was watching this guy marvinho dos santos riding the ART1401, and he switches to
a bigger stab to provide more lift, does it really provide more lift?:
Noticeable improvement in low end and pumping at slow speeds with a large stabilizer for me. Similarly, too large a stabilizer can make a setup feel overfoiled. So yes - a bigger stab provides more downforce in back which means more lift in front (sort of).
1 Like
If by âliftâ we mean the tendency of the nose to pitch up, yes a larger stabilizer does that. If by more lift we mean that it supports more weight at the same speed, or the same weight at a lower speed, no.
2 Likes
âMore Liftâ means you donât really understand whatâs going on. More Glide, lower stall speed, lower takeoff speed, more efficient pump. These are worth discussing. âMore liftâ isnât a thingâŚ
1 Like
It was just pointed out to me that my last comment was really shitty, and, upon reading it I kind of feel like a jerk. Sorry about that @stralen999
I feel like the above comments do the subject justice. Remember, the stab doesnât provide any lift, it just helps you keep the front wing in a position where it can provide lift. Independent of that a bigger stab is adding drag and downforce - the opposite of what you want. Also, the added stability from a bigger stab is counteracting the pump motion. Iâve definately had setups pump better with a smaller stab.
It can help you transmit more power by adding stability. If youâre not 100% in control 100% of the time more stab will help you by letting you transmit power more consistently. If 40% of you energy is being spent on balance and control and 60% is going into the pump a bigger stab could cost youn 10% in efficiency but let you put 80% into the foil.
Final caveat - at a certain point too much stab can overpower a front wing, Iâve had this on my small and delicate lift 120, probably not a concern here.
I would also say a higher aspect stab might be the best bet, a little more effective stability, less drag,
3 Likes
I have to admit that the âmore liftâ catchphrase drives me nuts 90% of the time.
(As in" move the mast forward for more liftâŚ")
For the same foil and fluid lift depends on speed and AngleOfAttack.Period.
But the Stab case is a bit of a gray area IMHO.
Because at very slow speeds (high angle of attack) it is possible that the stab is providing positive lift instead of negative.
So a big Stab could lower your stall speed by increasing lifting area.
I have no proof of this,it may be total BS.
Maybe KDW could chip in and lay the law on what stabs do and donât⌠
2 Likes
The way I see it the lift from a foil is the combination of the opposite forces from the front wing and stab.
Much like a sail and centreboard on a dinghy.
To be able to foil with no stab you need a bigger front wing so that shows the stab must provide lift.
I may be wrong but thatâs how. See it.
Front foil gives up force, stab gives down force, the result of opposing forces = lift
1 Like
How come James Casey using the 1250r says he either uses the 142 or 151r tails for his long distance upwind pumps? Whereas you would imagine the 120 would be more efficient? I personally use the 120 and feel itâs easier to pump.
You do not need a bigger front wing to ride without stab, you just need more skill to keep the Angles of Attack under control without the stab helping.
Iâve never seen or heard of anyone riding a 600 mono foil. They are all big
Iâll just add my experience with stab sizes with dock, flat water paddle up and downwindingâŚ
I definitely notice with a small stab it becomes easier to âpush throughâ the foil at lower speeds when pumping more aggressively to try to get it out of the stall zone that is largely encountered on launch. I presume this pushing through is stalling the tail more easily when itâs smaller, but I really donât know.
For example, with with the art Pro 1201 I donât think I had ever dead start with the 45 skinny but could on occasion with the 55 skinny. For paddle ups I had similar feelings where on small boards I could paddle up with larger rear foils easier than with the smaller rear foil. I would start lifting and then if not a fast enough speed push through, the larger rear didnât have this issue.
Once up I notice the tail in how easily I can climb up the mast, with too big a tail itâs feels harder to get the board higher. For downwinding I tend to like the smaller tail as it allows me to better get over chop or get high to push forward through swell or get the foil into swell energy. The downside I mostly found was it managed it a bit harder to paddle up at the start of our run where swell is tiny and slow.n
I have never seen anyone ride a monofoil ,just vids.
But bigger wings will have bigger chords and better pitch and low speed stabilty.
So that may be the reason, a stabless setup will create a bit more total lift at cruise speeds for sure so no need for more surface in terms of lift.
Kitefoilers have played with no stab ,positive lift and neutral (symmetric) stabs
The goal was to eliminare or reduce the stab drag.
AFAIK nobody has been able to get increased performance because the loss in stability makes those setups slower or impossible to ride at speed.
The monowing setups i know (Triton?, are low aspect designs for low speed foiling.
Also not sure if they have a a decent pump.
I am afraid that for now the stab is a very necessary evil.
I think this is generally accepted?
2 Likes
Exactly I use a bigger stab on my 620 front wing than on my 750 as it lowers the stall speed of the 620 for waveriding.
165 stab on 620, 145 on 750.
