For those familiar with the Starboard Plus fuselages - I'm not clear what the angles mean. For low wind - do they mean they have the stab flatter and flatter? Or do I have it backwards and it gets flatter with more wind?

Per their website:
Note: the 115 Plus fuselage is supplied with six angle spacers ranging from -2 degrees to +1 degree. The recommended Tail Wing Angle Spacer for the RacePlus is -1.5 degrees or -2 degrees:
-2? for wind speeds of 10+ knots (recommended default angle)
-1.5? for wind speeds of 8-9 knots
-1? for wind speeds of 7 knots
-0.5? for wind speeds of 7 knots
-0? for wind speeds of 6 knots
+1? for wind speeds of 5 knots

They go flatter as wind increases. to be honest I've only flattened the backwing myself for reaching, haven't found the need, even for holding the 9.0 in 30 knot gusts. A flatter stab will not make less power, just less power at the same speed. Meaning that decreasing the stab angle will really only help you if you go faster aswell, otherwise you'll just bring the whole thing out of balance. The reason i use it for reaching is because I'm faster on those angles, plus i dont need the power to go upwind!

Main foils along with providing lift have a downard torque acting at the point of lift. The combination of fuselage length, a lever, and tail area load the tail in a downward direction to counter act the downward torque acting at the point of lift on the main foil. Starboard sells a number main foils which require different tail down forces to balance them. Perhaps if a particular combination of wing, tail and fuselage don't balance, a small adjustment in tail angle will bring it into balance. I suspect that is what the different angle spacers are for.

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WhiteofHeart said..
They go flatter as wind increases. to be honest I've only flattened the backwing myself for reaching, haven't found the need, even for holding the 9.0 in 30 knot gusts. A flatter stab will not make less power, just less power at the same speed. Meaning that decreasing the stab angle will really only help you if you go faster aswell, otherwise you'll just bring the whole thing out of balance. The reason i use it for reaching is because I'm faster on those angles, plus i dont need the power to go upwind!

I understand the need for less angle at speed.* That's the part that's confusing...

Never mind, found this which is much, much more clear: https://starboardfoils.com/pages/2020-ifoil
"iFoil sets are supplied with six angle spacers (-2? / -1.5? / -1? / -0.5? / 0? / +1?) and with a new 255 tail wing that has -2? built in. The recommended tail wing angle on the 115 Plus and 95 Plus is -2?, so we recommend starting with the 0? spacer. You can reduce tail wing angle up to 2 more degrees by using the -2? spacer, for more speed and control, or increase by up to 1? by using the +1? spacer, for more power. "

The stab is set at -2 but the -2 spacer is actually subtractive ie -2 - (-2) = 0 It sort of makes sense but doesn't at the same time. The more I read both pages, I'm not sure they know what they wrote.

original text here: starboardfoils.com/pages/2020-race-plus

Thanks for taking the time to reply.

* Just saw an interesting youtube video where a fellow scratch-built a full size replica of a Spitfire. He said that in all the pics, at cruise speed, you could see a slight deflecton of the elevator and was pleased that his version displayed the same flight characterisitics, ie he had slight down elevator at speed.

Sorry for the hijack, but is the tail wing angle adjustable on the original 95cm fuse?

on the 95+, yes

Or simply with washers on the normal one.

Ok, thanks.

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da vecta said..
Or simply with washers on the normal one.

Washer under the middle screw was the advice given me here a long time ago. Just tighten gently so you don't crack anything. IIRC, credit goes to seanhogan.

I would like to read more on this subject and in layman's terms as well. There must be a good reason for creating so many stab adjusters . I would like to understand it more . Otherwise a stabil flight is most important to me as just one fall can loose me the race.

Unfortunately it's not a simple topic and a lot of variables come into play; what board you're using, what rig size, foil sail, etc etc. For example pre the 115plus fuselage I highly modified my board (jp135) to effectively move the front wing forward (moved all the straps way back , modified it to 91cm wide, parallel rails etc), this effectively makes the standard 115 fuselage in my board somewhat of a 'plus'. Under my feet the front wing on the standard 115 fuse is about 50mm further forward compared to the older foil 177. Sailing the same foil in those two boards back to back is night and day, my setup is waaay more powerful.

Now to the 115plus fuse, whack that in my board and it's pretty out of control haha! That said I like a powerful setup, if you can control it there are advantages. Ultimately what works for each individual will come down to experimentation, no two setups are really the same and everyone wants something a bit different. I do think ultimately you'll end up just using two stabiliser settings, a light wind setting for say 6-12kts max and then a setup for 12kts and above. For my setup this has resulted in -0.5 from 6-12kts (9.0 severne HG2) and then -2.0 from anything over 12kts, using the 9.0 up to about 16kts then the 8.0 above that. At my weight of 70kg the 10.0 is basically pointless as the wind range is tiny and the drag penalty is too high at my weight to haul it around overpowered. The -0.5 setup is crazy powerful, I have difficulty keeping it in the water over about 12kts downwind, the 6-8kt zone is where that shows, the upwind angles are where it shines. All of the other stab angles between -0.5 and -2.0 on my setup I found a bit of a compromise IE there will be a very small wind range where they are good but if you get caught either side of this range then you are in trouble. Using the two at the extreme ends of your determined spectrum gives you the best chance of being in the zone.

