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Old 17-02-2007, 04:12   #1
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Can a Rigid Dinghy Be Made 'Self-Bailing' when Left Moored to the Dock ?

Not exactly a sailing off into the WBY question............but I figure that as their are some clever folk here someone may have already come up with the solution.........or I will find that everyone else knows the answer

What would be useful is a rigid dinghy that I could leave moored to the dock in all weathers and when I returned to it was not half full of rain water or even semi submerged.

Over the years I have looked at other peoples dinghies and have yet to see a "solution". I am guessing that raising the floor above the waterline on a small dinghy (8 to 10 foot) so I could just leave a bung out to make it self draining would leave the vessel somewhat unstable, especially standing up.......

I am not after an automatic bilge pump. and would probably settle on "just" a few inches of water onboard, rather than half a dinghy.........

Any answer could be the tipping point for me to finaly turn some plywood into a dinghy. Possibly
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Old 17-02-2007, 08:14   #2
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Self-bailing dinghy

Raising the sole (floor) is the answer but it does present some problems. If you leave a drain plug out and the hole gets plugged with leaves your dinghy will fill with water and then the drain hole might be in free communication with the sea. Sinking therefore becomes a definate possibility. Unless the space between the bottom of the boat and the sole is enclosed completely or filled with closed cell foam and has enough reserve bouancy to float the weight of the dinghy so that it is above the drain hole she will surely rest on the bottom. (sorry about the longish answer).

As far as raising the level at which the passengers stand, this may not be a really bad problem depending upon the design of the hull. If the dinghy has a rather wide and flat bottom, raising the sole may only add two inches or so to the level at which you stand. OTOH if the hull is narrow and has a deep Vee the level will be raised considerably.

If you are starting out from scratch and designing and building the dinghy yourself, I'll bet you could come up with some hull that would work. Whether it would perform well in all conditions (be dry in a chop, stable when the wife steps on the gunnel) would be another story.

Richard

PS. I hate having to bail my dinghy after every rain and would love to see one that didn't need it.
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Old 17-02-2007, 08:30   #3
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A solution

I built a 16' planing powerboat with a very shallow Vee bottom and the sole only an inch or so above the waterline. I made a small well, about 8" x 8" as I recall, on centerline and up against the transom. The drain hole was located in the transom at the bottom of the well. Water would accumulate in the well and when the boat was hauled on the trailer the drain plug was removed to release the water. Since the sole was above the waterline and the boat had positive floatation (to keep the sole above waterline) removing the plug while the boat was in the water did not sink her. An added benefit was that the plug could be removed while underway (on plane) and the accumulated water drained out.

Keep in mind this boat had a very shallow Vee and a very wide beam. Maybe something of this kind can be built into a small dinghy.

Richard
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Old 17-02-2007, 09:42   #4
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I saw, the other day, a transom plug with a 'check' valve in it. When there is pressure greater on the inside, than the outside, water flows out. Otherwise, nothing flows in - there is also a screw on cap that can be put on for those of us who might not trust that while IN the dinghy.
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Old 17-02-2007, 10:32   #5
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How about an all around cover that is propped up in the middle to allow rain pun off? Keeps water from entering instead of a way for it to exit. This work well on my dingy.
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Old 17-02-2007, 14:09   #6
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"Air Floor"...

Those "air floor" inflatables look like the sole would be above the water line.
Something along those lines maybe.
The bottom compartment would need two drain plugs unless it was filled with foam.
Design would be easier if rowing was not a major option.
If it were beamy and the bottom compartment could be filled with water then it would be something like a liferaft.
Weight could get away from you unless construction was tightly controlled.
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Old 17-02-2007, 16:52   #7
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build one of these
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Old 17-02-2007, 16:53   #8
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Old 30-12-2010, 16:10   #9
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I know its nearly 4 years since this went up.
If you rig a diaphram type bilge pump with the handle with a short extension positioned over the side and a bungy cord attached to keep the handle up, then attach a line with a buoy and a weight adjusted so the line is just taught when the boat is level, when a boat passes the wave rocks the dingy and the weight pulls the handle down and the buoy and bungy lift it up thereby pumping out the water, its a bit fiddley to set up and the end of the handle is liable to get bumped by other boats but if you use a biggish fender it protects the handle.
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Old 30-12-2010, 16:46   #10
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Dang. The question raised much hope but the collective wisdom delivered so little.

Raising the sole will make the dinghy into a surfboard; keeping out the rain will fail. The only way would be some sort of floating dock either in situ or built in to the dinghy. All too hard compared to a few minutes bailing in gumboots.

Seems that for some problems there simply are no useful solutions.
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Old 30-12-2010, 17:27   #11
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I wonder how small a boat this would work on, and how much wind and wave action is needed?


Drainman Mooring Line Motion Bilge Pump
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Old 30-12-2010, 17:59   #12
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We built our 9' plaining dink to self bail, until we stepped in. Then we had to quickly put in the plug.

One just puts in a lightweight, aft sloping floor, (like 1/2" Kledgacell), above the water line. Then put in a 6" square sump in the back, and have its walls connect to the hull with epoxy fillets. Finally, a drain hole through the transom. There ya go!

We spent over a thousand hours on this one over 5 years. It was a "filler" project that we turned to with downtime from the BIG boat project. It was really slick and fast! It was even a decent row boat. It was however WET, especially when not on plane, like in a nasty chop.

Years later we got fed up and bought a light single floor RIB. It is a much better, DRIER boat. It is only inferior in that it is a pig to row. RIBS can't sink from rain water, and are easy to pump out. Self bailing would not be worth the weight of the extra floor model for us. (We do not have davits, but an aft wing roller instead.)

Hard dinks make sense if you want a good row boat. Then keeping it light is really important. The double floor we built in ours, increased the weight by about 40%!

Just a thought,

Mark
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Old 30-12-2010, 18:04   #13
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Quote:
Originally Posted by cal40john View Post
I wonder how small a boat this would work on, and how much wind and wave action is needed?
Drainman Mooring Line Motion Bilge Pump
80 quid for that! Seems it's a simple concept; energy from sea and wind to activate a pump. Hard to believe it could work but perhaps try a home version (parts a just a few dollars?) and report back?
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Old 30-12-2010, 18:13   #14
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I wonder what he has done since 07?

If the salesmanship of that fancy core stuff is any indicator then why not build a dink of the diviney cell or balsa core or whatever that stuff is and then just leave the plug out?
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Old 30-12-2010, 18:17   #15
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Portland Pudgy is a small foam filled ABS hard dinghy that is self bailing with the floor above the waterline. Looks like a bit of a pig to row compared to some hard dinks but better than RIBs...
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