Towing a Dinghy

[tjr818]

I am thinking of building a small dinghy to occasionally tow behind our CD27. Maybe I am over thinking this, but wouldn't the hull speed of a dinghy limit the speed of the sailboat? Would a round wineglass hulled dinghy like the Humblebee or the Auklet be harder to tow than a "V" bottom like the Eastport Pram or the Nutshell Pram? Would either of these really make much difference? I am for the most part a daysailor not a long distance cruiser.

[Ken Cave]

Getting in and out of your type of dinghy from your sailboat will be a major problem, as most are very tipsy
to say the least.

Try looking at an inflatable, as one can actually step onto the side and not worry about falling in, or tipping
the dinghy over.

We have used a 6 foot built for Mercury with a soft bottom that can be blown up into a v shape for easier
towing. I usually tow about three feet from the stern, and have been successful for the past 12 years
with it.

Older second hand ones are sometimes available, especially when the topsides become sticky. These are easy
to repair by spraying Marykate cleaner, then painting the top with MDR topside paint.

Hope this helps

Ken Cave
CD 28
LaConner, WA

[Stan W.]

Theoretical hull speed is not an issue because a dinghy in tow will plane. All designs are compromises. A soft chine hull generally tracks better but will still plane o.k. if it has relatively flat aft sections. A hard chined hull generally planes better but will still track o.k. if it has a skeg and a little bit of V in its aft sections. I don't know who designed the Eastport, but the others were designed by two NAs who certainly gave that compromise some thought and struck a reasonable balance. I have a Mertens D4/D5, which is a v-bottomed, hard chined boat with aft sections flatter than the Nutshell. It planes well, as one would expect, but it also tracks just fine.

[CD_Sailor]

I am thinking of building a small dinghy to occasionally tow behind our CD27 ... wouldn't the hull speed of a dinghy limit the speed of the sailboat ... Would [ a specific design] really make much difference? ...

Practically speaking, just be aware that you will be slower under either power or sail when towing. I suspect that differences between hard boats of various designs, and soft boats of various designs (including RIBs) will be measurable, but just barely so.

Dinghies are fun and useful, so just step up to the plate and forge ahead.

[2tocruise]

Just like everything else in boating, it's a matter of the compromises you wish to make. The designs you have mentioned will all meet your needs.

Generally, in order to tow well a dinghy will need good directional stability, or tracking, normally achieved via a skeg. You also want a dinghy that will not take on too much water from spray, so you need sufficient freeboard. Lapstrake construction is one way to help keep spray out (it's the practical reason why the plastic Walker Bay dinghies have molded laps). A stem bow will also generally cut the water better than a pram, giving less chance of burying the bow in a wave or get pushed around by cross chop.

Stability will make a bigger impact in usage than in towing, but generally a round hull shape will have less initial stability than a hard chine, making it more tipsy while using it. a pram will be more stable than a stem bow and will carry a bigger load.

The speed of your boat will be impacted by the dinghy being towed. Almost all of the "tender" size dinghies are displacement hulls. Towing them at cruising speed will put them on a semi-plane and making a bow and stern wake. The wake sucks energy from the big boat, causing you to lose speed. It will normally be somewhere in the 1/4-1/2 kt range. Flatter aft sections will help, as mentioned below.

And this happens regardless of what dinghy it is, even towing an inflatable reduces your overall speed.

As you mentioned wanting to build it I would also add that build difficulty will also be a factor. A round bottom wineglass hull is much more difficult to construct than a hard-chine V or flat bottom skiff. Material costs and availability matter too, it's usually easier to to get plywood than white oak suitable for steam bending wineglass frames.

last thing on design I'll mention is you will also need to decide how you will power the dinghy. A design that rows very easily will not power as well. A design for power can be rowed, but will not perform as well as a dedicated "rowing craft" would.

