60'+ or - 20' Ocean Racing Monofoiler Design Discussion

About 40 degrees on foils.

 

Doug
With the F3 style foiler are you using any manual or automatic pitch and/or roll control?

Rick W

 

If you look closely there appears to be a wands . Doug did mention previously that manual control is quite difficult, which does not surprise me at all.

With the F3 geometry one wand for each forward foil would create full stability.

 

Rick, the F3 uses a version of the dual wand system pioneered by Dr.Sam Bradfield. His help was instrumental in the success of the boat.
The wands work so that as the wind blows harder the leeward foil continues to lift and the windward foil pulls down. The symetric main foils are set up at a +2.5 degree angle of incidence with the rudder foil at 0 degrees. The boat is wider than it is long to reduce the foil loading due heeling moment.
I experimented on the foil design using oversize short flaps keeping the main foils to a T/c ratio between 6% and 9%(at the tips) using tips gleaned from the work of Graham Bantock.
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The boat probably could have been sailed with manual altitude control fairly easily but I didn't. Pitch control was 100% automatic with no control input needed whatsoever.

 

Doug
When you say the pitch control is automatic do you mean it is some sort of control system or inherent self-regulation without the need for external control input to some surface?

Also would it be possible to eliminate the roll control if their was very low heeling moment as I would have on a pedal boat? Simply rely on the surface proximity to reduce lift.

Rick W

 

<<<<because it is incredibly difficult to sail with manual(no wand) altitude control and no F&A movement of the ballast.>>>>

<<<<The boat probably could have been sailed with manual altitude control fairly easily but I didn't.>>>>

The above are both quotes from Doug. (???)

Moving ballast manually fore and aft is largely equivalent to manual pitch control.

I believe i am right in saying that in the case of a sailboat using three Tfoils there is no auto stable solution, therefore wands or manual control are necessary. And from my glider experience i would say a high level of skill would be required for manual control.

When there is no sail to deal with the options for auto stable geometries becomes much greater.

 

Pitch control was "inherent self regulation". The difference in the angle of incidence of the foils(main vs rudder) and the 80% loading(at min. takeoff windspeed) of the main foils are the main factors,I think. At takeoff, the rudder foil has 50% of the area of the two main foils but only 20% of the loading. There is a "crossover point" where the rudder foil is producing no lift and then negative lift. I think the low rudder foil loading gives it great control authority at very low angles of attack.
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I'm not sure that eliminating the wands would work for roll control esp. in any waves-but its worth a test in a boat with very little HM. Two full size Raves were sailed with manual roll control-they also required no pitch control input.
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T, I sailed the little monofoiler in the picture above with manual control only and it was incredibly difficult. The boat used movable ballast that I unwisely designed to move side to side and not fore and aft-and it needed to move F&A ! Quite a different set up than the F3 which would be fairly easy to control manually. I'm doing a much larger version of the "microfoiler"(6') that will be selfrighting(with ballast keel) and use a modified rc heli gyro to maintain veel heel. Will use very deep foils so I can sail it in the intercoastal w/o bottoming out.

 

Longitudinal dihedral (and its associated loading distribution) is certainly a requirement for longitudinal (pitch stability) but i can't see how it would be enough for dealing satisfactorily across a broad range of conditions.

To elaborate; close hauled the trimming moment from the sails is at its minimum whilst dead downwind it is at its potential maximum thus creating very widely differing loading distributions from that calculated from c of g alone thus requiring trimming as a minimum control. It seems to me that relying on surface effects is insufficient to satisfactorily deal with depth control in a sailboat without serious detriment to efficiency across at least part of the conditions envelope.

Doug , are you saying manual control of a model is difficult or easy?

 

Manual control of a boat like the F3(with very little ballast-only the battery) would be fairly easy because you would only have to control 1) roll, 2) lift, 3) sheet and 4) rudder.
Manual control of an rc monofoiler is much more difficult because to make it work you have movable ballast that is 40-50% of the total weight.
Your controls are 1) F&A movable ballast, 2) side to side movable ballast, 3) mainfoil flap(lift), 4) sheet and 5) rudder . The movable ballast is very fast and the boat is very sensitive in "feel". It is very difficult but the "microfoiler" could (barely) be controlled with practice. The new larger version will be drastically improved with a wand and gyro. The wand will be removable....

 

Ok thanks for that elucidation. Makes sense.

I still think you would need some serious concentration to manually control the F3 even if you say fairly easy (fairly is a relative term). Full size is much easier because you' re in it and get much more feedback than by just looking at something small a ways away, and because larger objects move much slower so reaction times can also be slower.

 

Doug, if you mean the wand system of Dr Sam Bradfield that i'm familiar with then that means there are two wands. Each wand controls depth of the foil it is linked to. Therefore they control roll and pitch. (and overall depth)

So i don't understand it when you say <<< Pitch control was "inherent self regulation".>>>>

I imagine you mean wand controlled or "negative feedback mechanical actuating system".

In the case of a non sailboat the heeling and pitching moments are very slight and do not vary much so you can make geometries that will have enough stability without control surfaces quite easily through correct longitudinal and transversal dihedral as well as with the negative ground effect. However in the case of a sailboat which has its thrust vector high above the boat , and this vector varies greatly in both magnitude and orientation , much greater stability margins are required.

<<<<also when running before the wind the craft had a tendency to pitch pole>>>>>http://www.foils.org/baker.htm(before using wands, basically using surface piercing foils to auto regulate depth)

The other thing i did not understand in your website is how the model switches between modes. I assume it is a wand release mechanism so that when you cannot fly you stop trying , so as to not inccur an induced resistance penalty. Is that correct?

