Thoughts on caulking alternatives

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G

gbroughman

Member
Joined
Feb 9, 2015
Messages
10
Location
USA
Vessel Name
MY Big Woody
Vessel Make
Grand Banks Alaskan
I am at the final stages of a major restoration project on a 1973 49' Grand
Banks Alaskan and have to make a decision on caulking the bottom. The boat is in a yard in Saint Pete Florida and I cannot find anyone who does conventional cotton caulking and have been looking into alternatives.

A couple of notes. The boat has been out of the water for over a year and after the initial wood shrinkage all of the seams opened up and allowed me to reef all materials out of them. The prior owner used 5200 as seam material and as one expects it pulled the wood off the sides of the seams in some places. Having spent days using a razor blade, I was able to clean them up somewhat. I developed a hatred for the stuff. There were three plank replacements I inherited, that used only 5200 (no cotton) and they will have to be cut out with a blade to replace them.

My initial distaste for 5200 has come full circle though. The replaced planks look like they are good for life and I started looking at that as an alternative to cotton caulking.

So without starting a word war of traditional methods I would like to know if anyone has tried using a modern sealant/adhesive as the only caulking? I would like to propose something different. This is what I am thinking.
1. Use a dado blade and/or a router to cut a consistent width seam, taking out the bevel.
2. Inserting a really thin strip of softwood at the stringers to minimize caulk intrusion into the boat.
3. After priming, fill the entire seam with a 5200 like product.
4. Water the hull inside and out to get to the proper moisture content.
5. Trim off excess proud material to get a flat paintable surface for bottom pain.

The pros of this method are
1. It is a permanent waterproof hull with wood continuing to be in contact with the water.
2. Plank separation due to fastener failures would not be a critical issue as each plank is "glued" to the one above and below.
3. In worm infested waters the likeliest infestations take place in the seam where conventional caulking fails.
4. Does not rely on a "soon to be lost" skill set of cotton caulking. Can be a DYI project.

The cons would be
1. The seams are somewhat permanent. In the case of a plank failure you would have to cut it out with a circular saw and plunge cutter in order to replace it.
2. Timing of installation with wood swelling and curing time could cause a squeeze that might break fasteners.
3. The time that the boat is out of the water and the drying shrinking process would have to be watched to avoid letting the seams open up enough for the bond to break.

I have been looking on the forums and the internet but have not found anyone doing this. Am I missing a big issue? Positive feedback would be appreciated.

Gerry
 
No but I'm planning there and the Grand Banks forum as well.
 
“ I can’t help but Have you posted your question on the WoodenBoat Forum?”

That won’t be pretty. :rofl:

In all seriousness It is a great question. I would be concerned about the planks shrinking when the boat comes out of the water. You would think that the 5200 would hold and the wooden planks would be torn apart?
 
Have you considered learning how to do it yourself? There are many videos on YouTube on how to do it. Only a couple of tools needed.
 
Russ even if he did learn he probably couldn’t come very close to doing the job a professional would do. It’s part of the cost of owning a wood boat. But no blisters will be found.
 
In the long run, wouldn't glassing the hull be easier?
 
Ask the people at BoatLife... I swear by their LifeSeal (not LifeCaulk) but would not use it b/c it won't hold paint. That said, they have been very helpful to me over the years.
The cotton is a huge job, I've done it on a 22' new boat. It seems like something from the dark ages but it is still used normally in new construction. If your seams are wide from drying, you need an expert too know how hard to roll/drive the cotton in and if they are too wide it will just go through. Normally seams are always primed b/4 the cotton goes in but the seam compound bond is then no stronger than the primer itself
Then the question comes what to put over the cotton. Conventional seam compound is too hard for a totally dried out boat and will not allow it to swell properly. Then if you put 52/4200 over it instead why not just use that.
 
I have looked into learning to pound cotton but agree with Nomad Willy that it would be an amateur job and there are no yards here that can be counted on to pull me if I need a redo. Glass is expensive and labor intensive. The input that I get from people is that it only prolongs the life of the boat for a while as it will rot from the inside.

To Brooksie, I will contact Boat Life and see what they have done. As far as the boat being dried out, it isn't anymore. We had one of the driest winters last year and the planks shrunk a lot to the point of wondering if the fasteners would hold. To remedy this I bought a sprinkler pump to draw salt water from the canal and set up a sprinkler system on the outside. I also bought two giant boxes of recycled terry cloth and lined all of the reachable spaces in the bilge and water it regularly as well. I am as close to being swelled up as being in the water.

