Towing Dinghys

[dhays]

Dave, I don't think your issue is totally related to weight on the stern. I think it is a function of speed. You are right at the speed where the dinghy wants to plane. If you could go 11 knots or more, your dinghy would probably pop right out of the water and happily glide along on plane.

With that said, going from an 8hp to a 25hp would not increase your weight greatly....at least I don't think. Especially if you could find a used two stroke...which is likely similar in weight to your 8hp four stroke.

You could be right about the speed. I never thought of that.

 

[dhays]

My swap was a significant upsizing, from a 10' RIB with a 20hp 2 cycle, to this 12' with 40hp and a console. It tows well, cruises very well at 20 knots, and I can lift it onto my davits. If I was in your present shoes, I would listen to your wife, and do whatever that requires, to get a faster, planing dinghy with a console. It is for her after all.

That is good advice, "happy wife, happy life" and all...

Two things that I really like about this boat are the Sea Wise davits and the Stealhead Marine crane. The option to either have the dink on the boat deck or on the davits is very useful. I wish I had the #800 version of the crane, but then I am not sure I would want that much weight up that high. Maybe being limited by the #600 capacity on the. crane is a good thing.

I am sure that all it would take is $$$. I could find a dinghy/motor combo that would have a console, be able to plane with 2 people (even big people like my wife and I), and be light enough for my crane and davits. Unfortunately, the $$$ is an inconvenient reality at this point.

 

[psneeld]

I have a West Marine single floor rib with an 8hp, 4 stroke Yamaha on it. It is pull start so it is lighter by a few pounds.

It flies with me and still gets easily on plane with a second 120 lb person onboard and I weigh around 220.

It planes well with me sitting right behind the seat with a 18 inch tiller extension and the other person on the seat or on the side ahead of it. Weird...but it is what it is.

Might try fiddling with engine trim and sitting wayyyyy forward, you might be suprised....and I hope you are not insulted if you have tried it all.

Either that..... or a different prop... or Honda needs a new hp ruler.

 

[dhays]

I will try some things out psneed. And no, I am not insulted by suggestions.

 

[Ka_sea_ta]

We have the same WB 10 with a console and 20hp Honda, it won't plane with 2 people sitting side by side behind the console... With one forward and one driving it will lift the stern out of the water.... Boat probably needs a 30hp to perform or I could lose some weight... This combo doesn't work for me which is why we tow a larger boat when we go for a longer trip... By the way have you tried towing the inflatable with a bridle that has two loops, the loops go around the tubes at the rear and rest against the transom... the middle of the bridle goes through the front eye forming the attachment point for the tow line... This way the load of towing is not the forward eye but the where the tubes attach to the transom...

 

[dhays]

By the way have you tried towing the inflatable with a bridle that has two loops, the loops go around the tubes at the rear and rest against the transom... the middle of the bridle goes through the front eye forming the attachment point for the tow line... This way the load of towing is not the forward eye but the where the tubes attach to the transom...

I am trying to picture this... You create two loops that go around and behind each of the tubes but as they go forward are run through the towing eye on the bow? The back end of the loops apply the force on the back of the transom but are guided by the towing eye?

 

[Ka_sea_ta]

The written description is tough to visualize. if you look from above the bridle loops will go around the tubes at the stern. the bridal lines will go forward on the outside of the tubes then pull through the forward eye... most inflatables have a ring,handle something on the side of the tubes you can run the bridal through...

 

[tadhana]

The better it rowed should mean the less power it needed to be towed.

Actually when you are rowing a dinghy you are at displacement speed, and it does not take much power to move the boat. Towing a rowing dinghy at less than its hull sped requires little power. The best hull form for rowing displacement speed is not the best hull form for planing speed. This is why "rowing/towing" dinghies tend to have chines such as you see on a Dyer an its imitators. As others have said, using my calibrated armstrong tensionometer there is a tremendous load when towing a nice rowing dinghy above its hull speed. A planing dinghy is much less load at planing speed.

 

[dhays]

The better it rowed should mean the less power it needed to be towed.



Actually when you are rowing a dinghy you are at displacement speed, and it does not take much power to move the boat. Towing a rowing dinghy at less than its hull sped requires little power.

This simple concept came back to me again yesterday as I spent a couple hours kayaking. The kayaks are 12 feet. They are very easy to paddle at a certain speed. However if you try increase the speed, you get to a point where the effort increases exponentially. The same holds true for any non planing hull, but to feel it in my muscles made it more "real".

