Well I'm no boat designer but do enjoy thinking of rigging enhancements like most other sailors. Since DH is so important on flexible masted F16's it would be really nice if it worked really well, ie, simple, lightweight, very low fricion. I've read Wouter's excellent posts on how he implemented the internal DH in his wingmast and I suspect the standard AHPC setup is pretty good too. But I wonder if anyone has considered or tried implementing a lever based purchase for the DH in a wingmast? These systems are used on backstay adjusters on big monohulls and they're now being used for on the fly DH adjustment for windsurfing sails. I'm sure you've seen them, they consist of a "L" shaped lever with a pivot at the bend. Some vang systems use them. They're very light weight, simple, low friction, and use fewer moving parts than cascaded or non-cascaded block based systems. The super wing mast seems ideal to put one of these inside since it's so large. So, anyone tried it? If so, whay not?

Jerry

You need quite a lot of travell length on the F16 downhaul. Between 6 knots and 20 knots I pull my mainsail 200 mm downwards. To get such a travell length would require a rather large lever. I know the lever system from the 49-er skiff.

At least that is why I went for the cascaded downhaul

Actually AHPC is now using my system in their new boats.

Wouter

Sorry about the hijack
[offtopic]Wouter did you get my PM, I need some feedback ASAP[/offtopic]

back to your normal scheduling.

Lever based downhauls have been tried on several different classes of cats over the years and to my knowledge, they have all been discarded. It would seem that the need to obtain adequate advantage from the lever system requires that the lever has to be "very long" or there has to be a multiple "pulley" system attached to it to obtain the needed amount of leverage. This has meant that either the "area" that the lever protrudes is very inconvenient (sheets get caught on it, etc) and/or, why have two systems together when one (a pulley system alone) will do the job of the two. There has also been "magic boxes" - where the pulley system is enclosed within a square or rectangular aluminium tube that is attached to the mast (or boom) and keeps every thing very "clean" BUT there has never been enough travel in the "magic boxes" for them to ever become "popular".

Thanks everyone for the feedback.

The amount of travel does pose a problem. In windsurfing rigs, you need lots of leverage for an interactive DH but not lots of range (maybe 40-60 mm). I assumed that one could cascade levers like one could cascade block based systems thereby keeping lever lengths shorter but maybe this gets too complicated.

By the way, how is the DH rigged in Verctorworks Blade? Something similar to your DH Wouter?

Thanks,

Jerry

I have never gotten it confirmed but I think I got an pretty good idea of how the Blade F16 downhaul works. It is actually a very smart setup. I still like my internal system because it gives such a clean look and I never have to take it off but commericially the VectorWorks system is the best. The internal systems are a little labour intensive to build while the Blade system isn't. Also the system used there can easily be put on all other catamarans out there. So if you are having trouble with you downhaul. Not powerful enough or too much internal friction than you may want to give this a try.




The two systems shown use the same basic idea but the one above is a 1:8 and the one below is a 1:12 . I seem to remember that the Blade F16 comes with a 1:16 even.

It will be easiest to explain the system by the 1:8 model; the other are exactly the same apart from having more loops in the blue line.

The red line is the line that you'll hold in your hand. probably 5 mm or 6 mm diameter with nice grib properties and as flexible as possible. The blue line is a thin high tension line that is strong but still flexible. A good combination good by 6 mm swiftcord for red and 3 mm D12 for the blue line.

On either side of the lines you'll see to schematics representing the swivel cleats that are riveted to the mast near the mast foot. Black lines are drawn to indicated that the swivelcleats and the lower 2 blocks are fixed to the mast and can't move relative to one another.

Then we follow the blue line. This starts and ends at two free hanging blocks than move along side the mast. The blue line first passes through two blocks that are fixed to either side of the mainsail (or a double block that hangs underneath the mainsail). The black lines here indicate that these upper blocks are fixed to one-another and to the mainsail; they move up and down together with the mainsail and so the movement here is equal to the downhaul travell length.

How does it work.

Well the sailor pulls on the red line (which can be continious by the way ! THAT is VERY handy). This induces a tension in the red line of say i unit of force. By virtue of the two vertical loops in the red line the force on each of the free hanging blocks is 2 units. Therefor in the blue line there is now 2 units of force. The sail is linked to 4 segments of blue line therefor the pull on the sail will be

4 times the force in the blue line = 4 times 2 time the force in the red line = 8 times the force in the red line => 1:8

By the same reasoning you get 1:12 in the bottom system.

Why this system ?

Well It allows to optimize the line diameters for low friction and smooth operation. Because of the cascaded nature the total friction is alot less than a standard 1:8 system using 8 loops. You can therefor excert the same downhaul force for less red line tension = easier control.

