Hydrofoil assisted V hulls:Where are they?

[xarax]

Successful hydrofoil assisted hulls, (where all, or a significant part, of the upright forces are provided by means of hydrofoils), seem to be notoriously absent from small powerboats, while, at the same time, win sailboat championships ! Why is this so ?

[Willallison]

Two answers to that.
1. They're everywhere....they're called hydrofoils
2. Less facetious answer.... simplicity, cost, and practicality.... try bringing a foil assisted monohull into the beach for instance

[BMcF]

..Yes.those with fixed (not retractable) foils are a bit much to handle...our 9-ton 13.5m trimaran with foils is launched and recovered by crane or large travelift only.

Draft while 'flying' is a mere 500 mm..but off the foils she draws 1400 mm. I flew her right on to a shallow mud flat once, whereupon she remained firmly 'parked' like a jackup barge until the tide came in some hours later and we refloated her...I shudder to think what the outcome would have been had I run her aground at high tide vice low tide...might still be sitting in the same spot today

We 'played around' with some schemes to build a retractable foil system for the craft...very complex and expensive proposition that we never pursued beyond 'concept' stages.

It's shame too because when our trimaran was flying, it was a truly remarkable machine in rough seas (up to 1.5m waves and you could still set a glass of water on the console and not spill a drop). Hydrofoil craft work great when properly deisigned and built..but having all that 'stuff' hanging below the hull(s) has always been a problem.

[TerryKing]

Originally Posted by BMcF

..Yes.those with fixed (not retractable) foils are a bit much to handle...our 9-ton 13.5m trimaran with foils is launched and recovered by crane or large travelift only.

IsThere a middle ground, where the attachment/mount of the hydrofoil makes it a 1/2 hour job to unbolt and remove the below-the-draft part at launch / haul (or an embarrassing grounding )??

[BMcF]

Originally Posted by TerryKing

IsThere a middle ground, where the attachment/mount of the hydrofoil makes it a 1/2 hour job to unbolt and remove the below-the-draft part at launch / haul (or an embarrassing grounding )??

Not an impossbility to design something like that, I suppose, but the foil system on our craft has a lot of bolts attaching struts to hull..and the pushrods for the flight control flaps have to be disconnected as well. It takes 4 guys about 4 hours to remove the front and rear foils on our craft..with the craft blocked up nice and high on terra firma.

The inherent problem is having the foils attached robustly enough to reliably support the entire weight of the craft at a few points (the hull strcutural design is unique to meet that requirements as well) is at odds with also having the foils be easily removed or retractable.

I think there is tremendous potential for the use of lifting foils on small powerboats-perhaps using some of the systems proven on boats like the Rave sailboat foiler. The Rave has retractable main foils and can be sailed off a beach with the foils vertically retracted then once out far enough a line led to the cockpit allows the foils(and wand altitude control system) to be pulled down and locked.
I once saw a video of a Yamaha bi-foil mini one person foiler flying around on just two foils-don't know whether or not they were retractable but see no reason they couldn't be designed to be-depending on how water gets to the engine and top speed.

[BMcF]

Some years back there were quite a few 'recreational' hydrofoil craft and add-on foil kits. The watercraft in this link are still quite popular..http://www.dynafoil.com/

The problem with retracting the foils or making them easily removeable gets larger as the craft does..at 9 tons and 13.5m, our hydrofoil testcraft is beyond the point where the simpler attachement schemes can hold up.

I always liked this little guy too..


..and this one