twin masts on cat thoughts on

[prograd]

It would seem from a pure efficiency standpoint a large single sail should be the most efficient at producing trust.

This is true, but I don't know how does it help to compare biplane and sloop rig. Both of these rigs use several sails.

Although it is true that all of the open ocean records are held by sloops, this doesn't automatically imply that sloops have an edge.
It may be that biplane just hasn't been explored enough, and sailors (and particularly sponsors) don't really want to risk too much with too much new stuff (Team Phillips won't get a another chance, Hydroplaneur lost a sponsor after capsized and broke, I wonder if same will happen with 50/50 cat, which would be sad).

It's easier to just build a bigger boat with bigger sails then to calculate and successfully implement totally new type of boat and sails.

I don't know why would biplane have worse pointing ability, it's the first time I hear about it. Actually googling shows quite the opposite, for example this was published in Australian sailing magazine, August 2005: "in a 5-12kt breeze the boat blew the doors off the rest of the multihull fleet, from a Farrier F24 trimaran to a 43ft Crowther cruising cat, --- In windward pointing ability the boat was not put to shame by the surrounding monohulls" (it talks about Radical Bay 8000).

 

[oldsailor7]

If you really like the idea why don't you go ahead and build or buy one.
After all there are still lots of Biplane aircraft being flown just for fun and pleasure. However when it comes to max efficiency and convenience, Monoplanes rule, ----even Canards, (Main and Jib).

 

[prograd]

Maybe monoplanes rule in human world, but that's not true for animal kingdom:

Evolution didn't wipe out dragonflies and they have been on Earth for a long long time (and they don't seem to be going anywhere).

The implication that because monoplanes rule in human aviation they must be the most efficient is just not really justified. And besides, you can't really extrapolate from planes (or dragonflies) to sailboats because speeds are different and amount of lift is different, hence efficiency. You have to run tests designed for sailboats and sailing conditions, there's no way around it (and this is the hard part).

On the other hand, if you leave efficiency aside for a moment, there are other reasons why one would prefer sloop over biplane (or other way around), for example pricing, or ease of handling (as Petros already pointed out).

 

[prograd]

Actually, Radical Bay 8000 is now available also with standard sloop rig, so these two rigs could be compared: a biplane rigged vs. sloop rigged Radical Bay 8000. I think this would be a fair comparison.

 

[jamez]

It would be good to see two otherwise identical boats face off. Incidentally the RB 8000 was an entry in the Norske Flerskrog Sailklubb “INTERNATIONAL MULTIHULL DESIGN COMPETITION 2002” as a sloop with ply construction. The balsa kit/biplane rig version came later. Also found this web page with some sailing vid/
http://smartyachting.com/files/news.html

 

[frenette]

Lets break the efficiency myth. We put jib, bow spirits, code 0's etc because piling on sail area works. As the rig gets taller the center of force goes up as well. So anything you can do without going taller gets closer to pure drive vs pure push the boat over.

That said the average wind world wide was quoted at something like 7 knots. Most of the races I start in are in less than 5 knots. So going a few feet taller in the mast in these conditions will as close to always be faster as this statement can get. Wind speed in light air goes up quickly as you go higher.

Dual free standing rigs are almost double the cost. You have major wind-age problems with the wind interplay between the rigs especially going down wind on a slower boat. So we all go well my new boat is so fast the apparent wind will always be foreword. And as we get lighter and lighter building material this becomes more true over time but in real life the sea isn't flat enough to pull this off for an entire race or cruise or ...

So if you are cruising on an are of a lot of wind having shorter masts that are easier to take the sails up and down, easier to trim... I may actually be a better rig.

The problem with most of the stuff I've seen on the web are drawings. Drawings don't talk back at you. Crew and owners always feel their boat is faster than it really is no mater how true this is a fast boat maybe. So the only way to really tell is to pull up race records on real boats that have actually raced.

I feel 2 identical boats will be favored in different wind/sea conditions so it's not simple as it could be. For really ultra light fast boats the delta could be very close or for over loaded boats the delta could be a big who cares. For the stuff in the middle the single mast will be faster almost all the wind/sea states most of us sail in.

That said I'm running simulations on a side by side rig with some changes to over come the problems of the interface between the masts. In a couple of years I may have an answer.

 

[brian eiland]

This is true, but I don't know how does it help to compare biplane and sloop rig. Both of these rigs use several sails.

