Early DSI Air Chambers

[algonquin]

I was just out looking at my early DSI. Wanted to pass this idea for comments.

I have the coaming boards off for refinishing and discovered that a 4" diameter PVC pipe will fit nicely along the sides and just behind the seats. Thought that if this PVC was capped and sealed at each end it would make some nice additional flotation. I was able to maneuver a 7 ½ foot length of the 4" pipe with a little tucked just under the aft coaming into the available space. I may pursue this by installing these air chambers along the sides with some smaller length sealed chambers aft under the rear coaming and a few in the storage are over the bow flotation chamber. The side chambers can be held in place by installing a slightly wider coaming board over them. Still working on ideas for securing additional chambers. I know on my boat I seldom use these spaces for anything anyway.

Any of you have any experience with this type of flotation ?

If this is worth pursuing it is has a definite cost savings. For about $30.00 you can build a bunch (fleet) of these sealed air chambers. Brad

[GreenLake]

I've thought about this space as well, but I use it to store my paddles....

[seandwyer]

....As have I. The pipe idea sounds much easier than some of the ideas I have heard about filling this area with foam and other boyant materials, but just like Green Lake, I keep my paddle in this area and when trailering my tiller lives tucked inside just beneath the deck. I really hesitate to get rid of this space in favor of more flotation. Is it nessesary? I say this, but then, I've never capsized - which brings a question to mind:
The Daysailer is said to be a difficult boat to capsize, and stable to walk around in etc, but certainly things can and do happen, but I wonder how often. With all the recent talk of improved flotation, flotation replacement and the instalation of additional flotation (beneeth the cuddy roof, or above the seats etc, how many people have capsized their boats, and how frequently? Is this something that happens a lot?

[algonquin]

I have read about quite a few on this site that have capsized. I have had one incident myself that was extremely close. The problem with this boat is it has a tendency to turn turtle when it does capsize making it extremely difficult to right it. Partly because all the flotation is in the bottom areas of the boat. The way I look at it is if or when you do capsize it is likely to be in adverse conditions and catch you off guard. With the recent talk about getting some flotation higher in the boat I believe this air chamber PVC will help. The areas I sail are large and can get pretty rough with unpredictable wind directions. Also not many other boaters are around to help with the rescue. I think these PVC air chambers may help. Brad

Something to read about DS capsizing:

http://www.arlingtonyachtclub.org/Fleet ... ation.html

[GreenLake]

I haven't managed in nearly ten years - when overpressed by a sudden gust, the boat seemed to want to round up sharply rather than heel too far.

I would separate a few things. Making sure the reserve buoyancy in the flotation chambers is not compromised should be a priority for everyone. Carrying around soggy foam will compromise the sailing characteristics, but worse, it could cause the boat to actually sink, by reducing the buoyancy below the minimum to keep her afloat.

Adding additional floation is intended to make the boat easier to self-rescue, but several posters have noted, if done in excess, or badly placed, it could have the opposite effect.

The way I see it, if the addtional flotaion really makes reliable self-rescue possible, in situations where there are no other boats/helpers in reach, it would be a useful safety feature.

However, I'm concerned that even with added flotation, the chances for a successful self-rescue are fairly low, unless other modifications are also done, for example, self-inflacting anti-capsize floatation at the mast top.

I recall reading somewhere on the forum or on this site about experiences by other, earlier DS owners. Can't seem to locate them just now.

[K.C. Walker]

I seriously doubt adding 4 inch PVC is worth the trouble. It's pretty heavy. I think if you capped off the end of the PVC pipe and dropped it in the water it wouldn't float very high. I think it would be interesting to compare the flotation with some swim noodles. My guess is that the swim noodles would win by a fair amount. My boat came with that area filled with flotation foam and then a piece of white formica fitted between the seat and behind combing. I thought it was original when I got the boat, it looks fine.

Capsizing a DaySailer is not something I really want to try. I've done it plenty of times with smaller boats, though. I did come somewhat close to capsizing in some very extreme conditions in August. I got about 6 inches of water over the rail. So capsize prevention is something I am refitting my boat for before spring. Cleating the main sheet is the mistake that got us into trouble. I am re-rigging with ratchet blocks on my sheets. If you can hand hold the sheet your reaction time is so much faster that you are far less likely to capsize.

The beamier the boat the more initial stability it has BUT once it does capsize the harder it is to right and the more likely it is to turtle. The extreme example is a catamaran. If the flotation is at the extreme edges, such as a catamaran, it's more difficult to right if the boat floats higher than the midline, because at that point the weight is already trying to turtle boat. The higher the capsized boat floats above the midline the harder it is to right it and the more likely it is to turtle. It seems that flotation down the midline of the boat is what makes it the easiest to right. Yes, it will come up full water but it rolls around the flotation rather than needing to be levered over it. How much and in what location I don't know, I guess I'd have to capsize my boat and then adjust.

