60' Moth-A Preliminary Detailed Design Exploration

Doug Lord · Sep 16, 2006

again

Randy, your exact words were: " However, if it could be built it has the potential to compete with ORMA 60's". Of course you've said a lot of things.....
One additional thing: for the Quad cat to even use two foils on each side and sail on only two at a time it needs to have really great sail control allowing the boat to constantly fly a hull upwind or downwind. If you added movable ballast-lets say the same as the monofoiler- you could increase the max RM of the Quad cat from 253,000ft.lb. to 434,000 ft. lb. but heres the rub: the control range of RM is between 253,000 and 453,000 ft. lb.-IT CAN"T GO TO ZERO- or below 253,000 while flying a hull.
On the other hand the monofoiler can go from 0 to max RM while on foils at any time giving FAR SUPERIOR CONTROL of RM.
So just from a control standpoint I think the monofoiler has a chance against a quad cat.I'm thinking that because of it's better RM control and selfrighting/selfrescuing capability the 60' monofoiler could be pushed harder in a race than the quad cat with far better control and seakeeping ability.
But generally-like I said in the first post -a well designed multifoiler SHOULD beat the monofoiler.
But the 60' monofoiler keelboat could provide speeds "competitive with ORMA 60's"(quote by RHOUGH) on a self righting and/or self rescuing platform.
It's a DESIGN EXPLORATION that you yourself have said has real potential against multihulls . You say it can't be built; others considerably more knowledgeable than you or me say that it CAN be built......
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RHough said:

Doug, I'm impressed.

I'll be the first to say when my knee jerk reaction is in error.

I still feel that SA/WSA is too simple to be of much value. Although Doug is correct that a boat with a higher SA/WSA ratio should be faster.

I took the liberty of generating some drag and power curves for Doug's 60' CKSDBMF and an ORMA 60' Trimaran. I considered both wetted surface (skin friction) drag and induced drag fom the foils on both boats. I did not consider wavemaking drag, spray drag, or foil profile drag. Both boats will probably have similar additional drag in these areas.

Bottom Line:
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Doug is absolutely right. The 60'MF is potentially faster than a displacement multi-hull.
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I used Doug's Figures for foil sizes and weights. The 60'MF rig ends up being about 100' tall, which just happens to be the limit for an ORMA 60.

The ORMA 60 has only a 151% advantage in Sail Carrying Power over the 60'MF

My calcs show that the 60MF should be able to lift and foil just over 10 knots of boat speed. The drag polar peaks at lift off, then goes down until the boat speed is 25 knots or so. The negative slope of the drag curve (pink) is due to fact that the CL required of the foils goes down faster than the drag due to skin friction goes up. I used an AR of 7.5:1 (15x2) for both the main foil and the rudder foil and a max CL of 1.3.

The drag curve for the Tri (blue) has a flat area from about 10 knots to 20 knots for the same reason. The foil produces the needed lift at lower CL values as speed increases.

Somewhere between 20 and 25 knots the MF has lower drag than the Tri and the MF enjoys a drag advantage at all speeds above 25.

I added a line (yellow) to show the relative drag of the two boats.

The violet line shows the 151% power advantage for the Tri.

Right about 35 knots boat speed the Power Advantage curve meets the Drag Penalty Curve and above that point the MF should be faster.

I did some basic rig efficiency calculations to get a feel for the total drag vs power available for the two boats. These curves are purple for the MF and brown for the Tri. It is interesting to note that below about 15 knots boat speed the MF has very little power to spare. From 15 to 30 knots the percentage of available power required to equal drag is almost the same, and above 35 knots the Tri has more spare power than the MF.

These very basic calculations show that at 50 knots both boats have power to spare. This cannot be true, since ORMA Tri's have not hit 50 knots. I made no attempt to estimate parasite drag for either of the boats. At boat speeds over 15 knots or so, the aerodynamic drag of the hull and rig start eating into that extra available power and in practice all the extra power seems to be used somewhere in the 40-45 knot range.
++++++++++++++++++++++++++++++++++++++++++++++
I still don't think that a 60'CKSDBMF can be built that will foil reliably if at all. However, if it could be built it has the potential to compete with ORMA 60's.
Click to expand...

