Boats and foils comparison

buckdouger

Anarchist
658
246
With only 6 foils total across 2 boats for the whole campaign I'm not expecting to see a 2nd pair from teams at least until the 2nd boats & maybe not even then unless they fucked up in a big way with 1st set.

Thoughts on the legality of changing anhedral angle?

Doesn't seem to require the unmodified material to remain in the same 3D location, allows for alignment of unmodified area for comparison.

I think that would allow angle changes with minimal mass change via a little bit of filler around the joint if its been designed with that intent.
Are you thinking something like below?

i.e. depending on whether you are allowed to make the comparison on any arbitrarily small volume (A to A, and B to B) , or whether you have to make the comparison on a global volume (C to C), you can either have the change being the purple/blue, or the orange/green volumes and associate masses.

Do they define 'component'? 

I suspect the C to C comparison is the intent, but maybe there's a loophole you have identified.

image.png

edit: duplicate image deleted

 
Last edited by a moderator:
Ok... so 3 have built bulbs and one has incorporated the weight into the full foil (probably making it a bigger area and a larger foil)

Wouldn't you want all of the foil in the water to be lifting in the boat?

Yes there is a drag cost to this, but isn't it better than a bulb that will have drag but provide no lift?

Any thoughts?

 

hoom

Super Anarchist
6,398
528
Orkland
Are you thinking something like below?

i.e. depending on whether you are allowed to make the comparison on any arbitrarily small volume (A to A, and B to B) , or whether you have to make the comparison on a global volume (C to C), you can either have the change being the purple/blue, or the orange/green volumes and associate masses.

Do they define 'component'? 

I suspect the C to C comparison is the intent, but maybe there's a loophole you have identified.

View attachment 342194

edit: duplicate image deleted
Exactly that yes.

 

Rasputin22

Rasputin22
13,388
3,029
Why would you want to?
If a sailor on the boat fell overboard and was lucky enough to miss getting quartered by the foils

pendulump.jpg


then you might still come to grief when the foiling chase boat hit you with its hydrofoils.

If those missed you still have to hope the 4 x 400 HP 4 bladed cleaver propellers don't turn what is left into chum.

Oh sorry, I'm behind the times, 4 x 450HP 5 bladed SS cleaver props at 8,500 RPMs are what the cool kids are running these days...

yysw253018.jpg


 

buckdouger

Anarchist
658
246
Are you thinking something like below?

i.e. depending on whether you are allowed to make the comparison on any arbitrarily small volume (A to A, and B to B) , or whether you have to make the comparison on a global volume (C to C), you can either have the change being the purple/blue, or the orange/green volumes and associate masses.

Do they define 'component'? 

I suspect the C to C comparison is the intent, but maybe there's a loophole you have identified.

edit: duplicate image deleted
image.png

Interestingly hoom's idea looks viable. Now interesting to think about whether it is worth taking advantage of..  In the example of playing with anhedral, the small purple/blue area of modification is the region of highest stress, and so any modification to this angle would either be engineered in with an adjustable junction (I think none are evident in pictures so far), or a modification would have to be done to scarf reinforcements from farther out toward the tip and in the bulb to properly re-build the corner area, at a cost to the benefit this method accrues. 

 

RobG

Super Anarchist
2,873
749
Are you thinking something like below?

i.e. depending on whether you are allowed to make the comparison on any arbitrarily small volume (A to A, and B to B) , or whether you have to make the comparison on a global volume (C to C), you can either have the change being the purple/blue, or the orange/green volumes and associate masses.

Do they define 'component'? 

I suspect the C to C comparison is the intent, but maybe there's a loophole you have identified.

View attachment 342194
I think the foils are connected with a lot more than a butt join + fillet. A foil wing is the entire wing, tip to tip, including the bulb but excluding the arm, flaps and foil systems. Changing from flat to anhedral is going to change a lot more mass than just the fillet.

Until the methodology for measuring the 20% of mass is known, and some realistic estimates for foil changes are available, it's fairly pointless to speculate.

 

justsomeone

Member
203
58
Australia
Until the methodology for measuring the 20% of mass is known, and some realistic estimates for foil changes are available, it's fairly pointless to speculate.
5.10 For components listed in Rule 5.1 that have a “Change allowance” mass percentage:
(a) When such a component is first declared according to Rule 5.5, the Competitor must declare to the
Measurement Committee:
(i) a component mass;
(ii) an IGES file of an exterior component shape; and
(iii) construction drawings showing the internal structure of the component.
(b) At all times when that component is installed on an AC75 Class Yacht with that yacht afloat:
(i) at least 80% of the mass of the component must match the original component; and

(ii) a common portion of at least 80% of the mass of the original component must remain un-
modified and must match all declared versions of the component.

(c) The portion of mass of a component that matches another version of that component is determined
by aligning the unmodified portion of the original and modified components and determining the
mass of all regions where the material substance remains unmodified and in the same place in both
versions of the component.
(d) Material that has been replaced with identical or equivalent material only classifies as an unmodified
region where replacement was carried out as a repair permitted by Rule 5.12.

