Thread: Is that a 12' GIS I see hull down on your horizon

Hi Joost,

The idea is high tech can make some things easier and cheaper. If it adds a heap of expense for .01 knot (enough to win a regatta) then I really thing it should be outlawed for the class.

Tommyboy, wing masts???? Well Fess up or post a pic of your normal ride! Super great having the experience to confirm the thinking here. Also confirm prices, also provide alternative suppliers! Super plus for a great post!

MIK

Hi all,

Brian Pearson wrote elsewhere about using ordiary Dyneema on his 12 foot Keyhaven scow:
I have raced for over 5 years with 3mm dyneema shrouds and forestay on my little 12' Keyhaven Scow dinghy, it has a lug rig and mine also had cabon mast and spars. The shrouds were attached permanently and the forestay on a clip so I could raise and drop the mast quickly.
The forestay clip was set up to be a good hard pull to clip on so the rig was reasonably tight for sailing. After a strong wind race I would notice that the shrouds were slack, so the dyneema had stretched. So I would move the clip up the forestay and then when I came back to the boat to race a week later, the forestay would be too short to be able to clip on. The dyneema seems to stretch and then recover. So it does stretch and recover repeatably. I understand there are versions of dyneema which dont do this, the type used for 4X4 winch lines I think. That must be best for yacht applications.
I can confirm it's far nicer than wire to deal with and great that you can make up your own shrouds. A pal made a very nice backstay for his racing yacht.
Brian

Thanks for that, knew I had written something somewhere about using 3mm dyneema.

The increase in strength from 3mm to 4mm is so huge that I reckon 4 mm would have been fine with very little stretch. This new stuff should really good.

It really is so very much nicer to use than stainless wire, very easy to splice. Dropping the rig into the boat after sailing, the dyneema just lays there, whereas wire is horrible.

the system of using a single stainless clip on the forestay works great, setting up the rig in exactly the same way each time you sail.

best to splice rather than knots. I think knots halve the strength.

Brian

Originally Posted by Boatmik

Tommyboy, wing masts???? Well Fess up or post a pic of your normal ride! Super great having the experience to confirm the thinking here. Also confirm prices, also provide alternative suppliers! Super plus for a great post!
MIK

Okay MIK,

The wingmasted boat was a refurb of a Crowther Twiggy and 44 ft Gougeon B-Section mast.

Incredible design - RIP Lock.

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Interior of an "Oldies" OSTAR boat

nav_station_MIK.jpg

A few miles away, while I was rebuilding my Twiggy, they built a Sam Bradfield designed foiler for a 37 foot OSTAR project boat for Phil Steggal (ex HOOD Sails, who built the sails for my first built from scratch trimaran).

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With three T-foils - the boat did fly on the foils in the 26+knot range which was pretty good for 37' then (that was 10/12 years ago now). Don't have info on why it never competed in the OSTAR - except that the boat build was fully funded - but probably not the actual race campaign.

Phil's notable OSTAR/CSTAR finishes
1980 3rd overall in Jeans Foster Tri-38(G) 18 days 06 hours 45 min
1988 4th Class 1 in Sebago Tri-60(I) 11 days 09 hours 55 min

Cheers
TomH / tommyboy

Hi Tommyboy,

Last year and early this year I had a half baked idea of buying a multi to live aboard so I could shift locations. The sailmaking project in the Philippines made it redundant in the end. Maybe a small multi for camp cruising around the Philippines later.

But it is really nice to see a twiggy with its floats the right distance out of the water. There is one in Oz that looks nice and is going cheap but with half that clearance. I found a video of it sailing in moderate conditions and the float is well under with the crossbeams kicking the waves around.

I had a look at a number of boats.
Crowther 37ft tri - no sitting accommodation in the hull.
Crowther 40 Spindrift - really nice boat, a bit old but in the end so much area to move in and out of anchorages and handle by myself.
Crowther Windspeed 32 by the best tri builder in Oz - Geoff Cruze. There are several around with the waterlines drawn halfway up the topsides because people have stuffed too much junk in them - one even had a tiled kitchen and "bathroom". But there was one really nice one I didn't get to see because it was at Tin Can Bay and the weather to get across the bay was bad the whole time I was in Queensland.

Lock Crowther sailed from the same beach that I lived on for a year - the year a certain 12 year old started sailing. He had an A-class with little wings on the bow of one hull - capsized so fast his competitors came back to say .. "Can you do it again Lock, it happened so fast we missed it". Also saw the John Haines/Crowther partial wing masted cat "Helios" set up for the first time on the beach. Awesome machine. The rig ended up being too tall.

Later on I had a few little conversations with Lock - truly one of the greats and smart and no ego. He had a lot of development in hull shapes that still leave everyone else for dead. One thing he wrote was that foils have similar lift/drag to well designed amas, so there is no real advantage.

I was reminded of this recently with the America's Cup cats. With Foiling they find that they can't do better flying than sailing on the hulls unless they are on two foils only - the NZ boat did trials with different configurations and found it needed foils retracted to beat hull only. So the moths might be the ultimate setup for lowest drag.

But I think the advantage of foils at sea is that you can go so much faster with much less reference to sea conditions. Hydroptere at 30 knots looks much more comfy than watching a similar sized non foiled boat action of flying off the wave tops, heeling to keep the leeward hull in the water, main hull droppind down and landing

A bit more on foil efficiency vs hull efficiency.

