51' Sailboat rescue: Mahogany Decking?

[Jason, VA]

I recently acquired a 1956 Ralph Wiley 51' Cutter sailboat named the Spirit. She needs quite a bit of work including having the entire deck replaced. It is a double-ender built with white oak ribs and fir planking on the hull. I won't get into my plans for the refit other than the decking is going to be replaced with plywood then glassed over. The original decking was pine running horizontally across the boat. The decking was fastened with bronze anchorfast nails. The original deck was comprised of 2" by 1" strips stood on end. My plan is to replace all of the decking at first with the plywood and then come back over with mahogany strips 1" by 1" epoxied to the plywood. Then I plan to seal and coat the mahogany with WS 105 resin/ 207 special coating hardener. Hopefully this should achieve a watertight finish. Is there anything I should be worried about as far as replacing the pine with mahogany? Would white oak be a better choice? Keep in mind that I currently have aproximately 900 BF of 5/4 rough cut honduran mahogany at my disposal. Any input is appreciated so long as I don't here any whining about the fiberglass. 1 layer of fiberglass applied in th 70's saved this hull so please don't get started on the purist crap.

[ 03-18-2005, 05:32 PM: Message edited by: Jason, VA ]

[Bruce Hooke]

As you may know, the usual approach to solid wood decking over top of plywood is to keep the solid wood very thin, as in 3/16" or so. The idea is that wood this thin will be constrained by the plywood from shrinking and swelling, and part of what makes this work is that the wood is thin enough so that as it tries to shrink and swell it does not have enough strength to break the epoxy bond with the plywood. So, one concern raised by your approach is whether you will get cracks that will allow water to get under the mahogany and provide a fertile breading ground for rot. Of course usually wood veneer decks are not sealed in epoxy, which should greatly reduce the amount of movement. Still, that is one concern to consider.

I guess the other question I would ask is why not build up two layers of plywood if that is what you need for strength and then go over that with a thin veneer of mahogany. What do you gain by 1" of mahogany?

That said, please realize that I am basically a small boat man, so this advice is based on my experience with boats MUCH smaller than yours. In other words, this advice may be worth what you paid for it! :D

[Jason, VA]

This is exactly why I asked this question. I have more than enough mahogany to due the entire deck. Typically the cost would be prohibitive for most people to due a deck in that fashion, but since the materials arent a problem I figured on 1" by 1" because I plan on nailing each plank to the next from the side by pre drilling and using bronze nails. There will be a thickened layer of epoxy under and alongside of each plank and the nails will serve the purpose of holding everything in place while the epoxy cures. If I were to scale it down and do more of a "veneer" at 3/8 to 1/2" thickness then fastening the planks to the deck and to one another would prove to be infinately more difficult I think. Your opinions are appreciated. Thanks

[Bruce Hooke]

With "veneer" planks one approach to hold everything in place that I have used is to run sheet metal screws down between the planks while the epoxy under the planks sets. A washer under the head of the screw holds the planks down and the width of the screw sets the spacing between the planks. After the epoxy has cured the screws are removed and the seams filled with either black epoxy or standard deck seam compound.

Another approach that I have read about (in the Gougeon epoxy book) but not tried is to hold the planks down with wide-crown bronze staples, the crowns of which are later clipped away and what's left is sanded flush. Bronze blends in well with teak, it might not blend in so well with mahogany -- you would have to do some testing.

Yet another approach might be to use staples with pads under the staples to allow you to easily pull the staples after the glue sets. BUT do some tests to make sure the staples can reasonably be pulled. The harder the wood into which the staples are going, the harder it is to pull them.

[imported_GregW]

Go to another thread in Misc.Boat Related and check out "George's Deck". It's pretty much what you are doing except on a new build.
Or use the link below, to get you there.

George's Deck (http://www.woodenboat-ubb.com/ubb/ultimatebb.php?ubb=get_topic;f=6;t=003885)

[Jason, VA]

I dont plan on having any gaps between the decking so the screw method with fender washers isn't going to work.

[sawcutmill]

"Horizontilly across the deck"? are you sure about that? usually it is laid Fore n Aft, bow to stern.
In regards to the above statement:"I dont PLAN on having any gaps"-- Plan on it, wood moves, that is why there are "gaps" called seams, on every laid deck I have seen.You could buy sheets of premade decking that would be seamed already, that might be the way to go. Teak decking Systems makes a product you might be interested in.good luck.

[rbgarr]

Did Ralph Wiley build as well as design your boat? If so, his yard is now Cutts and Case Shipyard in Oxford, MD [P.O. Box 9, 21654, (410) 226-5416]

You might consider talking over your ideas with them. They are probably most familiar with his designs and specific construction methods, and what might be the best way to use your mahogany in the reconstruction.