(e) When checking the shape of such a component against a declared IGES file, the Measurement Com-
mittee may make an allowance for unintended distortion of a component during manufacture.

(f) Competitors may declare a hypothetical “original component” which must comply with the relevant
rules for that component type, but is not required to be identical to the component when it is first
installed and afloat. In this case, the “original component” comprises those regions of the actual
component as-launched that match the hypothetical component, combined with the regions in the
hypothetical component that do not match the as-launched component and are presumed to have
been removed/modified to achieve the as-launched component. The component as first launched
must have corresponding declarations which must satisfy the permitted changes with respect to the
hypothetical “original component”.
(g) If the component when it is first installed and afloat does not comply with the relevant rules for that
component type, the Competitor must declare a hypothetical component that does comply with
those rules, in accordance with Rule 5.10 (f).

Clause c is the kicker

 
Last edited by a moderator:

RobG

Super Anarchist
2,873
749
If the chase boats had foils it would be to reduce the power required to keep up with the foiling monos but then they they would not have enough power to perform their tugboat duties.
A Mercury 400R running at 3,000 RPM uses 29.9 l/hr and at 5,000 RPM uses 69.8 l/hr. A full–foiling chase boat might theoretically keep the same engines and just throttle back to reduce fuel consumption (or shut down one engine and raise the leg) in the order of 120 l/hr.

I'm not going to guess how to get a standard outboard to operate on a full foiling boat. I expect they'd need an inboard with a drive that can be raised and lowered, or a jet.

Foiling might make it easier to operate a computer at speed.

 

hoom

Super Anarchist
6,398
528
Orkland
I think the foils are connected with a lot more than a butt join + fillet. A foil wing is the entire wing, tip to tip, including the bulb but excluding the arm, flaps and foil systems. Changing from flat to anhedral is going to change a lot more mass than just the fillet.
Certainly not a butt-join but at least some of the IACCs were setup with a joint socket setup designed to allow easy wing/angle changes & I'm thinking of something like that.

It'd have to be designed-in certainly & maybe those setups did involve significant mass-change (as measured by the rule) making it not as small a change as I was thinking it could be.

 

barfy

Super Anarchist
4,745
1,209
5.10 For components listed in Rule 5.1 that have a “Change allowance” mass percentage:
(a) When such a component is first declared according to Rule 5.5, the Competitor must declare to the
Measurement Committee:
(i) a component mass;
(ii) an IGES file of an exterior component shape; and
(iii) construction drawings showing the internal structure of the component.
(b) At all times when that component is installed on an AC75 Class Yacht with that yacht afloat:
(i) at least 80% of the mass of the component must match the original component; and

(ii) a common portion of at least 80% of the mass of the original component must remain un-
modified and must match all declared versions of the component.

(c) The portion of mass of a component that matches another version of that component is determined
by aligning the unmodified portion of the original and modified components and determining the
mass of all regions where the material substance remains unmodified and in the same place in both
versions of the component.
(d) Material that has been replaced with identical or equivalent material only classifies as an unmodified
region where replacement was carried out as a repair permitted by Rule 5.12.

(e) When checking the shape of such a component against a declared IGES file, the Measurement Com-
mittee may make an allowance for unintended distortion of a component during manufacture.

(f) Competitors may declare a hypothetical “original component” which must comply with the relevant
rules for that component type, but is not required to be identical to the component when it is first
installed and afloat. In this case, the “original component” comprises those regions of the actual
component as-launched that match the hypothetical component, combined with the regions in the
hypothetical component that do not match the as-launched component and are presumed to have
been removed/modified to achieve the as-launched component. The component as first launched
must have corresponding declarations which must satisfy the permitted changes with respect to the
hypothetical “original component”.
(g) If the component when it is first installed and afloat does not comply with the relevant rules for that
component type, the Competitor must declare a hypothetical component that does comply with
those rules, in accordance with Rule 5.10 (f).

Clause c is the kicker
Nice. Iges don't lie. So changes in space count.

But it still doesn't discredit the big bulb theory. Except for pushing a big bulb around.

 

Terry Hollis

Super Anarchist
A Mercury 400R running at 3,000 RPM uses 29.9 l/hr and at 5,000 RPM uses 69.8 l/hr. A full–foiling chase boat might theoretically keep the same engines and just throttle back to reduce fuel consumption (or shut down one engine and raise the leg) in the order of 120 l/hr.

I'm not going to guess how to get a standard outboard to operate on a full foiling boat. I expect they'd need an inboard with a drive that can be raised and lowered, or a jet.

Foiling might make it easier to operate a computer at speed.
The Auckland Waiheke ferry "Manu Wai" was a hydro foil and it ran from 1964 to 1973. It was retired because of operational problems.

1350 hp, inboard, and carried 75 passengers at a speed of 30 to 35 knots.

https://discover.stqry.com/v/4-ferries-of-waiheke/s/6724de97-285c-446c-87cc-a76480be9b53

 
Top