Slip Wand for foiler height and roll control

Yep, thats what I suspected.
Its a bit like a a trike vs a bike I suspect...trikes are "stable" at slow speed but can fall over cornering at speed. Bikes are stable cornering at all higher speeds, but can fall over moving slowly due to no static stability.
The bifoiler seems to be able to counter sailforce better with veel heel (leaning *into* the force) than the static method of "make it wide"...which as inherent limits, after which Bad Things happen. (I guess the same is true of bi-foil setup too, only the Bad Things will consist of breaking foils!) Regardless, the bi-foil appears more elegant and efficient to me with less boundary effects and nonlinearities.
I added small ammas to mine to take care of slow speed stability, and will rely on the "bike effect" of the bi-foil setup to keep me upright at higher speeds.

 

==================
Have you had a chance to sail a Moth or R Class foiler? Do you have an experienced Moth foiler friend you can run some of this by?
Best of luck!

 

Ozy
the reason leeway is largely meaningless in foilers is for the same reason that Bethwaite was unable to measure any leeway in high performance skiffs despite knowing that it had to be there to make the foils work. Namely if your boat is moving at 20knots SOG and like a moth you have about as much sideslip as a laser does, (about 7 degrees for the laser at laser speeds of 3 knots) then your foiler traveling at 7x the speed will effectively have 1 degree of leeway.

Note also that the reason for 'Veel Heel" is not just that it generates lift to weather. think through what happens to Righting Moment in a foiler if it heels to leeward. Probably the most common crash in foiling moths other than ventilation of the foils, is a crash to leeward in the bearaway or a gybe.

It is much safer to heel to windward where your recovery is to sit in, than to be centerline, where once the boat heels to leeward, you have no recovery. (well almost none)

So I would abandon the unnecessary complexity of your "leeway" bell cranks - they won't do anything.

And also take with a grain of salt what any of the other posters have posted in this thread. None of them have sailed a high performance skiff much less a foiler and none of them has designed a working full scale foiler

I have sailed a skiff - quite a bit in fact, even in and amongst foilers... but I too have never sailed a foiler.

In fact if you want feedback from folks who do foiling, I recommend going to the Dinghy Anarchy forum on Sailing Anarchy. You will find folks there with actual experience in these things like Phils - and sometimes even Bora.

Folks like Bora have been chased out of this site by certain poster

 

Pics

Cheers guys.
Alas, I have not sailed a foiler and was hoping to get some feedback from those that have. I guess the guys that sail them have no reason to hang around design forums though. Bummer. I realise that it is far easier to theorise than build. Having theorised and half-built many small aircraft (it gets scary dangerous *very* easily!), the move to a foiling boat is actually not too bad in terms of "what if I stuff it up?". Embaressment I can handle better then broken limbs!
Also having actively skydived for many years I realise that "expertise" is quite different in the sky as compared to around the bar. Similar in competition sailing.
Although I realise that full roll control is probably out of reach I want to see if some sort of slip/roll coupling is useful.

As to what I'm building...well pics are worth a thousand words.
All the main bits are now there, I just have to sort out a few details like the mast mount, rigging, steering, rudder trim, etc. Having a 3d printer makes engineering small parts pretty easy, and ABS dipped in polyurathane resin is amazingly strong! (a little bit of CF or GF helps too).
I will not be abandoning the idea just yet as it will kill me to get this far and not give it a go. The wand system is pretty cheap and easy to test out...and I'll revert to a simpler system if needed.

BTW. Rudder box will be mounted conventionally on the transom (may build a gantry), amma mounts are just sitting there, not attached. The "wings" will be sheathed to make a decent aero shape. The main foil will actually pivot from its mounting point forwards, it is not in its real pos. The main hull is in 2 parts that snap together like a large rowboat...it should fit in my car.
Yes, she is tiny, but so am I.
Failure to try is real failure...stuffups I expect and have learned to enjoy. I have learned so much fom building this baby that even if I end up with an unusual fishing platform with an outboard on the back it will not be a waste of time.
I'll post an update when she gets wet in a few weeks.

 

Baltic.
I hear what you are saying about leeway and recovery from a center position. I realise that I cannot put a bucket seat in the middle and expect to sit there and have the foil balance for me. (maybe a power boat version).
I'm hoping a nice wide deck with wings will allow me to recover from little perubations...gybing will be most interesting! (at least until > 1x wind speed?)
I've also thought a while about Phil's comments about roll authority and I am a little more confident that the additional drag associated with max lift flap position will assist somewhat in allowing the foil to slip to its balance point. (ie. the torque generated helps, not hinders where I want the foil to go). I think the dynamics are too complex for simple theories which is why I built...building is much more fun than yackking!

