Hey everyone,
thought I'd start a thread to see what peoples opinions are on the difference between moving your mast further forward or adding a shim to the rear of your mast base plate for more front foot pressure.
sometimes boards don't have tracks far enough forward so this could be one way to fix it, the other option is more tail wing angle but I want to keep the topic about these two methods.
I would think moving the mast further forward would move the pivot point forward between your legs as opposed to having the drive from your back leg with the mast further back. Adding a base plate shim increases the angle of attack of your front wing, by doing this does it increase the amount of drag also?
keen to see peoples thoughts on the topic. Cheers!
Shimming the mast plate will mostly affect the Take off behavior.
You are changing the initial angle of attack of your foil when you are floating and accelerating.
Too much angle will add drag and make the takeoff very abrupt,specially in powered conditions.Maybe stall problems too.Board will ride nose down in flight.
Too little and the board will accelerate a lot without the foil lifting, feels skatey and needs lots of back foot pressure to get the foil to "bite" and lift.This caused me stall problems because controlling the takeoff angle becomes very hard (like doing a wheelie) and it is easy to overdo it.
Board will ride nose up in flight.
What i do is place the mast in the balance position,or as close as possible (KDmaui method).
Then shim the mast plate for good takeoff behaviour.
This should result in an easy takeoff,with no foot position change from floating to foiling, a pretty flat board attitude in flight and the least inertia in pitch for liveliness.
With the crazy amount of boards&foils out there it is possible that some brand mixes will not work together well no matter what you do.Things are getting more reasonable with flat rockers in the foilbox area and more forward and sometimes longer tracks.
Hi Wicka. I can offer some insights in addition to MCRT's comments on foil angle of attack for take off ...
When you're up on the foil, the foils will on average ride horizontal, so shimming the mast plate changes the angle of the board to horizontal, which matters in a few ways. For example, if the nose is down too much, then: At high speeds with a brief touch down, you might get a sudden increase in drag and get throw out the front (more important if you want to do over 25 or 30 kts). Or the forward rail touches the water early in a turn turn causing a crash. Or for longer boards, the reduced water clearance with the nose down all the time makes your foil-mast to be effectively shorter. Or for bigger boards you might get a lot of aero drag and pitch instability if trying to go upwind fast in strong winds.
I'm always trying to learn and my current thinking (for board volumes just below neutral buoyancy) is:
1. Set the footstrap positions to choose a comfortable weight distribution for your feet when displacing (semi-sinking) and/or trying to get the board to skim or plane on the surface - necessary to get up on a relatively small front foil in relatively low wind power conditions.
2. Set the angle of fuselage+mast to get your desired fore-aft board angle to horizontal when on the foil.
3. Set the foilmast track position in the board so you have your desired average weight on front vs rear foot when on the foil.
4. Set the rear stabiliser angle to maintain your preferred balance of weight on each foot regardless of water speed, and/or set your rear stab angle so your foils+board pumps or changes ride height comfortably for you.
Regarding step 2 (board angle to foils), I've found that higher lift front foils are harder to work with and less fun, because they have more pitch variation and instability at higher water speeds, compared with smaller thinner foils which go fast and remain pitch stable without much effort.
Regarding step 3, I prefer not to set the mast track position for easy control of lift-off. Step 1 is far more important to me. Maybe this is more of an issue for different board shapes and volumes. We can also rotate the wing during initial liftoff to keep weight on the front foot if needed.
Regarding step 4, inefficient rear stabilisers can be confusing. This advice method works for me with low drag and high aspect rear stab foils, plus I've found that lighter+shorter boards need less down-suck in the rear stab to pull up from a dive.
I would never change the angle of my mast unless my board was riding way angled, and the. I would just sell the board.