That brings up another question. When boats are pulled in the winter. Does the moisture content in the wood dry out or freeze in place when the temperature goes to freezing? I am planning to travel up the east coast and it may need to spend a winter on the hard.
 
What's your budget? Maine has quite few skilled caulkers (not a soon to be lost skill here) who might be coaxed down to sunny FL this time of year for fair pay, travel expenses and lodging. Used a couple of different guys in the past on our old 40' wood boat.

Google "seam splining" as a possible alternative. Although I personally haven't seen it used below the waterline. Lots of discussion on the WoodenBoat forums.

I'd never use 5200 in the seams.
 
Can't help on caulking issues but that is a damn fine looking boat. Post some pics please.
 
Brooksie said:
Then the question comes what to put over the cotton. Conventional seam compound is too hard for a totally dried out boat and will not allow it to swell properly. Then if you put 52/4200 over it instead why not just use that.
Click to expand...

I used Slick Seam for years. Stays soft, squeezes out when the wood swells and can be painted over. The instructions say to launch immediately after application. I never did and had no problems.
 
You might try giving Moores Marine in Beaufort NC a call, they are as expert on this as anyone in the world. Perhaps they could refer you to someone down there in FL whose work they trust to at least give you a little advice. Worth paying something for, given the catastrophic consequences that could come into play.

https://www.mooresmarine.com/
 
"In the long run, wouldn't glassing the hull be easier?"

This is a Last Gap solution for a year or two of floating.

For any wooden boat the old tritional systems work.

Cotton is not Pounded into seams it is tapped in with a calking iron.

A 5 min job to learn but a thousand feet of seams is no fun.

Prime , cotton and then calking and bottom paint is the usual .

Using glue like 5200 would make a damaged plank repair far more difficult.

Do it like they did it in 1930 or 1960 (no difference) to most every wooden boat.

The softer seam compounds will stretch or compress as the boat swells up in the first couple of weeks afloat.

It was common on new builds or boats that were really dry to have boxes on long poles , open at the top filled with fine sawdust to push under the hull to help the first day or two.

A winter coat of soft bottom paint would be applied after a boat was hauled to slow winter dry out.
 
Last edited:
FF said:
"In the long run, wouldn't glassing the hull be easier?"

This is a Last Gap solution for a year or two of floating.

For any wooden boat the old tritional systems work.

Cotton is not Pounded into seams it is tapped in with a calking iron.

A 5 min job to learn but a thousand feet of seams is no fun.

Prime , cotton and then calking and bottom paint is the usual .

Using glue like 5200 would make a damaged plank repair far more difficult.

Do it like they did it in 1930 or 1960 (no difference) to most every wooden boat.
Click to expand...

I agree with FF. You have a beautiful well built boat that you have obviously worked hard on thus far. Finish the job correctly. As stated above there are many caulkers here in New England. Maybe give IYRS a call? They are graduating competent wooden boat people yearly.

IYRS | Boatbuilding School & Career Training
 
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It sounds like you have already done the hard part (reefing out the seams). Putting in new cotton is tedious but easy).

What I would do is:

1) swell the hull planking up by doing the following - a) Tent the hull from the waterline down to the ground with plastic sheet, b) if you have running water available put lawn soaker hoses under the hull and run so that they spray water onto the hull. No need to run them continuously if the hull is tented, just keep the hull damp. If running water is not available either put a couple of biggish humidifiers under the boat and run them, or twice a day pour 10-20 gallons of under the boat.After a week or so start pouring 10 gallons of water into the bilge every day.

A week or two of the above should swell the planks significantly. Then caulk the hull. If you can see gaps that go all the way through, roll or gently push the cotton into the seams being careful not to push it all the way through. Once the seams are all cottoned use Petit or Interlux above the waterline seam compound to fill the seams. Alternatively some people use 3M 4200 or 5200 of the SIKA equivalent. The down side of the synthetics is that the next guy to do the job in 10 years or so will not be happy with you.

Note - a multitool (oscillating saw) with a scraper blade cuts through 5200 like butter and won't damage the wood if you don't force it.

Note 2 - the people on the wooden boat forum will suggest that caulking can not be done by anyone but a 400 year old shipwright who uses only traditional materials.

Todd Dunn - 10 year wooden boat owner
 
Don’t even think of fiberglassing. IMO
Just thinking of the expanding planks fastened to the rigid FG skin ......
 
