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Thread: Wooden dinghy floatation

  1. #1
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    Default Wooden dinghy floatation

    Thinking about Floatation for my 12' clinker GArtside 130 cedar on oak 170lbs.

    Another fellow who built one with hardwood planking I believe, told me that he asked Paul Gartside who said that the boat should have enough inherent floatation.
    I'm not questioning Mr. Gartside's judgement but what has people's practical experiences been?
    Does one need more floatation?
    Is it an extra factor of safety ?
    I don't really have a nice shallow sandy place to try capsizing it.

  2. #2
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    Default Re: Wooden dinghy floatation

    The key question is: Once capsized and recovered, can you get back in and bail out the boat or get back under way?

    As a wood boat #130 might float but not high enough to do more than let you hang on waiting for rescue, hard to know without going for a swim. An open centerboard trunk can be a real problem, if the top is too low you have to bail faster then it lets water in. Foam blocks, drybags and fenders (all well secured) have been used to displace water from the inside of open boats and provide buoyancy, all have pros and cons. Glued boats you can easily build airtanks into but that is trickier on a traditional lapstrake hull like yours.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

  3. #3
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    Default Re: Wooden dinghy floatation

    Quote Originally Posted by stromborg View Post
    The key question is: Once capsized and recovered, can you get back in and bail out the boat or get back under way?

    As a wood boat #130 might float but not high enough to do more than let you hang on waiting for rescue, hard to know without going for a swim. An open centerboard trunk can be a real problem, if the top is too low you have to bail faster then it lets water in. Foam blocks, drybags and fenders (all well secured) have been used to displace water from the inside of open boats and provide buoyancy, all have pros and cons. Glued boats you can easily build airtanks into but that is trickier on a traditional lapstrake hull like yours.
    The question Steve asks is the question to be answered - if the boat will not float enough (i.e. water level below top of centreboard case or case top blocked) then it is very difficult to bail out. You might want to try a test capsize - then you will know for sure.

    I have been waiting for months for buoyancy bags for my Gannet - have now got fed up waiting for a supplier who can't be bothered so I will tie large fenders under the aft thwart (my bow has a sealed bulkhead so the bow will float) , fenders which I can use as rollers on a beach.

    Good Luck Neil

  4. #4
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    Default Re: Wooden dinghy floatation

    I'll guess, the boat will not sink and will float with the rail about 2" out of the water amidships, assuming it stays upright.
    Do with that what you will...

  5. #5
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    Default Re: Wooden dinghy floatation

    There are a few eye-opening dinghy self-recovery videos floating around that will encourage dinghy owners to consider adequate flotation.

    Example.

    https://youtu.be/OG4b-4I8AnM?t=6
    ​​♦ During times of universal deceit, telling the truth becomes a revolutionary act
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  6. #6
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    Default Re: Wooden dinghy floatation

    Flotation is important. If you capsize, there is probably enough wind to generate waves. Will it float high enough to allow for bailing?

    Also important is the free surface area of the water taken on board after re-righting. Lots of traditional hull shapes have swoopy sheerlines that allow a fair-to-large amount of water in. If the hull is open with nothing to limit the water sloshing around, a recapsize is all too likely. So, flotation that also works to take up space and limit the free surface area (and limit the amount of water on board) is also a good safety feature.

    Or, a hull with lots of interior structure to break up the interior into several small compartments--that's what I have in my boat, and it helps with post-capsize stability. It helps a LOT.

    Tom
    Ponoszenie konsekwencji!

    www.tompamperin.com

  7. #7
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    Default Re: Wooden dinghy floatation

    He didn't have his bailer on a lanyard? or an extra?
    I was surprised that he wasn't bailing like beejeesus as soon as he got in the boat the first time to reduce the shifting ballast and establish some stability.
    Was it in the sail the whole time?
    Very informative.

    Currently I usually carry 4 fenders, 2 quite oversized and 2 just oversized , I will make sure I make a point of attach them securely and strategically.
    plus a couple small dry sacks lashed on. My ABS beach rollers have pool noodles in them too though that's not tonnes.
    But that's it.
    I thought of opti bags.

