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Discussion Starter #1
Hello all! First thread on the forum (although my first attempt didnt go through, I believe the mods accidentally deleted or didnt approve and failed to communicate). Anyways wanted to get some input on flat bottom dinks. I purchased a West Marine PRU-3 on sale for $700 and I have an 2012 3.5hp outboard Merc (long shaft). Runs great as long as you know about the engines idiosyncrasies (viz running the carb dry and keeping the carb float clean etc). Anyways I slapped my outboard onto my new flat bottom dink and while fun at first I quickly realized the tracking when attempting to turn is absolutely awful. My turning radius at idle speeds was probably 20-30 ft. I played with turning the motor at different angles but no matter what I do in terms of how aggressively I steer I cannot get the dink to turn in an acceptable radius. It's almost comical- if you turn the motor: then the direction the dink is facing changes immediately, but the dinks direction of travel will continue on its old vector- basically sliding along! Terrible I say.

Wanted to get some opinions if people do any mods to these "glass" bottoms. In the time since I originally tried to post my thread (and when the mods didnt approve my post or deleted it- yes I am frustrated but figured I'd try one more post before leaving for another forum) and now I've glued on a 9" skeg. I took some 3M 5200 and attached a removable skeg. I'm going to let it dry before I attempted motoring but wanted to see if anyone else has tried this? I've seen mods with people adding more seating or a full size wood floor but havent found anyone adding a skeg or developing some kind of keel. I wasnt in the mood to spend another $500+ dollars on a V shaped dink because I am only using this for boat to shore in calm waters or maybe boat to boat transfer on the rare (once a year) occasion I sail alongside another vessel.
 

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No, you are not the first, though what I saw was lower aspect and farther aft (a pair of 1 1/4" lengthwise ribs). They said it worked.
 

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All non-RIB inflatables tend to slide a bit when turning, even ours which has a decent keel. When we want to make a sharp turn we just shift our weight and the dink will turn quite sharply.
 

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One of None
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You don't need a skeg, just put on some runners, three or four of them, one right down the middle, and yes shift your weight when you make turns.

It's almost guaranteed you will lose that skeg short order. You probably should have went with a V bottom, in the end you would be happier, but I
dont particularly love flat bottom boats.
 

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We have the inflatable keel model and it goes almost straight. a friend has a flat bottom and he glued on two pool noodles that he split down the middle. and it did help some. the keg is going to be a problem if you want to beach it. My kids think that half the fun of driving the thing is the fact that is does not always go where you think it will.
 

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I too found a flat bottomed dink frustrating! It was particularly bad when crabbing. We finally bought a rib which we like much better!

As far as suggestions; I was thinking of flying a noodle down the bottom as a work around. You would need to redo it often but hey, how expensive are noodles? Instead we got a new dinghy.


Sent from my iPhone using Tapatalk
 

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That is the "Fun" of a flat bottom inflatable with no hard chine. Look at it like a toboggan which you have to steer by shifting your body weight to the inside of the turn.

These add a whole new dimension to it all:
 

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Discussion Starter #8
Thanks for the insights all! My skeg is removable so shouldn’t be a problem beaching it if I ever need to do that. I do like the idea about using a noodle split in two or a runner. Once this skeg falls off I may try one of those ideas. It is a little “fun” to drive in the open but annoying if I have guests onboard who won’t know to shift weight around or navigating a tight marina or busy like the one here in NYC.
 

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There are also inflatable keel strips with some designed to be glued on the bottom and others simply placed under the floorboards and pumped up with air.
 

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If you want to turn tighter give it a burst of throttle.

Short flat bottomed dinks are notoriously squirrely.

A 9 ft V bottom [front] RIB is MUCH more stable esp at speed.
 

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Trick i learned is to think of it like a 4 tire drift in a sports car. Decelerate before the turn. Start the turn and accelerate briefly to slingshot the dinghy stern around. Decelerate. Then resume your desired speed.
We do this to some degree with our rib. It’s a foldable stern walker bay. Although rated for 15hp it’s overpowered with a tahatsu 15hp 2 stroke with one person in it and skates around. The above technique seems to help. Bad thing I note with any flat bottom boat is they pound on plane, and hobbyhorse or roll a bunch when going slow. Best thing is they sure hold a lot for their size.
 

