An interesting project - Bilge in sheathed timber boat

Hello all,

I've bought an old 25' timber motor boat off a bloke who'd started to prepare her for sheathing. She's a beautiful old girl, and was designed and built by a highly regarded yard in Sydney in 1948. She is planked with Oregon (Doug Fir) below the waterline and Queensland Maple on her topsides.

The previous owner (apparently a shipwright) has completely refastened her with stainless steel screws, sistered all the required ribs, and had started filling all the seams on the port side with thickened epoxy. The ribs are a very high density plastic that have been heated, bent into place, and have set - completely untraditional, but are rock solid.

Its been in this condition for a number of years, and as the timber has continued to dry out, alot of the thickened epoxy has come loose or where the bond is very good the timber has cracked.

I'm going to rout out the remaining epoxy in the seams and spline this boat with Oregon/epoxy splines and sheath her with heavy bi-axial glass. (I know this will attract howls of dissatisfaction from many ).

My aim will be to keep the bilge as dry as is humanly possibly by using dripless seals for prop and rudder stocks, and ensuring the ventilation is very good. The cockpit is fully covered as well, so she will be less likely to collect lots of rainwater in her bilge than some other boats.

My question is about what to do in the bilge. Should I leave it bare, or should I be applying a primer or linseed oil to slow the absorption of water into the timber before the water can evaporate?

 

bump,
and congrats on your purchase.
Do you have any photo's?
about your bilge question, I have no idea, but I would assume that epoxying the hell out of it would be one of the options too (though quite possibly not necessarily the best).
Good luck,

Hans.

 

It ain't traditional construction ...anymore.
And it ain't modern.
Plastic frames????????
Stainless fasteners below the waterline!!!!!!!!
Encapsulate it completely and hope like hell you have done a good job and water doesnt get to the fasteners.
I know what you are up against.:!:

 

Hi Roly,

You think I should replace the fasteners with monel or silicon bronze?

 

Depends what you are trying to achieve. If going to traditional and replanking
and caulking.......yes. As the expanding wood gets wet and wet stainless in the absence of O2 is subject to crevice corrosion. This I believe is minimised by certain purpose formulated stainless.
I guess the previous owner refastened with 316 at best,thinking of encapsulation.

If you are re-splining with the same density timber as the planking, with no provision for caulking, and sheathing the outside, then you are commited to to total encapsulation.
That is,epoxy sheathing outside and multiple neat coats of epoxy on the inside.
Then, hopefully moisture uptake of the dry planking is minimised.
The structural integrity of the hull will be reliant on how well the the boat was re-framed (reribbed) and re-fastened, as heavy sheathing on the outside would only surfice if in the range of a stand alone GRP hull. (If the frame integrity is suspect)

It is a difficult decision and ultimately is driven by your expectations of the finished product.
Best you have a b/builder/surveyor look at it and give their opinion.
Each case, IMO, on its own merits.

 

If you're going to use epoxy, then you have to go "all the way" or use something less costly like paint.

Epoxy on one side of a piece of wood isn't going to help anything. A thin sheathing of cloth will only provide abrasion resistance. If going epoxy you have to encapsulate to lock out moisture gain. Without total encapsulation, you'll still have dimensional changes because of moisture content, the same is true of a sheathing.

The problem with this approach, on a traditional wooden hull, is not every nook and cranny can have epoxy oozed into it. This will permit moisture ingress, where it will get trapped underneath other coatings., in joints and generally cause problems.

As a rule, it's much more difficult to incorporate epoxy and sheathings, into traditional wooden boats then any other type of craft.

As to the bilge, you can do either. Since you will not be able to truly encapsulate the separate pieces of lumber on your boat, you're going to have issues with sheathings and epoxy coatings. The only advantage to coating the bilge would be to apply an abrasion barrier (cloth sheathing) from things that may scoot around down there underway.

In other words, sheathing the hull will provide a marginal amount of scratch protection. If a thick enough skin is applied to the exterior, then you can seal up the outside of the boat, but at a greater weight ('glass isn't light). This isn't the problem with most wooden yachts. The water coming through the plank seams rarely causes problems (unless it's too much), it's the sweet water from morning dew, rain and condensation that cause the majority of rot related problems on boats.

You're correct in wanting a dry bilge, but this water usually comes from leaking decks, fittings, hardware, hatches, etc., which eventually finds its way to the bilge.

