Peoples Foiler-flying for the fun of it!

[matt b]

So what's the latest in the world of foiler development for the bigger sailor. I've sold my normal blaze so now is the time to live and die by the sword. I'm aiming to get the foiling blaze (blaze Xf ) in the water in the new year. I've located a local boat repairer to fabricate a transom fixing (see earlier post) once that's done the plan is to launch in Chichester harbour for testing and fine tuning.

[Doug Lord]

Originally Posted by matt b

So what's the latest in the world of foiler development for the bigger sailor. I've sold my normal blaze so now is the time to live and die by the sword. I'm aiming to get the foiling blaze (blaze Xf ) in the water in the new year. I've located a local boat repairer to fabricate a transom fixing (see earlier post) once that's done the plan is to launch in Chichester harbour for testing and fine tuning.

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Nothing much new in monofoilers, very surprisingly. Lots new in multifoilers-check the multihulls forum. The Pi28 claims to be a monofoiler yet it sails like a trimaran off the foils. You be the judge: Pi 28 / Gonet and Cie trimaran foiler
Also the Osprey and Whites Dragons both with their own threads in Multihulls. And almost every new A Class Cat races with curved lifting foils as do the NACRA 20 , Marstrom 32 and several C Class cats and almost every racing tri( except the Open 50's) including the Sea Cart 26 and the new MOD 70's and Banque Populaire V, now blasting around the world at 30 knots!
For monohulls there has been the emergence of the new DSS foil assist technology-here is an example: Quant 28-foil assist keelboat / DSS And a full flying 30' keelboat is now under development.

[ancient kayaker]

Introduction: I have a concept for a foiling assist system suitable for a solo flat-bottomed skiff. I may have posted a similar concept some time back in a different thread that I can no longer find, That would have lifted the hull clear of the water, requiring a second foil and there were concerns about attitude and altitude control which I think may be addressed by this revised approach. it may provide a safe and low cost introduction to foiling and may even be possible to market in the form of a retrofit kit for existing flat-bottomed sailboats with adequate forward buoyancy to counteract the bow-down moment of the rig.

Description: the single full-width foil fits into a recess across the bottom of the hull and has a flat-bottomed profile to leave a flat surface when retracted. It may extend beyond the width of the hull but flat-bottomed skiffs are usually fairly beamy so that may not be necessary. The foil is connected by external vertical struts - partially recessed into the sheer planks - to a crossbar some distance above the deck.

Operation: once the boat is planing or close to it, the foil is deployed by the sailor sitting on the bar to push the foil down to its operating level. In effect the foil supports crew weight but not that of the boat, which would be far less. The boat now planes easily and provides a horizontal reference eliminating the need for a second foil and surface sensing schemes. The foil may have to be deployed with the boat more or less upright to avoid problems as the RM of the hull will change during foil deployment, although some heel would allow the boat to handle waves better.

Design notes: the foil and strut assembly could either move in linear guides or have a pivoted parallel link to maintain its angle of attack. The arrangement will have to transmit the moment from the sailor sitting off-center, to the hull, to counteract heeling, without jamming. An arrangement is required to keep the rudder in the water.

Caveats: there may be some restrictions to this idea; it is not suitable for heavy wave conditions that could cause porpoising although it should handle anything an unmodified skiff can. It may be necessary to run controls to the crossbar, as I doubt it will prove safe to clamp the bar down to allow the sailor to move around.

[CT 249]

AK, at what sort of apparent angles can a sailor get so far inboard that they can push down on a foil at speed?

At those speeds, isn't the sailor's weight largely occupied in providing RM by hiking?

[Doug Lord]

Originally Posted by ancient kayaker

Introduction: I have a concept for a foiling assist system suitable for a solo flat-bottomed skiff. I may have posted a similar concept some time back in a different thread that I can no longer find, That would have lifted the hull clear of the water, requiring a second foil and there were concerns about attitude and altitude control which I think may be addressed by this revised approach. it may provide a safe and low cost introduction to foiling and may even be possible to market in the form of a retrofit kit for existing flat-bottomed sailboats with adequate forward buoyancy to counteract the bow-down moment of the rig.