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I see you are using a long shaft where a short shaft is normally recommended. Not sure if that is effecting performance.
 

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I simply run two small parallel keels from about 3/4 way from the bow down to the stern, sufficiently far apart that they easily allow the dinghy to sit level on them when hauled aboard--and make sure they are far apart enough that they clear the propeller blade turning circle. These keels do not have to be as deep as the propeller either.

A single keel works OK but obstructs the propeller circle and makes the dinghy lean to one side when on deck.
 

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Discussion Starter #14
There are also inflatable keel strips with some designed to be glued on the bottom and others simply placed under the floorboards and pumped up with air.
Any chance you could show me a product like this? I cant seem to find anything online. I can only find keel guards and some walker bay product that looks like it gets screwed on.
 

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Discussion Starter #15
I simply run two small parallel keels from about 3/4 way from the bow down to the stern, sufficiently far apart that they easily allow the dinghy to sit level on them when hauled aboard--and make sure they are far apart enough that they clear the propeller blade turning circle. These keels do not have to be as deep as the propeller either.

A single keel works OK but obstructs the propeller circle and makes the dinghy lean to one side when on deck.
Can you link me to a product for this?
 

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Jaredrada--

I simply made my own out of epoxy-saturated timber, shaped to fit roughly to the hull and made sound with epoxy bog then glassed over. I also drilled and countersunk a thick longitudinal section from a yellow HD polythene plastic from a gas main off-cut, I cut 2 length ways from the pipe and screwed them with SS countersunk screws over each one to protect the decks when hauled aboard.

If your dink is alloy, I would have them bent as a top-hat section from a wedge-shaped -minus apex sheet of alloy and riveted in place using tubular rivets, then rivet the polythene deck protecting skid-strakes over them into recessed holes instead of screwing them as in timber.

Why yacht dinghys, or any alloy boat sold for use as a tender, are not supplied with such elementary features in the first place indicates to me that most of the designers of these craft never had to haul one aboard, drag one up a beach, always used davits to retrieve them when sailing. Maybe they never bothered to ask any yachtsfolk for their requirements in an ideal tender or shallow-draft fishing boat

The only tender that covered all my requirements in one package as supplied and without titivating or modification was my Polycraft Tuff Tender. They did ask a great many boaters, and came up with a winner, so simple and elegant and comparatively inexpensive. It is heavier than an alloy boat, so needs two to haul it aboard unless one has it slung in davits, and I am sure there ought to be an American equivalent or something similar. If there is not, some company involved in the manufacture of water tanks or other plastic boat designs would do well to obtain the moulds and a licence to produce them.

I do not know why I ever tolerated the other dinks I have had for as long as I did after seeing all of my friends switch to these quaint little (unsinkable if foam-filled) utility craft.

But back to the dinghy you have. Because these have to be made and fitted to your own hull, there is little I can do to show you how--just a few guidelines to making your own. They should be bevelled to stand vertically when the vessel is aboard and cleated down. That means a little drawing first, and the use of a plane and a series of offerings and adjustments until it fits nicely--then some fairing compound if necessary to ensure a good fit. There are two curves to consider, the curve of the hull fore and aft, and the taper from the existing V to the strakes you are adding. The only way to fit them is to get them approximately right, then fair them with two-pack epoxy putty or make your own using phenolic micro-balloons and epoxy. Mine tapered from about an inch or less in height at the leading edge to about six inches or less at the transom, but they terminate on the transom to stop any flexing of the bottom when dragging the dinghy aboard or over obstacles or up the beach or on to a trailer. Landing them on the transom is therefore most important.

I think when you get it all sorted you will be delighted with the results. I was--it was as if I owned a completely different vessel. It rowed extremely well, before it was a pig, and it tracked beautifully in a cross-wind, something else it never did before.
 
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