# good light rowing dinghy plans?



## copacabana (Oct 1, 2007)

Does anyone know of any good plans to build a solid but lightweight rowing/sailing dinghy? Ideally I'd like to build it out of something light like divinicel and fiberglass (sandwich). Something about 8ft should do the trick. The idea is to haul it up on deck when sailing so I'd like something light. Has anyone built one they could recommend? Has anyone tried building one using a foam/fiberglass sandwich technique? Thanks in advance!


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## sailingdog (Mar 19, 2006)

I think a stitch and glue marine plywood design in that size range would be lighter than a foam cored GRP dinghy. Check out the CLC line of designs.


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## copacabana (Oct 1, 2007)

I thought a foam core would be lighter than ply, but thanks for the suggestion.


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## sailingdog (Mar 19, 2006)

copacabana said:


> I thought a foam core would be lighter than ply, but thanks for the suggestion.


In larger sizes, yes, but the smallest boats are often lighter in stitch-and-glue than in GRP. A stitch-and-glue boat doesn't even need to have a full coat of fiberglass on it, where the skins on the foam-cored GRP boat have to have a minimum thickness to guarantee the core's integrity and provide sufficient stiffness to the design. Marine plywood, even 1/8" is pretty stiff torsionally, unlike foam, once it is bent and held in that position.

For instance, the Chesapeake Light Craft's Eastport Pram is 7' 9" x 48" and only weighs 62 lbs. One 8' GRP/Foam dinghy that I found on the net weighed in at 130 lbs... People often underestimate how much epoxy or vinylester resin and fiberglass cloth actually weigh.


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## Mirari (Sep 13, 2006)

I'm planning the same thing but I want to stick to all composite so my plan is a fiberglass and carbon fiber dink with vinyalester resin. I'm shooting to keep the weight under 40 lbs. I happen to have a 7 foot pram mold but if I didn't I would build a quick and dirty pram mold using masonite with a little stitch and glue technique. There are plans out there if your not up to designing one yourself. I still plan to use my inflatable but this one will be designed with a removable seat so it can act as a cover for the rolled up inflatable. I never tow the dink so this one is just in case I need to kedge out an anchor or make a quick trip to shore and not bother blowing up the inflatable.


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## bljones (Oct 13, 2008)

Tooting my own horn:










Hard dinghy, low-buck style


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## JonEisberg (Dec 3, 2010)

Have a look at the designs from B&B, Graham has drawn some very sweet boats&#8230; I built a nesting Spindrift, really nice little boat that rows beautifully. If you built one from a material called Coosa, it could come in at a fairly light weight. I've never used that material, but have heard great things about it&#8230;

spindrift

Now, if you want to go ultra-light, have a look at Platt Monfort's boats, they're very cool&#8230; Whether they would stand up to the rigors of use as a yacht tender, of course, is another matter&#8230;

Geodesic AiroLITE Boats - ultra lightweight SOF canoes and boats; plans, projects and tutorials


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## deniseO30 (Nov 27, 2006)

Please be aware there are BIG differences in rowing boats compared to trade offs like flat bottom skiffs that row like a brick.


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## paulk (Jun 2, 2000)

Like Denise said. The Nutshell dinghy from Woodenboat is supposed to row and sail well. They have a number of other designs that might do what you need - including a Whitehall, but that's another thing entirely. Chesapeake Light Craft is expanding beyond kayaks too, and might be worth a look. One caveat: I've heard that if you go too light in a boat designed to be capable of carrying a load (not a single scull, for example), the boat doesn't carry well between strokes. There's simply not enough inertia to maintain speed.


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## Argyle38 (Oct 28, 2010)

JonEisberg said:


> Have a look at the designs from B&B, Graham has drawn some very sweet boats&#8230; I built a nesting Spindrift, really nice little boat that rows beautifully. If you built one from a material called Coosa, it could come in at a fairly light weight. I've never used that material, but have heard great things about it&#8230;
> 
> spindrift
> 
> ...


