Thread: Drop-in Sail for Quick Canoe

sorry for the confusion... The PDR is not in the pictures from the web site I sent you. I just thought you might remember it from seeing it sitting in front of the tent where they were making a Puddle Duck.

Pictures of all our PDRacers appear in an article Michael Storer did titled, "The Rally didn't make it to Dakar, but the PDRacers did." It is on his website somewhere.

All the best

I was not at the event so I never saw anything in front of the tent, unfortunately. Congrats on your daughter!

I'll go check it out right now.

Jonathan,

Nice to meet you. Congratulations on the first place ribbon for the PDR.

So many boats, so little time.

Paul

Pauls post #37 has this:

Dimensions for my new larger lugs'l for canoe William Henry Harrison. Sorry about mixing metric and ancient measuring systems, but I am comfortable with either and don't generally convert.


Mast: 10' – 2”, 39mm tapers to 29mm. Bottom section reinforced w/ glass
Yard: 7' - 3 1/2”, 30mm tapers to 27mm - hollow (maybe a bit too stiff ???)
Old yard: 7' – 4 1/2”, 25mm no taper - (too bendy)
Boom: 7' – 10”, 33mm tapers to 27mm - hollow


Luff: 56”
Head: 78”
Foot: 82”
Leech: 91”
Throat to Clew: 87”
Heron's Method gives area of sail (without figuring for rounding): 37 square feet (about 3.5 square meters)

Halyard: 26', (not longer) Dyneema / Spectra 4mm

Downhaul: 5' (5' to 6'), Dyneema / Spectra 4mm

I'm ready to make my sail.... and I'm sure that there is more to it than sewing up fabric to the dimensions above. ???
What should I be doing?

Hi Clinton,

Sorry it took me a while to get back... I couldn't remember my password.

Yes there is a bit more to making the sails than just the straight-line dimensions.. You can force belly into the sail by convexly rounding the head and food. Some concavity on the leach helps control flutter. I already had MIK's sail plans from his Puddleduck as well as from his drop in canoe rig, and had some correspondence with him as to properly scaling of the small sail from the larger one.

Resource which should be helpful:

Design of a 76sqft Lugsail
sewing a 76sqft lug sail
Constructing a Polytarp Balanced Lug Sail
As well as a discussion by Jim Michalak's which I cannot find right now.

When it comes to rigging, MIK's discussion is as elegant and straightforward as you are likely to find anywhere.

Hope this helps.

Paul

oh, should put this question in context.

I've seen this site and have MIK's plan for the drop in sail as well as his QC and GIS plans... I think I've read everything on MIK's site in regards to sails.

I've thought this out to death, and eventually plan on some major mods for a permanent mast step (and maybe a centre board) and rudder ... but for now I'll do the drop in rig and fiddle about working out where the mast should be and whatnot.

So, its make a very good sail, a servicable mast and the drop in mast/leeboard rig.... then the rudder.... then test, rethink and adjust before anything else.

After too much running around in shopping crowds I finally got some good ploy-something cloth and the local sailmaker sold me a 'short' roll of ANEFIL Poly sail thread for $5. Guess I'm all set.

Solway Dory are the leading Uk canoe sailing people. They have developed a really nice 28 sq ft "expedition" rig using a drop over lee board and your paddle to steer with. Here's the rig in action

[ame=http://www.youtube.com/watch?v=1YWbFUwVJ-0]YouTube - Solway Dory expedition sailing rig[/ame]

I have drawn up a similar size sail,3 sqm, in Sailcut4. One drawing shows the profile

https://docs.google.com/leaf?id=0B4B...M2UzM2Jl&hl=en

and this shows the separate panel shapes as xy plots.

https://docs.google.com/leaf?id=0B4B...NjFjOTc2&hl=en

Paul,

Thanks for those links. I guess I'll get started tomorrow and see how it goes.
I will ask you a few questions when the drop in rig is done, so we can set them up the same.

A few questions to start:

Do you think it is worthwhile to jig the lee board design so you can adjust its position?

The drop-in rig pivots the leeboard at the mast partner so adding a mizzen throws the CE way aft unless I rake both masts forward and shift the sails forward on the masts, which is what I have been working on today (or by separating leeboard support from the partner and stepping the main mast forward which I don't want to do just now).

e.g. what did you learn from the above quote?

Did you end up doing a rudder, or are you perservering with steering via paddle?

With a single person in the QC steering is not too bad, but I've sound with a front passenger, who isn't paddling or isn't paddling well, the extra weight makes a real difference to the 'turning circle'.
I'm thinking that a simple rudder attachment may be worth it especially when considering the fact that one hand will be managing the sail.
My decks are now fitted under the inwale, with a solid timber piece at the ends and glue blocks in there as well. (it was either strengthen it and warn people not to use it as a step, or contine to warn people not to step on it and drive nails through it to spike their feet. ITS NOT STEP PEOPLE!!)

