How to build a Daggerboard for a sailing Dinghy

[TheCrazyWolf]

Hi im Travis, Im sort of new to this I built my 7 1/2Foot dinghy last year and its set up with my Oarlocks seats and everything But Im going to put a sail on it and Ive heard I need a Daggerboard can anyone tell me A Site or give me some advice how Deep I would need and what the Width should be on the Daggerboard any help would be great and what I should build it out of would be great to Thanks!

 

[Peterduck]

Welcome to the board, Travis. Your greatest concern is not how big the board should be, but exactly where along the centreline you will put it. The position of these things is very carefully worked out by the designer of a sailing dinghy, and the relationship between the position of the centreboard and the position of the mast and sail are quite important; nay, they are crucial. If you get these wrong you will be most dissatisfied with the performance under sail of your wee boat. You'll end up rowing it in preference to sailing it. If you want a sailing dinghy, sell this one and buy one already set up. If you think that your skills are up to it, buy a kit from one of CB's advertisers. There are some very nice sailing dinghies available. Alternatively, sailing clubs often have dinghies for sale which are considered to be no longer competitive, but which would be fine for your purposes. Hasten very, very slowly!
Peter.

 

[cliffordpope]

Is this a self-buil kit you have made from plans, or something you have designed yourself? If the former, was it on offer in alternative sailing form, in which case you could copy the design?

If entirely your own design (as my 7 foot pram tender is) then the best you can do is just look carefully at similar dinghies and trust to luck and instinct.
Remember that fitting a trunk and cutting a slot will considerably weaken the keel structure - did you allow for that in the design, eg by making it wide enough?

Alternatively you could consider lee boards - simpler and easily adjusted to new positions, or even fitting a a deeper fixed long keel. Swallow and Amazon both sailed well, and each had advantages in different conditions.

I grew up with a home-made dinghy with a dagger board, and one major disadvantage pottering about in shallow water, as children do, is that you come to an abrupt stop when you run aground. A pivotting blade is better, but needs a bigger trunk of a different design, with its own weaknesses.
The Amazons stole the race by leaning over to one side and gaining a few inches of draught - Swallow slipped sideways when they pulled the board up.

It's all good fun though, whatever you do.

 

[Porthandbuoy]

If you're really keen to keep your old dinghy and sail instead of row, why not experiment with a leeboard? A spot of googling should give you heaps of info on the subject.

A simple leeboard could clip over the gunwale and water pressure would hold it against the hull while you sail. Tack, and simply swap the board over to the other side (secure it with a line though).

Yow would be able to move it fore and aft and learn a lot about centre of efforts without compromising the structure of your dinghy.

 

[donncha]

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The Amazons stole the race by leaning over to one side and gaining a few inches of draught - Swallow slipped sideways when they pulled the board up.

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Hate to be pedantic but Amazon had the dagger board and swallow had the ballast. Otherwise you are correct, just change the names of the boats around.

 

[Kukri]

[ QUOTE ]
Hi im Travis, Im sort of new to this I built my 7 1/2Foot dinghy last year and its set up with my Oarlocks seats and everything But Im going to put a sail on it and Ive heard I need a Daggerboard can anyone tell me A Site or give me some advice how Deep I would need and what the Width should be on the Daggerboard any help would be great and what I should build it out of would be great to Thanks!

[/ QUOTE ]

Some of the replies, whilst correct, are a bit "scientific" for a small dinghy!

I've fitted daggerboards to a couple of small prams and this is what I reckon:

Just locate the daggerboard box immediately ahead of the centre thwart - indeed, use two fore and aft members from below the thwart to locate it rigidly. Finish the top level with the thwart.

The daggerboard case can be a simple plywood box with a couple of fore and aft members to secure it to the hog or the plank keel (depending on the design of your dinghy).

If your dinghy has a narrow keel and you don't want to cut it, fit the daggerboard box off centre so it works through a garboard plank - this works perfectly well - maybe better, as you don't get stones in it!

For a dinghy of your size I'd make the dagger board two feet or so long, with the lower end in a semicircle so it does not matter which way you put it in. It should be eight to ten inches wide. Five eighths ply will do - threee quarters is better - exterior grade is fine for this job. Remember to West the edges - ideally epoxy and glass the whole board for a Rolls-Royce job.

Leave a good eighth of an inch clear on each side and a good quarter of an inch or more at each end - it needs to be a slack fit, because stones mud and weed will jam it, otherwise.

Fit a length of shock cord to hold it down and stop it floating up.

Remember to cut a handle in the top and add a lip to stop it falling through. You will want to fit a cap to the slot in the top of the case for towing the boat or water will spurt up through it. Use the same length of shock cord to hold this down.

You will benefit from making a drop blade on the rudder. Use a wing nut and bolt with a couple of good size penny washers on it and just push it down vertical with your hand - no need for elaborate "racing dinghy type" lifting blade arrangements.

She'll sail...

 

[cliffordpope]

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Hate to be pedantic but Amazon had the dagger board and swallow had the ballast. Otherwise you are correct, just change the names of the boats around.

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Thanks ! I had an uneasy feeling I had got it wrong.

 

[Lakesailor]

I made a leeboard for my trimaran. I has a clip that slips over the gunwhale and I clamp it with a G clamp.
You can just see it in this shot. I don't need to swap it over as the boat hardly heels.

 

[Bill1]

Why not just have a look at a mirror dinghy, it has about the simplist arrangement I know of, then simply scale to your own design. In fact it's very much as Minn suggested.

 

[TheCrazyWolf]

Hey thanks everyone for your help and advice,Well Its a small Boat but Ive seen small boats with Sails so I thought I would give mine a Try! this is these are the plans I used from http://koti.kapsi.fi/hvartial/dinghy1/simboii.htm Thanks again!

 

[Lakesailor]

ooer.

My thoughts are that the boat will be very unstable and needs beefing up to take a rig and transmit forces into the hull.
The floor will be too flimsy for the daggerboard forces and you will end up with any amount of extra seats and frames to absorb the twisting and flexing.
I found that even taking these things into account my 10 foot trimaran tore it's mast step out and so I have made a much more substantial frame to support it.

But give it a whirl if you want. Don't put a big sail on it though, or a tall mast.

Have a look at this http://www.dinghy.pl/26m_pram.htm

 

[Laundryman]

Okay, I know asolutely nothing about Dinghy sailing but i do have a centre board, seat and transome mount rudder with tiller which you are welcome to if they are of use. They look as if they have come off something similar to your boat.
Problem is I dont know where you are. If you would like to pm your email address or mobile no i will take photos and send them. You can then decide whether they are of use.
I live in Hertfordshire and my boat is cuurently in Portsmouth

 

[dur]

I agree with all of what Minn says (from my limited experience).

On our "Tippy" dinghy, the plate would be through the rowing thwart if there were one. Certainly we get the bidet effect rowing in a chop. She sails like a dream but then she is quite a different shape being narrow (and tippy!).
A bit of a skeg might make a difference and a lot of fine trimming can be sorted by adjusting the rig if you go the lugsail route. Good luck and have fun! Tippy