Minuet Yachts: a 2m fun boat-can the design be improved?

I can understand the fantasy dream appeal of a "micro" 60 type high performance boat that could give the impression and sensation of high performance. Unicorns, dragons, vorpal swords and cloaks of invisibility! I used to love playing Dungeons and Dragons about thirty five years ago. I pored over the Dungeon Master's Guide and thought Gary Gygax a genius. Escapism, pure and simple. The Minuet's magic is that the operator could envision themselves at the helm crossing the southern ocean while never leaving the safety of the breakwater.

A Minuet-sized mini-60 will never plane no matter how many magic foils you sprinkle on it. 350lbs displacement at 2 meters in length runs headlong into the miserable party pooper called physics. I'm sure you could "believe" it is planing though.

The Minuet's "magic" lies in the fantastic illusion of speed due to the operator's low eye level to the water, and it's tiny/cute portability. A three foot chop could be easily transmogrified into huge swells rounding the Cape of Good Hope.

I think the Minuet magic is probably pretty well refined and optimized already. I doubt there is much more performance (if any) to be found in two meters length, and I also think that changing the operator's position will reduce the illusion of speed and perhaps kill the magic. The light weight of the Minuet is a key to the performance already achieved.

Sure, you could make a two meter boat much more complicated (and expensive) to sail with lots of foils (DSS, twin curved boards), asymmetrical kite and whatever other features you desire. Would it perform dramatically better? Doubt it, but it probably would deliver the sensations and complication desired.

What matters in this market segment is the feel and sensation, not the measurable and factual. Go for it and build one - it will be a success in terms of what it delivers to you - but just don't line up against a 16 year old in a Laser.

--
CutOnce

 

Little 60

Thanks for the good comments. As you can see below, the concept of the Minuet has inspired a totally different boat-no longer 2m LOA. While the Minuet inspired the Little 60 they are only similar in that they are both under 10' long.
Upwind, the Little 60 would do hull speed and thats about 4 knots. Downwind is another story: the idea is for the boat to plane. But will it?
In sailboat design the physics are expressed in various formulas and ratios.
Three of those are applicable here( + Max RM and Max Pressure) :
1) SA/D-(SA in sq.ft. divided by the volume of displ. raised to the .667 power)
Little 60= 37(downwind only)
Laser= 25.58 (upwind and downwind)
Generally, higher is faster.Downwind the L60 is lighter and carries much more sail than a Laser but its DLR(displacement length ratio) is higher than a Laser so around a course the Laser would certainly win)
2) SA/ton( (2200/all up boat weight) X SA To plane a boat needs at least 500 sq' per ton:
Little 60=722(downwind only)
Laser=514
3) A convenient measure of Sail Carrying power is Bethwaites SCP= RM/distance of CE to CLR and then SCP/total weight( higher % is better) :
Little 60= 100(downwind only)
Laser = 62.1
and SCP/ Total Weight (generally used as a measure of a boats ability to plane up wind-used here just out of curiosity-any boat would need to be 30% or above to plane upwind) :
Little 60= 32.9 % (downwind only-but a reflection of the boats power to carry sail)
Laser= 18.5%
4) Total RM:
Little 60= Upwind 515ft.lb; Downwind 750ft.lb
Laser= 608.65ft.lb-upwind and downwind
5) Max pressure before dumping power(reefing etc):
Little 60= 1.46 lb/sq.ft.
Laser = .8 lb/sq.ft

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The sensation of sailing one of these will be a tremendous "cool factor" and planing off the wind will just add to that. Max planing speed approx. 12 knots for the Little 60.

 

Doug

Sweet! I want to build a proto!

Bob

 

Little 60

===================
Thanks ,Bob. Just heard from my friend and he goes along with the wider boat and " swivel and push" crew seat mentioned last night. There's no telling when or if we'll actually do this. I'm very interested but am commited to another project for a few more months(barring any more interuptions from Real Life). We will continue to refine the design parameters and get to the point that an actual design can be done. All comments are welcome as well as any ideas along the lines of a max performance version of the Minuet concept. The idea of no ballast and planing off the wind is really cool-maybe we can make it happen.
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"White Dwarf", in another thread, says he is 198lb and that this boat planes with his weight regularly. It is 8' LOA X 4' wide with 48sq.ft.SA. The Little 60 is 9'6" LOA by 4'6""(tonight) wide with a 250lb crew and 115sq.ft. of downwind SA......
For those still doubting: if you scale a boat up to another size-say this 8 footer up to 9.5',the weight varies as the cube of the length and the 198lb crew in the 8 footer becomes 331lb! So let me be clear-as pointed out in the previous post for numerous technical reasons and because of the known performance of the Firebug, the Little 60 will plane downwind. Interesting side note: DLR of Firebug= 284; DLR of L60=182(so far)

 

What is KM?