We have been quite happy with the towing performance of our 7ft hard chine, lapstrake, flat bottom dinghy. She is a William Atkin "Precious" design. We've towed her throughout New England, Long Island Sound, and the Chesapeake without issue, in seas up to 4ft. She is stable, tracks very well, and frequently receives compliments on both her looks and how well she rows. Atkin designed quite a few dinghies, all intended for homebuilders. He also wrote descriptions of almost all his craft that are very instructive. http://www.atkinboatplans.com

[Steve Laume]

Everyone has different levels of comfort when it comes to the stability of a dinghy. Coming from a background of canoes and kayaks, I am perfectly okay with a hard dinghy. Step in the middle when you get in. Sit on the side when you are bailing. I bought an inflatable last year for my Bermuda trip so I could carry it on board. I must admit that it was nice for climbing into while out snorkeling. They have their practical side but I find them kind of ugly, impossible to row well and I have heard more than one story of them flipping while under tow.

If I were choosing to build a new dinghy, the last thing I would consider is how well it would tow. More important to me would be that it row well, the level of skill required to build it, how heavy and pretty it was. If it rows well it will probably tow well.

Since you are not going to be able to take it on board I would also not skimp on length. The longer dink will be easier to row and tow. There is a practical limit to this and weight is part of that equation.

I have towed our CD-10 a good bit and love to row it. It is also very pretty behind it's CD mother ship. Feather is however, not very light. This makes it hard to get on and off some beaches, especially rocky ones. I have never felt it was in danger of flipping, even in some rather nasty tidal rips. It does not take on water unless the drain plug pops out or it is raining extremely hard. It does get a little wet if you are rowing into a short chop with two people and I suspect a pram might suffer more in this situation.

When towing I can hold the painter in one hand so it is not creating that much resistance. I use floating double braid for painters to keep the line out of the prop but usually shorten up when maneuvering. Once the big boat is on a steady course I will pay out line, snubbed around a cleat, until the dink is surfing down the front of the second stern wave. You can do this by eye but the fine tuning comes by feeling the resistance in the tow line. When set up properly I can hold a heavy, 10' dinghy with my fingers so I don't think it slows the big boat down much at all. A greater problem in following seas can be that the dinghy will surf up to the stern of the towing vessel or even pass it off to the side. This is when we let the dinghy ride a bit further aft. We almost always run two separate painters tied off to each stern cleat. This helps keep the tow behind the boat and adds another line for security. I also added a second eye to the stem of the dinghy so that I have a completely redundant system. This doubling was after a parting of company in very choppy conditions on Buzzards Bay. At least we noticed and were able to come around for a retrieval. We had room and I was not alone but would not want to repeat the situation under less favorable conditions.

So in short, build the boat you want to use and the towing will take care of it's self, Steve.

[hwh888]

I'm not sure you would save any money by building your own dingy. Add up the cost of marine grade plywood, paint, varnish, fiberglass matt, hardware and stuff you might discover you are into it for several hundreds of dollars. I know, I did it several years ago. Ended up with a heavy boat that cost me as much as a reasonable prices dingy. Granted it outlasted a PVC dingy by several years but in the end a bought dingy would have been the better idea. Not Easy to carry because of weight, a two person job. Ended up building a trailer to move it from dry to water. My advice, think twice before going ahead with the idea. Good Luck either way.

[tjr818]

I'm not sure you would save any money by building your own dingy. Add up the cost of marine grade plywood, paint, varnish, fiberglass matt, hardware and stuff you might discover you are into it for several hundreds of dollars. I know, I did it several years ago. Ended up with a heavy boat that cost me as much as a reasonable prices dingy...Good Luck either way.

Oh, I'm quite sure I won't save any money by building my own. You go to the lumber yard and the mahogany looks so nice....and it is ONLY a few dollars more. Then the bronze fittings look so much better than the stainless steel, epoxy is better than polyester, etc, etc.... I know, but what else are you going to do in the winter? I do appreciate the advice, and the good wishes. Thanks.

[Neil Gordon]

There have been times when the weather got snotty that I would rather have had the dinghy on deck and not behind me. My roll up stores well on the side deck at the shrouds and doesn't take all that long to deflate/inflate. It does create a fair amount of drag... I'd have to do some quick calculating to see how much extra speed I'd need to justify the extra dinghy time and how long a trip might need to be to break even.

[John Ring]

I am thinking of building a small dinghy to occasionally tow behind our CD27. Maybe I am over thinking this, but wouldn't the hull speed of a dinghy limit the speed of the sailboat? Would a round wineglass hulled dinghy like the Humblebee or the Auklet be harder to tow than a "V" bottom like the Eastport Pram or the Nutshell Pram? Would either of these really make much difference? I am for the most part a daysailor not a long distance cruiser.