Although it is true that all of the open ocean records are held by sloops, this doesn't automatically imply that sloops have an edge.
It may be that biplane just hasn't been explored enough, and sailors (and particularly sponsors) don't really want to risk too much with too much new stuff (Team Phillips won't get a another chance, Hydroplaneur lost a sponsor after capsized and broke, I wonder if same will happen with 50/50 cat, which would be sad).

It's easier to just build a bigger boat with bigger sails then to calculate and successfully implement totally new type of boat and sails.

I don't know why would biplane have worse pointing ability, it's the first time I hear about it. Actually googling shows quite the opposite, for example this was published in Australian sailing magazine, August 2005: "in a 5-12kt breeze the boat blew the doors off the rest of the multihull fleet, from a Farrier F24 trimaran to a 43ft Crowther cruising cat, --- In windward pointing ability the boat was not put to shame by the surrounding monohulls" (it talks about Radical Bay 8000).

This twin mast idea has me interested again,....and cruising designs DON"T always have to look for ultimate performance. Safety and ease of handling have to be considered as well.

 

[John Perry]

This thread comes at an opportune time since the Amateur Yacht Research Society has an on-line presentation about a biplane rigged catamaran in just a few days from now.
On Tuesday 14 November at 19:30 LONDON TIME Bernard Rhodes, who lives in New Zealand, is planing to get up early to give us a Zoom presentation about designing, building and sailing his cruising catamaran, picture below.

Back in the 1970's, while living in the north west of the UK, Bernard designed and built a small plywood trimaran 'Klis' and sailed it to New Zealand where he settled and lives to this day.

The Zoom link for the meeting is:
Join our Cloud HD Video Meeting https://us06web.zoom.us/j/2536740617?pwd=VFdMOGxWRDNzK1Z4NkxpTkU1a3ZUZz09

The meeting ID is: 253 674 0617 and the passcodeis : ayrs but I dont think you will need those if you join through the link.

 

[brian eiland]

Problem,....I'm no a big fan of loading more 'suspicious' STUFF onto my computer. My advanced age does not know what is OK, or what is taboo these days.

Is there someway you could summarize the material, and post that here?

Two items i find most interesting about this type rig.
1) the better bury and support of the free-standing mast in the hulls
2) the lower center of overturning moments per total sail area,...particularly with 'unannounced' micro burst as have occurred in the past

 

[brian eiland]

Too bad that Team Philips did not get a chance to compete in the 'RACE' ! I'm sure that gave twin rigs a bad reputation.

And remember it was not her rig that failed, but rather her forward hull structure

 

[John Perry]

Problem,....I'm no a big fan of loading more 'suspicious' STUFF onto my computer. My advanced age does not know what is OK, or what is taboo these days.

Is there someway you could summarize the material, and post that here?

Brian - not sure if this is addressed to me, but if it is, Zoom is a widely used 'platform' for holding on-line meetings so I would not think it is suspicious. This is a link that gives an explanation of what Zoom is and how it works:
Explained: What is Zoom? - https://www.webwise.ie/parents/explainers/explained-what-is-zoom/

The above link perhaps makes it sound more complicated than it actually is. If you have not used Zoom before and you click on the link below, or copy and paste it into your browser, I think the software (i.e. the Zoom desktop client) will automatically load onto your computer within a few moments and then you should see a button to allow you to join the meeting. You do need your computer to have, or be connected to, speakers so that you can hear the meeting. A camera (webcam) built into your computer or connected to it is optional but without it other people 'in' the meeting will see you only as a black rectangle.

Bernard Rhodes meeting is tomorow, Tuesday 14 November at 19:30 LONDON TIME
The link to join the meeting is:
Join our Cloud HD Video Meeting https://us06web.zoom.us/j/2536740617?pwd=VFdMOGxWRDNzK1Z4NkxpTkU1a3ZUZz09

As for a summary of the meeting something will probably appear in the Amateur Yacht Research Society magazine but it will probably only be a brief summary. You will receive the magazine if you choose to join the society - its £10uk pa payable by paypal to be an 'electronic' member meaning that you recieve the magazine electronically. For those in the UK we offer the option to receive the printed magazine by post for an additional £20uk pa.

Re. the failure of 'Team Phillips', that seems a long time ago now, but from talking to one of the people who built it they did have trouble with outgassing of the foam core affecting bonding of the skins and perhaps that contributed to the failure.

 

[brian eiland]

The French builders are keeping their long thin bows on, even when the central hulls are additionally loaded with headstays,...cheers