Jump to content

Recommended Posts

Compare tri's with this equation...    Length to the 0.3 power times Sail Area to the 0.4 power divided by Weight to the 0.325 power.  All dimensions in meters/kgs.  For weight use number of expected crew added in there and figure the published weights are 10% less than what you will really get.  For Sail Area just use published upwind sail area.  Bigger number is faster boat.  https://texelrating.org/wp/?page_id=31

Of course it is an approximation but will serve as a way to compare two similar tris.  

Not too many multihull polars published based on observed data, but some manufacturers use software to guesstimate them.  The ones I have seen basically show 1) 45 degrees off the wind to weather the boat goes a specific percentage of windspeed regardless of wind speed; 2) for most the fastest course dead downwind is to gybe 90 degrees; 3) most boats have a fastest point of sail with the wind abeam.  No earth shattering surprises, right?

You can get 2 of speed, comfort, cost.  If you want fast and comfortable; costs a lot.  If you want comfort and cheap, boat will be slow.  If you want cheap and fast, better forget the head (or anything resembling comfort).

 

Link to post
Share on other sites
4 hours ago, soma said:

How big?

good question , a corsair 24/27, for playing around the harbor $$ 25k to 35k

a corsair 28/31 or dragon fly 28 for the head and some over night stuff, $$ 50k t0 75 k

then the telestar 28 for some comfort less speed, one for 40K

any other idea's like to keep under 100k the less expensive the better

Link to post
Share on other sites

Once in a while you can find an F31 around your max.  I've always been partial to the Ultimate Cruiser even though it is heavier and slower...but nice creature comforts/layout (to me).

Link to post
Share on other sites

Christmas day, so bored...here is the calcs based on published data for Corsair Fboats.  The TE and TW are top speeds upwind and downwind (guesses).  F27 is actually a little faster than an F242.  Top speeds shown for F242 is based on my experience with one. The TCFs are a reasonable guess as to how much faster one boat is than the other upwind in average conditions.  Again, no surprises, bigger is faster, more comfortable and more $.  

image.png.218224e090622f436a4a3148cd816a9f.png

Link to post
Share on other sites
2 hours ago, MultiThom said:

Once in a while you can find an F31 around your max.  I've always been partial to the Ultimate Cruiser even though it is heavier and slower...but nice creature comforts/layout (to me).

open this up for PHRF corsair ratings

Corsair Trimarans Ratings and Adjustments (regattanetwork.com)

couldn't find it for dragonfly or telestar 28

Link to post
Share on other sites

MOCRA, as has been pointed out, seems to have the most complete ratings for tris. All F boats and Dragonflies should be there.

Since the subject is about ratings, is ORR multihull rule going to be the ultimate answer? Seems pretty comprehensive and a lot of monos have them.  I dont see many multis though

Link to post
Share on other sites

OP seemed to want to determine which boat under 100K$ gives most 1)comfort and 2) speed for dollar; MOCRA ratings won't really get you there since folks tend to have non standard sails to get an "edge" if they are racing.  Of course, the MOCRA rules have a rule for every attempt to get that edge (rotating mast diameter, 7/8 jib measurement, yadda yadda).  I'm surprised we don't see batwing sails with dips at the measurement points :).   Underlying the MOCRA rules is the same basic L*SA/W to various powers which, IMO, provides a good way to compare platforms.  Answer, of course, is an F27 which, though a venerable beast, is comfortable enough and fast enough and old enough that it provides the best (again IMO) compromise.  Second best bet is an 1995-1998 vintage F31.  In the triangle of choices, I chose cheap speed and eschew comfort. 

Link to post
Share on other sites

SImple answer is if you want comparatives to decide which multihull is best suited to your requirements, go to Texel or MOCRA or OMR rating web sites and get real measured information which includes additional sail area and modifications, not just sales/designer prototype data.

And be aware that some multihulls may rate more or less favourably under one rating system than another. Ie what looks good under Texel/MOCRA/OMR rating may not be as good (or maybe better) under PHRF.

Texel splits its ratings between “offshore” multihulls and beach ones, MOCRA make specific allowances for things like cabins, bunks, headroom etc, whereas OMR doesn’t, it rates beach multihulls alongside condo cats,  the rating being adjusted in the base formula, presumably on the basis of unusually light craft.

I understand that MOCRA also has a conversion equation/factor so that you can compare it to IRC rated monohulls.

Last time (long ago) I looked, Texel point blank rates trimarans slightly faster than catamarans, whereas the others don’t.

Another comparative which will give you another answer is to use Base Speed:

“Base SpeedTM (1.7*Lwl0.5*SA0.353/D0.253) This index gives an estimate of the average speed of a boat over 24 hours under average (or a variety of) conditions. It, too, takes into consideration boat length, sail area and displacement. It has been used to handicap fleets of sailboats of all typesmonohulls, catamarans and trimarans”.

Courtesy of multihull dynamics:

http://www.multihulldynamics.com/news_article.asp?articleID=119

Use real measured and rated LWL, Displ and SA from your preferred rating website.

  • Like 1
Link to post
Share on other sites
10 hours ago, Not for nothing said:

good question , a corsair 24/27, for playing around the harbor $$ 25k to 35k

a corsair 28/31 or dragon fly 28 for the head and some over night stuff, $$ 50k t0 75 k

then the telestar 28 for some comfort less speed, one for 40K

any other idea's like to keep under 100k the less expensive the better

F27 has a head and some overnight stuff. Not much but better than tent camping. Sleeps 3 pretty comfortably.

 

JJ

Link to post
Share on other sites

If you can find ORCAs rating sheet or SFBAMA you'll see real world ratings of a great variety of multis. All that mathematical mumbo jumbo is fairly useless.  Or you could just ask people who have raced on/against those boats for decades.  Not really any mystery involved.  Multithom probably has amassed thousands of hours observing the real world performance of every imaginable Fboat.  And really, what's the point?  If you can find an active fleet and you want to race, any decent multi will be fine, get one that's rated mid-pack and have at it.  For just having good sailing days any good multi will do the trick.  

  • Like 1
Link to post
Share on other sites
2 hours ago, mundt said:

.  Multithom probably has amassed thousands of hours observing the real world performance of every imaginable Fboat.  And really, what's the point? 

I stopped watching this stuff closely a decade ago because, I agree, what's the point?  Racing in mixed fleets is about learning a boat in all conditions since races are held in all conditions (zephyrs to hurricanes).  Racing for ego (winning in mixed fleets) is about ratings and $$$.  Racing in one design is about $$$.  So, by all means, race your boat to learn it in all conditions-it is another way to have fun with a boat.  The most fun racing is a venue where there is opportunity for camaraderie after the race for "lies and libations".  Speaking for myself, of course.  

  • Like 1
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...