Sinking the bottom a few inches deeper will certainly help the cause, but not as much as you may suppose.

I estimate the VCG of a person sitting with his/her legs extended (like on the floor) is between 7 to 12 inches, depending on the build and tallness of that person.

This ends up putting the CG of the person higher than the Vertical Center of Buoyancy of the boat almost no matter what. The important thing is to keep that person's VCG well within the Meta Centric Radius (MCR)of the hull. As long as that's done, the boat will at least float right side up.

Having reasonably high sides, even without flair, helps create a new MCR for the heeled hull, allowing a reasonable range of heel, before vanishing stability sets in.

I did stability calcs on this design, years ago, assigning the VCG at 12 inches above the waterline, using buoyancy shift to determine stability. I found the boat to be stable up to 45 degrees of heel, which I consider ample warning to either release sheet lines, round up into the wind, or fall off.

 

I have always assumed KM means Metacentric Height, although I’m not sure what word K represents. Its probably same as Vertical Center of Buoyancy. For my solo sit-on-the bottom canoe it usually comes out around 1.2-1.4 feet which is above my VCG.

For double-bladed paddling high sides are a no-no of course, and I consider myself lucky if my canoe designs will heel much past 20 degrees without flooding - but without being warned to holding on I would probably roll out of the boat before that anyway. The canoe has low primary stability and bobs over waves instead of rolling. It never ships water even in heavy conditions despite only 5" freeboard.

It's quite different from my kayak, which has too much stability and rocks when a wave goes past, but at least the cockpit keeps me inside. The kayak is my choice for observing and photographing wildlife, I can lean out and look over the side - dare not even think of that in the canoe . . .

This is a stretched version (8.8' LOA/8' LWL) of the the 7.5 foot design mentioned earlier, Km = 3.44' which is enough to walk around and should make a stable little row or sail boat. ONly needs 2 ply sheets and super-easy with no lofting required, but I'm not planning to build it though. Flooding angle is 40 deg with one aboard. Might make a nice catboat . . .

 

Little 60

AK, Sharpii, what do you guys think of the "little 60" so far? Pretty much every thing is close to being finalized except length(DLR)......


===============
--LOA 9'6"
--Beam 3.5'(may be changed to 4- 4.5' to facillitate sliding inside seat)
--Displ w/crew 350(250lb crew-allows wide range of crew weight by adding ballast in center for lighter crew)-boat could be lighter
--Upwind SA 50 sq.ft.
--Downwind SA 115 sq.ft (asy spin or Hoyt-Lord system)
--DSS extended 2.5'to leeward. RM from foil at about 20 degrees angle of heel at 8 knots(just planing) : around 300ft.lb-more than a three foot keel with an 80lb bulb canted 90 degrees! DSS effectiveness on this boat much less upwind approx. 40ft.lb at 5-6 knots.
--DSS foil fits in sealed trunk in bottom of boat. Vertical position of DSS trunk exit is critical to keep foil low enough relative to the surface-and is very difficult to achieve in a boat like this-could be a DSS deal breaker.......
--Twin curved daggerboards. On the Minuet the crew has to sheet the jib every tack-on this boat the jib would be self-tending so racing workload for crew moving daggerboards tack to tack would not be excessive*. Daggerboards could be made in same mold as DSS foil.
--Bow sprit moves side to side. Main is similar to model main and does not require full battens. Upper "gaff" fits in bushings at top of mast.
--Boat would probably use twin rudders to go with the twin curved daggerboards.* If desired, windward rudder could be raised with same action as raising windward daggerboard.
--The boat would be designed to carry 50+lb of ballast but would be tested without it. Possibility of crew moving to weather-problem is opening cockpit wider and facilitating swamping in a knockdown- and holding crew in position a 30+ degrees angle of heel. A narrower-more or less "form fitting" cockpit would keep crew in center. Crew seating could be designed to allow crew to sit angled to weather?
--Rig "gaff" similar to smaller model in picture above. Allows an advance planform w/o requiring full battens but I'm leaning toward a simple peaked up square top instead.
--Spinnaker system could be asymmetrical roller reefed on long or short bowsprit and bowsprit could be moved side to side if desired. Spinnaker could be left up like the WETA trimaran. H/L spinnaker system from model may be easier to handle but requires trough in forward deck ahead of forestay and a tube under the deck sealed from the inside of the hull.
------------