  8. #8
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    Default Re: Wooden dinghy floatation

    Toxo,

    Your boat can't sink, but will flood to above the centercase leaving you with a big problem.

    Options are:-

    1. Ensuring you can block off the top of the centercase so you can bail out the boat. This works unless you're weight in the boat added to so low freeboard means you can't bail it out faster than waves lap in in rougher conditions.

    2. Add Crewsaver buoyancy bags. You want one long thin one strapped securely and inflated properly under each side bench. You want a small one accross the boat under the rear seats, and youwant a pillow bag up in the bow. These will keep water out of the boat and hold water in the boat centrally to stop it listing excessively. Yo can swap the stern and bow bags for big fenders etc or dry bags.






    3. With a traditional boat if you wanted something more structural, you can build a non sealed 'buoyancy tank' - but it doesn't have to be sealed - and with a trad boat can't be, and is better not so it airs and drains, then fill the space with closed cell foam either cut to shape or pool noodles, balls etc.

    Easiest thing to do, is just buy those long narrow Crewsaver 147 x 23 bags for either side, put your fenders conviently strapped under the aft bench and see what'll fit up forward without being in the way. They come in yellow or pale blue.

    Holt also sell them, but they're aren't quite so long and thin if I remember.

    Oh and a rubber bucket ties on to the main thwart. A small shallow bailer tied to the bucket and a mopping sponge tied to the the shallow bailer. All nested inside each other, that's how I do it.
    Last edited by Edward Pearson; 10-26-2022 at 04:43 AM.

  9. #9
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    Default Re: Wooden dinghy floatation

    Anyone remember that little Bajau girl dewatering her dugout canoe from fully submerged by straddling the gunwales and tipping it back and forth to slosh the water out. It was remarkable...


    https://www.youtube.com/watch?v=_6r6I_W2d80
    Last edited by Edward Pearson; 10-26-2022 at 04:41 AM.

  10. #10
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    Default Re: Wooden dinghy floatation

    I have a couple of replacement seats for an inflatable boat. They are large, tough and reasonably priced.

  11. #11
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    Default Re: Wooden dinghy floatation

    Glue foam insulation under the seats. Closed cell foam insulation sheets, 4 x 8 ft x 2 inches are found at Home Depot, and elsewhere.

  12. #12
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    Default Re: Wooden dinghy floatation

    Hey thanks. i made removable foam blocks for my shellback dinghy, stacking 2" sheets, gluing them together and then glassing them with epoxy, then painted with brightsides or bilgkote (can't remember) They were for under the thwarts. Maybe I'll look and see what I can do of the same nature on this boat. I really like having the under the seat/thwart storage though. Ah well trade offs in everything I guess. No storage vs not drowning..what the heck

  13. #13
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    Default Re: Wooden dinghy floatation

    I was looking at these Edward but I can't find a price list anywhere!
    Are they free??? Yay!! A selfless public service!!??


    Quote Originally Posted by Edward Pearson View Post
    Toxo,

    Your boat can't sink, but will flood to above the centercase leaving you with a big problem.

    Options are:-

    1. Ensuring you can block off the top of the centercase so you can bail out the boat. This works unless you're weight in the boat added to so low freeboard means you can't bail it out faster than waves lap in in rougher conditions.

    2. Add Crewsaver buoyancy bags. You want one long thin one strapped securely and inflated properly under each side bench. You want a small one accross the boat under the rear seats, and youwant a pillow bag up in the bow. These will keep water out of the boat and hold water in the boat centrally to stop it listing excessively. Yo can swap the stern and bow bags for big fenders etc or dry bags.






    3. With a traditional boat if you wanted something more structural, you can build a non sealed 'buoyancy tank' - but it doesn't have to be sealed - and with a trad boat can't be, and is better not so it airs and drains, then fill the space with closed cell foam either cut to shape or pool noodles, balls etc.

    Easiest thing to do, is just buy those long narrow Crewsaver 147 x 23 bags for either side, put your fenders conviently strapped under the aft bench and see what'll fit up forward without being in the way. They come in yellow or pale blue.

    Holt also sell them, but they're aren't quite so long and thin if I remember.

    Oh and a rubber bucket ties on to the main thwart. A small shallow bailer tied to the bucket and a mopping sponge tied to the the shallow bailer. All nested inside each other, that's how I do it.