And this system fits entirely on the outside of the mast between the foot of the mainsail and the mast step. Nothing is internal in the mast (easier to build yourself) and you don't have downhaul lines running up along side the mast for some 5 to 7 feet and disturbing the flow there. See the attached pictures.









Wouter

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Here is a diagram on my setup on the blade. The middle blocks sometimes get caught with the boom. I will eventually modify it and put double blocks at the sail to remove the middle set of blocks. Matt informed me this is the same exact setup the Inter 20s use.

Thanks for sharing and taking the time to make those illustrations.

We have a similar setup on our boat, but the red line runs trough 2xdouble blocks (one on each side of the mast) that is the first part of the cascade. I'll see how hard it would be to implement the 1:12 cascade on our boat, and test it out if it's easy (perhaps going for 1:16).

Thanks, Wouter and Robi.

It looks like the DH in Robi's diagram is only 4:1?

Although easier to rig there is something very clean and uncluttered about an internal DH system.

Having the DH blocks catch on the boom is a nuissance so eliminating that possibility is worth the trouble. When I've built a similar system in the past, replacing the single blocks with a double block wasn't ideal since it changed the lead angles and the lines didn't feed perfectly into the blocks and had more friction as a result.

Are the blocks on eiter side of the sail's DH grommet pinned there or do they hang on a connector line?

So is it possible to get a 12:1 or 16:1 system like this that works properly without the intermediate blocks catching on things?

Jerry

Hey Jerry, my diagram is kinda hard to see. My system is either a 4X4 or a 2X4 making it either a 16:1 or an 8:1. I do beleive it is an 8:1 but I can be wrong.

The blocks at the sail are connected to eachother through a connector line.

your drawing suggests a 1:8 purchase.

Wouter

Yep, I'm not changing.

Although you must use a 3 staged cascaded system otherwise the friction is too much with the internal system. Ahpc use todo a 1:12 2 stage cascade system internally, but now they use the 3 staged internal system that I have. Simply because it works so much better.

Wouter

Wouter, do you think an 8:1 DH on the Blades superwing mast is enough, especially to allow you to easily adjust DH from the trap while singlehanding? To me it sounds kinda light on the leverage. Doesn't everyone else use 12:1?

Jerry

It is more than enough, I have used the system from the trap and single handed. Works like a charm.

I think 1:8 (when using a cascaded system) is enough for by far most conditions.

It also dependents on the way the sailmaker cut your mainsail. Redhead sail like alot of downhaul, while Goodall and Ashby sails like noticeably less. I don't in which camp Ullman sails fall (standard on Blade F16)

1:8 does leave alot less excess line on your trampoline which is a plus.

The only time I really enjoyed my 1:12 was in the very light winds of two weeks ago. Here I could really downhaul my mainsail, allowing it to become flat with only very little mainsheet tension. This low mainsheet tension in turn allowed me to sail with a significant amount of twist. But you can achieve this with a 1:8 system as well; just hunk on the mainsheet and then pull on the downhaul to the correct setting and release the mainsheet again. This will lead to the same effect.

I've thought about downgrading to 1:8 as the cascades systems develop luff tension so well, but as my 1:12 system is now fully sorted and operating without any hitches I think I'll stick to that. I solved the excess line problem in a very satisfactory way as well.

You'll be fine with 1:8 and besides it is very easy to upgrade the Blade F16 system to 1:12. Just fit one single block to the boom and a 3rd single block to the sail and run the second stage line through these blocks eee presto ! a 1:12 system. See the drawings in the other post.

Wouter

Wouter, do you think an 8:1 DH on the Blades superwing mast is enough, especially to allow you to easily adjust DH from the trap while singlehanding? To me it sounds kinda light on the leverage. Doesn't everyone else use 12:1?

Thanks Wouter and Robi for the feedback.

Wouter - I really liked your tips about light wind sail tuning in this and your other post. One thing I notice about the H17, and maybe this is becuase it's a unirig, is that you really need to put it through it's gears so get speed whether it's light or heavy. Two questions:

1) Is the same generally true of F16's?

2) For light wind, have you tried a fuller sail (less DH) initially to get moving followed by high DH for flatter sail (with more twist) - ie, using incremental DH as a way to go add a low gear in light wind? My experience is flat is fast, buy only when you're already moving.

Thanks,

Jerry

Wouter, if you were getting a Blade, would you keep the existing DH system or convert it into an internal system? If you converted it, would you use an 8:1 system or a 12:1 system? Lastly, is it correct to assume that if the boat turtles with an internal system, water can get into the mast?

Thanks

Jamie, is your question purely hypothetical, or does it suggest that you are getting a Blade? I ask because I have a Blade on order, and you and I happen to be in the same vicinity.

Mark.