Re-finishing Mahogany

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
BlueSmoke
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Re-finishing Mahogany

Postby BlueSmoke » Mon Feb 22, 2016 10:10 am

I am getting ready to sand and re-varnish the mahogany on my 1977 SPORT 15. The previous owner did a great job on the wood in 2012 but did not keep it covered as well as he would have liked too. The topside wood needs to be sanded down completely but the bottom looks mint--not a scratch and has never seen the sun.

I am wondering if I should leave the bottom side alone and just do the sun-drenched top as well as sides? Or, should I do a couple coats on the underside? Or none at all?

I am meeting with [the previous owner] in a few week to get find out the brand and stain he used so I can match everything.

The last picture shows the good side (scratches on sides are just dust and crap and wipe off)
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macfam
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Re: Re-finishing Mahogany

Postby macfam » Tue Feb 23, 2016 9:33 am

If you have sanded both sides down to bare wood, ALWAYS coat top and bottom. If you leave one side un coated, it will absorb moisture and expand, the coated side will not. This can result in warping of the board.
On mahogany thwart seats that I have refinished, they were down to bare wood, and the first coat of Pettit Flagship varnish was cut 50/50 with Pettit 120 Thinner. Second coat also thinned about 20-25%. Then I used Flagship with multiple coats, lightly sanded, vacuumed, and tack clothed between coats. Application was with foam brush. perfection!!!

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Dutchman
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Re: Re-finishing Mahogany

Postby Dutchman » Tue Feb 23, 2016 12:11 pm

If you went down to the bare wood use CPES to prime and stabilize the mahogany wood before you put on many coats of Pettit or Interlux varnish. Having prepared and varnished thousands of square feet from grey, bleached and OK looking mahogany I lean towards Interlux Schooner varnish for its deep gloss and hue with CPES as a start. It is water thin easily applied and will keep the wood from bleaching and rotting and will have less maintenance(recaoting) in the future.
Read and see the history behind CPES and reasons why on this website http://www.smithandcompany.org/CPES/index.html
EJO
"Clumsy Cleat"look up what it means
50th edition 2008 Montauk 150, w/60HP Mercury Bigfoot

BlueSmoke
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Re: Re-finishing Mahogany

Postby BlueSmoke » Wed Feb 24, 2016 11:01 am

thanks for the infomation!

I guess I am still trying to figure out if I can leave the mint side (pic 3) alone.

If the last stain and varnish is in perfect shape on one side. Do I need to sand it down and start over or can I just hit the top peeling (sunfacing side) and edges of the board to make sure its all sealed and leave this side in picture 3 alone.

Thanks

goldstem
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Re: Re-finishing Mahogany

Postby goldstem » Wed Feb 24, 2016 12:37 pm

just do the top, exposed sides. for sides that are almost never exposed to the sun, since they are already finished, no need to sand and refinish.
every time you do this, (every couple of years, usually) you re-evaluate the unexposed surfaces.

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Dutchman
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Re: Re-finishing Mahogany

Postby Dutchman » Wed Feb 24, 2016 2:20 pm

BlueSmoke I don't agree with not re-finishing the "good" side as goldstem said.
Yes you don't have to go to the bare wood but at transition from bad to good you must sand more aggressively and wet sand the "good" side and when getting to the final coat of the "bad" side cover it with 2 more coats too.
Bottom line for varnished wood to look good and last thou must sand and varnish many times.
Even if you and up with a slightly different hue between bottom and top it still will be sufficiently protected.
EJO
"Clumsy Cleat"look up what it means
50th edition 2008 Montauk 150, w/60HP Mercury Bigfoot

BlueSmoke
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Re: Re-finishing Mahogany

Postby BlueSmoke » Thu Feb 25, 2016 2:53 pm

thanks guys! I am thinking the wood would be prety good eaither way as it is in such good shape and never seen the sun covered 70% of its life. That being said the hard work is in the sanding down to bare wood, not the varnish/ rough sand repeat.

