Budget low tech kite hydrofoil DIY build a long

[Denisesewa]

Well its going on 2 years since I started the first foil build, since then I have learned alot about foils, what makes them work well and what doesnt as well as refining my build methods , ( still wood core and carbon). Its also been valuable to have ridden many different foils of various brands and sorting out which characteristics of each I like or dislike and what exactly provides those characteristics to a given foil, the small details in a given design make huge differences in performance. since I am now at the stage of being comfortable carving waves on a foil ( wave/surf kiting has always been my passion) I am trying to achieve the best foil for freeride/waveriding possible, what I have found is a light foil and board is more reactive and easier to make minor adjustments quickly, a short board with less swingweight is a pleasure to ride, my favorite at the moment is 120cm ( 4 ft x 19in) and light @ 6lbs. a shorter mast ( 35 in) feels more "carvable" on waves and more solid under foot with no decernable drawbacks ( since I dont race).
As for the foil specifics I started out building foils with low speed glider type airfoils, rather blunt entry with the high point of the foil at about 25%, same thing with the mast , I have since moved the high point back to around 40% with a fine leading and trailing edge, the first foils were forgiving to ride, slow and made noise the later foils are much faster, still very stable, super reactive to rider input and quiet as well as having very low speed foiling ability.
The plan form ( outline) design of the wings has also progressed , I have tried flat wings with winglets like the " Stringyfoil" Greg of BRM rides which worked very well although different than anhedral/ dihedral wings which I prefer, I also prefer a mid aspect wing for the type of riding I do.
So far many people have learned to ride on my foils, all of which have taken alot of abuse and are still going strong, all but one have been reshaped with a big performance improvement.
Anyway, its been a long road of building , discovery and learning to ride well enough to know what I want, I am just now finishing foil # 7 and believe it is another big step in the right direction, foil with board is just under 12 lbs. hopefully within a month or so I'll be able to give it a test along with my new LP FRS foil.

[tkettlepoint]

another great job myfriend.. If you are ever looking for a job building them let me know could always use a skilled hand like yours.

keep the pictures coming
terrie

[Denisesewa]

another great job myfriend.. If you are ever looking for a job building them let me know could always use a skilled hand like yours.

keep the pictures coming
terrie

Thanks Terrie !! I'd rather go kite with ya , work is over rated !

[tkettlepoint]

I agree very over rated. on day we will kite together.

terrie

[downunder]

Awesome finish mate Are you 'painting' epoxy or is this a varnish?

[Denisesewa]

Awesome finish mate Are you 'painting' epoxy or is this a varnish?

Its epoxy , "additive F" from resin research is the secret to a good finish, works with any brand of epoxy.

[downunder]

Ok, cheers for that. Will try to find it in OZ.

Another question: the wings and masts looks rock solid, can it be bent at all? Torsion? How blunt is the TE on this pic?

[Denisesewa]

Ok, cheers for that. Will try to find it in OZ.

Another question: the wings and masts looks rock solid, can it be bent at all? Torsion? How blunt is the TE on this pic?

The trailing edge was sanded to a knife edge before the fill coat and gloss coat of epoxy so with the added epoxy it is very fine, this is the stiffest mast I've built so far both in torsion and flex, less flex than MHL lift and about the same as LP ( which is almost nothing). the core is 3 sheets of 3mm 10 lb per cubic foot balsa with 9 oz uni between each layer, then two 7 oz uni , one 7 oz plain weave,one 7 oz uni at 45 degrees another 7 oz uni at opposing 45 degrees and 8 oz twill for the final layer. I normally use 3 mm baltic birch for the core, the wings are similar but baltic birch cores. final thickness of the mast is 14mm.

[Benicia Wind]

I'm new to this DIY foil obsession. My foil has a birch mast/fuse and plywood wings, it's really slow and ugly but amazingly it mostly works and is great for learning. I'm working on model 2, faster more stable good for strapless riding. You all have so much more experience in all this, maybe you could answer a few q's.
1. What do curved wings do better? I see most wings are curved but race wings seem to be flatter.
2. What happens if the mast is not stiff enough? My mast is not very stiff and I think this may be causing stalling problems but I'm not sure.
3. Does anyone have drawings or dimensions of their favorite wings they can post? Or perhaps even some old wings they want to get rid of? Be fun to play with.

Thanks all.

[Denisesewa]

I'm new to this DIY foil obsession. My foil has a birch mast/fuse and plywood wings, it's really slow and ugly but amazingly it mostly works and is great for learning. I'm working on model 2, faster more stable good for strapless riding. You all have so much more experience in all this, maybe you could answer a few q's.
1. What do curved wings do better? I see most wings are curved but race wings seem to be flatter.
2. What happens if the mast is not stiff enough? My mast is not very stiff and I think this may be causing stalling problems but I'm not sure.
3. Does anyone have drawings or dimensions of their favorite wings they can post? Or perhaps even some old wings they want to get rid of? Be fun to play with.

Thanks all.

In my opinion the profile (airfoil shape) of the mast and wings is most important, my first masts and wings were kind of blunt which caused ventilation issues, which I think is what you mean by stalling?
I can send you paper templates of my current wings if you like,( the ones in the pictures at the top of this page) I built these flat with winglets and curved ( 2 inch drop from center to tips) , the flat wings have a different feel and I personally prefer curved ( anhedral wings ) , my rear wings have about 3/4 inch dihedral. I consider these mid aspect freestyle wings.
The following picture is the profile of my first mast ( on the right) and my current masts( left), the difference in performance is remarkable.
Mast stiffness both lengthwise and torsional have a big impact on stability at speed and in carving turns, a flexi mast delays feedback to the rider so its more difficult to keep up with minor weight adjustments.