I have a Spindrift 10N (N for nesting). I like it a lot. It's definitely light enough, especially once split into the two halves.

My only complaints are:
Low freeboard. Could another 3-4" there.

Low Boom for the sailing kit. The little boat has a huge sail for it's size, but the boom is a bit low for operating while sitting on the seat. Sitting on the bottom, you tend to get a wet bum (see freeboard issue). I planning on having the boom raised (shortening sail) a bit to make it more manageable. I don't race so I don't really care about top speed.

The spindrift does row and sail very well.


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## sailortjk1 (Dec 20, 2005)

As sailing dog said, the Chesapeake Light Craft Eastport Pram is a very light dinghy and these boats row like a dream. You can even add a sail kit if you choose.<O</O
<O</O


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## sailingdog (Mar 19, 2006)

Mirari said:


> I'm planning the same thing but I want to stick to all composite so my plan is a fiberglass and carbon fiber dink with vinyalester resin. I'm shooting to keep the weight under 40 lbs. I happen to have a 7 foot pram mold but if I didn't I would build a quick and dirty pram mold using masonite with a little stitch and glue technique. There are plans out there if your not up to designing one yourself. I still plan to use my inflatable but this one will be designed with a removable seat so it can act as a cover for the rolled up inflatable. I never tow the dink so this one is just in case I need to kedge out an anchor or make a quick trip to shore and not bother blowing up the inflatable.


The problem is that you've got demands for a light boat, but it has to be big enough to carry a load, durable enough to survive contact with docks, the beach, boats, etc. Build the boat too lightly and it won't survive the use it is intended for.

A glue-and-stitch plywood boat with kevlar reinforcement for the exterior to provide some abrasion/puncture resistance is a good compromise for a home-built tender. I don't think you can make one with carbon fiber and fiberglass that will weigh under 40 lbs. and be strong enough to be usable.


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## Mirari (Sep 13, 2006)

SailingDog,
I built a dink out of the same mold 30 years ago with just glass matt and polyester resin. Also had a big Teak seat and rub rails. The weight as I recall was around 60 lbs. Since that time I have spent more than a few years working for a well known jet engine maker and have aquired materials and knowledge to greatly reduce the weight while increasing the flexural strength and stiffness. My test samples for this dink showed the hull weight at 18-20 lbs. using the carbon fabric I currenlty own. I added 20 lbs for the rub rail, fasteners, seats and flotation. This is not going to be a work horse dinghy but just an occasional use one for 2 people and a small outboard if I'm not using the inflatable. I will sacrifice a bit of ultimate strength to keep the weight down enough so I can hoist this up on deck without any assistance or mechanical advantage. 40 lbs is not a problem.


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## bljones (Oct 13, 2008)

My dinghy came in at 50 lbs without the benefit of carbon fabric and jet engine experience, so I think your goal is attainable.
However, if we reverse engineer this equation, does the fact that i have experience building dinghies mean that I am qualified to work on jet engines?


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## bljones (Oct 13, 2008)

The D4 is another good choice for a multi-purpose dinghy. With a little planning, you should be able to meet your weight goal. The basic plans are free and it is a relatively quick, low cost build.










Duckworks Magazine - Building a D4 Dinghy


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## Mirari (Sep 13, 2006)

bljones said:


> My dinghy came in at 50 lbs without the benefit of carbon fabric and jet engine experience, so I think your goal is attainable.
> However, if we reverse engineer this equation, does the fact that i have experience building dinghies mean that I am qualified to work on jet engines?


I just get to work on some of the material and design aspects. They won't let me touch the engine!


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## copacabana (Oct 1, 2007)

Bljones, that D4 looks nice, but how did you build it with a finished weight of 50lbs? The finished weight in the plans is 75lbs. 

