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 Post subject: twin tip hydrofoil
PostPosted: Tue Dec 09, 2014 3:01 am 
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Hi Hawaiis,

I have just dropped off a piece of aluminium louvre profile to a sheetmetal company. They are going to weld an aluminium plate on the top and a U channel on the bottom of the strut.

I am keen to try a twin tip first and then to progress onto a directional hydrofoil.

The U shape channel will have the open end on the bottom and the channel will accommodate a square aluminium tube of 25mm with a wall dimension of 3mm. I think we have allowed for 150 m in front of the strut and 150m at the back of the strut.

My idea is to have the ability to swap different set ups easily by unbolting the square 25m tube with the wings attached.

To use it as a directional there would be more of the square 25m tube at the back and nothing sticking out in front of the U channel.
I am keen to find out from you what would be the easiest way to make the wings. I noticed that your twin tip hydrofoil had flat outside wings and a curved (bigger) centre wing.

Is it ok to make these from aluminium?

Can you please provide me with dimension and distances so I can bolt them on and have a go.

Hopefully it is welded tomorrow. Will take some photo’s then to show the forum.

I am interested to get wings that will make it easy to get used to riding on a twin tip hydrofoil. At this stage I am not interested in any high performance. As long as it is easy and goes upwind.


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 Post subject: Re: twin tip hydrofoil
PostPosted: Tue Dec 09, 2014 3:18 am 
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3mm aluminum is marginal. Do you have pictures of your strut and fuselage?
The floor tile is12" square the titanium is .125" thick.


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 Post subject: Re: twin tip hydrofoil
PostPosted: Tue Dec 09, 2014 5:28 am 
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It looks like your fins are all flat. Is there any bend in them (anhedral or dihedral)? Also would like to know how far forward and back ward the middle of your front and back fins are from the strut.

Would even be better to get your recommendation on the exact size of fins ((front, back) (middle)) if I were to make them from aluminium and what thickness do I require.

The 3 mm square tube looks pretty sturdy. Do you think I need to put a wooden plug in it to stiffen it up more?


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 Post subject: Re: twin tip hydrofoil
PostPosted: Tue Dec 09, 2014 5:55 am 
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some anhedral will be better than no anhedral.
with aluminum you will need 6mm to 10mm in thickness.
the middle fin is 21"X5"X.125"
the two smaller fins are 11.5"x3"x.125" 6AL4V titanium.
You need to beef up 3mm aluminum or it will snap.


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 Post subject: Re: twin tip hydrofoil
PostPosted: Tue Dec 09, 2014 6:23 am 
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will it be anhedral on the centre and dihedral on the outside wings? Since I have an U shape channel and the square 25 mm tube theoretically for a distance of say 500 mm I will have double thickness.

How long is your total fuselage? The bit that is sticking out of the U shaped channel is not super long. I will try to get some photo's as soon as I get it back from the welders.

Thanks for your prompt replies


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 Post subject: Re: twin tip hydrofoil
PostPosted: Tue Dec 09, 2014 6:59 am 
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Anhedral on the main wing only, I just haven't got time to bend it yet.
The fuselage is about 700mm long.


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 Post subject: Re: twin tip hydrofoil
PostPosted: Wed Dec 10, 2014 9:37 am 
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wil wrote:

I am keen to try a twin tip first and then to progress onto a directional hydrofoil.

I am interested to get wings that will make it easy to get used to riding on a twin tip hydrofoil. At this stage I am not interested in any high performance. As long as it is easy and goes upwind.


Having read your profile, I see you like me are a certain age so please understand all that I say now is only ment to be productive and for your saftey.

Trying to learn on a TT KBHF is not a good idea at this time.
I have test flown probably the best designed one at this point and I can tell you it is MUCH harder than a DIR KBHF.
Consider this, have you ever seen an airplane that flys both ways?
It is simply very difficult to make a flying object stable to fly both ways.
And you must have 2 straps for a TT KBHF, not good to learn with.
The board does not have them same volume es a DIR so the water start begins with the whole assembly under water.
Please believe me I am a confirmed KBHF pilot and design builder and at this time TTs are a long way off.
I know of 2 funded projects that were abandoned because they failed!
This TT was conceived by FK24, the one I tried.
Attachment:
FKTTjump.jpg
FKTTjump.jpg [ 97.93 KIB | Viewed 1554 times ]

FK24 is "the man" at this point when it comes to innovation of KBHFs and a very skilled pilot.
He has built many TTs and says the A O As are super critacal. like +,- half a degree.
Wing profiles and shapes, sizes are also not dialed in at all.
But for sure flat without some sort of vert fin is not going to work well, very yaw unstable.
With a DIR you have the tail assembly acting as a stablizing component, you do not have this with a TT as is sym.
We know flat wings simply suck, without some sort of vert element and this is even more apperent with a TT.
Just a quick analogy,
IMHO learning to foil with a present day TT design as compared to a good DIR is like trying to ride a unicycle before a bicycle!
I will, am building a TT just for the challenge knowing that it is way unstable and super sensitive both to fly and build.
Wil,or anyone else, please do not risk your safty by trying to learn on an home built, untested TT!
I have all the design specs from FK but no need to share them now as they are a long way off from being user friendly.
MAYBE......with lots of trial and error by confirmed pilots and a thicker banana TT board with angled side foot hooks so that the inevitable crash is safe this can be fun???
Even FK is not happy with his builds and maybe the idea at the base is flawed?
@HW, if your TT flys and you can ride it? please post some video and , or photos.
If anyone is still up for lots of tuning, time, crashes, Fk24 has allowed me to share his lattest design in the spirit of progressing this idea.
In closing, I don`t want anyone getting the wrong idea that you can attach a not WELL designed, well thought out, TT foil assembly and go learn, you risk getting hurt, badly!
R H


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 Post subject: Re: twin tip hydrofoil
PostPosted: Wed Dec 10, 2014 10:33 am 
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RH:You probably never saw a helicopter fly backwards.
You must have seen flying saucers in TV.
Here is a video from 2013, there are a few more at Vimeo,
Please inform FK24 that I have a provisional patent since 2013.


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 Post subject: Re: twin tip hydrofoil
PostPosted: Wed Dec 10, 2014 1:38 pm 
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Location: France
Hawaiis wrote:
RH:You probably never saw a helicopter fly backwards.
You must have seen flying saucers in TV.
Here is a video from 2013, there are a few more at Vimeo,
Please inform FK24 that I have a provisional patent since 2013.

I fly R C helicopters backwards, read carefully, I wrote an airplane that flys both directions, much more like a KBHF wings in design, so your point?
Flying saucers :?:, in TV?
Bye the way good luck with your patent.
Prior art can be found easy as far back as 2007, and in more than just one (1) country and having multiple designs!
As for your video, we never see the T T foil itself flying?
R H


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 Post subject: Re: twin tip hydrofoil
PostPosted: Wed Dec 10, 2014 3:54 pm 
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Look like the French has not been very inventive lately,
Ladies and Gentlemen a bidirectional airplane and working hydrofoil by Americans with patents.
Imitation is the sincerest form of flattery.



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