Capsizing recovery is something that I've thought about some. If the DaySailer is difficult to self rescue why is it that we don't use some of the righting methods that catamaran sailors use? They use righting straps and righting buckets. The righting strap allows them to lean way back and the righting bucket (made of cloth) allows them to pick up another 150 pounds of water to hang over their shoulder when they are leaning way out.

Oh yes, another flotation tank to worry about sealing up is the mast itself. If the mast fills with water it's a lot harder to lever out of the water.

KC

[GreenLake]

KC, Your project of adding foam to the hull should have resulted in net floatation near the centerline - or not?

The masts (and booms) seem to have been treated with foam - you'll see it come out of any openings, but it seems to have been of poor durability.

I wish I had a chance to try a ratchet block under realistic conditions. Sounds intriguing.

[algonquin]

I seriously doubt adding 4 inch PVC is worth the trouble. It's pretty heavy. I think if you capped off the end of the PVC pipe and dropped it in the water it wouldn't float very high. I think it would be interesting to compare the flotation with some swim noodles. My guess is that the swim noodles would win by a fair amount. KC

I tried a 4' section and it was at least 2/3rds out of the water. As far as the noodles, they work but I'd rather have a hold of the pvc than a bunch of noodles. Brad

[GreenLake]

Any additional floatation is only useful if it is firmly anchored against floating away when the weight of the boat presses it underwater at the capsize angle.

That said, what's the weight of the empty tubes?

[K.C. Walker]

GreenLake, yes, I think the foam core did add flotation in the amount of approximately one seat tank and on center. When I asked Phill Root about what he might change if he were doing it again he said that he might go with a thicker foam to add more flotation. I went with half-inch (the same as Phill) because I found it as offcuts at a bargain price.

I've picked up 3 nice new ratchet blocks off eBay. I guess I won't get a chance to try them until spring, though.

KC

[MrPlywood]

I've been doing a little reading about buoyancy. Please correct me if I've got this wrong. From what I gather, one cubic foot of air (1,728 cu.in.) below the waterline provides ~63 pounds of buoyancy. A 4" dia. tube 6' (72") long would hold 904 cubic inches of air, which translates to about 33 pounds of buoyancy. I guess you would subtract the weight of the PVC to get the final figure.

Would that be worth it? Better than nothing I guess. But you would probably get better results cutting foam to size and fitting it in the space. With the PVC pipe you lose the "corners".

I was given a couple of flotation billets http://www.dockbuilders.com/styrofoambillets.htm
with the thought of cutting/carving them to fit under the gunwales, transom and the cuddy. (I could probably also cut them to size to fit into the seat tanks, but they are stiff as opposed to the squishable pool noodles.) The billet material offers 55 pounds of buoyancy per cubic foot.

I read the Arlington Club article which I found very interesting. Evidently the added flotation under the gunwales provided enough buoyancy at that spot to make quite a difference.

My concern is along the lines of "what if", similar to Brad's, since I plan to do some more bay sailing in the cold ocean water next year.

[GreenLake]

The "Arlington Club Article" can be found here.

It comes to the conclusion that flotation added between seats and gunwhales is in the correct location and cites actual experiments in righting boats before/after modifications.

Adding flotation in that area moves the center of buoyancy when the DS is capsized in two directions: towards the side of the boat, and away from the floor of the boat.

The former could be problematical if it raises the hull so far that the angle of the mast gets steeper - that's the concern that the most recent posts here were commenting on. The latter could be beneficial, because it moves the center of buoyancy closer toward the mast top than before.

The article states "The problem is simply a matter of leverage. Using the centerboard as a lever and the center of flotation in the hull as the fulcrum, the lever is longer" with the added flotation.

Carrying this argument to the extreme, the best solution would be to permanently affix hiking pads, similar to the ones designed by user calden, although his were removable.



Floatation added at that location would be even closer to the mast top, making a nice lever with the center of gravity of the boat on one side. The trick would be to attach the material firmly enough so the force of its buoyancy doesn't rip it from the boat when immersed.

[algonquin]

Some info about foam flotation. Brad

http://www.glen-l.com/weblettr/weblette ... ation.html

[ctenidae]

What about putting a couple of these under each seat and in the bow?

Seems like they'd be durable and easily maintainable, and possibly cheaper than noodles.

I'm intrigued by the possibilities of 2 liter bottles, too, and have been contemplating a combo of a layer of bottles, some 2-part foam, rinse, repeat. Thinking maintenance down the road would be a bear, though, and the karmic implications of the next owner wanting to redo something are painful.

[persephone]

I'd deep six the soda bottle route. Search my name in the posts I had a pretty detailed post on flotation last winter after working on my boat. Let my know if you can't find it and I'll hit the highlights.