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 Post subject: Re: the cheap, the bad, the ugly
PostPosted: Thu Jun 19, 2014 12:27 pm 
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Joined: Sun Dec 15, 2002 1:00 am
Posts: 252
Location: Slovenia
Your work looks nice!
I am all for doing things cheap if they can be done cheap and be usefull at the same time.
We should make a little competition - who can make the cheaper and easiest to bould foil and ride it (and show that on a camera) wins. If everyone would post their findings - what is good and what not - we (togather) could invent something cheap that also works.
Greetings,
Jaros


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 Post subject: Re: the cheap, the bad, the ugly
PostPosted: Thu Jun 19, 2014 1:45 pm 
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Joined: Wed Mar 01, 2006 7:51 pm
Posts: 255
jaros wrote:
...To put a foil shape in the whole wing would not be very easy to do.


First, you can try this method... at least for the pictures.

https://translate.googleusercontent.com/translate_c?depth=1&hl=fr&ie=ASCII&prev=_t&rurl=translate.google.fr&sl=fr&tl=en&u=http://constructionslightner.unblog.fr/2010/10/29/fabrication-des-derives-et-du-safran/&usg=ALkJrhjoIKsqTyc38TUclEHy1xAoyvaU-Q

Also, as a first attempt, you won't need to put too much energy in profiling the intrados (lower side of front wing. Just make a round leading edge.... the lower surface can be flat.

You'll get the best possible results using a table belt sander beacause you can control sanding angle AND pressure at the same time or even sanding every second.....
Image

How to make one ?

http://www.instructables.com/id/Table-belt-sander-lijadora-de-banda-de-mesa/

Safety instructions


A random orbit sander should give a neat result too (lowest possible speed)


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 Post subject: Re: the cheap, the bad, the ugly
PostPosted: Thu Jun 19, 2014 9:24 pm 
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Joined: Sun Feb 24, 2008 6:15 pm
Posts: 296
Location: France
Hello,
Please understand everything I am about to write to you is only so you do not waste your time.
Even the best profiled kiteboardhydrofoils do not seem to work with the strut directly over the front wing.
Your board will not allow you to center over the front wing and it is to small.
The strut L E and T E need at least a little NACA profiling thrown at them and 20 cm is way to wide and flat.
The fuse having so much flat surface area will create so much drag.
All your mounting hardware will also not help in the hydrodynamic area.
I am sorry but in that configuration it will never fly, I am almost sure, by anyone.
Completely flat wings are so unstable.
It seems that things that are hydrodynamic are not flat, at least over large percentages of the structure.
Please do not even waste your time trying to learn with that, you will not.
Again sorry to be blunt but I have built 5 foils from scratch and test flown many others but that is by far the least hydrodynamic kiteboardhydrofoil I have ever seen. Tough love.
My first build in 2008 and yes it is an air chair copy, it flew but just!
Attachment:
2008 FOIL.JPG
2008 FOIL.JPG [ 76.85 KIB | Viewed 853 times ]

19 layers 300 g f glass f wing almost flat bottom except for near L E. top Some NACA influence.
Rear wing 4mm alu again almost flat top, but semi naca by eye bottom.
Alu core wood filled strut 12 cm X 2.5 cm X 85cm
alu fuse with triangles for support at attach
The front wing has been reworked and used in a foil we use to teach even now!
I suggest that you try to get at least a little closer to what has been proven to fly.


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 Post subject: Re: the cheap, the bad, the ugly
PostPosted: Thu Jun 19, 2014 9:45 pm 
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Joined: Wed Oct 16, 2002 1:00 am
Posts: 5738
Location: Denmark
Great to see some honesty and wanting to help Revhed :thumb:

I would say, based on nothing but my knowledge and experience with physics and aerodynamics for 35 years, that it WILL work, but not that good most likely.

The main problem is, that you dont know HOW to foil yet !

So you dont know if it is a waste of time and junk, or if it is you that dont know how to ?

As said, the very best thing would be if you could get an experienced hydrofoiler to try it out !
Not possible in most areas (we are only two now, in our major part of our country).

That being said, MOST things will actually work to some extent, maybe tweaked a bit regarding AOA between wing and stabilizer.

Not sure I agree with Revhed about the added (parasitic) drag being such a huge issue, as I honestly think it WILL work, although not that efficient, but you know that in advance of course.

I take my hat off for you who build yourself, and really awesome - especially because the "task" is much harder because most have never been able to hydrofoil yet, so it is an almost impossible journey :o

RESPECT !

8) PF


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 Post subject: Re: the cheap, the bad, the ugly
PostPosted: Fri Jun 20, 2014 1:35 am 
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Joined: Fri Sep 11, 2009 3:15 am
Posts: 1510
from an r and d point of view u can move the front wing position with more holes so easily - r and d than involves making one complete foil at a time stuck in one position is ridiculous for learning

advice is great but actually making it and testing it will teach you so much so i would say even if it doesnt work you will be so much wiser for trying and able to progress the design.


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 Post subject: Re: the cheap, the bad, the ugly
PostPosted: Fri Jun 20, 2014 4:53 am 
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Joined: Tue Apr 08, 2014 9:51 am
Posts: 19
"I know the proper foil shape would be great, but lexan is quite hard to work with. If you send it to fast it starts to melt."

