The International Canoe

Hello,
I am in progress of building a new IC. I have designed a hull based on existing lines of String Theory. Can anybody tell me the effect of changing the heights of the chines? Are they typically in a plane parallel to the WL?

And how much slope do you all have in your dancefloors to get the water drained out? Especially when you have a very deep dished deck.

Cheers, Arne

I haven't (slapped wrist) studied the new rules shapes as much as I should have, but the general impression I've formed over the years in other classes where I've looked a bit more is that boats with lower chines are more heel sensitive, but faster if you do sail them right, especially in the transitional area when you are approaching what lead mine sailors would call hull speed. On the other hand they are also stickier in the light, especially if you want to heel the boat for other reasons and the rear corner digs in the water.

Hi Arne
My chines are not parellel to the WL. I don't know if thats right or not, but it seems OK. I can send you cad files of Monkey and Dragonfly if that is of any use, PM me, can send them as STEP files. The floor on both boats was taken to be 250mm deep at the dagger board and then 50mm (or so) at the transom, same I think as the Nethercotts. Keeping floor low is good idea, helps with balance. Hope design goes well, keep us posted
Alistair

Hi Arne
The Morrison design has chines that slope downwards towards the rear of the boat and are not parallel with the waterline. The chine starts about 2000mm from the bow and at that point is 50mm above the waterline. The chine slopes down to meet the waterline at 4500mm from the bow and at the stern is 20mm below the waterline.
At the centreline, the dance floor is 230mm above the bottom of the boat at the daggerboard box and 60mm at the rear, which drains the water effectively. I don't think you could go much lower.
Look forward to seeing your design!
Phil

To weigh in: the placement of chines is an endless debate. So it is a good variable in a development class.
Simply stated, there is no single correct answer, and all of them have trade offs. The nature of Rule 5(d) probably means that ICs will have a chine of some sort, but beyond that....

The height of the dance floor does have more simple constraints.
1) there needs to be enough support for the daggerboard. In practice this has been about 200mm. You need to balance the rigidity of the hull and daggerboard against the ability to sail with the daggerboard raised.
2) it is very convenient to have enough distance between the boom and the deck on center line to allow you to pass your knee under the boom when sitting in board. That is to say the distance from your foot to your knee. In my case about 650mm. This can be adjusted by the sail plan, but it something that I think about when designing a deck.
3) at the stern there needs to be enough volume to support the helmsman as he tacks and gybes with the seat in the aft position. If the stern sinks too quickly, the margin for error in maneuvers disappears and the canoe becomes harder to sail. You need to calculate this or use your design program to show how the hull will trim with the CG well aft. If the deck submerges, you lose stability in a hurry.
4) the rudder needs to be supported. In the past we have been happy with about 100mm between the upper and lower shaft bearings. We have had designs where this ha been reduced to 5mm, but that increases the load on the bearings and makes the fit even more critical.
5) in general, any surface above the load waterline will drain. If not over the stern, then down through the dagger board trunk. It is not fast to have a whole lot of water pooled up on the deck, so there is some merit to reducing potential for water to accumulate forward.
SHC

This is how it will look like:


And the planned mould:


Some more pictures here:
http://photobucket.com/arnes-ic-design

Very nice Arne!

It's interesting that you have made the freeboard relatively high at the stern. Are you at the minimum height at the beam measurement station?

Will the hull be carbon/foam?

Hi Chris,
the freeboard should be about 30mm higher than minimum at BMS. The mould has some extra "freeboard" for sealing the vacuum bag.
Hull will be made of carbon/foam. Either 200g/m² Biax +/-45° - 5mm foam - 200g/m² Biax +/-45° or 2x 140g/m² Biax +/-45° - 5mm foam - 1x 140g/m² Biax +/-45°.

Bases for the mould are under construction. frames will be cut soon, hopefully.

Arne

The rails for the seatcarriage will be parallel to the WL. Do yours slope down backwards?

First mould base. Frames will be mounted to the base.

Yes, on my boat the rails are about 100mm lower at the stern.

Hi Arne, I would keep the freeboard and the BMS to the minimum. My ( painful ) experience is that just climbing back into the canoe after a capsize you will want the lowest height possible. Approaching the OD height if possible. Also keep the dance floor low also - must drain of course - as Steve said, no use carrying around loads of water !