Building My First Dinghy

[psk125]

Originally Posted by ggray

There's the original Optimist as designed by Clark Mills to be home built of plywood (loose measurements).

Then there is the International Optimist, raced by kids for many years now, same boat but with much tightened specifications. Low level competition, I can't imagine anyone protesting as you will probably have a heavier boat.


As long as the boat is not left in the water, stored under cover, and dings repaired promptly, you could save the weight by skipping full 'glass coverage. Just seal well with epoxy. Weigh the boat first and see how close you are coming to minimum weight. For smoother edges along the taped joints, cut the selvage off the edges, if you have already bought tape, or cut the strips from cloth. Peel ply or packing tape on the cloth edges can save you some sanding.

A friend of ours made his son a plywood Opti. It outsailed the 'glass ones because it was not only lighter, but stiffer.

[MicHughV]

found some more old pics of my dink build...no fiberglass......my very first boat....a little small to be practical for sure...but hey.....it floated and didn't leak...if memory serves me....it took two sheets of 4x8x1/4" plywood, the stringers, rub strakes, keel, etc, was oak.

I have some pics of the dink under sail, but can't find them in my horde of old photo's

[ggray]

Nice job!

Stick to boatbuilding rather than photography!

[Spot]

I have an 8 foot non-marine plywood boat, glassed seams and bottom, epoxy everywhere else. It is not looking good after 5 or 6 years upside down in the weather when not in use. Had I bothered to paint it and/or tarp it, it would be in much better shape.

[MicHughV]

For me, building that dink was a big achievement. At the time, I barely knew which end of a screwdriver to hold.

Inspired by my success, I went on to tackle a bigger project, which turned out to be my home for many years.

[Jammer]

Originally Posted by Wilyum

I'm attempting to build a small 8' Opti and was wondering how many layers of FG cloth to lay down, the plan so far is a 6" layer of 6oz cloth on all the seams, overlapping in the corners, then 2 layers of 6oz on the exterior and interior faces of the hull. I'm using regular plywood, not marine grade, due to availability where I am so the main priority is to encase and waterproof this wood. Would 2 layers accomplish this?

- Using good quality BS1088 plywood will give you a stronger, lighter boat. Most commodity plywood, particularly fir, is more porous and absorbs more epoxy which increases cost making it a false economy.


- Use standard 8.7 oz seam tape on the seams. Do not try to cut your own tape from cloth because you will waste time and epoxy on the edges. Real fiberglass tape has woven edges not cut.


- I used one layer of 4" tape inside and one layer of 4" tape outside on my dinghy build and am happy with the results.


- Using one layer of 6 oz cloth inside and outside will give you a strong build. A second layer will add weight and cost. Weights are specified as oz per square yard, 6 oz cloth absorbs 6 oz of epoxy, so you're adding 12 oz per square yard of hull area. Do the math and see if the weight gain is worth it to you. I used one layer outside and a partial layer inside


- Use peel ply to reduce the amount of sanding you have to do, the amount of epoxy you use, and the weight of the completed boat.


- Use tape on seams as a separate layer rather than trying to overlap large pieces

[ggray]

Originally Posted by Jammer

- Use standard 8.7 oz seam tape on the seams. Do not try to cut your own tape from cloth because you will waste time and epoxy on the edges. Real fiberglass tape has woven edges not cut.

Since I mentioned cutting your own tape, I'll respond.

I learned of this from Russell Brown, and it worked well for me.

Russell suggested laying an appropriate size piece of cloth, for this maybe 2 ft by 3 ft, or maybe 1 1/2 to 2 ft off the roll, and lay it on a slighty larger piece of 3 or 4 mil clear plastic sheet that you have taped to your work table. Fully wet the cloth with epoxy, and lay a similar piece of clear plastic sheet on top. Using a metal strip as a guide, cut strips with a razor knife. Fastest if you have a metal strip the width you want the fiberglass strips to be. Wet the plywood where the tape will be (you did make neat fillets on the inside, right?), remove the plastic from one side of the strip and lay it in place, press it down and remove the top plastic. Go along the length of the tape with the wet brush kind of jabbing the tape to get any air bubbles out, and evening out the tape. Peel ply could be used at this point.

The edges of tape cut this way will lay a lot flatter than manufactured FG tape with woven edges. And the process goes fast. I'm thinking if you need to tape a curved joint, you could cut your strips on the bias, very hard to do without having the wet glass and plastic "sandwich". I've never done this, but I think it would work.

[singlespeed]

Not enough information provided. What is your primary intended use for the dinghy? Will this dinghy be a tender or a stand alone sailboat. If a standalone sailing dinghy, are you intending to race it, where weight and registry are the prime considerations.
What is the composition of the beaches where it will be landed, ie., sand, gravel or rock. If it will be a tender, how do you plan to store it? Weight can be critical if you will need to use a halyard to get it up and over lifelines using a halyard for deck storage. Will you be taking dogs to and from shore? Their claws can scratch through varnished wood leading to more frequent refinishing than just a single layer of light fiberglass in the interior. You need to evaluate what you will be using the dinghy for and the conditions it will be subjected to and an average basis, then base your decisions on that.

[Wilyum]

Originally Posted by singlespeed

Not enough information provided. What is your primary intended use for the dinghy? Will this dinghy be a tender or a stand alone sailboat. If a standalone sailing dinghy, are you intending to race it, where weight and registry are the prime considerations.
What is the composition of the beaches where it will be landed, ie., sand, gravel or rock. If it will be a tender, how do you plan to store it? Weight can be critical if you will need to use a halyard to get it up and over lifelines using a halyard for deck storage. Will you be taking dogs to and from shore? Their claws can scratch through varnished wood leading to more frequent refinishing than just a single layer of light fiberglass in the interior. You need to evaluate what you will be using the dinghy for and the conditions it will be subjected to and an average basis, then base your decisions on that.

Kids will be using it for lake sailing so its going to get abused, which I think calls for at least one layer of glass, it will be beached between outings but there are a lot of rocks close to shore that can get hit. Since its not marine grade plywood, avoiding water intrusion from deep scratches is my priority.

[Nicholson58]

Try this. Home made by fiberglass over foam. Positive buoyancy, storage, function. 20 horse. He built it on deck in Martinique.

[Bill O]

Nice job. As good as those new carbon fiber ones and much cheaper!!!