Mahogany Deck Problems - Delamination and Discoloration

[Randy Sweet]

I completed the building of the Downeaster 18 about 4 years ago. I spared no expense as I figured that I would only do this size project once in my life. Mahogany ply 3/8" ribbon striped Sapele on the deck. Over the past (2) years I have had (6) places where the deck has delaminated (blistered) and recently one place that has discolored to kind of a gray. For the most part I dry sail the boat. It lives on the trailer in the driveway with a cover on it and I take it out only when the weather is good. The deck is covered by approx 9-10 coats of Epifanes varnish. Anyone have any ideas on what is going on with this stuff. I bought it from Harbor Sales, it wasn't cheap. By-the-by, except for the deck, the boat has exceeded my expectations in every way.

Thanks,

Randy

[Mr. Know It All]

It sounds like bad glue in the plywood but could literally be a hundred different things. Can you post a picture of the questionable decking? Could it be from the way you're storing the boat? Do you air dry the boat out before you cover it. The cover could be trapping moisture and heat.
Peace---> Kevin in Ohio

[Randy Sweet]

I tried taking a picture with the digital camera but it didn't come out well enough to show the graying problem. As far as the cover is concerned, it is a custom made canvas cover which should allow breathability. I'm sure it gets moist under there from time to time, hot too. But it seemed better than having a cover that wouldn't breathe at all. Did I screw up ?

Randy ----

[Mr. Know It All]

If the cover breathes that probably isn't the problem. I still think if it's delaminating after 2 short years, it's bad wood or water is getting into the wood and causing problems. If you decide to replace the deck, find another supplier that carries BS 1088 marine grade plywood. You might also consider using CPES to seal the wood (especially the edges) that will help keep the wood moisture content stable and it will help the varnish bond to the wood. Another thing I would do is find a varnish that has ultra violet protection to make sure it's not the sun damaging your wood. I know a really good marine plywood supplier in Ohio that I would highly recomend. I'll see If I can find their website and post it for you. Hope this helps.
Peace---> Kevin in Ohio

[Mr. Know It All]

After looking at this site I noticed another thing to consider, The face vaneer thickness. .6 or 1.4 will make a difference for sure. It seems the decking always goes first because of sun damage. Try using the best wood you can find so you won't have to mess with it for awhile. Here is the site----> http://www.homesteadhardwoods.com/
Best of luck.
Peace---> Kevin in Ohio

[Don Maurer]

The Harbor Sales website lists ribbon striped sapelle as BS6555 WPB, with .6mm outer veneers and okoume inner veneers. I do not believe BS6555 is a marine standard. From the description, it sounds like it is exterior grade. I don't know how that differs from marine grade. Most likely, it allows for voids in the interior layers. Also, the outer layers are very thin, so any sanding or flexing to fit a crowned deck may open hairline cracks in the outer veneer.

[Randy Sweet]

To Don's comment, does anyone know where I can find the spec for BS 6555 WBP and BS 1088 WBP ? I've been searching on the web but all I can find is a wood supplier's interpretation of BS 1088. I'd like to compare them.

Thanks,

[Mr. Know It All]

There is some good information on BS-1088 on this site, but again it's the suppliers condensed version. If ya really wanna see the real deal you have to fax or call them. ---------> http://www.worldpanel.com/Marineplywoodsintro.htm
I'll try to see what else I can find, interesting question Randy :D

[Mr. Know It All]

Another condensed version of BS-1088----> http://www.buckwoodcraft.com/details_and_advice.htm
Hmmmmmm.......they must not think we can handle it.

[Mr. Know It All]

And here's a site that compares the BS-1088 and BS-6566 ----> http://www.edensaw.com/f_marine.htm

[ 09-04-2002, 10:05 PM: Message edited by: Mr. Know It All ]

[Ken Hall]

Randy, in Pelle's thread you mentioned trying to nurse the plywood along for a time. How were you planning to do that?

I ask because a gentleman just gave me an International Fireball (US#3226) and the port side deck has some checking and some delamination of the top ply (marine mahogany plywood, built in 1968-69 by the man who gave me the boat). Thanks to Mr. Know It All smile.gif , I know where I can get BS1088 meranti or okoume reasonably close to home at a price that won't get me murdered in my sleep, and I am leaning toward replacement of the port side deck. However, as the boat is built with ring nails and resorcinol, I'm a little concerned about disassembly--never messed with anything like that. Thus, my question.

[Mr. Know It All]

Ain't we lucky Ken :D They even put a map on that site so ya don't get lost trying to find Vickery, Ohio. How many sites post prices either? The 5 X 10' sheets are nice too.

[wolfietuk]

If delamination is not bad you can try injecting some adhesive and clamping. This may work on small spots. As for the greying, I have had mahogoney do funny things in sunlight. even turn green!

Rick

[Don Maurer]

Must be a typo. Here is a link for British Standards online. It lists nothing for BS6555, but BS 6566 and BS1088 are listed.

http://bsonline.techindex.co.uk/

[Randy Sweet]

Ken, by nursing along the deck, I mean fix each area that has a bliter or delamination. I slit the affected area with a razor knife. I then carefully raise up each side of the slitted veneer and poke (technical term) West epoxy under it with a knife blade. Cover the whole area with wax paper and set some kind of a weight on it. It is not difficult to do, but it does take time. After it is done, put a couple of coats of varnish on it and you could never tell where the problem was. However, if you have a checking problem, there is really no solution but thin fiberglass over the whole thing finshed with a clear coat of something i.e. epoxy.

Good luck,

[Ken Hall]

Thanks for the tip, Randy, that sounds effective.

Fiberglassing the side deck did cross my mind, too. Sparrow's decks are bright, but I know WEST makes a formulation intended to take a bright finish. It seems easier than trying to remove that piece of ply, though if I can figure out (or someone will tell me) a reasonable way to do it without wrecking the boat I don't mind replacing the affected piece. About 4 oz. cloth, ya figure? Factors to weigh, factors to weigh....

[ 09-05-2002, 04:07 PM: Message edited by: Ken Hall ]