Yes, it will affect speed of the towing boat. It won't limit the tow boat's speed to the smaller waterline of the dinghy, but it will slow things down.

I have two glass dinghies, one with a relatively flat bottom, and a wineglass shaped beauty that's a joy to row. When towed, the flat bottom dinghy goes up on plane instantly, and I feel very little resistance when I hold the painter while towing it. The wineglass dinghy, about the same length, doesn't want to go up on plane. I can see its bow wave getting longer than it's waterline and it starts to ride nose up in the fwd section of its elongated wave as my CD28 powers up & forces the issue. The tension on the towing painter is many times that felt when towing the flat dingy, and it slows the boat noticeably.

If I'm cruising long distances, I use an inflatable roll-up, and keep it on the fwd deck.

Cheers,
John

[tjr818]

Thanks John, That's another vote for a planning dinghy. Although I love the lines of Tanta-less, also the name. My grandmother was known as Tanta and we are now...Tantaless.

[Steve Laume]

So how many tenths of a knot are we talking about when towing any dinghy?

I would take rowing capabilities and beauty over a few hundredths of a knot difference in a planning dinghy vs something like Tanta-less or a CD-10. The CD-10 is actually a bit flatter in the stern. If we were most concerned about performance, none of us would be sailing Cape Dorys.

One more thing to consider in a dinghy is initial vs final stability. The flatter bottoms might feel pretty stable up to a point. The really pretty wine glass sterns and rounder bottoms will be more predictable and have greater final stability.

Life is too short to own an ugly boat, Steve.

[jbenagh]

I have been very happy with my Shellback; I have rowed and sailed the Shellback and the larger Nutshell. The Shellback is very similar to the Nutshell you mention (same designer, same construction, very similar form shape). She seems to combine nicely a relatively flat bottom (she is plywood after all) with rounded sides. As Steve mentions, she has low initial stability and very high ultimate stability (I need to find the pictures under sail in 20kt wind where the rail was below the water surface), very similar to Tanta-less. She rows like a dream, but in really rough conditions, her light weight gets pushed around a little bit and I really have to work to keep her on course. In the intro to the "How to Build" book, Jon Wilson says "she tows like a duck" which seems to be an apt description. They all can take a sailing rig and sail very nicely.

Best of all, she is a looker! You will get no end of compliments.

Of course, there are disadvantages. You need to build one yourself (about $1200 for the rowing model) or you will pay a lot ($2400). You need to maintain the paint yearly and throughout the season if there is damage although a few layers of glass on the bottom/garboard joint can help. They cannot take a motor but row so well that I don't consider that a problem. The Shellback is about 120 pounds which is really a two person lift to get above the tide line on a rocky shore (the larger Nutshell is about the same, the 7' 7" is about 90 pounds as designed). If you or the crew are careless, you will gouge the skeg and bottom requiring repainting and possibly bigger repairs. The gunwales are hard and really benefit from foam/cloth gunwale guard which is pricey and requires cleaning. Perhaps the worst is, that none of the Shellback or Nutshell variants will fit on board a CD30; even the 7' 7" Nutshell is too big to fit between the mast and the traveler.

Well, that's enough. I guess my point is, these are very nice boats but there is no such thing as a perfect dinghy when the mothership is 30 feet or less.

Jeff

[CD_Sailor]

... there is no such thing as a perfect dinghy when the mothership is 30 feet or less ...

Or 30 feet or longer.

For a few years I "endured" both a rubber boat ( reasonable Achilles with outboard) and a hard boat (one of which was a CD 10 with sails, oars, and an outboard), and even with this menagerie there were times when something else might have helped.

Moral: There is none.

[Dick Villamil]

you can significantly reduce "Dinghy Drag" by adjusting the painter so that the dinghy rides on the downside of the second stern wave of your boat. That way it is always sliding down the wave as you pull it. If it is on the first stern wave it could surf into the stern of your boat - therefore the second stern wave is safer. Obviously the boat speed affects the distance that the second stern wave is at therefore you shouild be able to adjust the dinghy's painter after you set your speed.