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Old 25-08-2015, 14:47   #1
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How much does towing a dinghy slow you down

With a 33 foot boat, displacement 12,000lbs or so, how much would towing an 11' inflatable dingy with 10hp motor slow it down?

In 5 knots of wind I suspect it would be quite draggy - in 10 knots? in 15 knots?

And at what point is it no fun at all dragging a dinghy?
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Old 25-08-2015, 15:02   #2
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Re: How much does towing a dinghy slow you down

a lot.... a knot or more... a foul bottom is even worse...
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Old 25-08-2015, 15:03   #3
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Re: How much does towing a dinghy slow you down

Try to pull it toward your boat when sailing sometime. The pull is pretty hard. having said that, at the point you have enough wind to sail at hull speed you may have enough reserve power for it to not matter. In lighter winds I would think it's pretty big. Towing can have many problems, I've seen dingys upside down with the motor head in the water etc. Also in bigger seas the dingy is at risk of loss, trying to pass the mothership on the face of a wave etc.
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Old 25-08-2015, 15:08   #4
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Re: How much does towing a dinghy slow you down

I'm starting to think a rollup with a 2hp motor might be a better option than donating to neptune....
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Old 25-08-2015, 15:13   #5
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Re: How much does towing a dinghy slow you down

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I'm starting to think a rollup with a 2hp motor might be a better option than donating to neptune....
Check threads for discussion of the Portabote...stow it on deck. Rows well.
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Old 25-08-2015, 16:52   #6
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Re: How much does towing a dinghy slow you down

We tow our 8'6" air floor dinghy for short hops and coastal passages. NEVER with the motor on it. For off shore or longer hops we deflate it, roll it up and stow it.

When we tow it behind our 42' 30,000# boat in light air (~10k) it cost us about 1/2 knot. At 15 knots it is negligible.


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Old 25-08-2015, 16:55   #7
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Re: How much does towing a dinghy slow you down

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I'm starting to think a rollup with a 2hp motor might be a better option than donating to neptune....
Yes rollups aren't too bad. 2-4 hp motors are pretty light too. Plenty of older good running 4 hp around if on a budget.
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Old 26-08-2015, 08:47   #8
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Re: How much does towing a dinghy slow you down

We used to have a hard bottom AB, 12 footer or so and towed it behind out Little Harbor 38. I experimented and found it slowed us down between 3/4 and 1 knot without the engine on it. With the engine it was between 1 and 2 knots.

We sold the AB and replaced it with a Achilles LSI88, which weights about half as much. Now we never tow, we flip the dingy up on the foredeck instead. It easy to do. I can do it by myself. Highly recommended.


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Old 26-08-2015, 08:51   #9
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Re: How much does towing a dinghy slow you down

When we tow a dinghy I try and adjust the painter length so it rides on the face of the uprising 2 swell following the boat. This is apparent when you are motoring and in calm seas as to what that distance is. the amount of pull is only the boat directing your dinghy as to where it needs to go.
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Old 26-08-2015, 08:58   #10
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Re: How much does towing a dinghy slow you down

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We sold the AB and replaced it with a Achilles LSI88, which weights about half as much. Now we never tow, we flip the dingy up on the foredeck instead. It easy to do. I can do it by myself. Highly recommend.
Doesn't that effect boat stability - i.e. having it lashed down on the foredeck?

Maybe its so light it's negligible?

How about these ... Achilles LT series ... 3hp ... and can be folded up into a bag.
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Old 26-08-2015, 09:06   #11
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Re: How much does towing a dinghy slow you down

I towed my RIB until I got the davits installed, just towing it behind the boat slowed be by at least a Kt, and I'm not that small or light a boat, dragging the thing up real close behind the boat so that the bow was against the stern and up in the air helped quite a lot, but the thing that took me totally by surprise was how noisy it was towing it, even well behind the boat, it was annoying.
I can't recommend towing, unless there is no other way.
I think the reason it's so much drag, is your well beyond it's hull speed
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Old 26-08-2015, 09:10   #12
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Re: How much does towing a dinghy slow you down

Sorry but with 33 to 11 ft you should decide which boat you want to drive.
I think towing a dinghy is never ever an option. Buy a 7 ft dinghy and stowe it on the foredeck. A 2,5 to 3,5 hp engine is suiteable for this dinghy.

Would you tow an fish trawler with a 500ft container carrier?
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Old 26-08-2015, 09:34   #13
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Re: How much does towing a dinghy slow you down

having been one of those folks seeing their dinghy fly like a kite, to come down upside down and be a sea anchor in a pop up Tstorm, suffice to say that my enthusiasm for towing a dinghy (always engine off) is down to near zero for anything other than calm weather for short hops..

My decision on a dinghy and motor was based solely on the ability to manhandle it.. resulting in a 10ft rollup inflatable floor dink and a 6hp/55lb motor that does not require an engine hoist.
This combination allows planing for 1 or mebbe 2 people, and the dink can be hoisted by the spinnaker halyard and fit upside down on the foredeck for day sails, and be rolled up and in the head for longer trips.

You can buy reasonable pumps that will do 80% of the inflation for quite cheap..

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I'm starting to think a rollup with a 2hp motor might be a better option than donating to neptune....
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Old 26-08-2015, 10:41   #14
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Re: How much does towing a dinghy slow you down

Bruce Bingham in one of his earlier design books has a good howto on dinghy towing. one point was a reinforced 3 point bridle which in itself was a big improvement.
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Old 26-08-2015, 10:46   #15
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Exclamation Re: How much does towing a dinghy slow you down

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Originally Posted by Mystic38 View Post
having been one of those folks seeing their dinghy fly like a kite, to come down upside down and be a sea anchor in a pop up Tstorm, suffice to say that my enthusiasm for towing a dinghy (always engine off) is down to near zero for anything other than calm weather for short hops..

My decision on a dinghy and motor was based solely on the ability to manhandle it.. resulting in a 10ft rollup inflatable floor dink and a 6hp/55lb motor that does not require an engine hoist.
This combination allows planing for 1 or mebbe 2 people, and the dink can be hoisted by the spinnaker halyard and fit upside down on the foredeck for day sails, and be rolled up and in the head for longer trips.

You can buy reasonable pumps that will do 80% of the inflation for quite cheap..
Indeed never tow a dinghy, can easily flip and then serve as sea anchor, also never tow with outboard on for obvious reason that the sea anchor now is even more efficient. An outboard that has been submerged lots of cleaning, greasing, might never wirk properly again.
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