V-44 Albatross World Speed Sailing Contender

[Doug Lord]

Looks like a well funded project that could amount to something:

http://verneyyachts.com/index.htm

 

[Marvout]

Aren't they only going half way with the concept? (I don't mean this facetiously at all...) Wouldn't you be able to get both wings up in the air, control them separately and get twice the drive area? Looks like there are four separate control areas. It appears like each wing has an upper and lower section. Run three of them for drive and the fourth for balance. A kind of fixed wing biplane Moth on steroids.

Marvin

 

[tspeer]

Aren't they only going half way with the concept? (I don't mean this facetiously at all...) Wouldn't you be able to get both wings up in the air, control them separately and get twice the drive area? Looks like there are four separate control areas. It appears like each wing has an upper and lower section. Run three of them for drive and the fourth for balance. A kind of fixed wing biplane Moth on steroids.

Marvin

No, the lift on the other panels would have to go the opposite direction to produce drive. The way they've arranged it, the horizontal wing to leeward produces upward lift and opposes the heeling moment of the vertical wing. It also helps cancel the trailing vortex at the foot of the wing for reduced induced drag.

The ideal case might be identical lift distributions on the two wings. Then there would be no net heeling moment and the net force would be along the bisector of the two wings. Of course, the wind conditions on the two wings will be quite different, and the spanwise lift distributions will be different.

 

[Marvout]

I guess I had presumed the (air) foils were symmetrical and could be trimmed for sailing either way. If they are asymmetrical like a plane's wing then what I suggest wouldn't work.

Marvin

 

[tspeer]

The sections looked asymmetrical in the renderings. I think that was one of the reasons for going with a flip-tacker configuration.

 

[Marvout]

The stresses in that design must be quite high. The impact of that thing landing must be pretty harsh. Or at least it has the potential to be.

I wonder if the cockpit is self leveling? Could be a bit disconcerting if you forget to 'tack' the cockpit.

MH

 

[NiklasL]

Looks like a pitchpoler because of the short length.

 

[cavalier mk2]

I wonder how it would work in a pacific configuration with the horizontal wing suppling downforce/upforce when needed .

 

[Munter]

I wonder if a compression strut between the wings would be more effective than a massively reinforced joint between the wings?

 

[RHough]

No, the lift on the other panels would have to go the opposite direction to produce drive. The way they've arranged it, the horizontal wing to leeward produces upward lift and opposes the heeling moment of the vertical wing. It also helps cancel the trailing vortex at the foot of the wing for reduced induced drag.

The ideal case might be identical lift distributions on the two wings. Then there would be no net heeling moment and the net force would be along the bisector of the two wings. Of course, the wind conditions on the two wings will be quite different, and the spanwise lift distributions will be different.

Tom, have you looked at the pitch stability information they posted? I'm struggling with how that is going to work. It looks more like a pitch instabilty system me?

R

 

[Doug Lord]

V-39

Randy, what do you see that leads to pitch instability? Maybe its staring me in the face and I don't see it?


They say:

" When the hulls are flying, the V-39 achieves longitudinal stability from a nose up pitching moment gained by a relatively forward centre of lift from the wing in ground effect and a relatively aft centre of gravity.

A degree of water ballast will be present in the stern of the main hull to maintain an aft CG.

Finally, the small hydrofoil at the base of the active rudder maintains the balance"


click on image and then again on resulting image:

 

[RHough]

Randy, what do you see that leads to pitch instability? Maybe its staring me in the face and I don't see it?


They say:

" When the hulls are flying, the V-39 achieves longitudinal stability from a nose up pitching moment gained by a relatively forward centre of lift from the wing in ground effect and a relatively aft centre of gravity.

A degree of water ballast will be present in the stern of the main hull to maintain an aft CG.

Finally, the small hydrofoil at the base of the active rudder maintains the balance"


click on image and then again on resulting image:

First consider what would upset the vessel in pitch.
The nose down pitch from thrust is balanced (literally) by the nose down pitch from the aft CG lever.
What happens as the wind speed changes in gusts?
Gust = greater trust = pitch down
pitch down = CG forward as wing rotates forward on pitch axis reducing (over powering?) the stabilizing effect of the aft CG lever = more pitch down
Pitch down = hull/fuselage frontal area increases forward of the CG = more pitch down

As the vessel pitches down the stabilizing force of aft CG is reduced and each degree of down pitch increases the pitch down force. The pitch down forces are not linear, whist the stabilizing forces are. This requires active input.

Now look at the CG placement and the location of the T foil. Both the trim weight water ballast and the T foil are off center. Any stability moment in pitch also produces a roll moment and a yaw moment.

Now we have:
Pitch down = need for pitch up correction
Pitch up correction (down force from T foil) also adds windward roll and weather yaw (from greater drag induced from down force)

Is the vessel sable in roll?
The total lift is somewhere to leeward of the CG, if the vertical height of the thrust vector as shown in the side view is extended to the combined lift vector shown on the front view the thrust acts at a point to leeward of the CG.
Gust = greater lift = windward roll + pitch down
Windward roll = increase AoA on T foil = up force from T foil
Upward force from T foil adds to pitch down.