  14. #14
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    Default Re: Wooden dinghy floatation

    I bought mine here...

    https://www.sailboats.co.uk/crewsave...SAAEgIzUvD_BwE

    Also Trident sell em including the Holt ones...

    https://www.tridentuk.com/gb/chandlery/buoyancy-drainage/chandlery-buoyancy-bags.html


    Theres also Pinnel & Bax

    https://www.pinbax.com/crewsaver-pil...iABEgLbEPD_BwE

    Pounds low at minute so it might be cost effective to post to Canada. For export they should remove 20% VAT off price i think but postage might be a bit, though they are not heavy.

    Crewsaver list Survitec as a distributor in Vancouver. Might be worth a call though they might not import them as dinghy sailing’s less of a thing than in GB.
    Last edited by Edward Pearson; 10-27-2022 at 03:40 PM.

  15. #15
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    Default Re: Wooden dinghy floatation

    I bought some Holt bags from Trident, shipping to the US was economical and fast. I had trouble finding them for sale in North America.

  16. #16
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    Default Re: Wooden dinghy floatation

    it is critical to be able to self rescue in wind and waves.

    I'm retrofitting an old dinghy from the 50's so you can more easily rescue from a capsize.



    The two problems to correct are the amount of water you had to bail and flotation height with the original flotation tanks. I just added the forward bulkhead to limit the amount of water in the boat and keep her from porpoiseing when swamped. I will enclose the area under the seats for added buoyancy. The plan is to also add a couple self bailers to the hull.

    My woodworking skills aren't advanced enough to make wood buoyancy tanks under the seats so I added thin bulkheads to hide buoyancy bags. I like the "beach rollers" from Duckwork's which appear to be repurposed big boat fenders. They fit inside and are easy to take out so you can use them as rollers if needed.

    Rollers - https://duckworks.com/beach-rollers/

    Freight airbags can also be used as inexpensive buoyancy bags too.

  17. #17
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    Default Re: Wooden dinghy floatation

    Those rollers are tough. Do the new compartments have ventilation options?
    ​​♦ During times of universal deceit, telling the truth becomes a revolutionary act
    ♦ The further a society drifts from truth the more it will hate those who speak it
    ♦ If liberty means anything at all, it means the right to tell people what they do not want to hear
    ♦ George Orwell

  18. #18
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    Default Re: Wooden dinghy floatation

    Yes, my original thought was to make nice air tight buoyancy tanks under the seats. Reality told me that water will find a way in and rot them out in no time from the inside out. The seat and bulkhead under are square while the beach roller is round so lots of opportunity for air to flow. The side under the thwarts is open to quickly remove the rollers should you need them. Should last awhile

  19. #19
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    Default Re: Wooden dinghy floatation

    An air tank is most efficient and rot's easily avoided if you just put a store bought watertight hatchlet to hold for the fifteen minutes or so self-rescue should take.

    That said, securing tubes under thwarts is greats, so long as the thwarts are secure enough to float off in you moment of need.

    There are many tricks to self-rescue, often idiosyncratic to vessel and sailor. Most are best. worked out in a bathing suit on a warm summer's day. So get wet and have fun.

  20. #20
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    Default Re: Wooden dinghy floatation

    I think good old pink sealed foam insulation will be my most economical solution.I'll get the 2" stuff and run a slab underneath each side bench, fill some space under the stern sheets and some in the bow, or a big spare fender.

  21. #21
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    Default Re: Wooden dinghy floatation

    Quote Originally Posted by Toxophilite View Post
    Hey thanks. i made removable foam blocks for my shellback dinghy, stacking 2" sheets, gluing them together and then glassing them with epoxy, then painted with brightsides or bilgkote (can't remember) They were for under the thwarts. Maybe I'll look and see what I can do of the same nature on this boat. I really like having the under the seat/thwart storage though. Ah well trade offs in everything I guess. No storage vs not drowning..what the heck
    If you get some muslin or similar cloth, wrap those foam blocks in that, two layers, and paint with enough coats of water based paint, the cheap stuff, they look better and last practically forever.

    John Welsford
    An expert is but a beginner with experience.

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