Tentative Details:
1) SA/D-(SA in sq.ft. divided by the volume of displ. raised to the .667 power)
Little 60= 37(downwind only)
Laser= 25.58 (upwind and downwind)
Generally, higher is faster.Downwind the L60 is lighter and carries much more sail than a Laser but its DLR(displacement length ratio) is higher than a Laser so around a course the Laser would certainly win)
2) DLR(Displacement /length ratio =Displ in long tons divided by (LWL/100)raised to the .667 power)=185
3) SA/ton( (2200/all up boat weight) X SA To plane a boat needs at least 500 sq' per ton:
Little 60=722(downwind only)
Laser=514
4) A convenient measure of Sail Carrying power is Bethwaites SCP= RM/distance of CE to CLR and then SCP/total weight( higher % is better) :
Little 60= 100(downwind only)
Laser = 62.1
and SCP/ Total Weight (generally used as a measure of a boats ability to plane up wind-used here just out of curiosity-any boat would need to be 30% or above to plane upwind) :
Little 60= 32.9 % (downwind only-but a reflection of the boats power to carry sail)
Laser= 18.5%
5) Total RM:
Little 60= Upwind 515ft.lb; Downwind 750ft.lb
Laser= 608.65ft.lb-upwind and downwind
6) Max pressure before dumping power(reefing etc):
Little 60= 1.46 lb/sq.ft.
Laser = .8 lb/sq.ft
7) Movable Ballast system(crew) seat swivels and slides side to side. Allows crew movement F&A and side to side.

---
updated sketches to follow-original rough sketch:

 

The 'KM' of my CoalCar-12 design is 2.5 ft, taken at its 9 ft max load WL, and a displacement of 500 lbs.

I was somewhat off when I said in my last post that it was "stable up to at least 45 degrees of heel." Actually, now that I dug up the diagrams, the six inch side deck will roll under at about 35 to 40 degrees. At that point, there will be some righting moment left, so the boat will flood before it flips, one of my primary design goals.

Once it floods, the wind can push it all the way over on its side, without dumping the skipper. Once the wind abates, the buoyancy belt on the low side will right the boat. The skipper, who has hopefully doused sail by now, will then be able to bail the boat out.

The ballast is intended to insure the boat rights itself (while half full of water) without any help from the skipper. It must be denser than water to work. Sand or gravel, is what I had in mind.

There will be enough water on board to float much of the skipper's weight. It would be like sitting in a bath tub.

 

A couple of questions.

1.) How does the skipper raise and lower the mainsail? (something he will have to do if the boat capsizes)
2.) How does he raise and lower the spinnaker? ( something he's going to have to do when ever he changes from downwind sailing to upwind sailing)

The paradox of designing a very small boat is that it is like designing a very large one.

With the large boat distance between vital boat keeping areas, such as the anchor, the halyard, and the helm is the primary concern. Especially if the boat is being single handed.

With a very small boat, the skipper makes up most of the displacement, so if he dare move much , fore and aft, he will put the boat wildly out of trim. So everything must be with arms reach, with the skipper having to move little, if at all.

Why go with the curved dagger boars when you have the DSS foil? That seems to make the boat needlessly more complicated.

I think what you have here is a very complicated small boat that won't go noticeably faster than a slightly bigger boat with much simpler (cheaper) technology.

If your design goal is to simply test these technologies at a smaller scale, then I think your design is justified.

If it is to make a boat that is just a few feet shorter than a moth foiler, then I think your design misses the mark.

With the 'minuet', I think the designer hit a sweet spot that will be very difficult to improve on. The IOR hull form, with its pinched bow, wide beam and displacement hull (they weren't designed to plane) and tall Bermuda rig, meshed completely with the desire for a tiny boat, with a reasonable range of stability, with no outside ballast, that is easily transported to the launch site, launched and retrieved.

If I were to change anything, I would try a balanced lug and an un-stayed mast. That would further cut down set up time. But then the boat would look odd and maybe have more top hamper.

Your proposed boat would likely be faster, and maybe three times as expensive. It would also take longer to set up, longer to launch and retrieve, and will take up more storage space.

I doubt anyone who would buy a 'minuet' would even consider what you propose.