The deck is strong enough now to be able to hold a small 'bracket' that can slip around the end of the deck, run back down the top of the deck and be lashed securely using the gun/in wale timber where it extends out the back. Add a saddle or 'gate hinge' to this for the rudder post. (better explained with a pic!) Seems to be a likely way to add a removable rudder for minimal cost/weight.

anyway, thanks for your help so far, its appreciated.

Thanks Mr keyhaven... looks like aluminium tube in the video?

I'm planning to add MIK's drop-in rig to my QC - plans in hand and eye on Austim timber merchants (nice oregon will hide nicely amongst jarrah purchased for the laundry bench )

Is the profile for the lee-board about the same as that for the OZ-Racer foils (subject to scaling to width)?

Generally, does the size of the underwater foil (centre/dagger/lee-board) scale with the sail area (for balance, in an ideal world)?

Thanks,
MichaelB,
Perth.

Hi Michael B,

Some would say there is a formula, but that is one of the problems with the internet. Too many things get treated as real information because of their "form" rather than whether they are true or not.

There is a formula that is often quoted - that centreboard or leeboard area is a certain percentage of sail area. It is crap! It doesn't take into account the speed of the boat which is much more important. The lift is proportional to the square of the velocity. So faster boats need less proportion foil area. Or smaller boats need MORE - which is much more to the point.

For light dinghies from 16ft or down I wouldn't imagine putting a centreboard in much smaller than the PDR/OZ Racer one. This is a bit under 3ft deptth under the hull (900mm) by about 10 inches wide (200mm).

There are a number of boats where owners have been disappointed with the sailing performance, or wondered why they couldn't get upwind against a strong wind and chop. Fitting a longer board has universally meant the boat is transformed into a real sailor.

Boats that have a main use as paddling or rowing boats, with sailing as an auxuliary means of propulsion often tend to have compromised foil sizes for ease of stowage or whatever. Some examples are Joel White's Nutshell dinghy - which has about a foot an a half of a narrow board poking out through the hull. A friend Mark has a Wee Rob canoe - which has tiny leeboards - I suggested as an experiment that he move the pivots to get a few extra inches in the water and it made a huge difference to the sailing - same too with the Granny Pram.

They just transform with more foil area/depth.

It is fine for great designers like these to make a knowledgeable compromise, but a lot of not so knowledgeable ones copy them!

Not to mention the plague that was beset the world with the usually bizarre and poorly executed boat in magazines like Popular Mechanics during the 50s and 60s that skewed peoples minds so that too small foils looked normal.

As far as ideal worlds go, in this best of all possible worlds, I like what Roger Penrose had to say.

They were talking about how all logical computers are necessarily similar and that you can make bigger ones up of huge numbers of very simple computers. The question was asked, how big would a computer have to be to simulate the universe.

Some of the brilliant men started scratching out ... there are this many particles in the universe, you would need this many to describe their motion, you can simplify because of these effects etc etc.

Someone sitting up the back piped up and said ... about 200mm by 150mm by 75mm.

Silence ...

The brain - what we see as the world is a simulation built up from sensory data.

Way cool! But we have to be careful about what we put in it as "hard and fast".

I have no idea why I saw that as relevant!

MIK

Thanks MIK, that makes sense. So the second take-home messages I've collected from you about foils is to make sure they're long enough, perhaps so as to get down below surface chop and confusion. The first one was that the profile is important, so use your template accurately.

I'm wondering about the dinky little rudders on some modern kayaks. They look to me as if they'd be barely in the water and I wonder how effective they really are.

[I once had a background in boundary-layer meteorology and air pollution modelling. The computer modelling is the easy bit: it's the real-world validation that's the mother of puppies. So I reckon the videos of trials by Paul and others can be worth any number of fancy formulae.]

Michael
Love to see your canoe on the river sometime.
Little kayak rudders can be very effective, I fitted a rudder with about 150 cm2 immersed area to an Avon River racing K2 (6.5m, 230kg all up). It worked very very well on the river. On the Estuary tho it did not have enough authority to counter weathercocking and it certainly would be overwhelmed by sail generated forces.
Wayne
Fremantle

Howdy,

I posted a reply to this several days ago, but like some others it looks like it has fallen foul of the bad internet connection at the time.

The rudder on a paddling canoe or kayak is not really for manoeuvring - try to turn a canoe or kayak in a right angled turn like you can with a good sailing dinghy. They are basically for taking out any imbalance between paddling on the left and right. They really in a sense "trim tabs" in the aeronautical, outboard motor and keel sense where the aircraft or vessel is tending to go one way or another leading to continuous control having to be exerted.

A trim tab is a small control surface that removes that effort by being set to counter the direction the boat or aircraft is wandering.

The main method of steering a canoe or kayak is paddling - you can get a right angled turn using the paddle! But the rudder (really a trim tab) can't.

MIK

Hi Wayne; might take me a minute or two to paddle from Guildford to Freo though!

Thanks MIK, that's exactly what I thought. I asked a couple of canoeists within reach about it and got confused looks and assurances that they certainly made a difference. (So I smugly retreated to my computer, Batchelor, Curry and Gentry. )