Good luck, and welcome to the Forum. You almost snagged Forum member number 10000 :cool:

[videoguy]

Jason one of the thinge you might consider is making a small 1/4 x 1/4 rabbit on one side of each plank and filling it with thickend white or black tinted epoxy.
http://www.imagestation.com/picture/sraid10/p618d8a5c8fa0b0af88051249cacec85a/fe08adf3.jpg
Of corse on my dory the planks are only 1/4 x 3/4
but I do like the look and it stands up well I re varnish every 2 years. smile.gif smile.gif ...Phil

[Thad Van Gilder]

I dunno if you're gonna do so well with a 1 inch "veneer" laminated over ply.

It would seem that you'd be way better off with a 1/4 inch thick veneer or :eek: planking the deck solid with all that swientia macrophylia you got

Damn. of all the the boats from dinghies to barquentines I've worked on, the only horizontally decked boat I've ever seen was an very old jersey garvey. No deck camber, but the sweep of the deck keep the rainwater from puddling.

-Thad

[carioca1232001]

I have posted the problem below on another thread (George´s decking) but feel it is more appropriate here:

The fore-deck of my 1962, 32 ft motor-cruiser is currently enduring the consequences of a massive cock-up that has only myself to blame.

To cut a long story short:

1. At the time of the first refurbishment as far back as 1998, I took off the aging deck planks and the underlying ply, until the fore deck beams were bared.

2. Instead of putting down some new ply epoxied-glassed over the deck beams as the naval carpenters had recommended - an "expert" at the club who told me NEVER TO INTRODUCE ANY NEW PLY INTO THE BOAT as it would certainly come under termite attack - new deck planks 1,5 cm (thick) X 10 cm (wide) were laid directly over the deck beams . These planks had a tongue-and-groove fit and copious amounts of araldite (epoxy-glue) were applied in between them and into the screw holes reaching into the deck beams, during the fitting operation. In my mind at the time, that was the recipe for ensuring a water-tight deck redface.gif

3. When the deck started leaking into the fore cabin below and to avoid the undoing the araldite-bonded deck planking, I moulded out and installed a polyester-glass mat (waterproof/tarp !) to fit exactly over the said deck planking, making sure that the periphery/contour of the mat was sealed with Sikaflex . Over the mat I installed some new 7 mm (thick)x 10 cm (wide) planking embedded in Sikaflex with screws reaching down into the first layer of deck-planking, perfectly confident that now the deck-sandwich would be water-proof. However, it is worse now than ever before as water is being trapped between the two layers of deck planking and the polyester mat. Smells mouldy too, which is sort of dangerous.

What do I do now ?

Option 1. Rip out the top layer of deck planking and whatever remains of the polyester-glass mat. Install a 4mm-6mm thick epoxied-glassed ply over the bottom layer of deck-planking. Install new deck planks over the ply with screws reaching down into the first layer of planking, and of course, generous amounts of Sikaflex.

Option 2. Rip out EVERYTHING and get back to square one, i.e., bared deck beams. Install 4mm-6mm epoxied-glassed ply over the deck beams and over this, new deck planks set in Sikaflex. This route should entail a tough time breaking the araldite- bonding between the first layer of deck-planking and the deck beams.

All suggestions and advice welcome

[fair&fair]

One of the nice things about a teak deck, whether natural, or glued to a plywood or fiberglass base is that it provides a really nice nonskid surface if untreated and left bright. It's relatively maitenance free, due to its natural oiliness, and it looks great to boot. It seems to me that gluing mahogony on top of the plywood and the sealing it in epoxy will just give you a slippery deck. Having all that mahogony must be nice, but it could be used for all kinds of other things. Someone mentioned teak decking systems above, and I would have to second that as a good option. Once you provide them with measurements of your deck, they will come up with a complete deck for you to glue to the plywood. By the way...I am by no means a traditionalist, but I really do think teak is a fantastic decking surface. Mahogony is a durable wood like teak, but not as much so, particularly if it's going to be walked upon. At the end of the day...I think your proposed method would actually work just fine. Once sealed and glued together to form a monocoque, the mahogony would not move all that much, but like I said, you would have a slippery deck...one that needs some artificial nonskid. If you need to do that, you might as well just use plywood and cover with glass and a nonskid paint, or plywood and dynel set in epoxy.

[Jon Curtis]

Jason, the problem I see using the mahogony epoxied down & edge glued is:

1) the epoxy will either split on the seams or worse the wood will split in between the seams.

2) Even 207 hardener won't hold up under the VA sun. Epoxy starts to weaken at about 120 degrees & It will be a maintenance nightmare if you try to keep it bright.

If you really want to use the mahogony, I would cover the ply with epoxy & glass like planned and then 5200 the mahogony to it. Use a polysulfied or something else (not 5200) for the seams. I have had good luck with west marine's multicaulk. 5200 will break down with uv & doesn't like teak oils. Then I would either oil it with something (see norwegian varnishing oil post) or paint it a light color. What are the covering boards made of or is the ply going out to the hull edge?

