l'hydroptere.ch

[DennisRB]

I thought the new hydroptere boat deserves a thread all on its own. I spotted a few pics courtesy of SA.

http://www.martin-raget.com/L-Hydrop...,f,g96,n1.html

Considering the success of its predecessor, I think we can expect some great results from this test boat.

What are the forums thoughts on this boat? So far I have not seen a pic of it up on its foils and it seems to have a bow down attitude in some pics when flying a hull. But thats probably just because the wind was too light for it to lift off?

http://www.hydroptere.com/_en/actu_d...actu=70#centre

This will look good in 60 foot.

http://www.hydroptere.com/_en/hydrop...xi.html#centre

[Doug Lord]

Good scoop,Dennis! Didn't know she had sailed yet. I don't think it is very much bow down-its probably the way the picture was shot.
This thing is a "model" of the 100'(or so) maxi that the Team Hydroptere is doing. I think its interesting that they've chosen a cat configuration-especially with the poor performance history of a lot of cats on surface piercing foils. The 60' Hydroptere is 80' wide and 59' long-beam=1.36 times length which keeps the center of lift of the main foils way apart and generates more RM than a narrower boat would. Haven't been able to find .ch dimensions but it is proportionately narrower than Hydroptere.
One very interesting design feature is the stepped planing hulls-the first that I know of since Parliers boat. But .ch has "variable geometry" steps that allow the drag from the step to be eliminated in light conditions.
I wish Team Hydroptere would explain in detail their thinking-would be fascinating.

more here: http://www.boatdesign.net/forums/mul...-15612-22.html

click on picture and you can see the step in the stb hull-port step appears to be retracted:

[DennisRB]

You are probably right regarding the angle of the pics I saw re the bow down attitude. I'm not sure if I should call .ch a cat or a tri? Its had to tell the difference sometimes these days. I would love to see some better pics of the variable steps.

I did see the pics in the other thread when I searched to see if there was a thread on .ch, but at 22 pages already, I thought it might deserve its own thread. I'm sure there will be plenty of updates eventually. I thought the larger one was going to be 60 foot but they say 30m which is pretty much 100 foot. Thats one big hydrofoil. The thing I like about the original is that it is a real boat which can sail in both directions in a stiff chop. This all while still being faster than those other contraptions that can only sail on one tack in a chop of less than 2 inches. If they can get a 100 foot version to cope with a rough sea state it will make for some exiting sailing to say the least.

[Doug Lord]

Found the dimensions. This is news in catamaran design because it is virtually square! Almost unheard of because the naysayers say it is too wide to tack. I know that several square rc model cats I made tacked on a dime--I think its its just a matter of the foils.
It is mentioned in at least two books and by Dr. Sam Bradfield that surface penetrations are a source of great drag for a hydrofoil-this thing has 4 surface penetrations, Hydroptere three -and for comparison the Moth has just two.....

"Catamaran of 10.85 meters long and 10.40 meters wide, with central peak structural the Hydrofoil. ch is equipped with rear lift assemblies, a control system of the foils very sharp and mobile planing hulls. LikeThe Hydrofoil60 feet, it will have a measurement system embedded ultra sophisticated" from here:

http://www.hydroptere.com/actu_detai...actu=70#centre

-----------------
Bingo! This picture from Giles Martin-Raget clearly shows the port step deployed! Also the foils have either been removed or are retracted and you can clearly see the single daggerboard in the "pod". The stb T-foil rudder is only partially lowered to work with the stepped planing hull. Dennis, you're 100% right about this boat deserving its own thread-thanks!
http://www.martin-raget.com/09-10-20...1658p96n0.html

[pogo]

Originally Posted by DennisRB

.... it seems to have a bow down attitude in some pics when flying a hull.

Only the flying hull has a bow down attitude while the leeward hull sails at 0°. Such a twist in the structure is normal. See picture 74.
http://www.martin-raget.com/09-10-20...58p160n73.html
Interesting in the first picture is that the boat seems to sail without step in the leeward hull (the spray comes from the foil being above the water).
Compare the grey waterlines of the bow-sections, the leeward waterline is parallel to the water-surface.
http://www.martin-raget.com/09-10-20...658p160n0.html
Few pictures later we als see no step under the starboard hull:
http://www.martin-raget.com/09-10-20...58p160n11.html




pogo

[Doug Lord]

You can see the step on the stb hull if you click on the image in post #2. They are using variable geometry that allows the steps to be retracted.
Good picture of the retracted main foils-but I don't think that is causing the spray-its the fact that the boat is using the deployed step....

[pogo]

Originally Posted by Doug Lord

Good picture of the retracted main foils-but I don't think that is causing the spray-its the fact that the boat is using the deployed step....

No.
In picture n. 1 the grey waterline of the bow sections of the starboard hull are parallel to the water-surface----retracted step.
http://www.martin-raget.com/09-10-20...658p160n0.html
With a step , having the waterline of the bow sections parallel to the surface , the hull would have a bow down attitude like this (windward hull):
http://www.martin-raget.com/09-10-20...58p160n73.html

pogo

[cardsinplay]

Originally Posted by pogo

No.

