Wansworth
Well-known member
Built a very light dinghy using two sheets of 8by4 4mm ply……no grp just good joints and well painted…….just one central mound and bow and stern using 9 mmply….pine gunwhales and other parts
Self building a sailable tender
- Thread starter Captain Sillyboxes
- Start date
johnphilip
Well-known member
Yachting World Utility Pram, sailing version had rudder, daggerboard and standing lugsail, I learnt to sail on her but cannot find any rigged pictures, very stable. Built from a Bell Woodworking kit. Oh I love nostalgia.
Picture circa1960. Some may recognise the green yacht in the background, literary connection as a clue. She is still on the same river.
Picture circa1960. Some may recognise the green yacht in the background, literary connection as a clue. She is still on the same river.
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Wansworth
Well-known member
Peter Duck
Captain Sillyboxes
Member
Thanks for all the suggestions. I've built an epoxy and ply canoe already so I have an inkling of the timescales and costs involved...
I want to avoid a centerboard due to the space it takes up in the middle of the boat. Yes, a leeboard would be an option but seems to add complexity, either it will slide down a housing like a daggerboard in which case you need 2 housings, and are constrained to not having curvature in that part of the hull. Or else its on some sort of pivot in which case the mechanism will need to be very sturdy as all the load transfers through a single point.
Seems to me that if you had a pair of bilge runners running the length of the boat they may only need to be ~5cm tall to offer a similar sized lateral flat area to what you'd get from a centerboard?
I want to avoid a centerboard due to the space it takes up in the middle of the boat. Yes, a leeboard would be an option but seems to add complexity, either it will slide down a housing like a daggerboard in which case you need 2 housings, and are constrained to not having curvature in that part of the hull. Or else its on some sort of pivot in which case the mechanism will need to be very sturdy as all the load transfers through a single point.
Seems to me that if you had a pair of bilge runners running the length of the boat they may only need to be ~5cm tall to offer a similar sized lateral flat area to what you'd get from a centerboard?
Wansworth
Well-known member
Chine runners acting as handholds on a inverted dinghy
Captain Sillyboxes
Member
Yep exactly. I don't mind if it doesn't even point that high, it would just be nice to have the option to whip out the sail when I'm against the current but have a favourable breeze, to conserve the battery on the outboard
B27
Well-known member
If you're sailing, there's only one thing worse than a slow boat, and that's a slow boat which makes a lot of leeway.
There have been a few dinghies where the centreboard case makes a good central seat.
Tranona
Well-known member
It really is not a severe restriction. You build it into the centre thwart and it helps stiffen the boat. It is not the area that determines its efficiency but its aspect ratio and position. Long shallow bilge keels are lousy at resisting leeway. The boats I built had simple ply dagger boards and fixed blade rudders and sailed tolerably well with a simple lug rig based on an Optimist sail. In fact I still have a complete rig including mast and sprit plus all hardware hanging up in my garage if you are interested.
As B27 says if you are going to the bother and cost of adding a sail it is worth doing it properly and getting the enjoyment out of sailing. If it is just a utilitarian means of transport stick with the outboard or oars.
MisterBaxter
Well-known member
Leeboards are fine if well designed as as mentioned they need to be designed in from the start, not added to a boat designed for some other arrangement.
The big advantage of either a centreboard or a leeboard is that you don't have to live with the drag when you're rowing. Twin bilge runners five inches deep would add a significant amount of drag and slow you right down when rowing.
The big advantage of either a centreboard or a leeboard is that you don't have to live with the drag when you're rowing. Twin bilge runners five inches deep would add a significant amount of drag and slow you right down when rowing.
Sea Change
Well-known member
I thought long and hard about whether to use cheaper ply, but decided that in the end it would likely be a waste of good epoxy as well as my time and energy. The ply is a significant portion of the build cost, but the epoxy is also expensive, and you'd probably end up using more if you were trying to protect cheap ply.
I also considered a composite build using nidacore. It's tantalisingly light weight, but has very different bending properties to ply. I found a blog by somebody who had attempted to build a Spindrift using it; he found it a bit of a nightmare, because the design relies on bending the sheet in to the correct shape. His dinghy ended up just as heavy as a ply one, and far more expensive.
I also considered a composite build using nidacore. It's tantalisingly light weight, but has very different bending properties to ply. I found a blog by somebody who had attempted to build a Spindrift using it; he found it a bit of a nightmare, because the design relies on bending the sheet in to the correct shape. His dinghy ended up just as heavy as a ply one, and far more expensive.
garymalmgren
Active member
My inflatable tender is approaching end-of-life.