SD I'll look into the ply option again. Tks. I still can't get my head around why it should be lighter than a foam sandwich. My boat's decks and hard dodger are divinicel sandwich to reduce weight so I just assumed the same would apply to the dinghy. Also, foam sheets seem to lend themselves to stitch and glue like plywood or even strip-planking, making the construction simple. Would glassing in some etxra foam ribs/stringers give it the stiffness and strength you feel is lacking in foam construction? I'd like to keep the weight down to no more than 50lbs, but it also has to be tough enough to be used as my main dinghy (after I happily torch the unruly and leaky inflatable one!)
Mirari, I'd love to make one in carbon fiber as well. Light and strong. A bit out of my skill set though....


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## QuickMick (Oct 15, 2009)

just wondering, once you factor in the cost of materials and the time involved, might it not be cheaper to buy one?


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## copacabana (Oct 1, 2007)

QuickMick, I live in Brazil and we don't have the same range of nautical products here. I can't find a hard dinghy here, off the shelf, that is well made and light. If I were in the US I'd just go out and buy one! What I wouldn't give for a Westmarine here!


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## Bill-Rangatira (Dec 17, 2006)

Have you considered skin on frame?


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## Barquito (Dec 5, 2007)

> Have you considered skin on frame?


Is that a Ed Gein design?


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## Alex W (Nov 1, 2012)

Skin on frame is a building technique. You make a lightweight space frame skin, then have a tight fitting fabric over it. This is a common technique for home building kayaks. In kayaks it allows you to build a kayak that is about half the weight of a similar fiberglass boat. I don't know if the weight will scale the same weight in dinghy sized objects.

I have a Dyer Dhow Midget. It is about 75-80lbs and I can see how to easily lose 10-15lbs from it (the bronze seat mounts are clearly too heavy, and the plywood transom could be replaced with fiberglass, and you can ditch the sailing gear), but I don't see how to get it down to 40lbs. The fiberglass hull is already extremely thin and light, and I don't think I'd want it any lighter.


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## Skipper Jer (Aug 26, 2008)

I would like a lapstrake dinghy, very light, collapsible (see porta-bote) capable of rowing, motor and sailing, and carry 3 people and be around 8 ft in length. And not cost an arm and leg.


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## manatee (Feb 27, 2013)

Isn't there a rule-of-thumb about boatbuilding that says something like:
light-
strong-
cheap-
---you can have any two of these in your boat.


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## peterchech (Sep 2, 2011)

I have built 2 kayaks skin on frame. Strong and very light, but wouldn't last long as a tender IMO. We tend to beat the sh*t out of those things.

A foam strip round bilged dinghy would be much lighter than ply, because the compound curves allow minimal material use. That said, a proper round bilged glued lap dinghy would also be very light. Both methods require much more time than a simple stitch and glue pram. Sailing time. 

I would just carry a kayak if I had the space, but since I don't I think I'm gonna build a very simple and cheap nesting dinghy. Half the weight.


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## copacabana (Oct 1, 2007)

In the end I bought the plans for Danny Greene's "Chameleon" nesting dinghy. I couldn't find any plans for a dinghy as light as I had originally wanted (40lbs) without having to sacrifice durability. The Chameleon nesting dinghy should weigh in at 80lbs and since it can be assembled and dissembled in the water, one can easily manhandle the 40lb halves quite easily.


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## JonEisberg (Dec 3, 2010)

Captainmeme said:


> I would like a lapstrake dinghy, very light, collapsible (see porta-bote) capable of rowing, motor and sailing, and carry 3 people and be around 8 ft in length. And not cost an arm and leg.


Wow, good luck with that one... (grin)

Something like CLC's Eastport Pram in a nesting version is probably as close as you're gonna get... I have difficulty picturing how anyone would configure a "collapsible" lapstrake design...

http://www.clcboats.com/shop/boats/wooden-sailboat-kits/eastport-nesting-dinghy.html


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