Author Topic: Mast position fore/aft on the fuselage. Care to speculate?  (Read 2426 times)

Thatspec

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Mast position fore/aft on the fuselage. Care to speculate?
« on: February 05, 2021, 07:29:31 PM »
Finally getting around to modding and making a couple of fuses to use my Gong wings on my Axis masts.

Does anyone have any real world experience (or even care to speculate) how moving where the mast attaches to the fuse (fore or aft) might change the feel of a foil system? I.E. could you say that moving the mast back on the fuse could be equalized by moving the mast back (or foward) on the board? (Seems there's more to it). There are a number of variables meshing these two system and I'll probably just end up splitting the difference but, since I have the option it would be interesting to hear opinions.

PonoBill

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #1 on: February 05, 2021, 10:27:28 PM »
It would partly depend on the rigidity of your fuselage and how accurate all the bits were. But if you move the fuse forward an inch and move the base back and inch, all other things being equal, I can't see how it would change anything significantly. It's the location of the wing and stab relative to the board and your weight that matters. Windfoiler stuff that originally was designed to use a fin tuttle box had long fuselages that move the wing forward to the position desired.

There's some dynamic stuff that will be different, the fuselage is being rotated in pitch around a different center, but eh, does it matter?
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Hdip

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #2 on: February 05, 2021, 10:40:58 PM »
I asked a guy who commented about this on a podcast recently. Hereís his reply

Yeah pretty much, axis and gofoil  have the mast placed far away from the front wing. Itís really nice with a wide stance or in a straight line but people with a smaller stance need to compromise with the foil tuning to get it to work surfing

Dwight (DW)

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #3 on: February 06, 2021, 03:58:27 AM »
Iím not buying the stance argument. All brands have available fuse lengths from long to super short. That plays into stance width the most.

Iíve owned foils with masts all over the place on fuselages. There is a ďfeelĒ difference when the mast is more forward, than back, on a fuse. It is not comfortable for me, when mast is too far forward on the fuse. The ride is nervous, less drive, more wandering.


Dontsink

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #4 on: February 06, 2021, 01:50:37 PM »
I think it should affect the directional stability of the foil ,the yaw axis.
Most tail wings have a bit of curve (vertical stab effect ) and even if they are fully flat they have drag that will tend to align the stab behind the mast.

How this changes the foil behavior in pumping or turns i have no idea :)
I know it makes some foils not suitable for some boards, because the boxes will be to far fwad or back.
The Takuma LOL has the front wing pretty far in front of the mast compared to a Naish foil.With most other foil brands somewhere in between.
Manufacturers should start giving some info on this, something like " xx size wing has the Center of Pressure xx mm's forward from mast plate front screws"

So you could get an idea of foil/board compatibility
« Last Edit: February 06, 2021, 01:54:20 PM by Dontsink »

Thatspec

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #5 on: February 06, 2021, 06:27:41 PM »
Awesome, I knew this was the place to pose a question like this  8)

It sounds like as long as I'm close, within a cm or two, I probably won't have a completely worthless hunk of aluminum (and a lot of chips). Unfortunately testing around here right now is well outside my tolerance for pain.

OBX Dave and others have done this mod already using a stock Gong alu fuse (a masterpiece of simplicity at $57, no great loss if it doesn't work), Dave's mod moved the mast forward about a cm. I've gone the opposite direction and lined up the rear hole so I'm back about a cm.

The next step is to make a real fuse from bar stock, 1" x 1 1/2" x 24" 6061 (about $21 a piece from onlinemetals.com), that will mate with the Axis Doodad (and carbon mast base). A lot simpler shape than machining out the mast shape (Unfortunately the stock Gong fuse isn't deep enough for the Doodad). It would be easy enough to make the slot long enough for a couple of different mast positions, better to just settle on one though, less drag.

Will keep you posted, all additional opinions appreciated :)

PonoBill

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #6 on: February 06, 2021, 08:11:28 PM »
Okay... Why? I know, crazy question, especially since I spent the evening designing an adapter to connect older Axis fuselages to the carbon masts. For the same level of effort I could just machine the fuselages to fit the carbon masts, but I'd like to be able to still use the aluminum masts. Kind of a reverse doodad.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

clay

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #7 on: February 07, 2021, 12:18:37 AM »
Iím not buying the stance argument. All brands have available fuse lengths from long to super short. That plays into stance width the most.