 

wide deck with wings won't help. The issue is the speed at which the leeward crash happens and the fact that it is self-accelerating: a little bit of leeward heel instantly reduces RM which increases heel which reduces RM even more which increases Heel...

Its a bit like loosing your footing on the trap and swinging into the boat whilst close hauled. I've managed a recovery or two, but usually end up swimming.


Nor is it that doers don't hang around design forums. its that THIS PARTICULAR design forum has managed to chase the foiling sailors out of here due to the behavior of one poster in particular. Like I said - go to Diinghy Anarchy at saiinganarchy.com and you will find them there. And since your's is a multihull you can also try Multihull Anarchy as well. One SimonN is very knowledgeable there.

The thing about foilers is that they really are finicky. And by adding this extra dimension of freedom before you get it flying, you won't know if what's not working is the leeway gadgetry or the foiling stuff itself. Best start off with it disabled.

 

Hi Baltic.
I know the deck won't "save" a leeward crash, but may allow for a bit of pilot correction prior to it getting too out of control. The Moth guys don't seem to need to hike too far on their wings, but I'm guessing they are using rudder and sheeting tension as well as weightshift. I'm hoping the slip/roll will assist to an extent that it makes it easier to stay upright...if it makes it harder then it will quickly go and lesson learned.

I have fond memories of losing footing on trap, digging the leeward hull and flying to say hello to the forestay on a Mosquito. Fun times. The sound that boat made at speed was unlike any dingy...I am hoping to hear again on my little beast!

Thanks for the tips. My test plan is to use a simple power drive to setup the foiling stuff (heave and pitch trim) and to ensure it is feasable in simple circumstances before trying sail power. As you say, there are too many forces and things to trim to try it all at once.
The slip detect arms on the wand will start small and will be one of the first variables to tweak once heave is sorted. If their optimum length ends up being zero then I have the basic Moth system only with two struts instead of one "centerboard". If the optimum length is longer then the system will have shown it's worth. If the thing simply will not fly then it will go to ensure it is not the *cause* of stability issues. All I have to do to switch it off is put a pin in.
Having tested a few other flying craft I'm aware of how finicky they are...but some theory, some maths, some tweaks, and a good progressive test plan may allow me to pull it off...if not then I'm sure lessons will be learned and I'll have some good footage.
The fact I'm designing for one thing: fun, also makes this easier as I'm not producing a boat that must perform in the light stuff or the heavy stuff...just good sailing days. I wouldn't build a big boat this way, but it's better than CGI vapourware.
I was hoping that the forum wars from a decade ago had subsided and folks had calmed down a bit. Not to worry: half the reason I posted this was to put it into the public domain to prevent patenting.

 

Well you seem to have your head on straight - well relatively so for anyone who has fond memories of cartwheeling a skiff So good luck... Hope to see you poke your head into Dinghy Anarchy as well - some good folks over there

Just for yucks - mind me asking as to how long ago you started this project and roughly how much you have invested in it?

 

Actually the Mozzie is a cat...and I wasn't so fond of the manouver at the time!
I'll definitely check out Dinghy Anarchy.

I started in earnest in October 2013 and am not really sure on total cost...probabaly about 2K including sail and mast. Most of the cost is in glue, resin, glass, paint, marine ply...and my lungs before I got smart about using masks and sanding outdoors.

 

Pretty nice - the reason I was asking was that one of the "experts" you were talking to has spent some 4 years building his prototype....of what you have built in 4 mos... LOL!!

 

Yep, a different approach to things. Some like to tinker and talk more than build and test. Whatever floats your boat...(sorry)
I'm not here to antagonise anyone though. All replies have been useful...each to their own.

 

Doug Lord and Baltic Bandit have a thing going for months on Dinghy Anarchy and this forum.

 

Yep, I've read the archives.
Personalities do not interest me, only facts and ideas that might be related to facts. Sanity checking ideas requires getting wet, everything else is not worth getting excited about.
I've done OK out of this thread and appreciate all the replies....and no one can go and patent this idea now if it works.

 

Ozandy,
When you get the chance I would like to hear about your 3d printing and how it helped this project. Or should I say I would like BB to hear it.

What is the overall length of your craft? Ballpark sailing weight?

How wide is your main foil and the approximate area? It looks surprisingly wide -good for low speed takeoff.

I think BB made a good point about leeway sensing -forget about it. Instead you could place your wands in a fixed wide position and that will add stability at speed. You could even add some manual control.

 

Grey - where have I said anything that is inaccurate and not constructive?