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Dan S · Sep 16, 2006

RHough,

Just to let yon know, you are up against the king of mental ************, who long ago went blind. Doug’s mo is the more “technology” the better, regardless if it’s beneficial. I’m sorry to tell you that you can’t win this war; all you can do is fight the good fight. I mean how can anyone compete against someone who has no job, and surfaces the internet all day.

RHough · Sep 16, 2006

Yes ... I have first hand experience trying to get Doug to think within the bounds of physical possibility.

It's kind of like trying to teach a pig to sing ... all you do is frustrate yourself and annoy the pig ... and it still doesn't sing.

RHough · Sep 16, 2006

Doug Lord said:

Randy, your exact words were: " However, if it could be built it has the potential to compete with ORMA 60's". Of course you've said a lot of things.....
One additional thing: for the Quad cat to even use two foils on each side and sail on only two at a time it needs to have really great sail control allowing the boat to constantly fly a hull upwind or downwind. If you added movable ballast-lets say the same as the monofoiler- you could increase the max RM of the Quad cat from 253,000ft.lb. to 434,000 ft. lb. but heres the rub: the control range of RM is between 253,000 and 453,000 ft. lb.-IT CAN"T GO TO ZERO- or below 253,000 while flying a hull.
On the other hand the monofoiler can go from 0 to max RM while on foils at any time giving FAR SUPERIOR CONTROL of RM.
So just from a control standpoint I think the monofoiler has a chance against a quad cat.I'm thinking that because of it's better RM control and selfrighting/selfrescuing capability the 60' monofoiler could be pushed harder in a race than the quad cat with far better control and seakeeping ability.
But generally-like I said in the first post -a well designed multifoiler SHOULD beat the monofoiler.
But the 60' monofoiler keelboat could provide speeds "competitive with ORMA 60's"(quote by RHOUGH) on a self righting and/or self rescuing platform.
It's a DESIGN EXPLORATION that you yourself have said has real potential against multihulls . You say it can't be built; others considerably more knowledgeable than you or me say that it CAN be built......
==================

++++++++++++++++++++++++++++++++++++++++++++++
Click to expand...

"" However, if it could be built it has the potential to compete with ORMA 60's". " ... allow me to rephrase to make my meaning CRYSTAL clear ...

"If you could built the Fantasy Foiler that requires anti-gravity and unobtainium, it has the potential to compete with a handicapped ORMA 60'"

Gee Doug what happens when the RM goes to zero?

What direction would the boat sail? (Hint: all you need is grade 8 math to figure out the answer)

The really great sail control is required of both boats ... it can't be done within the rules so neither boat has an ice cubes chance in hell of ever working.

Doug ... you seem to know all the designers that are "considerably more knowledgeable" than I ... get just ONE of them to post here in this thread in support of the Fantasy Foiler idea. Since they are "considerably more knowledgeable" than I am, why don't you quote them instead of quoting me?

You keep going on about it being a design exploration ... give me a break ... read Tom Speer's design exploration for his offshore trimaran ... calling your fantasy a design exploration is an insult to Tom's hard work.

You have not come up with one idea to solve any of the obvious problems with the "design" ...

I have no doubt that your 16 foot Aero-Skiff would foil in fine fashion according to your research ... what does the fact that it didn't foil well (or at all) tell you about how able your design and engineering skills are?

As far as I know you haven't been able to get a canting keel and sliding deck ballast to work reliably on a displacement hull ... much less a foiler ...

Admin · Sep 16, 2006

I'm afraid this thread is going in a very negative direction and will only get worse, so I'm going to do something uncommon for the forums here and go ahead and lock it. I only desire to keep the forums focused on ideas; personal attacks back and forth and back and forth are a waste of bandwidth. Locked.

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60' Moth-A Preliminary Detailed Design Exploration

Doug Lord Guest

Dan S Junior Member

RHough Retro Dude

RHough Retro Dude

Admin Administrator

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