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Old 03-13-2016, 08:16 PM   #1
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Dragging a dinghy with stern of dinghy tied to semidisplacement boat

Would that help with a semi displacement hull's resistance, so that it might use less fuel at slow speeds?
I was thinking the water flow around the rear of the main boat may flow more smoothly so maybe less drag?
Pretend the dinghy has a flat transom, the transom is 50% of the width of the semi displacement boat, and it is tied onto the swim platform of the semi displacement boat.

Other idea I just had was design a dinghy that fit up tightly to the transom of the displacement boat so that the dinghy was really functioning like a dinghy and like a swim platform.

I am kind of thinking crazy at the moment. Like a modular hull.
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Old 03-13-2016, 08:20 PM   #2
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have not personally towed a dingy backwards...but have seen setups where the dingy was towed backwards with the transom pulled up tight and clear of the water...the results were reported very good with very little resistance.
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Old 03-13-2016, 08:23 PM   #3
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No to the first and not enough information on second idea but would probably pull the transom off in any kind of seas.
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Old 03-13-2016, 08:30 PM   #4
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No to the first and not enough information on second idea but would probably pull the transom off in any kind of seas.
While there are always limits to everything...quite a few sailboats do tow their dingies stern first. With the transom out of the water...the transom is under little strain till the weather gets totally out of hand...but at that point..most boaters I know deflate and bring aboard....
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Old 03-13-2016, 08:57 PM   #5
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Is the dinghy too big to bring the whole thing onto the swim platform? Weaver Davits work very well.
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Old 03-13-2016, 08:57 PM   #6
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While there are always limits to everything...quite a few sailboats do tow their dingies stern first. ...
Haven't seen it. All dinghys were observed moving forward while being towed.
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Old 03-13-2016, 10:48 PM   #7
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Haven't seen it. All dinghys were observed moving forward while being towed.
May be an East Coast thing...especially for certain style sailboats where it is easy to do with reverse slope transoms.


Here is one with a more sophisticated rig.
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Old 03-14-2016, 12:01 AM   #8
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While there are always limits to everything...quite a few sailboats do tow their dingies stern first. With the transom out of the water...the transom is under little strain till the weather gets totally out of hand...but at that point..most boaters I know deflate and bring aboard....
What he said.

It's done all th time by some sailboaters. And I've seen a few powerboats do it as well
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Old 03-14-2016, 12:38 AM   #9
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I am kind of thinking crazy at the moment. Like a modular hull.
This world would be pretty mundane if nobody was thinking outside the box. If they could be hinged at the top of the transom(s) as well, you could tilt it vertically and save on marina slip fees
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Old 03-14-2016, 01:47 AM   #10
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Here's what I think psneed was talking about;

Davron Marine Products (Dinghy-Tow)
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Old 03-14-2016, 07:12 AM   #11
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Cool idea. Too bad they can't be used with rigids. I guess you also have to accept a certain amount of water collecting in the bow?
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Old 03-14-2016, 09:15 AM   #12
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Cool idea. Too bad they can't be used with rigids. I guess you also have to accept a certain amount of water collecting in the bow?
You can rearward tow a RHIB...the only trick is to get the stern out of the water...and yes water may collect but a little wont hurt and if accumulating too much...might be time to bring aboard anyhow (the trick is just not too late...but that goes for line towing too).

If the dink hits the rear of the boat...just fender it till moving where it is pulled away by water movement.
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Old 03-14-2016, 09:29 AM   #13
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Cool idea. Too bad they can't be used with rigids. I guess you also have to accept a certain amount of water collecting in the bow?
Why can't it be used with RIBs? I think there is one pictured on there web site.
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Old 03-14-2016, 10:49 AM   #14
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Originally Posted by sdowney717 View Post
Would that help with a semi displacement hull's resistance, so that it might use less fuel at slow speeds?
I was thinking the water flow around the rear of the main boat may flow more smoothly so maybe less drag?
Pretend the dinghy has a flat transom, the transom is 50% of the width of the semi displacement boat, and it is tied onto the swim platform of the semi displacement boat.

Other idea I just had was design a dinghy that fit up tightly to the transom of the displacement boat so that the dinghy was really functioning like a dinghy and like a swim platform.

I am kind of thinking crazy at the moment. Like a modular hull.
sdowney,
Would't be worth the effort.
Most SD hulls are condiderably wider than the 50% scenaro you thought up in your post. The dinghy would need to be almost as wide as the stern of the boat. Unless the dinghy stern fit the trawler stern very well any efficiency gain would be lost in turbulence.
Speaking of turbulence unless the dinghy was pushed down in the water untill the bottom of the dinghy was about 1" above the bottom of the trawler (and shaped the same re deadrise) there would be more big losses re turbulence. The bow of the dinghy (aft in the scenario) would need to be pushed down also but not nearly as much. If you don't push the dinghy downi the turbulence you're trying to avoid would just be going on under the dinghy.

Sound idea in surface theory but impossible to be practical even for many reasons I didn't bother to mention. You want more efficiency slow down, get a SD hull more like a FD hull or get a FD boat. And if you're not happy w the speed (or lack of) get a longer one. A longer boat would cost so much more in moorage you'd be shoot'in yourself in the foot. So for you I'd suggest taking off your swim platform and your bow uverhang .. being anchor or anchor and pulpit .. and stow your anchor on deck. Or just tollerate the inefficiency of all of the above.
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Old 03-14-2016, 10:55 AM   #15
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Originally Posted by psneeld View Post
While there are always limits to everything...quite a few sailboats do tow their dingies stern first. With the transom out of the water...the transom is under little strain till the weather gets totally out of hand...but at that point..most boaters I know deflate and bring aboard....
This method is quite common among sailboats cruising the Great Lakes.
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Old 03-14-2016, 10:56 AM   #16
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have not personally towed a dingy backwards...but have seen setups where the dingy was towed backwards with the transom pulled up tight and clear of the water...the results were reported very good with very little resistance.
Little resistance because the wetted surface area is greatly reduced. I agree it is probably an east coast thing as I've not seen it here or in Alaska.
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Old 03-14-2016, 10:59 AM   #17
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I have seen it here in Puget Sound, not terribly often however.
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Old 03-14-2016, 01:00 PM   #18
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On my dream power boat the transom would fold down to just above WL and the dink would simply be pulled aboard.

With an extra line or two to keep it centered the dink engine could also serve as a get home.

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Old 03-14-2016, 01:26 PM   #19
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Great idea FF,
But I wouldn't be very welcome at the Willard Rendovous w most of my stern missing .....
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Old 03-14-2016, 08:47 PM   #20
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Agreed, FF... My cockpit is exactly like that; 12' long and about 6" above the WL. 10' RIB slides right in (and out) with a quick pull or shove. Decided years ago to just leave the transom piece at home. And yes, 15hp 'get-home' at the ready, as long as you don't run out of dinghy gas.

Comes at a big cost, though, I have a 42' boat with the interior of a 30-footer. Everything's a compromise.
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