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superdave 03-04-2007 03:17 PM

Choosing finish for mahogany project
 
I am building a new hatch for my companionway, and am using African mahogany. I've heard a lot of stories on varnish, and don't really know what my best options are. I chose mahogany for the durability (especially UV), and even though it looks great, I'm not after a $10,000 finish (this is for my 23' Coronado).

So I'm looking for experienced opinions on what I should consider using to finish this hatch. I would prefer the best durability with the least annual effort, and whatever I choose must be very good about waterproofing and UV protection. My guess is that I will be staining the mahogany slightly (has a dark pink color now), but I don't know if that affects the finish at all.

Oh, also; since the hatch will have many planks side-by-side, what is the recommended way to waterproof? Can the type of finish handle this, or is some sort of caulking required?

Any and all help would be appreciated!

-Dave

Freesail99 03-04-2007 03:25 PM

I was at a boat show and they painted on epoxy and varnish over that. This was on plain plywood. When it was finished, It looked like a sheet of glass with a very nice "stain" or color. I have african mahogany inside my cabin, nice looking wood.

sailaway21 03-04-2007 04:03 PM

And what is the chemical treatment you do to it that gives it that deep red finish?
Experiment with a small piece for appearance testing. The epoxy will do a wonderful job of sealing/waterproofing the wood. The varnish will give it shine, depth, and lustre as well as protect it from UV damage. Regular spar varnish, not polyurethane varnish-it breaks down quickly under UV light and flakes off.

Sounds handsome.

ianhlnd 03-04-2007 04:40 PM

If the planks are glued to each other there shouldn't be any problem with leakage, be sure to use a proper sealer, Smith's 2 part epoxy sealer is about the best it is. Good thorough sanding ending with 200-220, then varnish with a good varnish, recommend Pettit 1015, fine sanding between coats, min 4.

Sounds like you've got some good wood, good luck on the project.

SailorMitch 03-04-2007 07:57 PM

I like using Epifanes products, particularly their Wood Finsh (a synthetic varnish) on my exterior teak. Another possibility is Bristol Finish, which is a two-part product that gives good results.

I'm unclear what you mean about the planks. If you are gluing them together, I'd use epoxy, which must be protected against UV (varnish over it.) You also can leave the planks separate, but then you have to notch the edges that meet so that the water cannot come in. Hard to explain, but, for example, on the very bottom board, the top edge would have a notch about 1/2 inch deep along the front edge (about half the thickness of the board itself). The next board up would have a similar notch on the back edge so that when the two meet, the water would have to go "up hill" to come in the hatch.

My companionway hatch is in 3 pieces and that is how they fit together. Make sense?

NOLAsailing 03-04-2007 08:06 PM

I'll second the suggestion for Epifanes Wood Finish Gloss. It is very easy to apply (sanding between coats is optional if re-coated within 72 hours) and I found the finish to be excellent. I also applied it to mahogany.

It stood up to 12 months in the Louisiana sun before I put on a few maintenance coats. However, the finish looked great even after the full year.

You can also build up with the WFG and do the last couple of coats with a more traditional varnish.

Here's a photo of the varnish on my companionway boards as I neared the final coats:

http://www.triton218.com/sitebuilder...ng-570x425.jpg

Goodnewsboy 03-04-2007 09:59 PM

Mahogany is one of those open grained woods that absolutely require paste wood filler before any finish is applied. Failure to do so leaves the grain open despite the finish, and water will get through.

Paste wood filler stain is offered by Interlux and Pettit, and it is very easy to use. (Colors are usually light or dark red and light or dark brown for mahogany)

Once the wood is filled (and stained) proceed with whatever finish you choose. Use something with UV filters in it. If varnish, put at least ten coats on, rubbing it out with fine sandpaper or scotchbrite between them.

When your masterwork is complete, consider a canvas cover to protect it!

superdave 03-04-2007 11:06 PM

Okay, thanks for the input! I think I've decided on the Interlux Interstain product for the filling and coloring. I would have just gone with one of their varnishes (likely Goldspar), but you've turned me on to the Epifanes varnish.

When it comes to Epifanes products, it looks like the "Gloss Wood Finish" is a bit pricier than the regular "Clear Gloss Varnish", and I see that it does not require sanding between coats. Does it hold up as well? It seems like perhaps the regular varnish is tougher... but easier scores points here, as well!

At any rate, I now feel like I have a full picture - thanks again!

-Dave

Goodnewsboy 03-05-2007 07:25 AM

A note about "no sanding required."

The sanding between coats is not just for adhering the next coat, but also for progressively smoothing the surface to that desirable final gloss. If you really want a smooth shine, wet sanding by hand with a rubber sanding block is the way to go.

If you go with varnish, remember that a new coat is needed whenever water fails to bead up on the surface. A quick coat applied at that time (after a light scrub with extra fine scotchbrite) will save a lot of stripping and refinishing.

I have an old Lyman runabout that has mahogany plywood decks that are varnished. They have never had to be stripped for refinishing in the 15 years since I renewed the wood. I apply a fresh coat every year or two and keep the boat covered when not in use. Score one for a cover.

At the same time, the varnished transom is never covered and it has likewise never been refinished since I originally refinished it some 20 years ago. The sun doesn't get to shine directly down on it, and it gets at least one new coat ever year.

Horizontal surfaces like your hatch get the worst sun exposure and need the most protection.

Freesail99 03-05-2007 11:20 AM

Don't forget to use the epoxy it will safe you a lot of grief later. I also think the end product will look better with it.


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