 

[Baker]

Another thing as it relates to planing your dinghy.....do most of you use those wings bolted onto the base of your outboard???? They do work....in fact they are a must if you expect your dinghy to plane. Without it, regardless of how much power, your dinghy will just point at the sky when powered up with only one person. With it, it will just pop out of the water almost level. Anyway, I don't mean to make this about dinghy planing and not dinghy towing.

I also tow my dinghy with the two side rings and not the center eye. I have a West Marine Dinghy. I use a West Marine towing bridle and tow the dinghy as instructed by West Marine. It actually works!!!

 

[psneeld]

If talking about drag on a sailing vessel under sail...certainly a bit different....maybe noticeable in light airs but on my 23 foot sail boat in over 10 knots of wind, dragging the dink was never noticed.

A 9 foot, lightly loaded, plastic sailing dink behind a 40 foot trawler doing 8 knots would hardly be noticeable on a flowscan compared to an increase of a knot of current or 10 knots of wind.

The better it rowed should mean the less power it needed to be towed.

Non issue.

20 something, low powered cruiser...much like a sailboat sailing in light airs...maybe a bit noticeable.

I will quote my own post...

A 9 foot lightly loaded plastic rowing dingy will get airborne in the right towing conditions...no...drag isnt a big desl having towed quite a variety of boats under quite z variety of conditiond..

At 8 knots you are dreaming it has much resistance.

Some rowing dinghies might .....but not what I was describing.

Most lightly loaded, smaller dinks offer hardly any resistance.

 

[BandB]

...do most of you use those wings bolted onto the base of your outboard???? They do work....in fact they are a must if you expect your dinghy to plane.

Wifey B: Only a pilot would use wings on an outboard to make it be like a plane.

Oh, I had to google since I'd never heard of such. Called Hydrofoils. Well, I don't know outboards. So I learned something today.

 

[dhays]

I also tow my dinghy with the two side rings and not the center eye. I have a West Marine Dinghy. I use a West Marine towing bridle and tow the dinghy as instructed by West Marine. It actually works!!!

My WM dinghy that I had towed well without a motor behind my sailboat. I made up a 3 point bridle using the bow ring and the two side rings. My Walker Bay doesn't have those side rings unfortunately.

 

[psneeld]

Having almost exclusively towed hundreds and hundreds of boats by the trailer eye...for the life of me I can't figure out why WM dinghies require you to use the tow eyes on the fabric.

It makes no sense to me.

I doubt it would affect towability, could cause more chafe, if the eye isn't durable enough for water towing - what makes them think it is a good point to tie to a trailer?, etc...etc....just no sense to me.

 

[tadhana]

The requirement to tow from the D rings is a function of the fact that for many years the WM dinghies were made by Zodiac. The Zodiac owner's manual is quite specific that you must tow by the D rings.

 

[psneeld]

Yeah...gather that...but why when assistance towing companies pretty much tow from trailer eyes when possible because of chafe and strength.

Are the trailer eyes on small ribs not as strong proportionately as larger boats? .....and if not .....who wouldn't make them stronger than a couple of fabric circles glued on?

 

[dhays]

I found that they towed well with a three point bridle. Most of the load was on the trailer eye.

 

[tadhana]

Towing from the D rings will reduce any tendency of the dinghy to wander. As an engineer previously with Zodiac, I can attest that it is possible to pull the u bolt out. Never saw a D ring fail though.

 

[Ski in NC]

Yep, if towing from a single point on the bow, under certain conditions it will go nuts. I switched to the d-rings, much better manners.

 

[psneeld]

My towing experience shows that a tiny little vee bridle like that would have much less effect than trim and some vee bottom. For a flat bottom dingy I could see a little better manners....maybe.


I am aghast that the tow ring would fail before those tiny glued on D rings.


I believe that the tow eye may be the weaker link, but to me for the effort of bothering with those silly D rings, I would have just beefed up the D ring.


I have over a thousands tows under my belt and have to say...bridles work to lessen veering...but ultimately it is the load that causes veering and the bridle ony lessens it.


A properly trimmed tow will ride great from a tow ring and almost no worries about chafing.


Aren't most of the custom eyes for towing large, heavy power boat dinghies just a single eye?...and not one place on each side like D rings?

 

[Ski in NC]

Different for bigger boats, the single eye there works fine. On a light softshell like mine, it would veer side to side and sometimes go slack and then take a hard snatch. That snatch really stressed the center tow point. If it does not do anything like that, single point is fine.

I towed a boat from Abaco to NC straight offshore. It behaved properly during the day, but at night we lost it twice and had to go back and find it. Lesson learned there is that tows act strange in the dark....

 

[psneeld]

Different for bigger boats, the single eye there works fine. On a light softshell like mine, it would veer side to side and sometimes go slack and then take a hard snatch. That snatch really stressed the center tow point. If it does not do anything like that, single point is fine.

