Well I sent the Rhino file of my 2010 foil to my mould maker (aka my brother) to start the mould construction process again, this time for the “Belmont” foils. Andrew has decided to embark on a rather small construction job, making Farrier F22 for himself, so the CNC machine has been getting a good workout lately. The cut time for a farrier float frame is about 15 mins, so it is heaps quicker than doing it all manually.
The design for my next foil is 100% mine, and has been heavily influenced by the current top of the pops, the Mach 2, combined with what I have learnt from sailing with my current foil. So what is changing and why ?
I have changed The foil planform to allow a flap that is significantly wider in the middle compared to the tips, which has been a feature of all Amac’s foils. My current foil has a flap that is pretty much rectangular ( i.e. the same width in the middle as the tips). Having it much wider in the middle and smaller in the tips should give better control with lower flap drag as the flap can achieve the same effect moving through a smaller angle.
I am no longer using the NACA 63-412 section, but I am keeping it “in the family” so to speak, by using a lower drag NACA section. In the computer it has 10% less drag for only a 3% lift loss at 15kts, so hopefully that will translate into a real on-the water gain.
I have designed two versions of this foil, a bulbed and non-bulbed version. Whilst I am still a not a true believer in the bulb like Amac, the bulbed version will allow me to swap between my BR horizontal and this foil, for back-to-back testing and vertical re-use. If this foil works really well, I will probably make the bulb-less one above.
Not to be left out in the cold, by current foil is be getting some tweaks for this weekend, so hopefully the wether will behave.
Great job and marvelous design!
We have thought about it but did not come that far. Thus using the full BR set and learning to squeeze more out of it.
Less drag / lift at 15kts is all fine and dandy
BUT If other foils are lifting out at 7kts boat speed and you need 8kts to foil in the light stuff because you have a lower lift section….then you’re toast…….as I’ve found out the hard way!
Be careful – light wind take off is a critical factor.
hey Bruce
Looks great, cant imagine in practise the take-off will hurt too much. you may need more AOA on the boat thats all.
Ive just cut the tooling for a new one as well, but I went the other way. planform looks pretty similar, but i used a higher lift section and cut down on area. be interesting to see how they perform. Have the potential now to make multiple horizontals now too.
good luck with it, post heaps because its a good read!
nick
is it just me or is the leadng edge in planform got a hollow?
@MartyJ Low end take off is definitely noted … if it’s not, then it’s only one horizontal.
@markla it’s just you
the leading edge planform is straight, the rendering just tricks the eye a bit.
Bruce why are you using a Naca airfoil instead of a Wortmann 63-137 or better still iyou want to use a really large flap a Du86-137/25. I lik your planform and cocncurrthat the bulb doesn’t seem all that sensible except structurally . Better to put the horizontal slightly forward and avoid coincident pressure peaks.
Cheers Chris
@Chris It is an evolution of what I am currently using, based on developments that have happened since I designed my last foil… that Wortmann section looks like it has way to much camber and the Du86-137/25 section is .. well … different.