Makes sense and not that much extra effort to rough it up and add a few extra coats while I am doing it anyways and the wood is already removed, painting station set up, and brushes wet...

sanding starts on Saturday!

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Dutchman
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Re: Re-finishing Mahogany

Postby Dutchman » Fri Feb 26, 2016 10:04 am

Good luck and post the results
EJO
"Clumsy Cleat"look up what it means
50th edition 2008 Montauk 150, w/60HP Mercury Bigfoot

BlueSmoke
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Re: Re-finishing Mahogany

Postby BlueSmoke » Wed Mar 09, 2016 6:01 pm

Got down to it today in the 70 heat wave in Boston!
Started with 80 grit on the belt sander - very light touch to get the old varnish off
moved to 100 on the palm then 120 on orbital.

What grit do you stop at before next step?

forgot to buy tackcloth and was getting late in day so decided to stop there.
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BlueSmoke
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Re: Re-finishing Mahogany

Postby BlueSmoke » Wed Mar 09, 2016 6:02 pm

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after pics with anchor hatch too. not pictured is side console.

Buckda
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Re: Re-finishing Mahogany

Postby Buckda » Fri Mar 18, 2016 2:24 am

You can start the finish after 150 grit or 180 grit sanding. Be sure to wipe the board down with a tack cloth before adding finish. Then 220 grit between coats if you let it cure (see instructions on the can). 220 grit before the final topcoat. Since you've taken it down to bare wood, you will want many coats of varnish. I'm talking, like, 10 to 12 coats.

BlueSmoke
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Re: Re-finishing Mahogany

Postby BlueSmoke » Fri Mar 18, 2016 11:04 pm

8 was the number I was going for so will see how it looks after 8 and go from there.

I am varnishing over some screw holes and plan on drilling a few more when I move the seat on top of the risers. My question is what do you recommend I put on the screws or wood to seal it while putting screws into it?. please keep in mind some day I will need to remove these screws.

Thanks!

macfam
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Re: Re-finishing Mahogany

Postby macfam » Sat Mar 19, 2016 8:12 am

The last slide of this attachment shows Stainless Steel wood screws(Phillips) with SS finish washers, and SS flat washers to prevent the finish washers from "cutting into varnish" preventing water to soak the wood, turning it black.
I prefer this method, but use NYLON flat washers vs. stainless steel flat washers. Ends up looking great!
http://smg.photobucket.com/user/HAPPYJIM/media/Ipe%20for%2013%20footer/MVC-006S.jpg.html

If you use the correct size screw, you shouldn't have to put anything on the screws to hold them. If I HAD to use something, I'd probably pick something "clear" or light colored.
For some projects, I've wet the hole in the hull with a bit of water, and with a toothpick, inserted just a tiny dab of Gorilla Glue, place board, insert screw and tighten. Gorilla Glue EXPANDS, so just a dab. It is tough stuff and water proof so far.

BlueSmoke
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Re: Re-finishing Mahogany

Postby BlueSmoke » Sat Mar 19, 2016 9:38 am

Thanks! finished product looks great!

Did you drill the thwart seat and riser out first? any tips on that process would be helpful!

One concern is my rails are not 100% vertical, I mean they are pretty close but also 30 years old...

macfam
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Re: Re-finishing Mahogany

Postby macfam » Sat Mar 19, 2016 12:59 pm

You can set your wood in place after varnishing(but COMPLETELY dry for several days). Pre-drill and screw in place, using your SS finish & nylon washers.
Not exactly sure what you mean about the rails not being vertical. Could you post a couple of pics?

BlueSmoke
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Re: Re-finishing Mahogany

Postby BlueSmoke » Thu May 05, 2016 10:49 am

The wood is done for now! (sorry about the photo orientation) The first pic there is some light that looks like a scratch, but its just a reflection...

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