Christmas Eve Hart st, Mount Maunganui on the Earl wooden surfboard

Here the versatility of the Eearl 10-6 can be seen as it navigates lumpy onshore conditions on Christmas eve. at Hart st in Mount Maunganui, Bay of Plenty New Zealand. In spite of the fact that the weather was sunny, the surf was up and it was a holdiay in a surf town of over 100,000 people no one else was out taking advantage of the swell.

Future Primitive Ghost 11 footer complete.

Here's the Future Primitive Ghost 11 foot surfboard prior to being launched for the first time.

Specifications:
length: 11feet
Width: 23 inches
Thickness: 1 & 7/8 inches
Weight: 20.5 pounds
Volume: 63 litres approximately
Fin:11 inch cutaway elliptical plan shape 'spitfire' with leading edge tubercules
Rocker: circular tail/elliptical nose
Bottom shape: slightly concave
Rails: Continuous 50/50 elliptical 'pinched'
Construction: parallel profile paulownia wood
Hardware: stainless steel leash plug and ss hand operated vent.

Three Future Primitives, from left to right: Ghost 11, Ghost 12 and Earl 10-6.

Elliptical planform spitfire fins and stalling behaviour.

The revolution' spitfire fins which are the usual subject of spitfire fin tests have a few problems when used as examples of elliptical planform fins. 

One is that they are not even close to an elliptical planform, the tip are in planform is way too tnarrow and is almost pointed.

Another is the thickness distribution, which is not elliptical. in that respect it follopws the spitfire wing whose thickness distribution was also not elliptical ( see the picture below). The revolution spitfire fin and the spitfire wing itself were both too thin in the tip area. this encourages tip stalling and is not the fault of the elliptical planshape, which as has been pointed out was not even used,

The revolution spitfire fin is also markedly raked, which is another deviation from the true elliptical planform.

Therevolution fin is also exceptionally thin overall in chord ratio as well as being too thin in the tip, this reduces the angle of attack capability of the entire fin and the tip in particular.


In short the revolution spitfire fin's stalling characteristics are not a fair test of the elliptical planform fin's capabilities.


Wing twist used to correct the poor thickness distribution:

 


With my elliptical planform fins the thickness distribution is either elliptical or slightly thicker in the tip area than a true elliptical thickness distribution, I also make sure that the chord ratio is not unusally high, this means that the fin panel used must be thicker than is usual.



 

http://thoughtality.com/the-spitfire-wing

If there is a tendency for elliptical planform wings to stall at the tip first, then it is utterly stupid to make the thickness to chord ratio at the tip less than that of the rest of the wing i.e. a thickness to chord ratio which diminished towards the tip.... which is exactly what was done with the spitfire wing AND the revolution 'spitfire fin'.

Although I have never experienced tip stall with my elliptical planform fins, I keep the thickness to chord ratio constant or increase it towards the tip, I do so because I've visualised the flow rather than by calculation.

I also move the position of the thickest part of the chord forward towards the tip, this also increases aoa capability and helps to prevent tip stall. Again I do this because I've visualised the flow rather than because of any tip stall problem.

The addition of leading edge tubercules makes the elliptical planform less relevant from a drag point of view but it is still a good planform in my opinion because it is upright and also because it keeps excessive area out of the tip where it inhibits rail to rail movement.

Here is an essay on elliptical lift distribution:


http://www.djaerotech.com/dj_askjd/dj_questions/ellthoughts.html

Besides, raked greenough fins feel gutless and vague.

Stainless steel leash plug HWS installation in Future Primitive 'Ghost' 11 ft surfboard

This leash plug will always stay secure!

Fins for the Pretender 9'5"

Paulownia cored graphite tunnel plus side fins for the new pretender 9'5"

http://www.olosurfer.com/images/vortex%20fins.jpg


http://www.olosurfer.com/images/squid%20surfboard%20with%20tunnel%20by%20Roy%20Stewart.jpg

World's greatest surfboard designs: Future Primitive Ghost 11

Setting a 'whalebump' tuberculed leading edge spitfire fin into a new future primitive Ghost paulownia wood surfboard.

Designing post modern olo boards which work.

With shapes like  the displacement tailed pintails for example, the area and volume is drawn out into a longer board with a finer tail. Because the tail can sink the board behaves like a shorter board when required and yet still has the length of rail when it is wanted.

Generally speaking boards which are designed purely as planing craft emphasise short wide tailed hulls, with the planing are packed into a shape which is as close to a 3:1rectangle as possible while still allowing control. Displacement hulls on the other hand try to distribute volume over as long a length as possible. My pintailed boards are hybrid planing/displacement hulls and thus they are based on a different set of principles. I try to get as much width and length as possible with the minimum of thickness and area.

Regarding very long boards, my designs allow great length while maintaining good control, other designs don't alllow this, so in a sense I'm doing it because I can... but there are well known advantages to a very long board  i.e. paddling wave catching and section making ability. The reason ( or one of them) why very long boards are not built often by other shapers is that they are stuck in the planing hull theory mode and such boards in long lengths become uncontrollable. Pure displacement hull boards like the ancient olo are also very difficult to control. as Tom Wegener and others  have found out, to their apparent delight

. I've developed a good perhaps even perfect formula and this allows greater freedom regarding length, as well as  greater joy in the water.

Earl 10'6"

Here the delightfully obedient and easy to ride displacement tail feature of the Future Primitive series surfboards can be seen in action during a bottom turn.

Displacement tails are unique to Roy Stewart surfboards.

http://olosurfer-woodensurfboardsatpipeline.blogspot.com/2011/01/planing-lift-and-displacement-lift-in.html


http://olosurfer-woodensurfboardsatpipeline.blogspot.com/2009/08/displacement-tail-extreme-pintail.html

http://olosurfer-woodensurfboardsatpipeline.blogspot.com/2008/12/surfboard-design-workshop-displacement.html