I towed a boat from Abaco to NC straight offshore. It behaved properly during the day, but at night we lost it twice and had to go back and find it. Lesson learned there is that tows act strange in the dark....

Bermuda Triangle gotcha....

 

[Nomad Willy]

What brings about all these problems w the duckie dinghies is the result mostly of hull aspect ratio. In tavern talk it means the little tubs are just too fat and short and usually overloaded. And the roundness of the tubes suck the stern down. A really stupid shape for a boat.

An 11' "tinny" would probably make a far better dinghy than the duckies. More room in it too as the sides aren't fat tubes.

 

[jleonard]

I would have to say that my 10.5 Achilles RIB (double hull) stays very well behaved when towing from the bow eye. Motor locked up.
But it's much more than 40 lbs of pull to move it. Dink weighs 160 and motor 80 (2 cycle Yamaha 15).

As far as planning, no sweat with my fat arse on the tiller and wife forward of the seat and a 6 gal tank mid ship. Needs maybe 1/2 + throttle to stay up. 26 mph with both of us aboard in flat water.
Planes very easily with 4 adults also.

 

[smitty477]

After towing a dozen or so various inflatable dinghies I have learned that only the RIBS will have a reasonable chance for an easy tow at anything above hull speeds. And even with RIBS it takes at least a 15' boat to track well at speeds in the mid teens or higher. Couple that with self bailing hulls and good attachment points and the tows are not a problem at all. When it comes to loads on the towing boat the smaller inflatables (12.5' - 15') towed at speeds in the range of 15-18 knots are barely detectable as the exact sea states and allover loads become the higher variable. Even when towing larger inflatables in the 19'-24' range at up to #3,500 #'s and more the effect is at or less than a 5% penalty at those speeds from our experiences. These are comparisons over the same cruising grounds with the same boat towing over 1,000's of towed miles (about 500-600 towed miles per season).
As a result we do not feel comfortable towing any soft inflatable unless confined to protected harbors and not really fond of towing RIBS in the open unless they are larger and self bailing with 2 good attachment points and a good bridle. We have been in some pretty foul weather with tows and have not suffered a problem with these guidelines.
YMMV

 

[Nomad Willy]

psneeld wrote;
"The better it rowed should mean the less power it needed to be towed."

Has a nice ring to it but ...........

dhays wrote;
"I tried towing my dinghy today and was not happy with it. 43' single engine boat pulling a 10' Walker Bay Genesis RIB with a heavy 8hp four stroke. I used the tow eye on the bow but the the dinghy bow rode so high that I was concerned that it would take on water over the stern."


These non planing hulls have huge drag above displacement speed. Hull speed for a 9' dink is less than 4 knots. Unless the run of the bottom of the hull is almost perfectly straight like a typical aluminum skiff the stern will get sucked down as evidenced by Daves post. When I tow a SD dinghy at 6 knots there is quite a bit of drag on the painter and the stern is down noticeably w no OB. But it's a SD hull that runs 8 or 9 knots w a 6hp OB trimed propperly. If it was a full displacement rowing boat like a Trinka the drag would be far more than my old dink that is a converted SD sailboat. It lacks the directional stability for a good rowboat. A good rowboat is always FD.


With the Duckies they are FD w the soft bottom. The RIBs are a combination of planing and FD. The center of the bottom on most is planing but the tubes get dragged through the water and the lack of the sharp edge of a transom break means the water outboard aft gets pulled up due to the curved shape of the tubes. Take the tubes off, put hard sides on it and they will plane beautifully. The duckies are a very bad composite design but they do some things well.

 

[Heron]

A 9 foot lightly loaded plastic rowing dingy will get airborne in the right towing conditions....

LOL...Had that happen once years ago when hit by a quick storm from the rear coming into Cambridge Md....8' rubber boat blew off to the side and started rotating on the bridle, throwing contents and oars everywhere. It was quite a thrill...

My current set-up may look goofy, but with 28' to work with it works for us. I don't tow unless I have to anymore though I spent many years doing it with both hard and soft sinks when we were sailors...

 

[psneeld]

People can cite how much drag a 8 or 10 foot dingy causes in relation to normal operations...well don't believe any of us then.

Empty they cause very little drag...which is what I would consider normal towing...fill them up....different story..

Go find out for yourself. Try it. Follow some simple guidelines and see. Not working for you. Don't do it.

 

[caltexflanc]

I used the tow eye on the bow but the the dinghy bow rode so high that I was concerned that it would take on water over the stern."

How long was the towline? Sounds like it was short, steepening the angle of pull. Short also means less elasticity, so more shock loads to the eye.