Description: the single full-width foil fits into a recess across the bottom of the hull and has a flat-bottomed profile to leave a flat surface when retracted. It may extend beyond the width of the hull but flat-bottomed skiffs are usually fairly beamy so that may not be necessary. The foil is connected by external vertical struts - partially recessed into the sheer planks - to a crossbar some distance above the deck.

Operation: once the boat is planing or close to it, the foil is deployed by the sailor sitting on the bar to push the foil down to its operating level. In effect the foil supports crew weight but not that of the boat, which would be far less. The boat now planes easily and provides a horizontal reference eliminating the need for a second foil and surface sensing schemes. The foil may have to be deployed with the boat more or less upright to avoid problems as the RM of the hull will change during foil deployment, although some heel would allow the boat to handle waves better.

Design notes: the foil and strut assembly could either move in linear guides or have a pivoted parallel link to maintain its angle of attack. The arrangement will have to transmit the moment from the sailor sitting off-center, to the hull, to counteract heeling, without jamming. An arrangement is required to keep the rudder in the water.

Caveats: there may be some restrictions to this idea; it is not suitable for heavy wave conditions that could cause porpoising although it should handle anything an unmodified skiff can. It may be necessary to run controls to the crossbar, as I doubt it will prove safe to clamp the bar down to allow the sailor to move around.

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AK, sounds sort of similar to the illustration below-"DeepDSS". Pushing the foil down at speed may be a bit much-maybe a tackle to do it?
I'd think you'd want the lift centered to the side like "normal" DSS and this(below) in order to take advantage of the tremendous RM generated while partially lifting the boat. More RM=more power to carry sail=more speed.
Help me to understand your concept better if I've got it wrong. Your thinking is in the right direction: foil assist is generally simpler than full flying and can have substantial benefits.....

Illustration: Deep DSS 3-a trunk on each side supports a vertical fin(retractably) that supports a hollow foil that can be extended to leeward by a line running up the daggerboards
click on image-

[ancient kayaker]

Chris: the crossbar goes the entire width of the boat and can, I suppose, extend further if required, so crew weight can be moved. I’m thinking more along the lines of extending foiling to the public rather than high performance though.

Doug: that pic is close to my idea, it just needs a crossbar between the strut* tops for the sailor to sit on. The foil supports only the weight of the sailor, the boat skims on the water. RM comes from the off-center position of sailor and to a lesser extend from the boat’s heel, although that isn’t much for a lightweight boat.

The sailor can also transfer a portion of his/her weight to the boat with a foot, which may add an extra measure of control although that will have to wait for a demo before its value is known. I suspect it will increase the RM somewhat.

*The struts are not used as daggerboards in this concept as the daggerboard must be deployed before the strut/foil assembly.

I’m making a sketch.

[Doug Lord]

AK, the foil is going to lift what it was designed to lift whether or not the crew sits on it. Wouldn't it be simpler to just deploy the foil and have the crew sail like normal?
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For what its worth ,here are examples of a foil designed by Jon Howe that requires no altitude control system whatsoever(and the first boat it was used on):

click on image-

[ancient kayaker]

Originally Posted by Doug Lord

AK, the foil is going to lift what it was designed to lift whether or not the crew sits on it. Wouldn't it be simpler to just deploy the foil and have the crew sail like normal?
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For what its worth ,here are examples of a foil designed by Jon Howe that requires no altitude control system whatsoever(and the first boat it was used on):

click on image-

I find it difficult to accept the entire boat balances on a single foil without any action by the sailor. I suspect it requires considerable skill and a lot of setup experimentation to get it to work, which is what I am trying to avoid.

I drew up a sketch and added it to my previous post . . .

[Doug Lord]

Originally Posted by ancient kayaker

I find it difficult to accept the entire boat balances on a single foil without any action by the sailor. I suspect it requires considerable skill and a lot of setup experimentation to get it to work, which is what I am trying to avoid.

I drew up a sketch and added it to my previous post . . .

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Howes foil used a rudder T-foil because it was a full flying design. A foil like yours that is designed for foil assist will still have part of the boat in the water acting to provide pitch control along with crew movement. So, in my opinion, you might be better off to just deploy the foil and allow the crew to sit where he/she needs to for RM and to aid pitch control.
I still don't get your thinking on the recess for the retracted foil: won't it cause a lot of drag since the foil is not lifting the whole boat clear of the water?

