Multi-Hull layouts evolution of theory and design

[kach22i]

What was the problem with this boeing hydrofoil hull? I'm assuming there was a problem, because you don't see this (pancake/spoon type?) configuration anymore.

http://www.boeing.com/history/boeing/hydro.html


Case in point classic old hydrofoil:
http://madisoncamerunning.com/Holly/cantrell.html



More current 3-point semi-catamaran:
http://www.rcboataholic.com/hulls/hullshydro.htm


Are the reason for the disapperance of the pancake/spoon hull was/is stability in waves?

I need to get a general feel for the physics at work here, and the evolution of planning hull theory and design.

Do you have to CUT the water to have stability?

[kach22i]

How about this for an easy question; what year was the turning point in hydoplane design.............going from a front 3-point to a tail 3-point?

What craft made this breakthrough?

[Eric Sponberg]

As I recall, the Boeing Hydrofoil was very expensive to build and operate for its time. The market was fairly small and could not afford it. Also, I believe it was not naturally stable when on foils, and it required some pretty awesome computer power for the time which itself was fairly expensive.

Eric

[jehardiman]

1) The Boeing jet foils and other, military, hydrofoils dissapeared because the strut mechanisum proved to be too fragile to handle floating object impact, and the prodigious fuel consumption. Also any system malfunction that caused power loss resulted in a "crash and burn" where the vessel fell off foil and rapidly slowed....generally throwing anything not strapped down into the forward bulkhead.

2) Flat hydroplane hulls still exist, and they still have the problem of getting airborne. With modern (post WWII) supercharged and GT engines the hulls could be built small and light enough to develop significant aero lift. Modern hydroplanes are actually limited by the aerodynamics vice the hydrodynamics. Most current unlimited racing hydroplanes are still three-point (forward forks and tail), but have so much power available that large flat surfaces on the sponsons are unneccessary. Additionally, the deadrise of the sponsons act as a stabilizing force much like the dihedral of wings and some hydrofoils.

Edit obvious typing mistake

[kach22i]

Originally Posted by jehardiman

2) Flat hydroplane hulls still exist, and they still have the problem of getting airborne. With modern (post WWII) supercharged and GT engines the hulls could be built small and light enough to develop significant aero lift. Modern hydroplanes are actually limited by the aerodynamics vice the hydrodynamics.

So if I can draw some conclusions............................

1. Flat hydroplane hulls are safe and efficient below a certain aero lift threshold.

2. Racing hydroplanes three-point (forward forks and tail) are supreme in the unlimited catagories, but have no clear advantage over the older 1950's to early 1970's style in the lower HP and speed ranges.

[jehardiman]

The hydrodynamics of hydroplanes is all about surface friction. You want the maximum lift so as to have the minimum surface in contact with the water. Hydroplanes with large flat lifting surfaces actually need little ripples to attain maximum speed (so as to span the ripples and reduce surface in contact with the water), however, if the ripples are too big the bow can get pushed up too much by the impact lift at speed and then air will get under the boat and they will flip. The modern high deadrise sponsons are to ease the ride at high speed to make them somewhat less prone to pitchover.

[kach22i]

Originally Posted by jehardiman

Hydroplanes with large flat lifting surfaces actually need little ripples to attain maximum speed

I wonder if anyone had experimented with textured surfaces.

Like this:

http://new-brunswick.net/new-brunswi...bluewhale.html

Or


http://www.airventure.org/2006/galle...july24_25.html

Or
http://www.fototime.com/AC533B3461C74A9/orig.jpg
http://www.thedonovan.com/archives/week_2005_07_17.html

Or


http://aerofiles.com/_sa.html

[jehardiman]

In the water, not the skin.......

Look at some of the early Harmsworth Trophy boats (such as Maple Leaf IV)for the proper way to cause this effect with the hull. Many non-hydrofoil racing boats of the 1910's and 20's had multiple stepped hulls.

BTW, ribblets are outlawed by the latest rules of sailing. See Rule 53.

[FAST FRED]

" I wonder if anyone had experimented with textured surfaces."

At one time the rubber mfg were promoting an antifouling that actually was 1/4 in scuba suit rubber , epoxy glued to the hull.

Claimed a 10% speed increase or 10% drag reduction BUT the material was impregnated with Mercury as antifoulant ,, much ungood .

Pulled from market.

FAST FRED

[Alan M.]

The pleats in the whale's throat are not there for speed, they are to allow it to expand to swallow huge amounts of water. The corrugations on the Ford Trimotor were there for structural, not aerodynamic reasons.