View Full Version : Cosine Wherry floatation

Jim Redding
05-03-2015, 09:59 AM
Here is a question for you Cosine Wherry guys.

The original Cosine Wherry book, Rip, Strip and Row, published in the mid 1980s, recommends glueing a couple cubic feet of foam under the thwarts for floatation. Clearly, this would not be to the esthetic benefit of the boat though if it let someone survive a swamping in a bad location, they wouldn't be worrying about esthetics. But I have only seen one Cosine Wherry with these foam blocks installed and I have never seen a picture of one so outfitted. Even the people who published the book don't have the foam blocks in their own Cosine Wherry.

Other than glueing on blocks of foam, there is no other obvious way to add floatation to this rowboat. And I question the value of these blocks anyway. Would 2 cubic feet of foam blocks make the boat float high enough to allow it to be bailed out in any conditions other than calm water? And it is hard to see how someone could turn the boat over in calm water without trying to.

Other than the guy who I know, have any of you Cosine Wherry builders out there added these foam blocks?

What are your thoughts on this?

05-03-2015, 10:19 AM
First you need to determine the type of self rescue you're talking about.

1. If you want enough flotation to be able to reboard in choppy seas and bail it out, you'll need a lot of flotation, a big bucket, and practice at reboarding from the water. It is quite possible that very confused and heavy swell would keep this from being successful -- even reboarding and lying down in the boat might result in more water coming over the gunwales than can be bailed out at any given time. You'd be better off with partially decking the boat AND adding flotation for this sort of situation.

2. Next level is having enough flotation to be able to reboard in calm waters and bail it out. Not as much flotation needed, but still a big bucket. This would be for an accidental swamping, possibly with kids or dogs behaving as kids and dogs usually will...

3. Next level is having enough to be able to swim the boat to shore or hook it up to another boat for a tow to shore or the ramp. I expect that most Cosine builds would meet this without any flotation, but a few fenders tied under the sternsheets and bow would make this easier.

I'm not a fan of attached or sealed flotation, as you lose the space permanently even if not needed (like narrow river rows where you're never more than 50' from the shore) and add the possibility of rot. And you might have to beef up the attachment of the thwarts to the rails (small bolts with washers?), as the two small screws might pull free if the boat swamped in rough water and the bailing took time. But it would provide reasonably space-efficient flotation for the center of the boat. From what I've read here, you also need flotation in the ends of the boat, so that would require bags or foam in the bow and stern.

I recently participated in the Open Ocean Rowing Center's regatta from Sausalito to Point Diablo outside the Golden Gate, then back around a course in Richardson Bay. The wind and tide combined in un-predicted heavy confused swell and a number of boats turned back rather than risk capsize near the north tower of the GG Bridge -- me amongst them. At least three or four of the racing shells went over but everyone managed to get back into the shells safely.

To get ready for this I added two Holt Opti flotation / buoyancy bags, available online and from West Marine. I also really needed flotation in the ends, and should have added a kayak / canoe bag in the bow and under the sternsheets, but didn't have the time or the money. I put eye straps on the inside of the bottom and along the thwart rail, designed to hold the flotation bags as low as possible when swamped. I recommend reading the recent thread on eye straps here, as some brilliant ideas for low-profile and low-toe-impact eye straps were posted.

The placement may have been better lower and more centered, but the ability to move around the boat is still important, so I left room down the center of the inside to walk or store gear. I'll be making new eye straps and probably move the buoyancy bags down a bit more towards the center, but since they're cylindrical they only go so low when fully inflated.

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Jim Redding
05-03-2015, 10:50 AM
Thanks, Thorne.

Rick in Pender Harbour
05-03-2015, 04:49 PM
I've built 10 of these,working on the 11th, and have only put flotation in one. I can't even remember why, but I used airtight chambers under the bow and stern seats, with deck plates on the vertical surfaces for access. This is the only way I would consider putting in permanent flotation, I think foam is an invitation for trouble. The flotation bags that Thorne shows look great for trips that might carry a bit more adventure, but my boats mostly spend their time in bays or rivers, on sunny calm afternoons.

Best rgds



05-03-2015, 05:49 PM
One nice floatation system that I have seen that looks good in a traditional boat (but not seen in a Cosine Wherry yet) is a variant on the foam-blocks-under-seat method: Carve floatation blocks to fit under the seat thwarts, then take them to your friendly neighbourhood sailmaker or canvasworker and have them build a white or cream Dacron zippered bag for the blocks. A nice snug fit makes it look just dandy. Have them stitch two or three lengths of 2-inch Velcro on the side that will be against the seat thwart. Glue the other side of the Velcro to the seat thwart and press the floatation in place. It will stay there through pretty much anything except surf-riding or maybe a trip down the Snake River Canyon. You can remove them for drying or storage, and can swap out the foam block anytime if it gets damaged or stinky.

Jim Redding
05-03-2015, 06:21 PM
I like this idea of Velcro attached foam blocks. Between this and Thorne's strapped on flotation bags, you are giving me good ideas. I don't like the idea of permanently mounted flotation blocks but something that is mounted only when needed seems like a good option to have. I expect that I may sometimes be in locations/conditions where enough flotation to bail the boat would be prudent. The problem in Washington state is that the water is bloody cold and hypothermia is to be feared. If you swamped and couldn't get out of the water soon, you would be in real trouble. I want to be able to go out in the San Juans and not just stay close to the Anacortes shore.

05-03-2015, 06:22 PM
I used four large fenders strapped under both thwarts, if I thought the conditions warranted this. Worked for rowing within half a mile of shore (usually closer), in warm weather. Only capsized once, and was able to row to shore with the boat still mostly swamped. No good for serious water, though.