fuselage

[meteo]

I own a LF hydro foil, and once a got pretty good on it, I wanted a bit more speed… I was cruising at 10 kts and my top speed was 16kts… but anything above 11 kts was very unstable, the foil just wanted to “dive” down… I had to be extremely alert to go fast and I could not hold it more than a few seconds(less than a minute)… so one day I decided to lengthen the fuselage by 20% from 610 mm I went to 730mm…

Wow… I could not have imagine a better foil… super stable and for the first time, I was able to do a 30 minutes outing without falling once… but my cruising speed went form 10 kts to 11kts and my max speed was now 17kts, not much of a gain, but the board felt much more stable in the 12 to 16kt range…

The LF Company also must have learned about this, because they now produce the hydro foil with a 780mm fuselage…
I have enough knowledge to understand that the speed will probably never be faster than 17 to 20 kts, because of the “size” and “shape” of the wings, but anything above 17 kts if fast enough for me, if the board just stopped wanting to dive down at high speed…

My question is the following: how long can I go on the fuselage… 1000mm, 1200mm??? There has to be someone who has tried it!!!

[tkettlepoint]

longer will be easier to ride but will slow down the speed because of the wet surface area. But then if you start trying high AR wings you may gain some speed..

terrie
www.jellyfishboards.com

[meteo]

longer will be easier to ride but will slow down the speed because of the wet surface area. But then if you start trying high AR wings you may gain some speed..

terrie
www.jellyfishboards.com

Hummmm! The fuselage is very small less than 5 cm2, and the added length multiplied by the added circumference is not that much… I might lose a few percent on top speed, but I was told someone has clocked more than 21 kts on the original LF foil… Hey, losing a few percent on 21 kts is not bad if I can get it to be more stable at 16kts….

Not many responses… Well I decided to try it myself… just made a 920 mm and a 1220mm fuselage.

Unfortunately, cold weather has settled in with strong northerly winds… 10°C (50F)… Brrrr… let’s hope I can try both of them before returning to Clearwater, Florida… I have no tools over there...

[Peter_Frank]

I like the longer fuselages - just like a high performance glider has a really long fuselage, and smaller stabilizers

I dont think the added fuselage surface can outweigh the necessay added stabilizer area/drag.

So a longer fuselage is IMO better, eventhough there is some practical nuisances of course

The dynamic behavior and feel is a totally differet issue, that will take a loooong time till we get the hang of

PF

[0dmz0]

I also have LF foil and would love to get some more stability on it! Can you share some pics and details?

[meteo]

I also have LF foil and would love to get some more stability on it! Can you share some pics and details?

Pretty easy to do…

I went to my local metal shop and for 4$/foot, I bought a square aluminium pole 7/8 by 7/8 inches, long enough so that I could cut out a 29 , 36 and 48 inch fuselage…

I then bored 7 holes in them. 5 holes were made to be tapped for a 8 X 1,25 scew, and two bigger ones for the 8mm screw to go through it… I used a milling machine to have the required precision to achieve this without problems.

That’s about it… I also used a bit of epoxy and microbolloons to round out the front and back of the fuselage similar to the original fuselage…

Since I do not know how to “upload” photos to the forum pages… I made a small video of the 736mm (29 inches) fuselage

https://www.youtube.com/watch?v=KlDLhR-2suw

[Zeeko]

Hi

Nice building!
But I would like to check what is the stability you are looking for. As maybe your trouble is a yaw too free.
For that, it is more simple to add a vertical twin tip fin on the back of the fuselage.
Also, if your trouble is a too sensitive pitch, this is maybe due to a trimming of the AoA of the back wing you can do.

What is the target you are looking for.

ride easy
Nicolas

[meteo]

Hi

Nice building!
But I would like to check what is the stability you are looking for. As maybe your trouble is a yaw too free.
For that, it is more simple to add a vertical twin tip fin on the back of the fuselage.
Also, if your trouble is a too sensitive pitch, this is maybe due to a trimming of the AoA of the back wing you can do.

What is the target you are looking for.

ride easy
Nicolas

Here’s is what I am looking for :

The ability to maintain the speed of the foil with ease… shooting for 17kts

with the short fuselage, I was able to maintain 10kts easily, and had a top speed of 16kts.. with a longer (20%) fuselage these values were increased by 20%, and there was an added bonus… I was now able to jibe(changing my feet) on the water, without falling, much more easily…

I have since then made a 150%(910mm) and a 200% (1220mm) longer fuselage.. I have tried the 1220mm fuselage once, and to my surprise, it was so stable that I was able to jibe(change my feet) while on a foiling stance… but the cold weather is here… and my test was only 30 minutes before I froze… going down to Florida this week to do more test…


I have tried changing the "pitch" of the rear wing... I double it... did not see much difference, but I was told by the LF designer that their new rear wing is better...


I have tried a Spotz with a free race wing. I was surprise, easy going… speed much faster… probably better suited for what I want to do… but for the time being… these experiments with the fuselage of the LF foil is costing me only 10$ per fuselage, and are VERY easy to do… I have nothing to lose and probably a lot to gain… the increase in stability for air jibes is probably true for ALL types of hydro foils…

[Bille]

...

I have since then made a 150%(910mm) and a 200% (1220mm) longer fuselage.. I have tried the 1220mm fuselage once, and to my surprise, it was so stable that I was able to jibe(change my feet) while on a foiling stance…


but the cold weather is here… and my test was only 30 minutes before I froze… going down to Florida this week to do more test…

...

How did your test in Florida, turn out ?

I'm curious what would happen to your 200% test ; if you reduced the size of the tail
proportionally to the increase in fuselage length ?
It should go faster ; and still be more stable , if when compared to different full scale
sailplanes, i have flown.

Bille

[meteo]

How did your test in Florida, turn out ?

I'm curious what would happen to your 200% test ; if you reduced the size of the tail
proportionally to the increase in fuselage length ?
It should go faster ; and still be more stable , if when compared to different full scale
sailplanes, i have flown.

Bille

HI Bille ... Today I tried my 150% test... I was sooooo pleased that I wounder If I am going to test my 200% again... I dont have my tools with me and I would need to do small adjustments... for the 200% ... but eventually I will do it....

Got a chance to try out my new fuselage at 150% longer than the original 910mm(36 inches) instead of 610mm(24 inches)… OHhhhhh yes…. 120% longer was good, 150% is better…

My cruising speed is faster, jibing and changing my feet is easier, staying at a “set” height for going over shallow water is easier… I did not try a “top” speed because the “hole” in which I was playing was too small 500 meters X 500 meters… but I did reach 17kts…
Air jibes are almost there… I don’t try them… I just take the board close to the water, change my feet, and usually as I change my feet, the board starts foiling by itself, and when my front foot is in the foot strap… I am already on a foiling stance…
The only “drawback” that I can see, is that my speed being faster… I have to adjust my technique for turning into a jibe… the wind speed was only 12 kts… and I was easily going 14kts… this must be ridiculous for good riders, since on average they are almost always going faster than the wind speed… but for me it is a new challenge…