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Steve Clark View Drop Down
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Post Options Post Options   Quote Steve Clark Quote  Post ReplyReply Direct Link To This Post Topic: Buzz Singlehanded Project
    Posted: 15 Jul 05 at 2:50am

Always amazes me how hard people think about sailing a doublehanded dinghy singlehanded.  It occurred to me about half a second after I saw a photo of Paul Elvstrom steering his 505 from the trapeze.

The answer is that long tiller extensions are very easy to build/ aquire. Most boats will tolerate being sailed a little high and light while you get the jib trimmed, and it isn't that big a deal to grab the sheet and swing out. Been doing it for years.  Something like a 29er, which in my mind is a really small doublehanded boat ( ie requires really light teams to be competitive) make a pretty nice singlehander. To be really nice, add a mainsheet head knocker cleat and two sheet cleats for the kite. Oh, use a double tiller extension.

Any other assymerical dinghy can get the same treatment, the caveat being that if the rig is really big, ike a 49er or 14, one guy isn't enough to stand it back up after tipping over...  Other than that, geeze.

SHC

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Post Options Post Options   Quote No. 5 Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jul 05 at 6:56pm
I used to sail my Hornet single handed occasionally if I was without crew. It was good fun, gybing the kite was no problem with twin poles and i used plastic conduit as a tiller extension. Went well too, I used to overtake RS600s no problem.
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Post Options Post Options   Quote Bram Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jul 05 at 5:30am

 

I usually try to avoid these forums, however, this one seems civilized and you guys are asking some good questions.

 

Regarding weight:  The Swift has a higher power to weight ratio than any of the other single handers.  We clearly found the point where lighter is not better.  USA 001 weighed 235 lbs all up and with USA 002 I decided to use hybrid and s-glass to pull 30 lbs out of the boat without sacrificing any stiffness.  It was clear that USA 002 was more difficult to tack in a breeze.  As we discovered, the problem with power is that it typically becomes drag when the boat is head to wind and if you don’t have enough inertia to keep the boat going you end up with a layline boat (not efficient enough to be tactical).  We solved much of this problem by going to a much lighter rudder / rudder cassette, mast. and spinnaker pole.  In addition we made the mast smaller in diameter and eliminated the lower spreaders.  If you build a Swift to the class rules, it is now legally possible to bring the boat in just under 200 lbs or about 20 lbs heavier than a Musto.  The Swift loses much less distance tacking than a Musto.  We could pull out at least 20 lbs by going to Nomex core with likely only a small sacrifice in top end competitiveness.  The result would be a boat that is faster in a straight line, harder to sail, and much slower tacking and gibing. 

 

Regarding choice of composites:  We are in the middle of some extensive composite testing and should have the results ready soon.  We are testing foam, Nomex, and cedar cores with various skins (all epoxy matrix but with s-glass, carbon, and carbon Kevlar hybrid).  The idea is to find the composite that changes the least after undergoing thousands of small flex cycles.  You will often hear about boats in various classes that have been sailed for years and are still competitive, however, if you look at the results in classes that are dominated by professional or semi professional sailors, you’ll find that few boats place in the top 25 after they are 18 months old.  The simple way to test boats (all other things being equal) is to pull all of the rigs on until you have a common forestay reading—say 23 on the new Loos gauge.  Next, pull all of the forestays on another ½” and see which one has the highest second reading.  That will be the fastest boat we believe.  You will almost always find that it will also be the newest boat unless the class being tested is made with wood core.  Top quality ski manufacturers have nearly all gone back to wood core after years of trying honeycomb and foam.  Wood cored skis are heavier, but they will typically flex the same for a number of years.  Boats are not skis, however, there are a number of unsupported out—of—column areas in nearly every design that are susceptible to the same forces—especially where those curves are under compression.

 

I hope this helps explain our thinking on these matters.  Look for Hydromat test results soon from Gougeon Brothers on these composites.  On our website, we’ve already completed some puncture and water absorption testing that is pretty interesting.  Also, there is some preliminary computerized static flex test results posted.

Bram Dally

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Post Options Post Options   Quote Blobby Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jul 05 at 6:22am

Bram,

First of all let me say I am very impressed with the Swift and the fact that you have been able to build a class with 60 new boats in construction around the world so quickly - especially without the massive marketing muscle of the major manufacturers.

But to continue the civilised debate:

Originally posted by Bram

I usually try to avoid these forums, however, this one seems civilized and you guys are asking some good questions.

Regarding weight:  The Swift has a higher power to weight ratio than any of the other single handers. 

 

Not sure on this - looking at your website you have compared sail area to weight - but power does not come from sail area alone - it also comes from righting moment.  The Swift is only 2m wide so the righting moment is only 80Kg x 2m = 160Kgm when the helm is on the wire & ignoring the weight of the boat.  It doesn't matter how much sail you stick on the boat, that is the maximum righting moment you can generate.

 

I would agree that the Swift generates its power low down due to the area of the jib, which does give you more driving force for a given righting moment but saying it has a higher power to weight ratio than an 18ft skiff which is twice as wide with 3 times as much crew weight (6x greater righting moment) and only about 3 times the weight seems optimistic to me.

