Balanced lugs and Duck Punts

dylanwinter · 7 Dec 2011

While waiting for some timber to arrive for my Duck Punt build I started messing about with some spars and whisker poles in the garage

I put together a lug sail using an old genoa and was amazed at the power and flexibility of the thing

there are some snaps on this page

http://www.keepturningleft.co.uk/scuttlebutt/ktl-vlog-duck-punt-build-2/

the Duck Punts usually use rigs from Optimist dinghies - 35 square feet

my little sail is closer to 20

is there anyone out there who might be able to tell me roughly how long to make the leach, luff and spars to get my 35 square feet and would I need to shift the mast position to keep the centre of drive in the same place - or does that not matter

I think I need to increase the angle of the top boom - but I do not want the rig to be too tall - I don't want to capsize

the sail will be made out of old ones I have here in the garage

Needless to say the Optimist sail that Dan Tribe has offered to loan me will be more efficient - or will it?

the idea of building the boat is to explore the creeks of North Norfolk and to sneak up on some birds and seals

Dylan

Lakesailor · 7 Dec 2011

Sorry, we couldn't find that page

Why don't you head back to the home page?

?

Twister_Ken · 7 Dec 2011

dylanwinter said:
the idea ... ... to sneak up on some birds

Dylan

Reminds me a bit of Harold Steptoe.

dylanwinter · 7 Dec 2011

works for me

http://www.keepturningleft.co.uk/scuttlebutt/ktl-vlog-duck-punt-build-2/

I have been re-watching some of the balanced lugs I filmed on the Norfolk Broads

http://www.keepturningleft.co.uk/category/boat-archive-02-great-boats-encountered-along-the-way/

they look very useful and easy to build and tweak

Searush · 7 Dec 2011

Sprit rigs are virtually square (or oblong) so 5'x7' or 6'x6' are the sort of size you want.

Sprit size is approx sq root of 74 or 72 (depending on shape chosen) plus a foot or two to overlap & attach to the mast = 8'6 plus a bit, say 3m or 10' should do it.

For balance you can lean the rig forward or aft (like a wind surfer does) and also the paddle you use as a keel & rudder can be moved forward or aft. You can draw it all out & calculate the centres of effort & lateral resistance or throw it together & play. I suspect you will go with the latter.

dylanwinter · 7 Dec 2011

frightening

Twister_Ken said:
Reminds me a bit of Harold Steptoe.

damned frightening when you realise you are probably closer in age to his dad

now then.....

balanced lugs...

http://www.keepturningleft.co.uk/bo...-along-the-way/ktl-169-single-lugsail-dinghy/

dylanwinter · 7 Dec 2011

where does the 74 or 72 come from

Searush said:
Sprit rigs are virtually square (or oblong) so 5'x7' or 6'x6' are the sort of size you want.

Sprit size is approx sq root of 74 or 72 (depending on shape chosen) plus a foot or two to overlap & attach to the mast = 8'6 plus a bit, say 3m or 10' should do it.

For balance you can lean the rig forward or aft (like a wind surfer does) and also the paddle you use as a keel & rudder can be moved forward or aft. You can draw it all out & calculate the centres of effort & lateral resistance or throw it together & play. I suspect you will go with the latter.

I don't understand

but I am a stupid person

can you say the same thing in simpler language

mast height

- top boom length

bottom boom length

leach and luff dimentions

and yes I do intend to experiment - at least until the oppy rig arrives

Dylan

Searush · 7 Dec 2011

Crikey, not sure it can get much simpler, but I shall try.

The sail is roughly oblong or square (your choice) but lets say 7' high (luff) and 5' wide (foot), so your mast must be a little over 7' to reach down into the boat below the boom, 10' may do it, but 11' will give you a slightly higher boom (easier for us oldies to duck under).

The boom needs to be a little over 5', so 6'6 will probably do.

The sprit runs diagonally across the sail, so you need Pythagoras to work out the length. (7x7) + (5x5) = 49+25 = 74, the length of the diagonal is thus the square root of 74. Now, 8x8=64 & 9x9=81, so our answer will fall between the two, probably a little under 8'6", but we have to have an overlap at the bottom to attach it to the mast, so call it 10'.

You do not need a "top boom" the sprit should hold it taut. You should also be able to eliminate the boom too (like a Thames Barge or similar to a Drascombe)) which will make it safer/easier to sail, provided your sheet lead is a reasonable distance aft.

Is that better?

Poignard · 7 Dec 2011

Some information here that might enable you to get the right proportions

http://www.allthingsransome.net/literary/knight5.htm

DownWest · 7 Dec 2011

Dylan, put this up on WBF and Todd Bradshaw will give you all the info. He is a specialist in such sails.
SR has explained it well, but in more general terms.
DW

dylanwinter · 7 Dec 2011

sprit always at 45 degrees

Searush said:
Crikey, not sure it can get much simpler, but I shall try.

The sail is roughly oblong or square (your choice) but lets say 7' high (luff) and 5' wide (foot), so your mast must be a little over 7' to reach down into the boat below the boom, 10' may do it, but 11' will give you a slightly higher boom (easier for us oldies to duck under).

The boom needs to be a little over 5', so 6'6 will probably do.