You could try to use a coarse file for shaping the Lexan so you minimize the heat generated.

Tuning should be quite a challenge without an experienced rider. When tuning my wings, I put one washer (1.5mm) between the fuselage and the wing to change the angle of attack and it was the difference between fighting the board nosing down and riding level. A friend bought a Sword and mounted it on his own board and he moved the mast attachment point 5 times before he could even ride it.

It will probably take A LOT of trials before you figure out what works.

Good luck


Attachments:
Red Wings.JPG
Red Wings.JPG [ 809.83 KIB | Viewed 698 times ]
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 Post subject: Re: the cheap, the bad, the ugly
PostPosted: Sun Jun 22, 2014 11:00 pm 
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Joined: Sun Dec 15, 2002 1:00 am
Posts: 252
Location: Slovenia
Hi,
Like I promised, here is a short report.
I have been in the water with my foil for 2 sessions, cca 1 hour each, than too tired. No foiling jet. Here is how it went:
Thanks to instructions from this forum, handeling with the foilboard in the water was not that hard. I could easilly position the board, put the feet in the footstraps and power the kite - but here the easy part stops. When I stend up on the board I allmost emediatelly fell of again. I tought that rideing with the board stuck to the water should be easy, but boy was I wrong.... Only after 2 houres I was able to ride (with the board in the water, so no foiling) for a short distances. The drag felt from the foil in the water was huge compared to when i am rideing the board with normal race fins. I do not know if that is the case with all foils or just with mine (not very hydrodinamic shape). It felt like there is not much I could do if the board startet to edge to much, I was not eble to turn it straight again so I crashed.
There were a few times when I got some speed, just before a crash, that I felt like the board is lifting from a water for a few cm, but then I fell... But I can not imagine foiling this thing anytime soon, it is just too dificult...
Well, like I thought from the beginnig of my project and like many of you also said - now I know nothing. Is it me and my lack of skills or is it the design - don`t know! Is the foil worth upgrading - don`t know! Should I make another project, this time not so cheap and not so fast - probably! We will see...
But there is one bright part in the story - the foil and the board stayed in one peace, nothing broke, nothing fell of. But this still can happen when I will actually fly with it... :o
Greetings,
Jaros


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 Post subject: Re: the cheap, the bad, the ugly
PostPosted: Mon Jun 23, 2014 4:38 pm 
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Joined: Sun Feb 24, 2008 6:15 pm
Posts: 296
Location: France
jaros wrote:
Hi,
Like I promised, here is a short report.
I have been in the water with my foil for 2 sessions, cca 1 hour each, than too tired.

REPLY,
Sorry ,but of course you are tired trying to drag your t bar and wings thru the water.

The drag felt from the foil in the water was huge compared to when i am rideing the board with normal race fins. I do not know if that is the case with all foils or just with mine (not very hydrodinamic shape).

REPLY;
Once again your t bar and wings are simply not hydrodynamic enough, period!
A normal foil will add a little drag which is normal but not at all like yours.

There were a few times when I got some speed, just before a crash, that I felt like the board is lifting from a water for a few cm, but then I fell... But I can not imagine foiling this thing anytime soon, it is just too dificult...

REPLY,
Please do not waste anymore time as I already told you, much more important to not hurt yourself and so much worse with 2 straps!!! :nono:

Is the foil worth upgrading
NO!

- don`t know! Should I make another project, this time not so cheap and not so fast - probably!
YES!

,
Jaros


Once again I am just trying to save you from hurting yourself and wasting time.
I and all my foil friends that have seen your foil would not even test it, sorry again, but not worth it!
Go back and have a look at designs that work, there are many.
Understand NACA profiles at least a little.
And my biggest advise is learn with a front foot hook or at least only 1 (one) front LOOSE strap and MOST important is to have someone who know how to fly test your kiteboardhydrofoil so you know it will fly!

R H


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 Post subject: Re: the cheap, the bad, the ugly
PostPosted: Mon Jun 23, 2014 10:01 pm 
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Joined: Sun Dec 15, 2002 1:00 am
Posts: 252
Location: Slovenia
Revhed thank you for your help. I totally agree with you. I will try to make something better during the winter if i will have the time. I hope the hydrofoil scene will evolve around here also, so i will be able to find someone who will be able to try my design. But first i will have to make something i will not be ashamed of showing on the beach with... :D
You are right that there are many designs that work, but finding any really usefull information about dimensions and other on the net is another think.
Anyway, it was a funn little project. I gathert some information that will help me in the future (thickness, glass layers, waterstarting,...) i will put it in my personal museum, and maybe try it in the future when i will be experienced hydrofoiler. :o
It looks like you give a lot of tought about being safe with straps. What do you think about "mushrooms" for strapless rideing instead of a front hook?
Thanks again!
Jaros


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 Post subject: Re: the cheap, the bad, the ugly
PostPosted: Tue Jun 24, 2014 1:04 am 
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Joined: Tue Dec 10, 2013 7:05 pm
Posts: 60
jaros, I tried the "mushroom" just the other day and it didn't help me. It's not possible to get enough grip on the knot. I have been trying strapless and that is also very difficult. Maybe you should try the foot hook from NSI. I have some, but I am still trying strapless.


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