No reputable builder I've met, would recommend stainless fasteners for a boat, unless a short life span was expected. In short, stainless steel will rust just about as quickly as mild steel underwater or buried in wet wood. This effect is dramatically accelerated when saltwater is involved. Stainless is only rust free is exposed to air (free oxygen).

 

An interesting project...

As above. Get rid of those stainless steel fittings as fast as you can. As for the bilge - a good coating of pitch has served many a generation. Failing pitch - try a couple of coats of auto 'underseal' - but it takes far longer to dry.

 

OK, thanks everyone. That's the information I was after.

On another tack, what are your thoughts on removing each plank one by one, cleaning the interior surface, a few quick coats of unthickened epoxy, and back on with the stainless fittings. Thickened epoxy between plank and (roughed up plastic) rib. Then I should have total encapsulation of planking and fasteners when the sheathing goes on the outside.

Keep in mind, this hull is completely bare, and relatively new fasteners are in place which will come out quite easily. Its 25', and probably has 25 planks on each side, so this isn't a huge job for a guarantee of a good end result.

 

Ultimately total encapsulation with epoxy will let in enough water to cause problems.If you stick to recommended BB practises you can sleep easy and get the longest life from your work. Once again, depends on your expectations.
How long is ultimately.......proportional to the thickness of you encapsulation (mm) X maintenance (1--->5) divided by years spent on a mooring.

I replanked my hull and it had zinc screws still perfectly intact after 30yrs in the ocean with only filler & paint to protect them.Some of them (20%) were shot.I wouldn't use them, or SS below the waterline.
X-yachts have a glassed (polyester) galv.m.s. grid in their boats?? God knows how long the life expectancy of that is???

 

Does anyone know if there is a way to tell the difference between SS fasteners and other materials, ie monel etc? I have just assumed they are stainless, but I could be wrong.

Any advice would be appreciated

 

My boat was made with monel fasteners, and most of the screws and even nails said such on it, but this was over 40 years ago. Don't know what they do now.
Someone else should chip in soon and help you with that one.
Somehow I would be doubtfull that they would be monel simply for the price of such today.

Your best bet IMO would be to talk to the previous owner. Even if you figure out on your own they are stainless, you will want to know what grade they are.

oh and...
PICTURES PICTURES

 

M

Brands01, monel screws often have an M insgnia on the head , they'll probably be of a traditional "woodsrew" appearance with countersunk head- tapered shank & cut thead the staino screws will be more likely of a self tapper style of either pan or countersunk head. Monel screws are also very slightly magnetic- but so are some staino!Regards from Jeff.

 

Sand the heads on several fasteners and use the color as a guide. Stainless will appear silver and have rust stains if in an underwater application or in wet wood. If this screw was extracted you'd clearly see thread break down from rust, with possible cracks and surface pitting very likely.

Monel (great stuff) is a nickel/copper alloy will have a greenish/yellowish tint to a darker silver base (70% nickel).

Bronze is a copper/tin alloy with other things added (like zinc) to improve its qualities. The color is usually dictated by it's copper content. Phosphor bronze is copper looking (95% copper), but slightly yellow, while Tobin bronze (60% copper) is distinctly yellow. Most of the bronzes found in boats will have a fairly yellowish look to them, when sanded clean.

If you're finding bronze fasteners with lots of reds and oranges, you've probably got some "fastener sickness" issues causing de-zincification, which if not fixed, will eat all the affected fasteners to nothing.

Again, no reputable builder will install stainless fasteners, if long life is expected. Iron and stainless fasteners are used in down and dirty building methods, where the boat isn't designed to survive many decades. If a simple and inexpensive build is desired, then use cheap fasteners, but don't expect to pass this craft onto your grand kids. If you want the boat to survive you, your kids and their kids, then you have to use the materials that will tolerate the environment.

 

Looks like the fasteners are most likely stainless - they haven't been in the water yet, but they don't look like anything else

 

Savagely hunt them down and remove all. We call this "getting the iron out" in restoration work and it's absolutely necessary if long life and the well being of the vessel is of primary interest. Sometimes it's a vicious digging expedition to gobble them up, but it has to be done to insure any reasonable life span. Replace with bronze or monel, maybe even plastic stables or composite fasteners.