubt now deteriorated) canvas in between, and ash ribs. I’ve stripped off all the old ‘copal’ varnish back to bare inside and out, done some woodwork repairs, and it’s now ready for revarnishing. Although it’s been stored for the last 40 years or so the seams between each external diagonal are really very good considering, but will obviously not be watertight. This is a credit to the quality of the workmanship and its construction – the fastening of the diagonal strips being done with about 5000 clenched copper nails. If the canoe was a boat to be left permanently in the water the seams are quite good enough to be expected to ‘take up’ satisfactorily - but that won’t be the case as obviously canoes spend most of their life out of the water! I really don’t want to coat such a beautifully original hull with epoxy if I can possibly avoid it. Has anyone therefore got any bright ideas as to how the hull could now be made reasonably watertight without the use of epoxy? Could 6-8 coats of Epifanes varnish, well brushed into the external seams, be expected to do the job? Any advice would be much appreciated. Hopefully some photos are attached.

 

[Paul Miller]

Hi Patrick,

You are on the right track with the brushed coats of Epifanes. I would start with the classic varnish and not the Wood Gloss.

I've found that the Wood Finish stuff does not like to dry solid if it pools or goes in a crack with the vanish would be thicker. The Gloss Clear will dry hard down in those cracks better than the other stuff. Then I'd go back to the Wood Finish to build up fast.

I've done a number of all wood Canadian canoes and it does keep them water tight.

Good luck,

Paul

 

[PatrickG]

Thanks, Paul

Could you please clarify. I'm not sure what you mean when you refer above to what seems to be three different products ' classic varnish', 'wood gloss' and 'wood finish' I normally only use the product called 'Epifanes Clear Gloss Varnish - starting with thinned coats and then building up over 6-8 coats to get a high gloss finish. Is this the product you would use to start with in order to fill the seams ? I have looked in the UK Epifanes catalogue and I can see there is in fact a product called 'Wood Finish Gloss which appears to need a minimum of 8-10 (!)coats on non-oily wood like mahogany. Is this the one you mean and if so why would you use that as opposed to continuing with the Clear Gloss?
Many thanks - your help is much appreciated

 

[Paul Miller]

Sorry to be confusing about the product names.

I used two different terms to identify the "Epifanes Clear Gloss Varnish", which you should use first followed by the "Wood Finish Gloss" and then finally topped with the Clear Gloss Varnish.

The Wood Finish Gloss will build 2 to 3 times faster than the Clear Gloss Varnish and you don't have to sand between coats. You might want to try some. I'll lay down 2 or 3 coats, then sand and lay down 2 more sand and then top with Clear Gloss a few more times sanding between coats.

The problem with the Wood Finish Gloss is when pooled or on thick in a spot it takes for ever to dry rock hard and that's most likely part of the formula that lets you get away without sanding between coats. It maintains a chemical bond of sorts. If you get the same pooling or puddle of Clear Gloss is will dry rock hard all the way to the bottom of the pool or puddle.

Attached is a picture of a few all wood canoes finished in that process.

Paul

 

[PatrickG]

Many thanks Paul, that explains it. I've never used the Wood Finish but I will now if it speeds up the process. Do you always gloss the inside hull? I was thinking of using Epifanes Rubbed Effect to get a satin type finish but I would be pleased to tke your advice on that. Those photos show what an excellent job you do! Thanks.

Sorry to be confusing about the product names.

I used two different terms to identify the "Epifanes Clear Gloss Varnish", which you should use first followed by the "Wood Finish Gloss" and then finally topped with the Clear Gloss Varnish.

The Wood Finish Gloss will build 2 to 3 times faster than the Clear Gloss Varnish and you don't have to sand between coats. You might want to try some. I'll lay down 2 or 3 coats, then sand and lay down 2 more sand and then top with Clear Gloss a few more times sanding between coats.

The problem with the Wood Finish Gloss is when pooled or on thick in a spot it takes for ever to dry rock hard and that's most likely part of the formula that lets you get away without sanding between coats. It maintains a chemical bond of sorts. If you get the same pooling or puddle of Clear Gloss is will dry rock hard all the way to the bottom of the pool or puddle.

Attached is a picture of a few all wood canoes finished in that process.

Paul

 

[Paul Miller]

Patrick,

You have asked the questions often discussed on this forum; shinny, semi-gloss, or matt.

Shinny will show every defect and is required if you show a canoe, but many people like the softer look of semi-gloss or a matt finish in an older boat or canoe. Most canoes had a shinny finish when original, but when the varnish oxidizes the finish will have a semi-gloss to matt appearance.

It's personal preference.

Don't forget to post pictures,

Paul

 

[Rollin Thurlow]

Even the best varnish does not make a very good waterproof gap filler. The wood is going to move and the seams will crack. If the seams are open or if you can run a knife blade down between the seams, I would squeeze a bit of 3M, mahogany colored, 5200 into the seams. Its strong and very flexible. The 5200 comes in std caulking tubes but if you squeeze some into a smaller plastic syringe then you can get a fine bead to squeeze into the seams, or you can just push it in with a putty knife. The 5200 can be cleaned up with denatured alcohol. Its kind of messy but does the trick.

 

[Gil Cramer]

5200 is used quite extensively with great success, but I personally won't use it because of the difficulty of removing it in the future. The manufacturer, 3M, now has a better method of removal,but I'm still skeptical. I prefer to use varnish thickened with wood flour to fill the gaps,after many coats of varnish have been applied. I accept the fact that it might need to be re-done every year or so, but it can always be removed with stripper.