I'm in the Tidewater area of VA, are you up north?

[wolfietuk]

A friend is putting a teak deck on his owens much like Jon describes. teak cut to about 1/4" laminated down with 5200. A 1/4" gap between 1 1/2" slates, filled with a black seam compound and sanded smooth. Everything can move fine. My front hatch is done the same way with mahogony and holly, with no gaps (at 20" movement isnt a real problem). It is CPESed covered with 2 oz cloth and epoxy and about 10 coats of varnish with uv protection. After a season in Charleston SC (used by a family weekly) it looks great. but it is slick as owl s--t. I was going to do the whole deck,but didnt want the matainence. it will be revarnished every year, think about that.

Rick

[Jason, VA]

The original decking was pine and laid side to side and it held up fairly well for the better part of 5 decades. However the original boat had a flush deck. I am going to put a small elevated cabin on it to gain some more room inside so that will cut down on the deck area to be covered. I could tongue and groove the wood and then epoxy it together which should minimize the amount of movement from 1 board to the next. Again your opinions are apprecieted, but teak isn't an option. I prefer mahogany and will be going that route since I already have the materials.

[Buddy]

207 hardener won't hold up in UV, especially set face up to the sun. It will quickly turn a cloudy yellow. Must be clear coated with UV absorptive varnish or UV reflective paint so...whatever you do to the mahogany won't involve an epoxy top coat.Could you oil or use a wood dressing? I can't thing of an mahogany decks except the varnishes ones on classic runabouts, and then those aren't made for mere mortals to walk upon. Beautiful, gloosy, slippery varnish.

Also, most of the success of strip overlaid decks DEPENDS on the pretty wood strips to be on a fraction of the thickness of the plywood underneath. Really thick ones can and will absorb water vapour, swell across the gain as is the nature of the cells, and the stress will relieve itself by buckling and breaking the factory glue bond between the first two veneer layers of the ply.

If you could bring yourself to consider a dynel and epoxy over your ply, then paint the deck, you could get a much more long lived and low maintenance deck, and then use you time and mahogany to make beautiful varnished deckhouses, coamings, and interior furniture for your boat.

[outofthenorm]

Jason, I know that you don't want any of what you so delicately called "that purist crap", but I submit the opinion that if the wood you have really is Honduran mahogany and not some lesser species, then using it for decking seems like inappropriate use of a scarce and truly remarkable material.

If using it for this purpose is a durability issue, then I think you're in for a surprise when the inevitable (and it is inevitable) water incursion happens. The encapsulated honduras will turn black and rot to nothing quicker than thought. Mahogany likes to be dry, or at least well ventilated.

If it's a cost issue, you could sell the mahogany for three or four times the cost of quarter sawn douglas fir or yellow pine, both of which make a fine looking, long lasting deck and you'd have a ton of dough left over. Or it would probably be a straight swop for milled teak.

Finally, from a seamanship POV, whether it's honduran or not, have you considered the fact that your new deck will be heavier than the original by a significant margin, maybe hundreds of pounds heavier? Above the waterline, every pound counts - even on a big boat.

Just one wooden boat guy's opinion of course.

- Norm

[Torna]

As Buddy mentioned, think about Slippery.

With all this beaut mahog, it seems you're planning on finishing it bright. Beautiful indeed!

But get some spray on it and into a rough sea and that sounds like a recipe for bruized shins, stubbed toes, or WORSE.

So next season you'll add some anti-skid to your varnish - rats, it doesn't look so pretty anymore.
And then the anit-skid is gonna trap dirt & gunk. Rats: dirty, rough, varnished wood. Can't see the beauty of the mahog, could've used any ol' wood under there.

In reality there are very few (I can't think of any) bright decks on sailing vessels. Mebbe there's a reason for that.

2c
-leif

[Jason, VA]

Couple of links you might want to check out since West System 105/207 combination wont stay clear. According to WS you are supposed to apply a UV resistant varnish over top of the epoxy. The purpose of the finish is to extend the life of both the wood and the varnished finish so you dont have to revarnish every season.

http://www.epoxyworks.com/18/product_207804.html

Here are some examples of its use:

http://www.epoxyworks.com/20/Teak_deck.html

"The teak surface may be left natural or finished with marine-grade teak oil, marine varnish or WEST SYSTEM® 105 Resin/207 Hardener and a high quality two-part polyurethane varnish."

http://www.epoxyworks.com/18/varnish.html

"Two-part clear polyurethanes are known for superior UV resistance and scratch resistance compared to traditional varnishes, but they have shown mixed results when applied directly to wood. They also tend to develop cracks due to expansion/contraction of the wood. Two to three coats of epoxy also provide a stable base for clear two-part polyurethane finishes. Applied over epoxy, they perform beautifully together and outlast either coating used by itself."

