4 Meter mono foiler project

just some frames and stongback stuff, looks like I'm doing all the stanchons on the CNC next Friday if the CNC guy can get me in that day......he's also having a hard time opening all my DFX files, so we'll see. (I'm doing a male mold, so lots of foam fairing in my future no mater what. )

 

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I realize it's too late on your current boat but it's been bugging me for a while: I would hope you would be amenable to modifying the rule to allow the LOA to be 4.55m and allowing a potential designer to eliminate the gantry.
The gantry(in my opinion) is a rule induced abberation which is NOT necessary for a successfull foiler design. In fact, there are really good reasons why it should be eliminated:
1) by allowing the hull to be a bit longer the available hull buoyancy is increased so the L/beam ratio can be increased reducing resistance and allowing the boat to achieve takeoff a bit sooner.
2) In my humble opinion, it is somewhat ugly and help creates a "contraption" appearance to some onlookers.
3) When taking off without an F-box(angle of incidence control) a gantry (and transom)drags when the boat is pitched bow up.
4) The ONLY reason for a gantry is to allow the foil footprint to be better on a boat NOT DESIGNED FOR FOILS IN THE FIRST PLACE.
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So whataya say,can the rule be amended to allow "gantry-less" designs 4.55m LOA?

 

just a couple of questions dougie

- have you seen your own "barge foiler" pictures, now thats the definition of ugly, and it has a "contraption" appearance to all onlookers.

- aren't you the guy who used a Motogrip as a tiller control?

why don't you leave the guy build his boat, don't you have a model foiler to go build?

 

no need for that, there is a forum for that kinda thing, Sailing Anarchy

- I think I would lean more towards optional gantry, if you don't want one don't put one on if your going to use one, It can't be longer than 55cm. That way designers could design from there own standpoint. I wanted to design a boat that had a 4 meter hull, that was the first point in my criteria, I would be more inclined to get rid of the gantry all together than to extend the hull, 4meters is such a nice length.


I'm more worried about workability and proof of concept than little evolutions. It looks like I'm going to have an AOI control for the main foil, so I'm not even sure if it would matter that much.
That and I like the Ganrty look, not sure why, looks like a cool wheely bar for my water drag racer. That and who doesn't like a little carbon "bling" on their boat?

 

Sr-71

Aw,schucks....
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Have you figured out how to do the incidence control?
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Seen this pix? Look at it closely....

 

Um.........what pic :?:

 

I thought I got rid of that! I tried to post a pix of a unique monofoiler with twin vertical fins/struts but it wouldn't post. It was a "BMP" file....

 

is it off of a website? mabe just post a link.

 

Interesting perspective on gantries. I can't say I agree with some of the reasoning.

1) Longer hulls weigh more than the same overall length platform with a gantry. Eliminating 18 inches of hull and replacing it with one or so pounds of G4 tubing will weigh less.

2) In addition to longer hulls weighing more, there is significantly more wetted surface area. The length to beam ratio may be higher in a longer boat, but the increased drag due to more wetted surface area would be an issue to quantify.

3) Ugliness (and beauty) is in the eye of the beholder. From a pure engineering standpoint, beautiful is achieving a desired result in the simplest manner. Function dictates form, and that form is technically beautiful if function is achieved.

4) If on-the-water main foil angle of incidence control were a prerequisite for sustained and regular liftoff and foiling, it would be present on all foilers. Most designs need adjustability for a tuning period and during design refinement. Once a design is dialed in, most adjustments can be simplified or eliminated. A gantry equipped foiler may have less drag when angled bow-up - you don't know until tow-testing is done with both options and the drag measured on a load cell. Any other opinions are just wild-assed conjecture.

5) It is a designer's prerogative to achieve lifting foil separation and balanced lift by whatever means they determine best. If they choose a gantry to increase the distance, that is their choice and it is as valid as any other method. You or I have no place criticizing someone else's choices unless there is a repeatable body of evidence to the contrary. The Mirabaud space frame foiler takes this to the logical extreme.

Although difficult, effort must be made to separate personal opinions and irrelevent aesthetic preferences from scientifically determined data.

 

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1&2-Narrower hull would trump both weight(by making the whole boat lighter) and wetted surface-reducing wavemaking drag by increasing L/B ratio in addition to eliminating the drag(well documented in Veals blog) of a gantry in the water. Not opinion-fact.
4- not true. Most people had not realized how "shifting gears" by changing the mainfoil angle of incidence from take off to cruise to high speed cruise could reduce drag until John Ilett came out with the F-box. The benefits are well known by many hydrofoil designers- not just Ilett. Fact-not opinion.
--"Any other opinions are just wild-assed conjecture." Dead wrong.
--Mirabaud,of course, does not have a "gantry".
--Most monofoilers DESIGNED FROM SCRATCH AS FOILERS do not use gantrys.
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And by the way: I was asking a question of Sam in regard to the rules of his proposed SR71 Class. My comments are not criticisms of him but are the reasons why I wanted to see the gantry as an option rather than mandated for a 4.55m foiler.
He has repeatedly asked for comments regarding those rules.

 

bistro's, you crack me up, always trying to mix "science" and "testing" with performance sailboats, thats just a bad idea.

all good points,

"I" especially like the lighter/less drag argument. (thats what I think as well)



as far as angle of incidence control, I think it might be a great idea for this project. First, because a lot of respected and experienced mothies are looking into it and think it's worth messing with. And second, I'm not real sure how this hull is going to sit in the water, I don't want to guess and then find out that I need to yank out the foil case and change its angle.

 

Sam, I think if you calculate the reduction in beam by eliminating the gantry for a given displacement hull you'd find that the longer(narrower) hull would weigh the same or less than a shorter boat with a gantry.

 

well, its unfortunate that a narrower hull will also be "tippier" and therefore harder to sail. I think its going to be pretty hard to keep this boat upright to begin with.

thats true, you never know where your going to get the next good idea. I love any and all feedback.

Sam

 

I don't remember: what were or are your objections to (removable)buoyancy pods like these on the M4? Tames a skinny boat-and I have personal experience with pods on a small "tri" with a L/B narrower than a Moth.

 

I have none, I plan to use some at first as "training wheels" untill my skill level goes up. But I plan to remove them when I don't "need" them anymore, alot of the appeal that the monofoil concept holds for me personally is the balance aspect. if that wasn't the case, I would be building a scaled down trifoiler like hydroptere.