The sprit runs diagonally across the sail, so you need Pythagoras to work out the length. (7x7) + (5x5) = 49+25 = 74, the length of the diagonal is thus the square root of 74. Now, 8x8=64 & 9x9=81, so our answer will fall between the two, probably a little under 8'6", but we have to have an overlap at the bottom to attach it to the mast, so call it 10'.

You do not need a "top boom" the sprit should hold it taut. You should also be able to eliminate the boom too (like a Thames Barge or similar to a Drascombe)) which will make it safer/easier to sail, provided your sheet lead is a reasonable distance aft.

Is that better?

so the sprit is always at 45 degrees - I did not know that

and

can you have a balanced lug without a boom?

how can that be achieved?

I had assumed that you needed some sail ahead of the mast to balance it up

am I wrong again?

Dylan

Even Chance · 8 Dec 2011

Good on ya Dylan for building a wee punt.
Im also waiting on some marine ply arriving so I can build my son a boat for his Xmas. I have chosen to build a simple flat bottomed 10ft long skiff with a 10mm thick bottom, and 6mm thick side panels. It should be light enough to car-top (I hope!!). 3 sheets of 6mm and 2 sheets of 10mm should be arriving in the very North of Scotland tomorrow. That leaves me two full weeks of building time to get a basic hull finished. I can then give it a simple rig after that. I havent settled on a rig as yet. I already have a small winter boat for using that I restored last year. I made its balanced lug rig and sails myself. It has now grown a bowsprit and bumpkin as well as a mizzen mast.

As for your rig, I'd suggest a balanced lug for simplicity and short spars to keep in the hull for easy storage.

What length is the duck punt? 20sqft seems a wee bit on the small side. Im planning around 50sqft for my lads boat. A flat bottom gives you huge stability remember!

Good luck, all e best,

Barry

electrosys · 8 Dec 2011

Even Chance · 8 Dec 2011

What youve described is a standing lug rig. Very simple, but in my opinion, not as good looking as a dipping lug or the boomed balanced lug rig.
The balanced lug is what I percieve to be the best combination of the three types.

Heckler · 8 Dec 2011

Searush said:
Crikey, not sure it can get much simpler, but I shall try.

The sail is roughly oblong or square (your choice) but lets say 7' high (luff) and 5' wide (foot), so your mast must be a little over 7' to reach down into the boat below the boom, 10' may do it, but 11' will give you a slightly higher boom (easier for us oldies to duck under).

The boom needs to be a little over 5', so 6'6 will probably do.

The sprit runs diagonally across the sail, so you need Pythagoras to work out the length. (7x7) + (5x5) = 49+25 = 74, the length of the diagonal is thus the square root of 74. Now, 8x8=64 & 9x9=81, so our answer will fall between the two, probably a little under 8'6", but we have to have an overlap at the bottom to attach it to the mast, so call it 10'.

You do not need a "top boom" the sprit should hold it taut. You should also be able to eliminate the boom too (like a Thames Barge or similar to a Drascombe)) which will make it safer/easier to sail, provided your sheet lead is a reasonable distance aft.

Is that better?

Steve
I am impressed, was going to do the same calcs but you beat me to it. Fred drift, girls doing GCSEs, leading up to it I actually remembered how to calc triangles etc! They were impressed, however as the years went on, Miss double maths used to laugh at me! Never been much good at abstract stuff!
Stu

Georgio · 8 Dec 2011

Balenced Lug rules...

Well done Dylan,
Balanced lug is the way forward, simple and powerful with a low CoE just make sure you have a good downhaul and/or kicker to control the twist. Also a slightly bendy Gaff will help the rig automatically depower in gusts.

I’m currently building a 15ft Goat Island Skiff with a 105sq ft balanced lugsail and can’t wait to get it on the water, should be sometime in the spring with some luck.

Here is a good resource for setting up lugsails…

http://www.storerboatplans.com/GIS/GISRigging.html

and some general info here..

http://www.storerboatplans.com/Faq/tradrigperformance.html

Hope this helps

Searush · 8 Dec 2011

For simplicity, Sprits beat Lugs especially if you eliminate the boom, but you could do that for either. Simply lash the sail to the mast & have a small head pocket for the sprit & lash the bottom of the sprit to the mast - with partners perhaps?

Applescruffs · 10 Dec 2011

Bzzzzzzzzzz

Ever thought of a schmall electric motor to power ye wee jobbie?? paddle power also acceptable. Just a thought !!

maxi77 · 11 Dec 2011

Just an observation, I sailed balanced lugsails way back in the 60s at the Moray Sea School, based on the rigs used in old Scottish fishing boats. The tack was secured right forward at the bow and to tack you had to lower the sail, shift the whole lot aft so as to get it back on the other side of the mast and hoist again, not to bad with half a dozen young fit lads.

I also sailed with dipping lugs on RN 32 ft cutters, and montagu whalers. There the tack was secured on the mast about where the boom was. This made the sail rig almost like a gunter rig with the gaff almost vertical unlike the almost horizontal of the balanced lug. Tacking simply involved 'dipping' the gaff round the mast, hence the name.

In all cases the sails were loose footed.

A quick google for Zulu fishing boat and Montagu whaler will show you pictures

Poignard · 11 Dec 2011

Applescruffs said:
Ever thought of a schmall electric motor to power ye wee jobbie?? paddle power also acceptable. Just a thought !!

Something like this?

http://vimeo.com/7088641

Balanced lugs and Duck Punts

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