Read the comments at the bottom as well.

carbonicboats: Sweet Spot Part 2

MIK

Wood: a hyper-advanced composite.

Originally Posted by Boatmik

Hi Tommyboy,
Maybe a small multi for camp cruising around the Philippines later.

Lock's Buccaneer 24 is a lesson in simplicity - especially his rapid building method for the hulls - and could be applied/tranferred to many small boats of general interest. Might even be able to be used for a slender trimaran up to 30 feet for camp cruising around the Philippines. Longer and slender is my choice when a bit more displacement is needed for cruising.

Originally Posted by Boatmik

Hi Tommyboy,
Later on I had a few little conversations with Lock - truly one of the greats and smart and no ego. He had a lot of development in hull shapes that still leave everyone else for dead. One thing he wrote was that foils have similar lift/drag to well designed amas, so there is no real advantage.

"In the day", NEMA (our multi club, New England Multihull Association) members were home to many of the inspiring and innovative boats of that era. We regularly invited top designers to speak at our meetings (Newick, Harris, Cross, Brown, Marples Bueler, Crowther, Irens, Green, among others). I do remember that Lock was one of the few who would actually answer technical questions about his designs and trade-offs and he explained until we understood - he was very generous and revealing with his 'trade secrets' -- it made others appear secretive by comparison.

Originally Posted by Boatmik

Hi Tommyboy,
But I think the advantage of foils at sea is that you can go so much faster with much less reference to sea conditions. Hydroptere at 30 knots looks much more comfy than watching a similar sized non foiled boat action of flying off the wave tops

And before Hydroptere, Dave Keiper in his foiling trimaran Williwaw ( DAK HYDROFOILS - Williwaw ), took his boat across the Pacific in the late 60's if I remember and showed us all how valuable foiling was in terms of seaworthiness in bad conditions. His book is well worth the read (he did a CD too) if you can find them.

TomH

Originally Posted by Boatmik

A bit more on foil efficiency vs hull efficiency.

Read the comments at the bottom as well.

carbonicboats: Sweet Spot Part 2

MIK

A very interesting insight into the tradeoffs with drag induced by the foils vs natural hull efficiency. That the A class can foil at 12 knots is one thing, but at that speed, the hulls are still way more efficient than the foils and full foiling only becomes more efficient above 18 kts. I wonder what this efficient speed is for the AC72s? Likely very much higher and then, will foiling be a waste of time? It will be interesting to see what the final configurations will be for the AC 72s come the business end of the competition. They appear to be anticipating this and that is the reason for fully retracting foils. However, the cost is still there in terms of the beefier structure needed and hence weight, so more drag than not. Very interesting indeed.

The toe-in of the foils is fascinating too. I like the simple way this has been achieved, but it's nevertheless still an extra task to have to manage each tack. However, there is not much tacking or upwind tactics in multihull racing as they invariably are "banging the corners" (and definitely no slam dunking!) as is the case with mono racing, so I suppose it's not an issue.

Also interesting is the way that the rudders are not just along for the ride and have to contribute to side force lift as well to prevent leeway, so the tillers on these boats are no longer feather light and the skipper has to live with lots of weather helm.

It's a whole new ball game and definitely not sailing as we all know it!

Howdy Tommyboy,

Agree with everything. I've often looked at the Bucc24 - there's a nice one in sydney for sale along my walking trail. Building ... It is pretty simple but I think that now it is possible to make it simpler still. So it is as a possibility as a starting point ... just a little down the line.

Sydney one for $16500 on Gumtree



Trimaran 24 Ft Crowther Buccaneer | Sail Boats | Gumtree Australia North Sydney Area - Lavender Bay

Building cabin boats is a big time suck though Maybe later ... next year? This year the sailmaking gig.


Bruce...
Same thing has to explain foils and hulls. Physics is ultimately the same. The number that is there for comparison is lift/drag. Crowther said at least 20 years ago that foils and slender hulls were not much different. I think we would have to add now "in low, moderate, and lower high speed ranges".

MIK

Hello MIK,

You image link failed on all browsers that I use - were you linking to a local file?

The actual ad on gumtree (as on 25 Mar '13; first listed on gumtree 23 Mar '13) is here:

<http://www.gumtree.com.au/s-ad/laven...eer/1012237801>

Cheers,
Alex.

MIK, I Hope that foot is getting much better by now and you're off those crutches.

I made a close inspection of Max's stays this morning and there are several broken strands. This is a real PITA and I should have looked at them more closely before today. I really don't want to risk the mast coming down after all the work I've done as it would surely go right through the hull if that happened.

What size Dynex Dux are you contemplating for the Balls? I have found a supplier in Sydney. The smallest diameter they have is 5mm, so was wondering if that would be OK for the Moth? I was hoping for 4mm but it seems unavailable locally in that size.

Hi Bruce,

I think you will get a few giggles with a big size rigging like the 5mm. It is pretty fat ... think of 4mm control lines!!!

Also remember that the stuff is so light and compact that ordering internationally ain't a silly notion.

MIK

Mmm, don't want to get laughed at, so will go the ss wire route. Seems that 5mm is the smallest diameter made in Dynex Dux.

http://www.hampidjan.com/media/PDF/D...ad20lres13.pdf