 

The F3 ,as well as most of Bradfields recent designs, have two wands: one on the port side and one on the starboard side on the main foils-no wand on the rudder foil. They are independent of each other but both are set for the same altitude. The fact that they are independent of each other is how they develop RM. They have no affect on pitch whatsoever. The setup allows pitch to be regulated automatically by the rudder hydrofoil with no input required at all-"inherent self regulation" as Rick put it. No operator input for pitch was ever necessary with the F3. As I tried to explain: that was possible because of the low to zero loading on that foil.
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On the first two F3's I had servos attached to the springs that pull the wands "against" the water. The servo arm could be moved to completely release the spring tension dramatically reducing wand drag. Totally unnecessary on the model since it foiled in such light air. Also experimented with rudder hydrofoil flap control and that had virtually no affect except to slightly change the attitude of the boat so those servos were removed.
Originally had the battery on a carbon tube and hooked up to the mainsheet so that when the sheet was eased the battery moved back. The battery was about 1 lb and it made no difference at all in two boat testing.

 

Well, like a lot of these tings it seems to boil down to semantics unfortunately.

Rick said<<<<When you say the pitch control is automatic do you mean it is some sort of control system or inherent self-regulation without the need for external control input to some surface?>>>>

Now to me (i cannot speak for what Rick meant) 'control system' would mean wands or nfmas, whilst inherent pitch stability would mean it is pitch stable without any kind of nfmas.

The fact that there are two independent wands at the front (when foilborne the windward/leeward foils are hydrodynamically the frontmost end) means that you are controlling roll and pitch.

<<<They have no affect on pitch whatsoever>>>is therefore not really correct.

This can be demonstrated by making a single wand that detects roll angle only and you will then know for sure if it has inherent pitch/heave stability.

With your/ Bradfield's system the rudder foil automatically trails behind the levels set by the main foils. Three wands shoud always be superfluous when the system is designed correctly with appropriate longitudinal dihedral.

You could make it work as well with one wand detecting roll only and another wand at the front detecting heave only it would be the same but with specialised function wands. As is, the wands each have dual purpose. Basically both together ('collective') work as as pitch/heave control and each separately ('cyclic') work as roll control.

So much for pedantic semantics. I hope we are in agreement here on these fundamentals.
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<<<Also experimented with rudder hydrofoil flap control and that had virtually no affect except to slightly change the attitude of the boat so those servos were removed>>>

Once you establish a given loading distribution (taking into account trimming moments from sail thrust) the longitudinal dihedral for the particular geometry is set, so changing the attitude of the rudder foil when the the main foils are at a locked depth (due to the wands) does not actually change the overall attitude of the rudder foil, rather it just elevated/depresses the stern of the hull.
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<<<<Originally had the battery on a carbon tube and hooked up to the mainsheet so that when the sheet was eased the battery moved back. The battery was about 1 lb and it made no difference at all in two boat testing.>>>>

Now there is a really smart idea.
I am surprised though that you could see no difference. At the very least i would expect to see a difference in running trim.

How far could the batt-pack travel, what fraction of the model mass is the batt-pack and how large is the model?

 

Really... not to interrupt the love fest between you two guys, Doug and TCubed, but what the heck does this have to do with the thread?

It looks to me to be another sidebar attempt to talk about a boat that can't ever get out of its own shadow. Come on, Doug, you are so quick to denigrate those who have but a wisp of an idea that strays from your original discussion and here you are with TCubed, blathering on about model boats that are not at all like the type so defined in the thread title? Model friggin' boats, for Christ's sake.

Get it together boys, or take your love-in to another thread.

Hey, Ancient Kayaker. Where were you when these guys drifted off the topic, making things incredibly moot for anybody else? Where were your heady pronouncements about folks who were taking the topic away from the original discussion, about argumentative posturing, etc.? You know, the same folks who were making it testy for others to follow? Come on, man, step on up to the plate and take your swings on behalf of all things orderly. If you don't, you look like you are a member of “Team Lord, the disconnected ones”. You wouldn't want that would you?

60' + or - 20' monofoiler my butt. This is more inanity and there is not going to be any 60' monofoiler. Douglas, you can fess-up anytime now about the folly of it all. Not only is there nobody out there pursuing this crazy path for foilers, they have decidedly left the room, just like Elvis. Julian Bethwaite is off doing things with his Dad regarding other sizes of boats… as you well know, and he has little, to no, energy, or money, to buzz together a design, much less a fully constructed and functional boat of this type.

How long has it been since this crazy thread was begun.... two years and some change and not one single effort to build, much less design a 60' monofoiler of this type.

When are you respected fellows going to get a grip and start dealing with reality? Models are one thing. A functional, proof of theory, full-sized product, is quite another.

Let us all know when that happens... until then, please keep your model foiler heroics to yourself. They have no merit within the confines of this thread.

 

Chris
I might have to apologise for side tracking the thread as Mark Drela and I did on another of the foil threads.

Since I started my pedal boat project about six years ago I had an objective of running the length of my 1500m lake at 12kph. I can now do that. After I saw Decavitator and the Flyak my new objective became to get down to a river rowing course and push past a rowing eight going hard. I feel the only way I will do this is on foils. Mark has achieved sustained flight around 12kts with 220W in a boat and this is an output I can achieve for at least a few minutes. I might need to lose a bit of weight to improve my power to weight.

My first effort at foiling resulted in uncontrollable roll and I have been considering the best method to control roll and pitch. Hence the discussion on that topic. I am certainly not intending to build a 60 footer. Something about 6m with total boat weight of 15kg is the aim.

My intention is to roll down "T" foils that I engage when I want warp speed and release when I want a more relaxed pace.

RicK W