Sep 23, 2011

All you need to know about Raceboards

Clinton Filen – Board Designer – Airush HQ, Cape Town, South Africa

This is an interesting blog to write from the perspective that the progression in the race shapes is moving much quicker than most other board design and has various factors affecting the final design outside of the norm. These include the perspective of emerging rules for the race category, specifically if you look at “One board rule racing” while considering the variety of conditions one might be racing in. Another area is the rate at which the riders are improving their skill level to deal with progression in design and what might work best, for the more recreationally oriented rider.

Without a doubt almost anything I say below has a sell by date, as development is often very cyclic in nature, as the boards get better we can run different fins, as the riders get better they can run bigger/different boards and the same for kites etc. An example is our first Monaro V2 prototypes were simply uncontrollable with double foiled 22cm fins, as the fins created so much drive off the wind you would just explode. As soon as we went to single foil, the control went up significantly. Right now a good racer could run vertical double foil fins 10cm longer and still keep it together.

Range of use & Skill level
The first consideration for your race or freerace boards is your range of use and skill level. Currently there is relatively clear line between a board that is made to go upwind faster than anything (especially in light wind) and the sacrifices you have to make in ease of use, more specifically with reaching and downwind. So at this stage I would say that if you are a recreational racer or racing with anything smaller than a 12 metre you should avoid a race board over 60cm with fins any bigger than 26cm for the biggest set.

You should see this trend change after a year or two when board designs become more controllable and the skill level of the average recreational riders improve.

If you are looking for a board to go blasting around on and having fun, even in marginal wind, I would be very cautious about the newer generation all out race boards unless you are prepared to put the time in to learn how to ride them and are working towards a racing career. Something like the Airush Sector 60 (V1 or V2) would be your best bet by far.

Quad Vs Tri Vs Single
This is currently one of the big areas of debate and to some degree I feel this is a question of control, versus efficiency. We have tried most configurations from single, to twin, to tri fin and inverted tri fin (Single fin in the front). In theory I would say the less fins the better when you are looking at pure efficiency, however as soon as you only have a single centre of lateral resistance the stability challenges become significant.

Currently our test results give us the best control in the quads and the best angle upwind. The weakness is drag so we opt for thinner foils and in most cases on our production boards we have asymmetrical foils to aid control.

Symmetrical foils vs. asymmetrical foils

This is a significant debate even in our own team. In places that are windy where control is more of an issue, asymmetrical foils (or flat foils on the inside) are the preferred choice. This is most obvious if you have a board with cant on the fins, as this increases the control problems significantly. Full vertical fins with symmetrical foils, specifically with the top racers in light wind are increasingly popular however this has drag and control challenges.

Fin Placement/ Further apart vs. closer together
The further apart you put your back and front fin sets the stiffer the board will be. BUT this is a generalization and has very much got to be considered in conjunction with how far forward your fins are. The further forward you put your fins, specifically your front fin set, the harder the board is to control. If you have your fins further back the board is generally easier to control but does not edge upwind as well.

Cant (Angle away from vertical)
Generally if you are used to riding a board by edging it to windward (Twintip style), then a board with canted fins will be much easier too use and more comfortable. Vertical fins require the board to be ridden dead flat or with a leeward cant. Theoretically riding the board flatter is faster, as you limit the amount of drag created by the trim angle resistance from the rail, but that doesn’t help if you crash and explode every 30 meters, or you simply cannot get comfortable.

Our initial wide body development found 60cm to be a very comfortable all round size even in higher wind racing. Our race team will still be on 60cm wide boards such as the Sector V2 or Monaro V2 above 30 knots. This size also works very efficiently in light wind for intermediate racers and freerace. 65cm, like the Monaro V3, and over will give you an advantage in lighter conditions and bigger kites, specifically upwind. For reaching racing, the game changes completely and boards such as the Sector 52 V2 maintains a huge amount of control at speed. But keep in mind most course races are currently straight upwind and straight downwind. However, emerging categories such as boardercross, slalom and long distance require completely different boards that focus primarily on control on a reach, something a full blown raceboard is not really designed for.

Where does volume come into play?
This is open to debate as I would generally argue that once you are planning buoyancy is almost irrelevant, until you start to encounter some displacement such as dropping off the plane or engaging the rail to leeward when going upwind, specifically on vertical finned boards that need to be edged over to leeward.

What about kites?
That’s another whole exciting topic, all of this tech talks and I think I need go for a quick wave session to clear my head. But I will ask Mark our kite guru to

put together an overview on angles of attack, ideal foils and of course the much heralded aspect ratio in a later blog.

Next week Airush kite designer, Mark Pattison, talks about the ins and outs of developing the upcoming season of race kites.