 

I like the swiveling seat idea but like Bob, to me it seems too complicated. If it turns out to go like a bat out of hell it should catch on though.

 

Little 60

==========================
Thanks for the well thought out comments, Sharpii!

1) Hadn't got that far-probably with a halyard led to the cockpit. Mast will be sealed and there may be some masthead floatation.
2) Either by hand with a halyard/downhall led to the vicinity of the cockpit if the Hoyt-Lord model system is used or-more likely- the sail will be roller furled and left up upwind like the Weta.
3) I agree.
4) I think it is essential that the skipper be able to easily move side to side and fore and aft-this is essentially a dinghy and without that facillity performance would be severely compromised.
5) The daggerboards need to be there because we don't want a single board. The idea is to sail as much like the Open 60's as possible. As for DSS, there is a good chance it won't fit in properly but I have a lot more work to do down the line to figure that out-with the help of Hugh Wellbourn. The Open 60 Class association as approved DSS and -if they don't go one design-we may see DSS on a full size 60. Besides, I want to experiment with it.
Both the daggerboards and DSS foil can be made out of the same mold -and that means a compromise in the daggerboard curve. If the DSS foil turns out not to work with this hull the daggerboards will have significantly more curve,hence significantly more vertical lift.
I completely disagree with your assesment of the performance potential ifhalf of this stuff works. The numbers say that the performance potential is pretty outstanding ,particularly off the wind. But at least two of us that are interested in this thing like the challenge and techno design "complexity."
6) I'd say the design goal is for us to experience a little bit of the Open 60 experience and to perhaps allow others to do the same.
7) This concept has nothing, even remotely, in common with a Moth foiler.
8) Well, the Minuet has inspired several of us to think of the possibilities of something like this. It is a really neat little boat! It has to be said that anyone who really likes the Little 60 concept would prefer it to the technology encompassed in the Minuet.
--
Thanks again for the comments....

 

Little 60

=========
AK, compared to many, many race boats it doesn't seem that complicated to me-maybe I should say it is "deliciously complex" in a performance sailing way? It is not conceived of, necessarily, as a backyard builders boat: it is an all out technologically advanced(I hope) carbon and foam race boat with features found on no other "sit-in" singlehander anywhere. The design aims to "celebrate" its Open 60 lineage.
Keep in mind, the full size Open 60's are among the most tecnologically advanced racing monohulls and are also single handed!
Thanks for your thoughts...

 

Doug you may want to do a weight study. from that you can create a displacement curve.
That will tell you how much boat you will need it the water. Your sketch looks a little arse light for what your trying to carry

 

Little 60

=====================
Thanks,there is a lot of work to do if I decide to do a complete design. Still working on the basics, like length. The biggest question is whether a DLR of 185 is acceptable or not. It can probably be made longer with very little weight gain. Second question is what is an ideal angle of heel for the DSS foil to be effective on a reach-and how will that impact planing. Then what shape of hull will permit that at the estimated weight. To answer the second question that I'll have to talk with Hugh Welbourn.
Can't go too much further now, at any rate....

--In the rough illustration below note the position(red line) of the upwind Center of Buoyancy-it will be very close to this point on the final design- which is 53% of the LWL aft of the forward end of the waterline. Down wind this will shift a bit aft and the bow will pitch up and the edge of the lee side of the transom will be a bit below the static waterline when the boat is on a plane:
click on image-

 

Little 60-design discoveries

To properly immerse the DSS foil at 2 chords below the surface the boat would have to sail at about a 20 degree angle of heel. The boat would use a 4.75" chord 63412 foil section for both the curved daggerboard and DSS foil. At approx. 8 knots,if the lee daggerboard was deployed it would be capable of producing about 76lb. of vertical lift along with the approx. 160 lb of vertical lift from the DSS foil for a total of 236lb of vertical lift at 20 degrees(minus sail down force(canting mast?)). The all up displacement as of now is about 350lb so approx. 67% of the boat would be supported by "foil assist".
However, the est. pounds per in immersion is 94, so if the foils develop 236lb of vertical lift then the boat will rise 2.5" + planing lift, reducing foil distance from the surface to 7" or 1.47 chords or a bit less. Unacceptable.
At the same time the lift would reduce the wetted surface about 5 sq.ft. or
5.1 times the planform area of the DSS foil. Good.
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This is all based on approximations and estimates but what is clear is that the hull design will have to be substantially different than the first sketches show.