tar as leveler

Between the frames of my Garden designed, Bent Jesperson built wooden cutter, Jesperson used a tar of some kind as a leveler to avoid water laying in pockets between frames. The tar protected the wood and afforded drainage to the bilge pump. When first exposed the tar was nearly solid but became somewhat fluid (oozed) in hot weather. With some hull repairs nearing completion the boatwright is proposing to do the same using a roof cement/tar, one that can be poured in place but will solidify. The new planking has been treated with Boracare then Smith's CPES. I am looking for comments on his proposal and, if positive, recommendations for what to use. Help much appreciated; thanks.

 

Sounds logical.

Its always worthwhile to fill voids in the bilge that might trap water. With metal boats Cement is often used. " Chockfast " is the modern industry standard pourable goo that is used to fill bilge cavities.

I dont know if Chockfast, which dries hard, is suitable for a wooden boat that must be flexible. Tar, with its inherent oozzy mess is probably best.

http://www.chockfast.com/

 

Do not use Chockfast......it's rock hard when set.

"Tar" comes in many forms...it's all black goo......We use Modified Asphalt here in the temperate PNW.....it does not melt with our temps, but I know it gets bloody hot in the Chesapeake.

Modified Asphalt from Hal Industries (Vancouver) Type G SEBS, in a 60 lb keg about $100 from commercial roofing supply companies. You need to heat it to pour, it bonds really well to most wood and seals all checks and seams, stays flexible but not gooey.....

 

Since tar and gasoline or diesel fuel dont get along well , what method is used to fill machine space bilge cavities on a wooden boat ?

 

Cement

 

Tad, I see you are not far (relatively speaking) from Victoria, BC, where Jesperson's shop is located. How long has the Hal Industries product been in use there. I believe Daedalus was the 2nd boat he built in his own shop, completed in 1975. Could he have used Hal's modified asphalt?

Tom

 

Daedalus,

I couldn't say...you could call Eric and ask...but 36 years was a while ago and they may or may not remember. They don't do much plank-on-frame stuff these days, but they have done some six metre restorations recently. Bees wax is also used for this purpose but it's worse than the asphalt for melting.

Were you having melting issues when the boat was hauled for repair? If so it will be much better once she's back in the water and the bilge is cooler.....

 

They use something similar in aircraft bilges as well. Moisture condenses on the inside of the skin and drains to the bottom of the fuselage. The trapped moisture can freeze at high altitude and it can also cause corrosion in the alloy structure. So they have bidge drains to allow the moisture to drain overboard, I had written a replacement procedure to up date them many years ago when I worked at Boeing.

They use a real durable rubbery compound for smaller low points. It is mixed in two parts, BMS 5-95 is what it was called IIRC (spec number). It is also fuel resistant. On the larger "guppy ponds" they used a plastic filler much like auto body "Bondo". I do not know if this would be suitable for a wood hull because commercial aircraft get torn down and inspected on regular intervals and I have seen this stuff shrink and crack, and trapping moisture.

I have seen thick layers of roof cement (Henery's brand) also shrink and crack, so I would think you want something to say soft and flexible so it will stay bonded to the wood structure. Silicone caulk might be a good bet. But I would stay with what has proven to hold up well in wood boats, sometimes the "old fashioned" stuff still works best.

 

Tad,

Not at all, re melting. It was only when the garboard plank was removed and tar exposed that it began to seep out. It served it's purposely admirably all those years. I'll try contacting Eric. The Hal Industries product sounds like the most suitable.

Tom

 

Michael and Petros,

Thanks for your input. Tad's suggestion of the Hal Industries modified asphalt seems the best option from what I've learned. I will followup on that. Thanks again.

Tom

 

What was used in the bilge was probably hot pitch, likely poured in with the boat blocked level. It's an old school trick, often used to protect pocketed frame heels, from designers that didn't have any building experience. Restores cuss the stuff, but it is admittedly effective in some regards, it's a ***** to remove. I've seen two versions a real petroleum product and that made up from pine tar and other assorted home brew concoctions. Both seem to work, though roofing tar (black mammie) if applied heavily will crack substantially. You'll probably need a "hot mop" mixture of this type of goo, which can tolerate being applied heavily without splitting, excessive shrinking, etc.

 

Tar and pitch are pretty interchangeable words.....There are two general types of pitch....plant based and petroleum based.....the plant based one is commonly called resin and seems to have been taken over by the herbalists....costs about $10 an oz......it's apparently disappeared for other uses.......

Petroleum based pitch is what's available now, in one form it's called bitumen, which is asphalt......one of the problems in roofing with asphalt was that it dried out (stretched) over time and cracked...letting water in.....So the clever chemists came up with modified asphalt, which can stretch (dry) without breaking a great deal more than the old unmodified version....thus making for longer lasting roofing......I've no doubt you'll find a local supplier of modified asphalt in Virginia or Maryland.

 

Thanks all for the help. We'll try a roofing supply house in our neighborhood. Really appreciate the input. I'm much more comfortable going ahead with this.

Tom

 

Sounds like a lot of trouble to me, what about illiminating the places of water accumulation by removing the offending frames and re design, or what about holes.

Holes in wood is easy --its not like steel.

Once the planks have been fitted to the ribs what is there to stop water.

 

Frosty, the major repair work is substantially complete. Removing frames would amount to starting over. I think the guy doing the work for me would say too that drilling holes in the locations required would be difficult, and further that drain holes can plug. I've passed along the recommendation of modified asphalt. Thanks for the comments just the same.