How about yaw?
Gusts increase lift = pitch down + windward roll + weather yaw
Weather yaw = greater speed at WIG tip as it rotates = increased windward roll ...

I could spend more time trying to figure out if the vessel is stable on any axis but you get the idea.

Stability in 3D is an aircraft thing. Stability has a static aspect and a dynamic aspect. Consider a broomstick. Hang the broom stick from one end. It has both static and dynamic stability. If you push it from vertical it will return to vertical and settle back to it's original position (unless the suspension point is frictionless and there is no air resistance). Now suspend it from it's centre of mass. It will be stable in any position but will not return to any position. When the suspension point is moved to the bottom, it will be stable only as long as the centre of mass is directly above the suspension point. Sure it is possible to walk around with a broomstick balanced on your finger tip, but I'd hardly describe it as stable.

I just don't see this ending well. I could be wrong and I don't see something obvious ...

R

 

[cardsinplay]

I take it, then, that you've looked at the CV's of these guys, as well as their invested sponsors and you still think there's something terribly wrong?

Hmmm....


I did see the caveat.

 

[Doug Lord]

First consider what would upset the vessel in pitch.
I just don't see this ending well. I could be wrong and I don't see something obvious ...

R

================
This isn't an answer but its-maybe the begining of an answer. I looked in Darrol Stinton's "Design of the Airplane" for his remarks on forward sweep.
1) " forward sweep avoids premature tip stall, because the root stalls first. Ailerons tend to remain effective, but pitch up still occurs. However, forward sweep has an adverse effect upon directional stability.........."
2) " Forward sweep causes vortices outboard to be shed ahead of those inboard. Tip stalling is suppressed by off-loading outboard sections. The spanwise lift distribution of a forward swept wing is nearly elliptic and further forward than for one swept back. This, with root losses helps to shift the aerodynamic center 7 percent to 10 percent further forward than for a swept back wing."

 

[RHough]

I take it, then, that you've looked at the CV's of these guys, as well as their invested sponsors and you still think there's something terribly wrong?

Hmmm....


I did see the caveat.

When was the last time I have been proved wrong and was not happy to learn from the experience?

Have you never seen a design error from someone with good qualifications?

I did not say "terribly wrong" did I?

Let me be very clear, I don't see obvious positive dynamic stability. It is entirely possible to fly such a vehicle, helicopters are the most obvious example.

Possible to fly and able to set a record are two different things. The Monofoiler speed record program got farther along than this one and I have not seen a full scale machine yet. Not saying we never will but it has been a few years. There are videos of proof of concept models.

Sponsors?
Design software, engineering consultants (the employer of the project founder), and a laptop with x-foil ... equal invested sponsors? No mention of money?

The CV's?
Egineering Lead/Founder works for Consultant Sponsor
Project and Marketing Lead old school chum of founder
and a CFD guy that has sailing experience ...

Inspired by an article in ‘The Engineer’ March 2008 edition about the speed sailing team, l’Hydroptère and their preparations for setting a new world outright sailing speed record, Tim began working on an innovative layout for a sailing boat which has led to the v-39 ALBATROSS project and the forming of a passionate and highly motivated team as it stands today. We are achieving a high degree of team efficiency and productivity by keeping the team structure as flat as possible, spreading both responsibility and authority

Keeping a three person team structure flat is not much of a challenge. I don't see much experience actually building anything and no past successful designs are cited other than models. Hell if the models that I've designed and built count I can I list them and impress you?

The single most impressive statement they make is this one:

What Defines and Limits the Top Speed?

The top speed of the boat is the incipient cavitation speed of the keel and rudder (the speed at which cavitation first occurs)

and second is:

Setting the drag

The aim of the pilot is to control the speed of the boat to hold it just under the incipient cavitation speed of the keel. He does this by controlling the height of the boat above the surface, thereby setting the amount of keel/rudder penetration. The keel and rudder are the largest contributors to overall drag.

This is an important point, since it means the overall drag does not effect the top speed of the boat. It does however, effect the true wind speed required to reach the top speed. If the overall lift / drag ratio of the boat is poor, it will necessitate a stronger wind, which would produce larger waves. This would give rise to a restriction in locations to where the speed record could be set.

These statements are the ones that lead me to look closely at the project, since I feel that they indeed have a good handle on what the limits and challenges are.

Randy
Free Flight and RC Model Aircraft Designer and Builder
RC Sailing Vessel Designer and Racer
LSF Level 1 Glider Pilot
Racing Sidecar Engine Builder, Chassis Designer and Builder, Professional Racer
Crew Chief Sports 200 team and Spec Miata team
Trimmer, Navigator, Tactician 2 time YRA Champion Crew
USSailing Certified Race Officer

Are you impressed yet?

LMAOROTF