With the 145 on the 620 I stall coming out of white water hits, Iâm 85kg
One thing that I admit to not understanding is how does an airplane fly upside down? With that in mind, a stab doesnât just pull down, so too big a tail can make some foils less âliftyâ and Iâll need to shift my weight back to balance the foil. A larger tail with a short fuse can work wonders, as can a small one with long fuse⌠so you might find the short fuse that lets you pump quicker with a bigger rear is a plus, or riding a slightly too big front with a long fuse and small tail allows a bit of slide (drag) to help turn at high speed, and so on. But a small front over powered with a large rear just sucks.
An asymmetric profile foil can provide positive and negative lift depending on the Angle of Attack.
It is very inefficient at providing negative lift (lots of drag, higher stall etcâŚ) but doable.
Dedicated Acro planes like an Extra 300 have symmetric wing profile so they fly the same upside down.But this is the exception,symmetric wings have bad perfo vs asym ones.
Noâbigger stabilizers (tails) do not provide lift. In virtually all hydrofoil configurations, the tail provides downforce, not positive lift. This downforce acts in the opposite direction of the lift from the front wing and is necessary for stability, particularly when the center of mass is forward of the front foilâs center of lift.
This downforce adds to the overall load the front wing must support. In other words, the front wing is not just lifting the rider, board, and foilâit also has to offset the downward force generated by the tail. This is fundamental to achieving pitch stability, but it comes at a cost.
The cost is drag.
Whatâs more, this drag is compounded. The tail generates its own drag due to the downforce it creates. But because the front wing must now generate more lift to counter both the riderâs weight and the tailâs downforce, it also generates more induced drag. This is what I refer to as
âTails Count Twice.â
In practical terms, Iâve run the numbers and found that the tail can contribute up to 30% of total system drag.
So while larger stabs can make a setup feel more stable or easier to control, they do not provide âliftâ in the useful, upward-sustaining sense. They actually increase the total lift required and, consequently, the total drag.
For a deeper dive: The Tale of Tails â The Tale of Tails
Stable Aircraft Design
And a similar graphical view of a foil configuration:
2 Likes
Hereâs a test I performed six years ago: I simply removed the tail.
The biggest revelation? I had to move my front foot back by 8 inches to achieve stable flight. My footstraps had been dialed in for riding with the tail, and they worked allowing me to teach my 2 daughters (115 lbs and 130 lbs) to foil behind a 5 HP motor and me (190 lbs) to foil in ocean waves. The setup was proven across a wide weight range and foiling environments.
Once I removed the tail, you can see I had to shift my front foot back and therefore the center of gravity back about 4 inches to compensate. Why? Because the tail was creating a nose-up pitching moment through its downforce. With that moment gone, I needed to move aft to restore trim and stability.
This real-world test backed up the numbers Iâd calculated earlier. At the time, the setupâGoFoil Maliko 200 and a large GoFoil tailâproduced an overall lift-to-drag ratio of about 12:1. Thatâs relatively low by todayâs standards. Modern high-aspect front wings and smaller tails have improved these ratios significantly, reducing tail-induced drag.
Still, the principle remains: Tails Count Twice. Their downforce not only adds direct drag, but also forces the front wing to generate more liftâwhich means more induced drag. While todayâs equipment has mitigated this effect, it hasnât eliminated it.
3 Likes
Yes butâŚ
The tail can provide positive or neutral lift at speed, it has been tried in kitefoils years ago.
Not worth the drag reduction in our type of foil because the loss in stability is a bigger factor.
I flew the Airbus 340-600 for a few years and we had this clever fuel system that would put fuel in a tailtank in cruise, CG would shift rearwise and the stab would work in positive lift modeâŚof course this was a FlyByWire aircraft that could manage the unstable configuration.
For approach the CG would be shifted forward again in a more traditional position with tail pushing down.
I think some competition gliders can be flown like this too,not sure.
Anyway,our tails provide downforce pretty much all the time,not discussing thatâŚbut what is happening at the slowest speeds,highest AnglesOfAttack,right before stall?.
If you have your tail shimmed for high speed i think it is very possible that in this high nose up angle the tail may be working in positive lift mode.
But again, i would like to know for sure,from someone who has run CFD models etcâŚ
Bigger tails do feel glidier when slow and easier to pump out of a hole.I think many of us have felt that in the water.
But is this due to positive lift or just due to higher stability of the system?.
3 Likes
Super cool feedback. As you realize my math is standard aeronautical bedrock and you are introducing a 100 year newer concept at cruise with computer control . . . . even then Airbus switches back to traditional weight forward configuration for takeoff and landing to prevent crashes (due to tail stall . . .)
There could be an application for very efficient pump foiling, maybe even downwinding. But for now all the production tails (appear to) have and inverted airfoils designed specifically by people for stable hydrodynamic flight.
I agree that bigger tails feels like they pump better but the numbers donât support the âfeelâ. Until the feelings align more perfectly with the numbers there is probably an opportunity.
Note: I have experienced far better pump (>10% say) from shortening the fuselage from 640mm to 560mm for example. The theory is that the shorter fuse destabilizes the system making the nose pitch up faster, simulating the effect of a smaller, lighter board and allowing you to get to your pump faster. This could be what a larger stabilizer is doing, offering more downforce for pump recovery.
2 Likes