good light rowing dinghy plans?

[sailortjk1]

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.

[sailingdog]

Originally Posted by Mirari

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.

[Mirari]

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.

[bljones]

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?

[bljones]

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

[Mirari]

Originally Posted by bljones

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!

[copacabana]

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....

[QuickMick]

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

[copacabana]

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!

[white74]

Have you considered skin on frame?