Sikaflex Carvel Planking

[Huntsmanvb]

I was recently at the Chesapeake bay maritime museum, and I spoke with the people who were building some skiffs. They were flat bottom, cross planked with Carvel sides.

The bottoms were made by cutting a dado in the joining faces of the bottom planks, filling the dado groove with plenty of sikaflex, and then installing the plank. The excess sikaflex oozed out and was removed.

The sides were made by hanging a plank, drilling several holes in the top edge, and placing dowels in the holes. The next plank had matching holes in its bottom edge, to receive the dowels. Everything was covered in sikaflex, and the top plank was hammered down onto the dowels.

It "looked" like it was producing a water-tight and massively strong structure.

[Ian McColgin]

You might take this to the Building section.

It's a slightly funny way to do it and uses more Sikaflex than I'd use. If they really have the process down, perhaps on a production with templates and all basis it saves enough labor to be worth it but it seems to me a bit silly.

Depending on the skiff and bottom design sikaflex can be used as a combination glue and caulk for long plank bottom seams or even for cross plank seams, but I don't see the need for the groove. For the side planks - carvel on a flattie skiff is a bit odd but whatever - since the planks will be screwed to the frames, why the edge-to-edge doweling?

Either there are some folk down there with winkles I'd not run into - a very high possibility - or some museum volunteers with their own eccentric notions have taken off.

[erster]

Caulking splines are fairly common. So are bronze dowels in the end grains of solid planks, dating way way back.

[Huntsmanvb]

To be more specific, they were Smith Island style skiffs:

[wizbang 13]

How did they get the planking holes into alignment?
The whole process seems over complicated for a wee skiff.
This boat is STILL going to get wet and swell. And get heavy. The sika will prevent it from leaking while the boat is fresh, I suppose. Other than that , well.

[Huntsmanvb]

How did they get the planking holes into alignment?
The whole process seems over complicated for a wee skiff.
This boat is STILL going to get wet and swell. And get heavy. The sika will prevent it from leaking while the boat is fresh, I suppose. Other than that , well.

I guess the concept is that it avoids caulking, which is complicated in itself. They are using thick plank, the boats are really not light skiffs.

Also, I believe the boats are being built on commission or for sale, and it may be hard to sell an outboard work boat that is not 100% tight the moment it hits the water.

I may try this method soon with PL, I mostly posted it for comments/concerns due to my similar questions regarding the effects of expansion.

[yzer]

I've had good luck using a softer formulation like Sikaflex 291 LOT to patch limited sections on batten seamed hull sides. This Sikaflex matches seasonal expansion and contraction very well. With wider seams you may find that that topside paint will crack along these seams after several seasons, but the sealant remains intact. Repair is easy if a full re-coat is not needed. Along more narrow seams I haven't seem any cracking of the coating.

[Eddiebou]

Several years ago, a large marine supplier recomended Sikaflex 521 UV to me to caulk some deck seams. I did a mock-up and worked out the application procedure before using it on the real boat. No problems.
After the deck seams were all caulked and cured and looking good, I primed and painted.
The paint would not cure on the Sikaflex, Period.
I called the customer service number and after being transferred from Canada to New Jersey to Texas, I just gave up.
I don't even see 521 in their catalogue now.
It was obviously the wrong material for the job I had in mind. Don't assume, "It'll be OK", without testing the whole procedure. G'luck

[yzer]

Traditional varnishes, sealers and topside paints adhere very well to Sikaflex 291 or 291 LOT in my experience. I used 291 LOT to seam fir cockpit decking and coated it with Pettit Clear Sealer followed by varnish. I couldn't be happier with the results.

[yzer]

Several years ago, a large marine supplier recomended Sikaflex 521 UV to me to caulk some deck seams. I did a mock-up and worked out the application procedure before using it on the real boat. No problems.
After the deck seams were all caulked and cured and looking good, I primed and painted.
The paint would not cure on the Sikaflex, Period.
I called the customer service number and after being transferred from Canada to New Jersey to Texas, I just gave up.
I don't even see 521 in their catalogue now.
It was obviously the wrong material for the job I had in mind. Don't assume, "It'll be OK", without testing the whole procedure. G'luck

Sika makes many formulations of Sikaflex for particular applications. Without good information mistakes will happen. Sika does not recommend 521 for deck seams. Here are some of the applications for 521 UV:
http://usa.sika.com/content/usa/main...btn_Search.y=0

Sika recommends these Sikaflex products for marine applications, including the 290 DC deck caulking.
http://usa.sika.com/en/solutions_pro...1a006sa02.html

[traceymunson]

In the Chesapeake Bay Maritime Museum's boat shop, we generally build traditional boats built the traditional way. But we will make exceptions to suit the needs of the owner. We do not build with plywood, so the cross plank bottom had to be made water tight. Generally a cross planked bottom needs to swell and the boat should be kept in the water.

The boat you observed in our shop is being built to order and the owner will keep the boat on a trailer, launch it and run it hard. The sikflex 291LOT is not as much an adhesive as a sealant. The idea of the dado was the give a little more sealant to the seam.

The topsides are an interesting use of the sika too. Quite often in large bay boats the topside planks are drifted vertically with galvanized drift rods. One of the advantages of this, along with a very strong hull, is it keeps planks aligned in between frames. Dan Sutherland's idea here was the dowels would do the same thing in the skiff with not too many frames. And again the sika meant the planks did not have to swell tight.

The results speak for themselves. The skiff looks great, does not leak a drop when launched and is fairly light weight. The sides and bottom are both white cedar which has an innate ability to swell just enough and not too much. So if the skiff is left in the water for a period of time, the planks will swell to the sika but will not swell so much as to buckle or warp the way yellow pine would.

Our Boat Yard Manager Rich Scofield prefers to caulk a hull traditionally with cotton, but it is more maintenance and we always have to keep the owner's intentions in mind. And you always have to wonder what our "traditional fore bearers" would have done with sika and epoxy. You can learn more about our Apprentice for a Day program by visiting http://www.cbmm.org/l_boatyard.htm