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Are booms fast on multi's ? - old thread


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MrWolf

Posted: Wed Oct 15, 2008 12:26 pm Post subject: Are booms fast on multi's ?

 

following on from my comments regarding Tim Clissold's cat pulse not having a boom , what are your thoughts?

I bet Pulse would be faster with a boom.

 

tim's response regarding Jibs doesn't wash with me because you need all sorts of Fore/aft adjustment on Jibs and have the clew quite close to the lead point. No way that it is as adjustable on Pulses main.

 

also, just what is lighter ?

if a boom holds out the corner for you is it not possible that it is the lightest solution possible ?

 

Or is everyone else wrong ?

 

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Sundreamer

Posted: Wed Oct 15, 2008 12:28 pm

 

I noticed the new tri Cubic doesnt have a boom. Hard to tell if it worked or didn't but it's not an idea/look that grabs me

 

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Clipper

Posted: Wed Oct 15, 2008 12:36 pm

 

One obvious thought is sail area.

 

If you want to get foot and leech tension by angles etc (like the jib) it is likely you will need to sheet from behind the clew, and hence may be forced into a shorter foot?

 

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ScottiE

Posted: Wed Oct 15, 2008 2:42 pm Post subject:

 

Sundreamer wrote: I noticed the new tri Cubic doesnt have a boom. Hard to tell if it worked or didn't but it's not an idea/look that grabs me

 

 

As the helmsmen that day I can tell you that up wind it is definitely not quicker. Downwind gybing is pretty easy though - you just flick the boat where you want!

Clew and head positions are extremely difficult to get right simultaneously up wind - the main sheet angle has to support foot tension as well as leech tension. I found that when I heaved on the main to stand the head more upright I flattened out the lower portion of the main too much causing it to stall. taking the traveller further to windward did not work too well to resolve that. I felt that some form of barber -hauler might help support the clew more but then you'd have additional sheets flailing about which can't be safe either. The other issue with the traveller track was that it was horizontal - but the main sheet was closer to 45deg. Therefore the bearings on the back side of the car will be taking all the load. The amount of additional control that a boom offers is significant for a race boat I think - you control foot tension using the outhaul and leech tension control using the mainsheet. I'm sure with a few more hours on the boat we'd markedly improve sail setup though - the boat was only in the drink for a few hours before we went 'racing'!

 

 

However Wolfy I don't think that TC's arguement is that its quicker just far safer for a cruising boat.

 

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samin

Posted: Wed Oct 15, 2008 7:53 pm

 

 

MrWolf wrote: I bet Pulse would be faster with a boom.

 

I agree!

 

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Tim C

Posted: Thu Oct 16, 2008 5:22 am

 

MrWolf wrote: following on from my comments regarding Tim Clissold's cat pulse not having a boom , what are your thoughts?

I bet Pulse would be faster with a boom.

 

tim's response regarding Jibs doesn't wash with me because you need all sorts of Fore/aft adjustment on Jibs and have the clew quite close to the lead point. No way that it is as adjustable on Pulses main.

 

also, just what is lighter ?

if a boom holds out the corner for you is it not possible that it is the lightest solution possible ?

 

Or is everyone else wrong ?

 

 

Tim you need to have a good look before making some of these comments.

The foot on my mylar main is infinitely adjustable. At the clew there are two sheet positions, and for up wind work the attachment point can be varied between the two.

Downwind there is a shelf foot, that is usually rolled away upwind. The shelf foot is adjustable to fill out the foot of the mainsail by tensioning the clew toward the mast, the same as easing the outhaul on a boomed sail.

Going flat off downwind, without a kite on, yes the main looks average, but that is not a racing mode. With a gennaker on the main is over the end of the traveller track, so leach tension is adjustable via the mainsheet.

By far the worst part of not having a boom is putting the sail away at the end of the day. But once you have a few techniques with topper and lazy jacks it all works fine.

If you look at the Race track rankings, and my last rating of .98, there is no other multihull with as much accommodation as Pulse ahead of me. It seems the trend has been to mid sized multi's that are only really good for racing, not cruising as well.

Finally, if no one tried different things there would be no progress. Just because it has always been done that way is no reason not to try something different.

 

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ScottiE

Posted: Thu Oct 16, 2008 7:47 am

 

Tim C wrote: The foot on my mylar main is infinitely adjustable. At the clew there are two sheet positions, and for up wind work the attachment point can be varied between the two.

Downwind there is a shelf foot, that is usually rolled away upwind. The shelf foot is adjustable to fill out the foot of the mainsail by tensioning the clew toward the mast, the same as easing the outhaul on a boomed sail.

 

 

 

Tim - can you point to any images - sounds intriging

 

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samin

Posted: Thu Oct 16, 2008 8:00 am Post subject:

 

ScottiE wrote: However Wolfy I don't think that TC's arguement is that its quicker just far safer for a cruising boat.

 

 

Is this the case TC or do you actually think its faster with no boom?

for an example, If a sistership of pulse was built, with a boom, therefore adding say 500mm to the foot of the main, so an extra 5m2 to the mainsail would it be faster on average in a variety of conditions? I think it would. Its not to say its not a good idea to not have a boom, or that experimenting is a bad thing.

 

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Tim C

Posted: Thu Oct 16, 2008 9:11 am

 

samin wrote: However Wolfy I don't think that TC's arguement is that its quicker just far safer for a cruising boat.

ScottiE wrote: Is this the case TC or do you actually think its faster with no boom?

for an example, If a sistership of pulse was built, with a boom, therefore adding say 500mm to the foot of the main, so an extra 5m2 to the mainsail would it be faster on average in a variety of conditions? I think it would. Its not to say its not a good idea to not have a boom, or that experimenting is a bad thing.

 

 

It may be the case. But I think the high aspect ratio of the main is efficient as it is, and extra sail area can be added with extras on light days. I haven't got a great screacher/code 0 set up at the moment.

It is a 14.8m mast on a 10m boat, it is not like the 8.5s where they have relatively short rigs, so adding area to the foot is desirable.

 

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Tim C

Posted: Thu Oct 16, 2008 9:21 am

 

ScottiE wrote: The foot on my mylar main is infinitely adjustable. At the clew there are two sheet positions, and for up wind work the attachment point can be varied between the two.

Downwind there is a shelf foot, that is usually rolled away upwind. The shelf foot is adjustable to fill out the foot of the mainsail by tensioning the clew toward the mast, the same as easing the outhaul on a boomed sail.

 

Tim C wrote: Tim - can you point to any images - sounds intriging

 

 

Having said all of the above, I can't find any really good photos to show. This is perhaps a start, you can see the shelf foot extending to the base of the mast, and the clew being pulled forward. Of course the shot was taken as I was going high by the looks.

Compare to an upwind photo, where there is more aft pull.

Note I made this main 5 years ago. I may well do things differently now, especially at the head.

 

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Tim C

Posted: Thu Oct 16, 2008 9:29 am

 

I'll try attaching the downwind shot again...

 

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No images were available - can those that have images relating to the above please post to this thread, Thanks :)

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