I could just buy another. But I have a dream of building a rigid tender from plywood and epoxy with glassed seams.
Alternatively, please tell me all the reasons why this idea is ridiculous
Not ridiculous, but......
The alternative to buying another inflatable or building a tender is to buy a dinghy and modify it to suit your needs.
That way you will have a tender straight off, get sawdust on your hands fixing/ modifying it AND save a heap of time and money.
An old dinghy will have the rig, sails, centerboard and rudder ready to go.
Gary
I could just buy another. But I have a dream of building a rigid tender from plywood and epoxy with glassed seams.
Alternatively, please tell me all the reasons why this idea is ridiculous
Not ridiculous, but......
The alternative to buying another inflatable or building a tender is to buy a dinghy and modify it to suit your needs.
That way you will have a tender straight off, get sawdust on your hands fixing/ modifying it AND save a heap of time and money.
An old dinghy will have the rig, sails, centerboard and rudder ready to go.
Gary
The Q
Well-known member
Selway fisher have a huge amount of boat designs , there are quite a few dinghies that would be suitable.
GP Dinghies up to 13'
Though if it were me I'd design my own,
That's my own design little boat out playing with the big boys on Sunday ( has no sail number).
GP Dinghies up to 13'
Though if it were me I'd design my own,
That's my own design little boat out playing with the big boys on Sunday ( has no sail number).
howardclark
Active member
I have just finished my second tender - picture below. I had the same concerns as you - weight as I get older , good to row ( considered a sail but decided no) or motor, strong and long lasting.
I decided against ply because ply is quite heavy. Instead I went for 6mm cedar strip- bought the plans for about £50 , the strip is bent around frames then the frames removed, and then the hull is glassed, leaving an extremely strong monocoque.
The dinghy lasted 18 years until a 50’ boat lost control and crushed it.
The design allows for a centre board and sail plan and the length is adjustable just by altering the frame spacing - 8ft to 12 ft is feasible.
Red cedar doesn’t rot easily ( hence used for garden sheds! ) and so you don’t have the same worry as you might with keeping water out of ply.
It’s not the cheapest construction and I don’t claim any great skill at building. If you want more details just pm me
Ist dinghy after 15 years use and new one.
I decided against ply because ply is quite heavy. Instead I went for 6mm cedar strip- bought the plans for about £50 , the strip is bent around frames then the frames removed, and then the hull is glassed, leaving an extremely strong monocoque.
The dinghy lasted 18 years until a 50’ boat lost control and crushed it.
The design allows for a centre board and sail plan and the length is adjustable just by altering the frame spacing - 8ft to 12 ft is feasible.
Red cedar doesn’t rot easily ( hence used for garden sheds! ) and so you don’t have the same worry as you might with keeping water out of ply.
It’s not the cheapest construction and I don’t claim any great skill at building. If you want more details just pm me
Ist dinghy after 15 years use and new one.
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Minerva
Well-known member
That looks lovely! Just the ticket for pottering around an anchorage
wombat88
Well-known member
I don't know where the OP is but there a plenty of rough tenders for sale in the Chichester Harbour boat auction, link is somewhere else on this site. Some have what look like dagger board slots. You can solve the problem of what to do with 'end of life' grp boats and have a bit of fun at the same time.
Boat Auction 2024 - Chichester Harbour Conservancy
Boat Auction 2024 - Chichester Harbour Conservancy
Sea Change
Well-known member
There are so many different tried and tested designs out there, I'd not have the confidence to invest hundreds of hours building my own design and wondering if it would turn out to be a lemon. But hats off to those who managed to do it.
MisterBaxter
Well-known member
If you pick the right design it's a lot quicker than that... I built a Phil Bolger June Bug, which is 14' long and built to sail or row with a maximum load of 450kg, and it took me 25 hours, not including painting. The cost was three sheets of ply, some softwood and the paint; I used Semparoc (formerly Balcotan), a foaming polyurethane glue which is very forgiving and much cheaper and easier to work with than epoxy. I did use a bit of epoxy to seal the join and the plywood end-grain along the chine though.
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Sea Change
Well-known member
How long do you expect the boat to last?
Any tape on the joins?
MisterBaxter
Well-known member
It's about six years old now, stored outside that whole time with no cover on. I think I might put a coat of paint on it this summer but otherwise it's doing fine. No tape on the joins. It's flat bottomed with vertical sides so the only real seam is at the chine, which has a softwood strip on the inside which the sides and bottom are glued and screwed onto. I then painted the external edges of the ply with epoxy and smeared thickened epoxy along the seam.
I did use good paint though - Hempels multicoat from memory.
This is the boat:
