New High Performance Monofoilers

Bistros!
Thanks for replying. I understand, Tom Speer is the man to discuss with, not Doug. I feel a little bit said about Doug. We have to watch out for Ernest Seaman (spelling), though. When Doug was exused from the R/C sailing some years ago Ernest rapidly made his best to replace Doug.
Regards,
Booster

 

From what I have been told, this "ernest" person was excused from that forum as well. Perhaps it was a nom de plume for the other excusee.

 

while I would never want to interrupt a perfectly good argument I do have a good old fashioned stupid question

if I wanted to run a semi displacement hull at cruising speed ( in the case of this boat its about 10 knots ) would I get any appreciable benefit out of providing a little lift with several small inline foils affixed to the keel one forward and one aft. My thinking is that if I even just get ten or twenty percent lift will it offset the extra drag enough to make it worthwhile

some one throw me a bone
the rest may commence with round 2
and may the best man win

waves hand in a vertical motion between the combatants and steps back quickly

B

 

Sounds more like a take-on-all challenge!

I would start by rephrasing your question, would the additional drag of the foils be offset by the reduced drag of the hull with a lower effective displacement. Now we have something that can be analysed. For a given type of foil it should be possible to obtain lift/drag values for various areas over a limited speed range. If you have the lines of your boat you can feed them into something like FreeShip and get hull resistance at various displacements. I can't answer your question directly but perhaps that will get you going on your own answer. Let us know!

As for the rest of you, keep it quiet out there, some of us are trying to get some sleep!

 

First of all, there never should have been an "argument" here. And there is no need for one to continue.

Basic physics dictates that there is no such thing as a free lunch. If adding lifting foils would automatically result in higher efficiency and higher speeds, every hull out there would have foils. Oil tankers, military ships ... everything excepting submarines would have lifting foils if it reduced fuel requirements and increased speed. This isn't new technology we are talking about here.

Very light weight planing hulls that are pushed to speeds well above hull speed seem to benefit from lifting foils significantly reducing wetted surface area, allowing much higher speeds using the same power required for planing.

To achieve benefits from lifting foils, reduction in drag from the reduced wetted surface area has to exceed the added drag of the lifting foils - or why bother? Net drag has to be reduced for there to be a benefit. Keeping the drag from the lifting foils to a minimum is best achieved by low hull weight - with less mass to lift, the will be less drag from the foils.

All this to say I doubt adding lifting foils to a semi-displacement hull would result in improved efficiency at semi displacement speeds. Unless the foils are lifting a significant wetted surface area out of the water, there is little to no net benefit.

The benefits available from lifting foils are much easier to quantify at much higher speeds. Most of the boats described in this thread are lightweights traveling at well over 10 knots while foiling - many capable of exceeding 20 knots or more.

--
Bill

 

KissKut Monofoiler

Here is a new picture from Hugues De Turckheim, designer of KissKut. I guess it is a monofoiler because it is supported off foils on the single hull. It has a bi-foil system when foiling...Here is a link to the original thread: http://www.boatdesign.net/forums/sailboats/kisscut-new-swiss-foiler-29106.html
The designer said the project has been delayed and that he would keep me abreast of developments. He did not answer my question on projected cost. Future updates by me will be here.....

 

no weather heel sailing

 

KissKut

Why do you say that? I see nothing that prevents veal heel-what am I missing?

 

Well, the matching-up, as it were, has taken place at the Moth World Championships, held at the Columbia River Gorge over the summer. The results of how Bora "matches-up" with former champion Rohan Veal is as follows:

#1 and World Champion.... Bora Gulari

#6 and now resigned from Moth competition... Rohan Veal.

It should be interesting to note that Bora won this title going away from the rest of the fleet due to superior boat speed, handling and tactics in the often tricky conditions present every day in the Gorge.

Going Away.... and Doug wasn't anywhere near the action. What a shame.

 

well...

why is there "tow" in the front wheels of cars. also why are there differentials when the rear wheels are linked.

do a little connect the dots.
alternatively think about what limits ride height and weather heel in a moth

 

=============================
I don't like the two struts and don't see a reason for them(on this boat) but so far I can't see something that disqualifies the thing from using veal heel. I think the mainfoil looks too large but thats hard to judge since the level of detail is not that good. When I get a chance I'll lay it out to scale and see if there is something that shows up then. By the way if you're going to the South of France Hugues will show you the boat and take you to see Hydroptere. PM me for details...

 

KissKut-16.5 degrees veal heel

I see some problems with veel heel-if anybody else does and can articulate it I'd sure like to hear it. Appears I have the wing angle slightly too low-that means max veel heel would be greater than this while maintaining the same clearance between buoyancy pod and water as between hull and water. I still don't like the twin vertical struts or the 7'(est) long main foil. A couple of things are immediately obvious: there is too much mainfoil area* and along with the twin struts that results in a drastic increase in wetted surface with veal heel when keeping the leeward tip the proper distance below the surface.

* estimated 3.5 sq. ft.; foil loading with 320lb crew=93lb/sq.ft. Moth foil loading=160lb. approx. This foil could be shortened to approx. 4' with a 6" chord. and have the same foil loading as a Moth with TWO people on board. That would help everything...

Rough Sketch @16.5 degrees veal heel:

 

kiss 2:nd order Kutta

Hi!
KissKut seems speedy. The Reynold numbers will be high. Weber will be pleased with high numbers. Strouhal may be pleased if a horn is installed. To really kiss Kutta 2:nd order vortices a better cunningham is needed in the Sketch above.
Regards,
Booster

 

KissKut --no veal heel?

Found this answer on DA to the question of veal heel for a twin strut boat like KissKut:

from fmg on DA :
"Gui - The boat should work fine healed to windward; although it does have the added WSA of the 2nd strut and that two struts doubles the number of surfaces to cause ventilation on the main foil. Ventilation leads to crashes and crashes = SLOW (which is also why a RACING FOILER SHOULD NEVER JUMP, FYI Doug). Also, with the dual struts healing to windward mightn't be completely necessary in order to get a good VMG upwind, as there's more surfaces providing lateral resistance in the upright condition."-----------------
And along with my previous sketch these picture's are worth 1650 words:
Both boats shown have twin struts-one is Bethwaites Foiling 49er with a canard configuration and the other is Clive Everests experimental twin strut foiler with a conventional configuration-both are shown sailing with veal heel- case closed.

 

Doug:

Nothing in science can be proven by quoting forum posts or posting pictures. Proof is a mathematical and scientific determination, not an opinion.

Veal heel as you like to call it is a condition in which the combination of lift vectors from the heeled foils generate additional windward lift beyond that of a vertical foil. This manifests itself in faster VMG windward than a foiler going upwind in a perfectly vertical state.

Many boats can heel to windward while sailing upwind. That is no indication that their VMG is better.

The twin strut foilers you use as "proof" for your concept are heeled to windward - to that I agree. I do not accept without sufficient data that their VMG is improved by doing so. This is the crux of the issue - given the increase in surfaces that can cause ventilation and the problems with a hydrodynamically more complex configuration, there may be no improvement in upwind VMG (and objectively there may be some improvement). Without testing, data collection and analysis you can not draw conclusions. There is not enough information to draw any conclusions as you have.

To be perfectly clear, I'm the guy who proposed a concept featuring two-strut main foil which you completely dismissed and ridiculed a month ago, so I am not against the concept. I'm actually happy you've come to think of my concept as workable! My idea is now Doug Lord approved!

You can't confuse science with conjecture. Case NOT closed.

--
Bill