In picture n. 1 the grey waterline of the bow sections of the starboard hull are parallel to the water-surface----retracted step.

With a step , having the waterline of the bow sections parallel to the surface , the hull would have a bow down attitude like this (windward hull):

pogo

Excellent image analysis, Pogo.

[Doug Lord]

Originally Posted by pogo

No.
In picture n. 1 the grey waterline of the bow sections of the starboard hull are parallel to the water-surface----retracted step.
http://www.martin-raget.com/09-10-20...658p160n0.html
With a step , having the waterline of the bow sections parallel to the surface , the hull would have a bow down attitude like this (windward hull):
http://www.martin-raget.com/09-10-20...58p160n73.html

pogo

=============
I think you are mistaken........A boat planes with a slightly bow up attitude which is exactly what I see in that picture.(0040)
The second picture appears to be the boat sailing with the steps retracted..... Interesting to see in the second pix that the pod appears to touch the water.....

[pogo]

Originally Posted by Doug Lord

=============
I think you are mistaken........A boat planes with a slightly bow up attitude which is exactly what I see in that picture.(0040)

There is no bow up attitude, and, we can only guess that the boat is in planing mode --but there a links and principles.
What we see is that the stem is slightly out of the water and no attitude of the starboard hull.

It is not implemented that a planing hull must (always) have a noticable bow up attitude.
A hull for planing is always designed for a certain speed, it`s ideal speed.
The positive angled forward sections benefit from dynamic lift, while the negative aft sections are more or less thrown into/onto the valley of the bowwave and the wide transom acting as a stabilizer.
I called it level-planing---my own boat* does it at about 20kn speed on a broad reach.
The same happens on the first pic with l`hydroptere.ch under screacher/code 0.
With big screacher we see it here, no step, no attitude but dynamic lift bringing the stem out of the water.The whole boat is lifted nearly parallell to it`s designed WL at rest :
http://www.martin-raget.com/09-10-20...58p160n77.html
It`s planing mode with the forward sections attacked by the water at about only 2°.
Using the steps would be shown by 4-6° angle of the waterline in the bow sections (visible on the windward hull), resulting in a worse lift/drag ratio of the forward sections that wouldnt justify the loss of wetted surfaceof the aft sections---- in those lightwind conditions in pic 0040.
http://www.martin-raget.com/09-10-20...658p160n0.html
It`an experimental craft.

*Planing Catamaran!

pogo

[cardsinplay]

Another collection of astute observations based on direct experience, Pogo. Each time you post, I get another glimpse into the issues present for these wildly out of the box boats.

Thank you for your contributions.

Cards

[Doug Lord]

Originally Posted by pogo

There is no bow up attitude,
pogo

---------------------
Thats interesting: from the intersection of the stem aft at least 5-8' of the bottom is clear of the water. As to running angle: to me there is clearly more running angle(and more wind) in 0040 than in any other picture and it is highly likely that they can control the running angle to some extent with the rudder T foils. The part of the boat aft of the step should not contact the water when the boat is fully on the step-there are no "wide aft sections" at the back end of the boat.
It will be exciting to watch the progress of this boat....

[DennisRB]

Could it just be the foils causing the attitude and apparent planing of the hull in these pics? Are these foils designed so they are totally out of the water in light winds?

Image 15 gives a good close up of the variable step fully closed.

http://www.martin-raget.com/index.ph...mpage=14&pre=g

[pogo]

Originally Posted by Doug Lord

---------------------
Thats interesting: from the intersection of the stem aft at least 5-8' of the bottom is clear of the water. As to running angle: to me there is clearly more running angle(and more wind) in 0040 than in any other picture and it is highly likely that they can control the running angle to some extent with the rudder T foils. The part of the boat aft of the step should not contact the water when the boat is fully on the step-there are no "wide aft sections" at the back end of the boat.
It will be exciting to watch the progress of this boat....

I can only see the first 2-3`out of the water.
Where do you see 5-8`of the bottom out of the water ?
You only wish 5-8`of the bottom behind the spray from the retracted foil out of the water.
Of course they can control the angle/attitude of the boat with the inverted T-foil, but in that picture they don`t.
Of course the area behind the the step shouldn`t touch the water (you`re kidding with basics) , but, in step down mode
-- which is not the case in pic 0040.
On the picture you can see via the parallel sterns that both hulls are running parallel and flat without attitude (check it out with two sheets of paper on your screen, layed to the sterns).
Only the waterlines of the foward sections are not parallel--port hull stepped, starboard hull not stepped.
http://www.martin-raget.com/L-Hydrop...8,3,fr,fd.html

pogo

[pogo]

Originally Posted by DennisRB

Are these foils designed so they are totally out of the water in light winds?

Yes.
In all pictures the foils are out of the water.
http://www.martin-raget.com/L-Hydrop...8,3,fr,fd.html
The foil`s slot in the hull generates a lot of spray, better visible than in pic 0040 here :
http://www.martin-raget.com/09-10-20...58p160n73.html


pogo