So as it stands now I will probably use 1" Wide X 1/2" Deep strips of mahogany, tongue and grooved, epoxied together and down to the deck. Coated with 105/207 WS, with 2-3 coats of a 2 part varnish. This is going to mainly be an ocean going vessel with dual headsails both on roller furling systems so when underway only 1 person will need to handle the boat. Keep the comments coming they are appreciated. And hopefully soon I will have a website up tracking our progress on the boat. Thanks again for all of your input.

[Charles Burgess]

Mahogany won't last long as a decking material no matter how you lay it on.

Southern Yellow Pine is an excellent decking material and is a lot like Teak in regards to durability and being able to leave it raw. Looks great after a holly stone session.

Yes, the color is a little different, but it is a traditional decking material...even used on many of the clipper ships during the 19th century.

Laying ply over the deck beams sounds like an easy solution to traditional decking...but in reality it takes more skill than simply using the traditional approach. Since SYP isn't too costly at all, I recommend a straight foreward traditional technique...you can achieve amazingly watertightness with a router to do your own tongue&groving.

[Thad Van Gilder]

I have worked on a few bigger boats with laid mahoghany decks.

They were all either painted or oiled, but they did last as well as pine or cedar or flat gran doug fir, it seamed.

-Thad

[Puka]

Good attitude Jason. The object for me also is to use optimum products, to get sailing in the shortest possible time.

[chucksw]

Hi Jason,
I've used the West 105/207 Epoxy with varnish. It is great for brightwork trim and for hulls and decks of canoes, kayaks and small boats. On the deck of an oceangoing boat, the epoxy/varnish treatment will be treacherous footing. One slip and you will be alone in the ocean or hanging from your lifeline. The deck treatments I think to consider for this would be oiling the decks, leave them bare wood, or paint over the epoxy with non-skid granules mixed into the paint or apply a material like treadmaster which is a rubber non-skid material glued to the deck.

Chuck

[Jason, VA]

Thanks for the encouraging comment Thad, it is most definately appreciated in this thread. What about grip tape? I was thinking about some thin strips in critical footing areas. It should give plenty of grip, its cheap, and it can be removed when its time to refinish will minimal effort or damage to the decking. Any thoughts?

[Art Read]

Uhmmm... Primarily an ocean going vessel? With epoxy/varnished, athwartship laid mahogany decks? You haven't spent much time at sea yet, have you? No offense, but I'd consult with a professional boatbuilder before proceeding with your plans. Your mahogany might be "free", but your time sure as hell ain't. And you just may want to sell that boat one day. I've gotta tell you, one look at the deck you propose installing, and I'd move on to the next prospect on the broker's list. (Just my opinion...)

[Art Read]

"The purpose of the finish is to extend the life of both the wood and the varnished finish so you dont have to revarnish every season." :D

Now I KNOW you haven't been at this long... Ever heard of "snake oil", son?

(BTW, done any calculations on what your proposed "raised deckhouse", combined with your new, heavy deck, will do to your center of bouyancy, righting moment, trim or load waterline yet?)

[ 03-23-2005, 01:57 AM: Message edited by: Art Read ]

[Art Read]

"What about grip tape?"

Works great on skateboards. Last about a week at sea. Ever been aboard a boat who's owner decided to put some on the companionway steps? Even there, protected down below, it starts peeling up half way through the season. (And just try to keep it clean...) Take a walk down the docks at your local marina and look at what the boats with "non-skid" surfaces applied to the decks have. Kind of a dark gray, diamond pattern, thick, PERMANANTLY applied layer over the gellcoat. Good traction, but plain hell on your knees or knuckles when you're out there wrestling a headsail down a hatch...

"Purist crap" has such a large following because it works. Back lots of boatyards all over the world are filled with forgotten "experiments" taken on by folks who thought they knew better than all those tradition bound old farts in the boatyard...

[ 03-23-2005, 02:31 AM: Message edited by: Art Read ]

[Chayco]

I am guilty of self promotion...but appropriate to this particular thread.

Biggest...(only ?) complaint against teak decks is the cost. Island-teak.com has 3/16" thick strips @ $6.65 USD per square foot. Low overhead..one man operation. Enough said.

Sikaflex has a new deck caulking compound, 290 DC that is supposedly formulated to work with teak. 3m 5200 for bedding with Sikaflex 290 DC for caulking ? Opinions...experience ?

Regards...Ken

[Jason, VA]

OK so definately a resounding no on the grip tape..not a problem. How about taping off strips on the last layer of varnish and using the sugar/salt method that has undergone debate on this forum as well. Also cheap, effective, and the majority of the threads I have read people have been split 50/50 as well. Any thoughts?