Iíve owned foils with masts all over the place on fuselages. There is a ďfeelĒ difference when the mast is more forward, than back, on a fuse. It is not comfortable for me, when mast is too far forward on the fuse. The ride is nervous, less drive, more wandering.

I have had a similar feel experience.  Also found moving mast back has the opposite effect and dampens/delays movement/reactivity in a way that creates a easier ride for beginners, and can lead to "speed wobbles" at higher speeds/bigger waves.
Aloha, I welcome and appreciate all responses of positivity and good feeling.

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supunk

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #8 on: February 07, 2021, 11:26:07 PM »
This was how I made my Gong/Axis convertor if itís any help. I used a stock Gong Hellvator to Allvator convertor fuse which has a large rectangular slot already milled in it. It was just a case of machining a custom doodad and drilling and countersinking a couple of holes in the fuse. It moves the Axis mast approx 5mm forward of the Gong mast. Works really well. Think Gong are now out of the convertor fuses as so many people have made the mod. It would not be too difficult to make a custom fuse. I am currently getting one made to allow me to run GoFoil foils on my Axis mast. Hope pics are helpful. Cheers. Chris
« Last Edit: February 07, 2021, 11:52:42 PM by supunk »

supunk

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #9 on: February 07, 2021, 11:30:42 PM »
Think the pics are of a Kite fuse I did the mod on which is shorter in length but sure you get the idea. Sorry pics came out so large. There are more pics on my Instagram account chrislucas735 if you are interested.😀
« Last Edit: February 08, 2021, 12:09:27 AM by supunk »

supunk

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #10 on: February 08, 2021, 12:38:58 AM »
It looks like Gong are no longer producing the convertor fuse as it is no longer listed on their website ☹️

jondrums

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #11 on: February 08, 2021, 09:54:22 PM »
I'm pretty sure there is a progression podcast with Kane which talks about mast positioning relative to the front wing.  If I recall correctly Kane says it really matters a lot, but doesn't really say exactly why or what is best.

Hdip

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #12 on: February 08, 2021, 11:13:33 PM »
My above quote is from KDMaui. *Shrugs* people way smarter than me make these wings. I just want to go weeeeeeee.

Thatspec

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #13 on: February 10, 2021, 11:05:54 AM »
Okay... Why? I know, crazy question, especially since I spent the evening designing an adapter to connect older Axis fuselages to the carbon masts. For the same level of effort I could just machine the fuselages to fit the carbon masts, but I'd like to be able to still use the aluminum masts. Kind of a reverse doodad.

There was an even older Axis fuse that won't accept the carbon mast? So the HPS series is their third fuse. I'm relatively new to Axis gear, and perfectly happy with what I have so the question of why is reasonable  :)  I probably only used my Gong kit 3x last season and my Axis kit 70+

Having just picked up the Axis 86cm carbon, I want to be able to use it with both Axis and Gong wings. Much harder to make an adapter to use Axis wings on a Gong fuse. There's no good reason why, maybe to avoid buying the Gong 85cm carbon mast as I have the 100cm version already and the Axis alu mast system is second to none.

It was easy enough to mod a stock Gong fuse to fit a 19mm alu mast shape (ala OBX Dave's version). I'll bet anyone with a sturdy drill press and a 3/8" 2 flute end mill could do a reasonable job, just has to be flat on the bottom of the slot. Starting from bar stock is going to be a much bigger deal with my little mill, especially tapering it all down to accept an Axis tail. Since we're going back into a serious winter situation here, it's probably time to sit down and finally really learn to use the Fusion 360 software and send the file and bar stock off to the big mill

That adapter is a nice clean solution Supunk. I'm wondering how much shorter that fuse is? The stock Gong fuse is 21.5" end to end.


supunk

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Re: Mast position fore/aft on the fuselage. Care to speculate?
« Reply #14 on: February 11, 2021, 09:22:48 AM »
Hi Thatspec. The kite fuse was around 8cm shorter than the regular fuse plus it would only take kite foils not surf foils. I no longer have it to give you an exact measurment of its length.
It should be possible to mod a Gong fuse to take an Axis wing. I did a mod on a Neil Pryde Glide fuse. It works well  :)
« Last Edit: February 11, 2021, 09:25:02 AM by supunk »

 


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