Not being an engineer I don’t really have much of a base to comment on this, but I have a life long passion to learn.
That said it’s my perception that once the rider is up foiling in a level consistent attitude the pitch angle of the foil is also consistent. It is neither climbing or descending. Therefore the weight that is above the foil shouldn’t have much effect. If the pitch angle changes then the weight becomes a factor again.
I understand that the energy required to transition more or less weight to the level “neutral” position would vary. That part seems very logical to me.
It’s like i explained. Maybe easier to understand like this:
The lifting force is created by the flow around the wing: same speed and angle of wing gives the same lifting force.
If you load the wing more, then more lifting force is also needed - otherwise forces are not in balance and we will start to fall downwards
How to get more lift?
Either increase the speed or increase the angle of the wing. A force balance will be found with the higher lift, higher weight on wing so you won’t be going up or down.
A drag/lift curve of eppler 817 profile:
(which is a wing profile i think was used on older hydrofoils)
Cd is drag coefficient / Cl is lift coefficient
Alpha is angle of wing towards flow
You can see on the Cl vs Alpha plot that it starts to create positive lift already at negative wing angles and the lift peaks at roughly 7.5 degrees upwards angle. At higher angles than that the wing stalls.
I’m just beginning the tweaking - try different thing stage and I’m finding it amazing how much difference that changes in setup make.
I also totally get the faster you go the more interesting the crashes get. There was a point when I windsurfed a lot that top speed was everything. At some point along that path I discovered how hard water can get even when it’s not frozen😎
That’s some crazy speed. I calculated that with full throttle I might reach +40 km/h. I’ll try to reach that some day, but about 35 km/h is my limit so far.
Up to 40km/h is OK with my setup, needed to ajust the backwing to have less lift at high speed.
Crashes below 35km/h are not too hard but above it can hurt. It is important to protect the eardrums, either with ear plugs or pads in the helmet.
It all depends on your willingness to get slammed😄
I got a concussion a while ago and after that a harder fall isn’t worth it, it’s the end of my riding that day basically…
However, I find that the faster wings get stable at high speed so it can be a duller feel in the riding than one might expect. When in doubt, throttle it out!
32km ride with the Veloce MT + Fast 40cm wing. Very choppy weather, but also very fun. Seems like the wing wants to go fast, like discussed earlier. 25-30km/h produces the best efficiency I have ever seen, sometimes under 40 Wh/km. But at 20km/h, the Curve MT + Fast stab is more efficient. I don’t know which setup I like more
Veloce MT + Surf stab felt held back by the stab. The Curve MT + Fast stab was a really fun and carvy setup, suitable for some longer exploration as well.
My board has a sandwich structure, and it seems that the foam core wasn’t strong enough around the front of the mast mount. I noticed that the bottom of the board had a slight dent around the front of the foil mount. So I decided to tear the foil mount section open and make a solid core around the area with epoxy resin + CF. I am using 600g CF for the core and 200g CF for the outside section (pictures coming later). Here is my current progress. External layers will bond the solid section into the original exterior CF.
Second round of 600g CF. Added three full layers and one shorter layer to even out the surface. The idea is to have a raised section towards the rear of the board, and have the CF flush with the original exterior surface on the front of the board. This creates a good mounting angle for the mast. Now waiting for the epoxy to cure.
Three final layers of 200g CF done. After curing I will inspect the surface, sand the edges and possibly add another layer of epoxy as a finishing touch.
Done for now. I am eager to get back to eFoiling because the season in Finland is short. I’ll blend the clearcoat during the winter. I am very happy with the modification.