 

A Musto is again about 1m wider and weighs 10 - 20Kg less than the Swift, so more righting moment and less weight should give better power to weight...

 

Originally posted by Bram

We clearly found the point where lighter is not better.... USA 002 was more difficult to tack in a breeze... if you don’t have enough inertia to keep the boat going you end up with a layline boat (not efficient enough to be tactical).  We solved much of this problem by going to a much lighter rudder / rudder cassette, mast. and spinnaker pole.  In addition we made the mast smaller in diameter and eliminated the lower spreaders.  The Swift loses much less distance tacking than a Musto.  

 

 

Not sure you can say lighter is not better based on this - but you can certainly say that a lighter boat needs to have lower drag to be able to maintain as much momentum through the tacks as a heavier boat. 

 

Originally posted by Bram

Regarding choice of composites:  We are in the middle of some extensive composite testing and should have the results ready soon.   Look for Hydromat test results soon from Gougeon Brothers on these composites.  On our website, we’ve already completed some puncture and water absorption testing that is pretty interesting.  Also, there is some preliminary computerized static flex test results posted.

The testing results will certainly be interesting - I seem to recall Southampton Uni did a similar load of testing back in the early 90's for the design of foam sandwich lifeboats for the RNLI.  There must be published papers on this out there in the ether somewhere.  There is definitely a different perspective on this in most of development classes - but it has to be said that the Swift hull is a one design and you are looking to get 20 years life out of the boat, whereas most of the comments I have seen here come from development class enthusiasts where longevity is probably of a lower priority since you know that gradually faster boats will evolve and the hulls will be sold on to those entering the class wanting to learn the boat not win championships.

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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jul 05 at 1:00pm

Thought the swift was a mono.

 cats get to use their full beam in righting moment as their pivot point is the leeward hull or centerboard

I'm sure the Swift designer knows what he's talking about .

.

 

 

 

 

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Post Options Post Options   Quote Barty Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jul 05 at 3:36pm

Blobby

Just to pull you up on one point........

Originally posted by Bram

I usually try to avoid these forums, however, this one seems civilized and you guys are asking some good questions.

Regarding weight:  The Swift has a higher power to weight ratio than any of the other single handers. 

 

Note the section in bold.  Your comparison to righting force between the swift and the 18 is surely worlds apart and not what Bram said???

 

I would guess that Bram has been involved with yachts and that he is comparing static sail area/displacement ratios which, as you say, do not give a accurate view of dinghies.  I think that this would be a theorectical ratio as with cars.....600hp and wet road = slow !!!!

 

One final point to consider is what if the extra weight is in the gunwales?  Surely this increases the righting moment and hence more of the power available can be harnessed?



Edited by Barty
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jul 05 at 4:36pm
Originally posted by Barty

One final point to consider is what if the extra weight is in the gunwales?  Surely this increases the righting moment and hence more of the power available can be harnessed?


Doesn't help significantly - don't forget the weight ios also in the other gunwhale... Only bit of a monohull where weight makes much difference to righting moment is the tiller extension...
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Post Options Post Options   Quote Steve Clark Quote  Post ReplyReply Direct Link To This Post Posted: 19 Jul 05 at 5:07pm

A few points:

"Power" is a very vague term and can be used to describe different things. I'm pretty sure that what is being referred to here is Sail Area/ Displacement which according to some pretty much defines down wind performance.  Frank Bethwaite and others have tried to establish simple coefficients to prove that heir boats are faster or to establish some sort of numerical basis for ranking the performance of boats.  These are almost always misleading if used in isolation. It is, as we say, more complicated than that.

There is nothing wrong with cedar as a core material. It is particularly effective if you are building some nice boats with compound curves and you don't want to go to the trouble and cost of building female tooling.  It works well, bends consistantly, fairs well, has great mechanical properties and is relatively cheap and available.  The Swift Solo construction is a good example of appropriate technology. Is it better than any other composite core stack? Probably not, but who said it has to be anything other than a practical way to build a pretty nice little boat. 

If one wanted to build more than a couple of Swift Solos, you sure would want to have some female molds and a core that didn't take as long to assemble.  Matching the mechanical properties of the cedar/ carbon glass laminates would be pretty tricky.

SHC

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Post Options Post Options   Quote Blobby Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jul 05 at 1:42am
Originally posted by Bob Inn

Thought the swift was a mono.

 cats get to use their full beam in righting moment as their pivot point is the leeward hull or centerboard

When you trapeze your centre of gravity is about 1m above your feet. 

2m beam divided by 2 = 1m

1m beam + 1m of legs = 2m

Is that clear??

 

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Post Options Post Options   Quote Blobby Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jul 05 at 1:43am
Originally posted by Barty

Blobby

Just to pull you up on one point........

Originally posted by Bram

I usually try to avoid these forums, however, this one seems civilized and you guys are asking some good questions.

Regarding weight:  The Swift has a higher power to weight ratio than any of the other single handers. 

 

Note the section in bold.  Your comparison to righting force between the swift and the 18 is surely worlds apart and not what Bram said???

 

And i said LOOK AT HIS WEBSITE where he clearly does compare the Swift to the Musto, RS600 and 18 ft skiff.

 



Edited by Blobby
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