So why do we even need them; because the front wing is further forward on the 115plus the moment resulted from that wing is a lot larger...laymens terms, the lift is further forward. At a certain stage, IE the higher speeds seen at larger wind strengths, this amount of 'lift' will become too much to control, in order to control this we reduce the angle of attack of the front wing. We do this be reducing the stabiliser angle which results in a lower angle of attack of the front wing once it's settled into a state of equilibrium. This is also why when you have done this it becomes harder to fly it if the wind drops....angle of attack lower = lower amounts of lift for the same speed = harder to fly the foil.

That's ultimately an overly simplistic description but as with most things empirical testing will yield results. The Starboard recommendations are a good guide but may not suit everyone's setup. It's something you really have to test for yourself, start by following their specs and test it. IE at the low wind end test the -0.0 shim then come in and try the opposite of the spectrum the -2.0. Note how it feels, what angles you can pull, what speeds? Same at the high end, try -2.0 and then try -0.0 (good luck hehe), note down the same things. It won't take you long to get a good read on it if you are methodical about it.

I would also say the 115plus fuse is aimed almost purely at racing, it's about getting those last few % performance out of the foil in every condition, particularly the light end. I think as an all around setup that you can set/forget and enjoy almost every condition the standard 115 fuse is a better fit for most people who aren't out and out racers.

Also note all my testing has been done with the standard rear stabiliser, I don't have the new rear stabiliser which has a standard angle of -2.0; IE it goes -2.0 to -4.0 using the shims rather than -0.0 to -2.0 with the standard rear wing. I'd say this new rear stab is more aimed at winds over 15kts....it would be on my setup anyway.

2.0 degrees down angle on the stab is pretty much standard for most foils. Some people in Hood River did a bunch of measurements on a range of foils.

LP also includes a set of color-coded stab cradles to adjust the down angle.

Otherwise, for those foils for which the stab is connected above or below the fuse, people have experimented with plastic shims or washers to fiddle with the angles.

^^Huh? We are not talking about most foils here, we're talking about a specific foil, a high aspect race foil at that. The 115plus is so far at the opposite end of the spectrum to the freeride foils that most people on the Hood River ride that comparing them just clouds and confuses the discussion.

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segler said..
2.0 degrees down angle on the stab is pretty much standard for most foils. Some people in Hood River did a bunch of measurements on a range of foils.

LP also includes a set of color-coded stab cradles to adjust the down angle.

Otherwise, for those foils for which the stab is connected above or below the fuse, people have experimented with plastic shims or washers to fiddle with the angles.

Maybe for freeride foils with the average fuselage length, but claiming its standard for most is quite daring. There are a lot of design options like fuselage length and the position of the mast on the fuselage which have an influence on what your stab angle should be. On top of that, the difference between 1.7 and 2.2 degrees (for example) is noticable and might be lost in measurement error. Its really hard to really measure the angle of attack of the profile.

I wouldn't dare even base my startingpoint for trimming the angle on "2 degrees ... is pretty much standard for most foils"

Racefoils are definately not most foils either. My loke race has an angle very close to 0.

The point was that down angles are a thing in this sport. Race, freeride, SUP, kite, all of them have stab angles as a design and performance feature. Being able to change the angles is definitely a fine-tuning feature that is of interest mostly for racing, no question.

The LP FRS is a freeride foil that works really well for slalom racing. Those Gorge Cup racers really like to fine-tune the stab angle with LP's color coded cradles. On-beach discussions between races attest to this. I just use the red cradle for freeride fun foiling.

No question that the longer lever arm of a race foil fuselage makes the stab angle more of a performance tweak. Those angles are usually much smaller than angles on shorter fuselages, like the zero degrees on White's Loke.

The fixed stab angle on my Moses 105 Race (110 cm fuselage) is -1.5 deg. I have not heard about anybody shimming to adjust this on the Moses.

I have to admit the stab spacers are confusing to me....
for instance I just measured my set
which is a 800 wing on a 115+ fuse with the original stab.
i have a -2 spacer in and with the front wing zero the stab measures 1.35 deg
Leading edge down so in lift mode.
This measurement was taken alongside the fuselage.
if I measure closer to the wingtips then the measurement is very different.
this is the starb race set.

Again I don't think it really matters what the actual values are, the '-2.0' is just a reference that you can correlate to a sailing condition; Does that actually mean it reduces stab trim exactly 2 degrees, I don't know. Test over a wide range of conditions, work out what setting works when and then just apply it, it's the only real way.

In real terms someone saying, you need to be running a -1.0 degree shim in 10 kts is only relevant to them and their setup, imo. It's also why the starboard settings should be just used as a guide....but they are a good guide in terms of; "okay I want more power, right, add more stab angle, -0.0 shim etc"

I should also add that even in reduced stab trim mode, IE -2.0 there is still positive stabiliser trim (leading edge down) like you measured. Much like an aircraft the 'system' needs a certain amount of longitudinal dihedral or it is very unstable.

Rough definition from for those playing at home;
Longitudinal dihedral; the angle between the zero-lift axis of the wing and the zero-lift axis of the horizontal stabiliser.