Lightweight plywood and epoxy dinghy designs

B

Blue Nun

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www.roryowen.co.uk
I need to get a very lightweight dinghy to get out to the mooring. It must be very light to carry on the roof rack and must be able to carry me and luggage in open roughish water and me + 2 passengers in smoother water. To be rowed and take a 3.5hp outboard. Has anyone built anything suitable or have a link for any designs.

Will 6mm ply be strong enough?

Can I get a wheel or wheels for it?

I have a very limited budget and very limited woodworking skills, so a simple design would be best.

Rory
 
Google "free boat plans" - there are many sites with free plans to download including "1 sheet" dinghy plans (one sheet of 8'X4' ply). There are too many to list so have a go yourself and keep us posted on progress.
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"Artificial intelligence is no match for natural stupidity"
 
Thanks Cliff. I have found plans on the Internet, but I wonder how easy they are to build and whether they will cope with open water. My mooring is so exposed that I often get wet in an inflatable dinghy, and I don't really know what to look for in a dinghy design.

Rory
 
Something with a higher free board than an inflatable, maybe around 10' perhaps.
I built one a few years ago - it is not so difficult with the proper tools and facilities and patience.
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"Artificial intelligence is no match for natural stupidity"
 
Worth looking for plans that give you the panel shapes for stitch & tape construction. This makes building a lot simpler, and can give you a lighter boat.

Stitch & tape? The plans should give you the shapes of the individual panels to construct the boat. Cut them out from plywood, & you will have 4-6 wierd shaped long strips of ply. drill holes every 4" along the edges & tie the strips together with scrap copper wire (or cable ties). If your cutting was accurate, you should have a boat shaped object. Tape along the seams on the inside with fiberglass tape & resin. Turn the object over, cut off the protruding copper wires & tape the seams from the outside - you now have a hull.

Selway Fisher produce suitable plans. I have built from their plans & they seem to work
 
I have built 2 Sabot dinghies over a period of years. The first I used 3/16 inch plywood which while ok was a bit too thin. This is a great shaped dinghy being made primarily for sailing although I didn't fit centreboard or rudder. With one person on it rows like dream and has carried 4 with not much freeboard.
When building from plans you can easily increase free board although this design was made to be cut from 8ft X4ft ply sheets.
This design was built on normal boat building process. ie build bow and stern transoms. Mount on a strong back frame (upside down). make tempory bulkheads 2 or 3. Then attach gunwhales chines and keelson.
The ply wood is glued and nailed (rivetted) to the transoms, gunwhales and chines then trimmed to exact size. The bottom is simillarly attached. Remove from strong back and fit a thwart to sit on and for strength and another at the stern which can be made a air tank. and a covered bow area is good for strength and to defect some water.

My biggest problem was that being short 8ft and beamy the gunwhales and chines had a large bend imposed on them. It was difficult to get the wood to curve and to stay in position. Perhaps steaming would have helped.
I have never tried stitch and glue so that may be easier.
I loved the little Sabot shape and size and have often hankered to build one out of aluminium however I don't think I have the skills or the will but I do find the present F/g dinghy seems to get heavier and heavier as the years go by.
Wheels.... although I havn't done it yet, seem best to be mounted on the transom extending upwards. The dinghy is carried upside down. Stern on the wheels on the ground bow in hand. Although some people have successfully used wheels that stow above the transom and fold down to below the transom to wheel it upright.
I dont have far to drag the dinghy so just drag it on the keel across the sand about 15 netres but the keel is wearing through.
Incidentally one person rows from the middle. 2 persons are best if they both row from the middle 3 people and you have one in stern one in bow and one rowing, or 2 rowing one in stern if you are rowing into a wave. 4 poeople you have 2 in stern one in bow one rowing.

good luck. olewill
 
Meant 10' long not free board - ooops
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"Artificial intelligence is no match for natural stupidity"
 
visit duckworks and you'll find loads of resources. John Welsford's "tender behind" (silly name - great boat) or a Bolger Nymph would be good starting points. Also get a copy of Paysons "Build the new instant boats" isbn 0-07-155966-3 for more ideas. I built my own dinghy to a friends design last year especially for this type of work. Lots of buoyancy built in and massive freeboard. It does look a bit like a bath tub (most often heard comment is "which end do you put the taps"!) but it keeps me safe and dry even in quite a big chop... Took about six weekends to build - most of which was taken up waiting for epoxy to go off - basic shape was established after day one. Used 4,5 and 6 mm ply. Not overly heavy, (kept on davits), but very strong.
 
I have a Fyne boats 8' pram dinghy which I built using stitch and glue and it really was very simple to build. It can be carried at a push by one person although its shape makes it a little awkward. It tows well behind the boat.
If your mooring is exposed I would caution you as to boarding etc. In choppy water it can be an adventure as my wife found out one day. at least her life jacket worked. The boat tends to sit high on the water so has a tendancy to move around and as you climb on or off can slide away from you.
It easily carries two people and overnight baggage etc.
I put a small old volve penta 2 hp motor on and it worked well but again, the o/b tends to make her tender (pardon the pun) when climbing in and out.
If I had the choice and I may still do so, I will go to an inflatable next time
 
I got plans to build a very small plywood tender from PBO published around 1986?We built that it was just big enough for two rowed quite well,looked precarious with two in but worked well,and stowed on my carpenter friends contessa 26 deck was very light he built his with 3mm marine ply i think?

If PBO have fredom of information its a good place to look.
 
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My mooring is so exposed that I often get wet in an inflatable dinghy, and I don't really know what to look for in a dinghy design.

[/ QUOTE ]
Does your inflatable have an inflated kel. It makes a lot of difference to how well it copes with waves.

If you build a boat, make sure it has the buoyancy required should you get swamped.
 
Made one years ago to my own design but inspired by a Jack Holt design.

Much the same requirements as you regarding weight and load carrying capacity. I can load it on the roof rack single handed. A cardboard model and lead shot tested the design for load carrying and a larger hardboard model tested the design fot feasibility of construction.

6mm may make it too heavy, mine is only 4mm, I think, but with hind sight I would make the bottom thicker.

It was designed so that it could all be cut from two sheets of exterior grade ply. Exterior ply is good enough for a dinghy provided you look after it and you don't get cheap stuff in the first place. Mine is still in good order and generally admired at the boat yard after 29 years. It stays there all summer upside down and is covered up at home during the winter. A few offcuts of hardwood from a local boat builders were also needed

I built in some buoyancy.

Stitch and tape is the method I used, having previously made a Mirror and a canoe that way. With the light panels all you need is copper wire stitches at strategic points then the rest can be laced using monofilament fishing line. I got that idea from the canoe.

The Mirror is suggested else where but the amount of buoyancy limits the space for gear. The hull weight of 100lbs minimum makes it too heavy to load onto a roof rack singled handed without fancy loading gear (although I did it once and once only) and not many wives are strong enough all tall enough to help either. It's a great Sailing dinghy though.

Check out the current PBO design. It could be just what you want.

Wheels are useful. Mine has a flat bottom with two small skegs that carry an axle for two small wheels that had fallen off supermarket trolleys.
 
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