Once you get through this moving forward keep her in the water all the time if you can. Only haul her for 12 days tops for scheduled repair and paint bottom. We have a 46 Alaskan that has followed this process religiously and she is doing great.
 
I'm assuming the planks on your boat were assembled of the same wood and method as the ones on the GB50 we once owned. One yea,r when we hauled out in Port Townsend, WA., we placed her in a large building that had been used for building 100'+ yachts. Unknown to us was the fact that under the concrete floor was a working radiant heat system. It was amazing what that system could do to wooden planks. We ended up having Dave Thompson of PT caulk the bottom before launching. It is my memory that the carvel planking was not caulked originally. We didn't do any pre-soaking of the hull. Very little leakage occurred and no problems for years after. Other times we have been hauled for up to 3 months with no problems.
 
Look into “bear poop.” It was used on the west coast for years to do commercial boats, its a mixture of portland cement and latex rubber and every wooden tug on the coast used it. Call one of the local commercial yards here and ask where to get it.

Here is some “local knowledge.”

“...On others, a long spline cut to a wedge shape has worked in repair to glued-edge boats like Knarrs and IODs where a seam had opened, to restore the glued-edge structure.
An eastern Canadian method is cotton-caulked seams with routed-in battens over instead of putty.
In heavy planking, such as tugs, the old common method is no putty in the topsides, just pounded full of oakum, and portland cement as putty in the bottom seams over the oakum.
West Coast caulking style for over 1.25" plank is a choker of cotton, caulking the job complete, then a line of good soft long fiber oakum over that leaving a seam about as wide as it is deep, then red lead paint, then topside seam putty or underwater seam putty as the location requires.
"Bear S**t" is a NW USA seam putty mixed from powdered Portland cement and black roofing patch tar, applied below the water over the caulking.”
*
“Start with the second seam down in the topsides. If you over-caulk your 'learning' seam, you'll push the sheer strake up and off the boat.
The proper irons are crucial and you only need two for this job, a very thin OO size that you loop the cotton in with in 'tucks' and then caulk it in the seam with, and one about 1/8" for 'making' the cotton or tamping it down evenly.
The process starts with the butts first, leaving a 1" tail hanging out anywhere you stop, then the seams, crossing the butt tails and trapping them in. All the seams run out at the stem, again with the tails, last seam is the 'devil' or stem rabbet/garboard which traps all the plank tails.
After these steps you're there.
The proper caulking mallet (eBay, searches "caulking or caulker or caulk") helps, but for just one boat, a square wooden carpenter's mallet will serve. Not a round one, you can't control the blows right.
Here's a couple places to look.
http://forum.woodenboat.com/showthread.php?115648-Very-dry-carvel-hull-caulking-techniques
http://www.nwboatschool.org/programs/Course_Detail.aspx?processID=23”
*
 
Last edited:
caltexflanc said:
You might try giving Moores Marine in Beaufort NC a call, they are as expert on this as anyone in the world. Perhaps they could refer you to someone down there in FL whose work they trust to at least give you a little advice. Worth paying something for, given the catastrophic consequences that could come into play.

https://www.mooresmarine.com/
Click to expand...

I didn't think of Moore's Marine. They would have the skills for sure. They just completed a big job on a 97 foot yacht my grandfathers company built in 1929. I think they replaced several planks.
 
I believe Huckins, Chris Craft and Bertram are all Florida based. Calling them might lead to a qualified cotton seemer. Also, calling a distributor/manufacturer of the cotton material and asking who they ship to near you might lead to a skilled applicator.
 
Huckins is a great idea. The yard is very active and top notch, a lot of experience with oldies too. I'm pretty sure Bertram never made a wooden boat and they are on their umpteenth owner. Ditto Chris Craft if they still exist at all.
 
Glassing an old hull only works fairly well if the hull is:

1. Plywood

2. Strip planked w narrow planks.

With wider planks .....
The wood expands and contracts due to water content. The glass in resin does not. The glass will crack and then peel. The adhesion will fail due to the sheer forces on the wood to FG.
THEN the boat will need to have the FG removed. Most just get discarded.
 
This subject of caulking seams brings back fond memories of my store from the fifties. We sold caulking irons, mallets, reefing irons, cotton and oakum.

The oakum made the store smell eonderful! It was treated with pine tar. I have a bar of pine tar soap in my medicine cabinet that I sniff once in a while
 
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