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 Canard Hydrofoil? (initial planning)

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dgm3333



Kitesurf depuis/since : 2017
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Age : 43
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MessageSujet: Canard Hydrofoil? (initial planning)   Mer 2 Aoû 2017 - 0:01

I'm keen to make a canard hydrofoil, which would be stable for a beginner (me).
I've seen (but never ridden) a Zeeko spitfire.
I prefer the idea of canard for the weight-back riding style, (as well as the idea that both wings lift, which seems cooler to me).
So advice is requested regarding this project

Plan so far:
Using Twill weave 12k 380g 33msi CF throughout.
Cores will be alternate layers of flat and 45deg CF sheet, with 3 layers wrapped around the outside (one at 45deg to others).
I'm trying to decide whether there would be any benefit in stitching the layers together with CF Tow (or possibly Kevlar tow to decrease risk of total loss in case the whole thing broke off, but I'm a bit less keen on this due to the water issues)
I'm not sure how many layers of CF are required for the various parts, so advice on this would be appreciated. Most builds only seem to use a few layers to add strength over what often seems to be a 'filler' core, so is there any reason you couldn't have essentially a hollow or honeycomb core (eg for wing) which would decrease weight but maintain strength. My cf sheet is 0.4mm thick which would mean 30 layers in some portions which seems overkill.


Main components
I want to make 3 masts to stage the learning, and as my kid will prob want to try: 25cm, 50cm, and ~1m, with Epler 837 profile. This will take either m6 ss threaded rod embedded in the mast or m6 SS bolts from the fuselage and mounting plate (with a standard 165x90 plate), I'm still considering casting a waxed or nylon bolt (which will provide a moulded thread and can be removed after casting), vs helicoil, vs internal SS nuts (or longer threaded couplers) vs drilling and tapping the CF (not sure of the various strength vs electrolysis issues). I'm not keen on monobloc as prefer to be able to exchange components.
Fuselage just 2x cf sheets (90+45deg) rolled to make a solid cf tube/cone

WINGS
I've basically copied the Mark Todd design for wings. This has sl swept tips which should decrease tip turbulance/drag.
My logic is that a flat wing will be very easy to make, also I understand very maneuverable, but I'm open to being convinced as anhedral would presumably be more stable and may be better as a learner foil.
Obviously the front/stabilizer wing will be above the fuselage, and the rear/lifting wing below to try and minimise effect of turbulance on the main wing (but remembering both will be lifting I figure I can live with that), maximum L/D angle for Aquilla airfoil is 5deg, so that would be my initial setup for both wings. Main wing has 606cm^2 and stab has 201cm^2 (my weight is 55kg w/o gear)
The AQUILA 9.3% smoothed airfoil has an essentially flat underside (mine will be dead flat as I plan to cast it on a sheet of glass to improve finish), so also much easier to make than Eppler or alternatives.

I have created an excel spreadsheet to plan it, and this will automatically provide the outlines to cut from the carbon fibre sheet.
This is shared on Dropbox if you would like to view and comment.
NB it's very messy, as it currently uses spreadsheet formulae to generate the outer profiles, but a vba macro to generate the internal contour lines as per image, and is not well commented its also trimming/scaling the airfoil to maintain minimum of 2mm thickness (but I might drop this to min of 1mm)...


(Download here)
I'm also thinking I'll probably make the wings out of foam initially then cast a wax mold for leading edge and topside (since much lower effort to achieve a good de-mold surface which would decrease ultimate finishing)
Then paint the wax mold with epoxy/microbubble mix to provide the outer surface.
lay my precut CF sheets in the mold, then attach the bag-mixed epoxy attached to one end (I find it's much cleaner to mix my resins in a plastic bag then I can apply like a piping bag. I can also attach this to the mold and allow the vacuum to push/draw it into the mold.
I'm not sure whether much benefit in de-gassing the epoxy, as I'd usually be doing this to achieve a crystal clear finish whereas strength is the issue here and the CF will be the major strength component,
Finally oven cure at 90deg...
Anyway, any thoughts on my plan (esp issues around designing the canard) gratefully appreciated.


Dernière édition par dgm3333 le Ven 11 Aoû 2017 - 17:01, édité 4 fois
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franckite24

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MessageSujet: Re: Canard Hydrofoil? (initial planning)   Mer 2 Aoû 2017 - 10:21

good luck !!and welcome!!
we folow your construction project!!! Very Happy
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jm33

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MessageSujet: Re: Canard Hydrofoil? (initial planning)   Mar 8 Aoû 2017 - 11:11

Vivement les premières photos et surtout les premiers essais !!
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