[P Flados]

Originally Posted by Doug Lord

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I still don't get your thinking on the recess for the retracted foil: won't it cause a lot of drag since the foil is not lifting the whole boat clear of the water?

For either flat bottomed, or shallow V, I have previously considered a retractable foil.

Fully retracted is better for launching, navigating the shallows and very light air.

It does not need to be a "flat bottomed" foil. Start with a foil with a small curvature on the bottom. Many good cambered (asymmetric) foils fall into this category. Blend the bottom prior to the foil in front and taper off smoothly from the trailing edge.

If the boat is to have a flying hull, you do not need to to worry as much about smooth water flow with the foil extended. If the foil is just for assist, the surface without the foil is more important.

Water goes around leading edge bumps pretty good as long as things behind the bumps allow for attached flows. Smooth trailing edges are important, but easy.

I tried to draw something up using a thicker than actual section. The blend behind the foil would probably need to be more gradual.

[ancient kayaker]

I wonder if the recess in the bottom of the hull might behave like a step by assisting in separation, but in any case the boat's weight without the sailor should be so light that the wetted should be small.

If the hull and foil are designed to work together - which would obviously be best from a performance point of view - A non-flat bottomed foil may well be better than a flat-bottom, by reducing the "valley" in the hull bottom.

Another possibility would be slightly curved struts and trunks, so the angle of attack varies from negative when tucked under the hull, to eliminate the after edge of the recess, increasing with deployment to create lift. I think there will be some experimentation required to get the best out of this idea. Until then it will impossible to be sure what the outcome will be without some fairly expensive and sophisticated modelling software.

My bathtub is too small; once my pool thaws out in the Spring I may try a model . . .

[CT 249]

Originally Posted by ancient kayaker

Chris: the crossbar goes the entire width of the boat and can, I suppose, extend further if required, so crew weight can be moved. I’m thinking more along the lines of extending foiling to the public rather than high performance though.

Ok. In my very limited experience and as I understand it from others, there'd not be much difference in the sensation if the boat flies so low, but each to their own.

[P Flados]

Originally Posted by ancient kayaker

Another possibility would be slightly curved struts and trunks, so the angle of attack varies from negative when tucked under the hull, to eliminate the after edge of the recess, increasing with deployment to create lift. I think there will be some experimentation required to get the best out of this idea. Until then it will impossible to be sure what the outcome will be without some fairly expensive and sophisticated modelling software..

You obviously saw the same issue I noted.

After drawing the picture I posted, it became apparent that good foil AOA for operation results in a bottom profile that was clearly not optimum, either retracted or extended. Designing in an AOA increase with a slightly curved strut would be a big help.

This will allow the rear lower surface of the fully retracted foil to be essentially flush with the nominal hull surface.

[ancient kayaker]

Of course, there's no pressing functional need for the foil to go underneath the bottom, it could stick out on either side above the waterline, but that would create some structural problems requiring advanced materials so I would prefer not. Also it could hinge up and down sideways but again I prefer simple.

My thinking is, the bottom shape doesn't matter a whole lot if the boat can get up enough speed for the foil to take significant weight, and as mentioned before, with a bit of thought the foil retraction slot can serve as a step with the foil deployed . . .

[Doug Lord]

Originally Posted by ancient kayaker

Of course, there's no pressing functional need for the foil to go underneath the bottom, it could stick out on either side above the waterline, but that would create some structural problems requiring advanced materials so I would prefer not. Also it could hinge up and down sideways but again I prefer simple.

My thinking is, the bottom shape doesn't matter a whole lot if the boat can get up enough speed for the foil to take significant weight, and as mentioned before, with a bit of thought the foil retraction slot can serve as a step with the foil deployed . . .

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Thats interesting, AK! You may be able to significantly reduce the size of the step if you look into Eugene Clements step designs-but they require an aft t-foil. A foil near the front of the step is an interesting thing to ponder.
I'll post his booklet if you're interested. Foils combined with steps are an interesting design direction for experiments-good thinking....