Class legal?

Tiger Mike:

I had to send off the drawings to an engineer friend of mine so I did not make a mistake.

Indeed the drawings are right. 12 to 1 and 16 to 1. I sent him the following illustrations without purchase listings (which are in black): http://members.aol.com/ddelave/sailing/downhaulpurchases.jpg

This is his response:


Later,
Dan

Ahh - figured it out . That link makes it easier to understand. I run a very similar system to your 16:1 but have less rope. To get over the distance problem, I have the floating block running between the front & rear beams with another turning block to pop the line out at the correct angle.

Michael

Hey Dan,

This discussion has intrigued my engineering mind!

Some notes on this:

To figure out the purchase of a cascade, you multiply the purchases of each part. Your first system (12:1) seems at first glance to be a 12:1, consisting of a 2:1 (green) on each side cascaded with a 6:1 (blue/red) (2:1-6:1, 2 X 6 = 12:1). However, it is really a double-ended 4:1 (green), which is split to be on both sides of the mast, cascaded with a duplicated 3:1 (blue and red) (4:1-3:1, 4 x 3 = 12:1). The duplication of the 3:1 has no purpose other than to allow the adjustment to be made from either side.

Your 16:1 is the same deal - initially can seem to be a 2:1 (green) cascaded with an 8:1 (blue/red) (2:1-8:1, 2 x 8 = 16:1), but is really a double-ended 4:1 (green) cascaded with a duplicated 4:1 (blue and red) (4:1-4:1, 4 x 4 = 16:1).

This is not a bad system - the routing problems of running lines to both sides of the mast and still getting a smooth-running system are tough. Plus, the room you need for the cascade really isn't that bad. If it was truly a 2:1-8:1, for a 12" downhaul range, you'd need 8 x 12" = 96" or 8' of travel available between the green-blocks (doable on the mast, but waaay up there). Since it's a 4:1-4:1, you'd only need 4 x 12" = 48" or 4' of travel between the green blocks - certainly doable.

To minimize the duplication of the second part of the cascade, as well as minimize the travel needed by the first part, what if we went 8:1-2:1? See below:



This is all made with easily available components. The entire 'green' section is the "8:1 Downhaul Kit with Double Blocks" from Murray's; two cheek blocks per side that are simply turning blocks; either a double block or two singles (probably work better with two singles) attached to the sail; and a ring to tie off the 2:1's (if you could find cheek blocks with beckets, it would be perfect, but good luck with that). This could probably be integrated into the boom gooseneck.

For 12" of range at the sail, you need 2 x 12" = 24"or 2' of distance between the lower downhaul component and the upper turning cheek blocks - no problem! Mount the lower downhaul component just below the boom; mount the upper turning blocks 2' + some above that on the mast. The lower two turning blocks could be one on either side of the boom; the two singles are on a captive-pin type shackle, attached to the sail.

I think this is a way better solution than mounting under the tramp or the front crossbar - doing that means the downhaul will affect mast rotation since you can't run the line directly through the center of rotation. Have we made a tradeoff vs the original?

Edit - part way in to this, it's way too long for a forum post. Gonna write this up as an article or two, maybe get it in the Hotline!

_________________
Tim
Unofficial Fleet 72 Communications Officer and Div 4 Webmaster
http://www.hobiefleet72.org
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I put Dan's original drawing for a 16-1 on my Tiger, and with minimal preset, you can black band the main with no problem. My crew could not do this with the 12-1 (one of Dan's old drawings). Thanks for all the info. Now if you could get me upwind with Nigel, I'll be O Tay. Rick

Rick:

I am glad that the system I drew is working out for you. How have your recent regattas gone? Are you planning on Lake Carlyle?

As for beating Nigel: Nigel can be mortal if you take Alex off the boat. I am not saying slow, he is still fast. If he has Alex on the boat with him they are a magic team. That is the same thing that happens with Greg and Jacques. Together they are incredible and separately the become more credible. These are all hard guys to beat on their worst days, so the second thing to consider is lassoing them at the start and ride for more than the mandatory 8 seconds.

I do not know if Nigel and Alex have given a clinic, but I know that if you ask them a question about speed they will answer it. Though, I will bet, you will not keep them answering too many questions while they are thinking about and setting up for racing. Maybe you can just ask them one question at each event. Ask them something that is important to helping you pick up the pace.

Greg and Jacques are about to give the Formula 18s, on the West Coast, a clinic. They have just come back from the ISAF World Games and have a lot of knowledge to impart. There are at least 10 boats that are planning on showing up and all of us are looking forward to it.

Later,
Dan

I'll be at Carlyle. We've been finishing with Mike Krantz and Dave Lennard a little behind Nigel. I'v been sailing with him for 25 years and am progressing the wrong direction, but having fun doing it. He and Alex don't do seminars, but will help get you up to speed any way they can. They make the Infusion look good, but it seems mortal in other hands. Good sailing, and seeyou in the fall, Rick

tjp,

Thank you for a very descriptive post. I'm sailing on an 8:1 at the moment and it's just not hacking it. I like your 8:1 on to a 2:1 idea, particularly how you don't have a cascade running way up the mast. I definately think a cascade is the way to go. When you get into such High purchase systems the friction will become a very significant effect.

My question is do you have a problem with the double blocks in the 8:1 scraping up and down the side of the mast? Also, what blocks did you use for yours? I was looking at using the Harken 16mm airblocks (little steel cheek ones) as they have pretty much the same breaking strain as the larger blocks.

Thanks,

Andy G

_________________
AndyG
Tiger F18, Landenberger sails
Ireland