Yep those older 295 boards more glide onto plane. Dont need to bear away as much. The newer 240 stuff is more of a pop onto plane.

Gestalt said..

decrepit said..

Gestalt said..
Early planning require width when designing planing hulls. There are ratios that can be applied. Length isn't going to help.

Not sure about this Gesty.
Theoretically, width with a big fin is more efficient in light winds when planing. It has a high aspect ratio lifting surface, so less drag.
The other advantage of width, is being able to control a big fin.
However, for early planning the hull has to function efficiently in displacement mode. Here length is the key, long and narrow is better in displacement. The hull is at less of an angle when climbing over the bow wave, and this is amplified in shallow water with ground effect making a bigger bow wave.

But I could be wrong of course

I don't think you're wrong. but we are now talking about 2 different design objectives. I mentioned in the bit quoted above "width with respect to planing hulls"
is imax building a planing hull or a displacement hull? 10-13knots is planing hull territory in my mind.

I'm going for planing.

peterowensbabs said..

decrepit said..
Had to put my glasses on but I finally found her!!!

Personally I love the SHELL BENZINE wall art.

My father in law pinched it when they held the Grand Prix at Phillip island in the 60 s

Imax1 said..

Gestalt said..

decrepit said..

Gestalt said..
Early planning require width when designing planing hulls. There are ratios that can be applied. Length isn't going to help.

Not sure about this Gesty.
Theoretically, width with a big fin is more efficient in light winds when planing. It has a high aspect ratio lifting surface, so less drag.
The other advantage of width, is being able to control a big fin.
However, for early planning the hull has to function efficiently in displacement mode. Here length is the key, long and narrow is better in displacement. The hull is at less of an angle when climbing over the bow wave, and this is amplified in shallow water with ground effect making a bigger bow wave.

But I could be wrong of course

I don't think you're wrong. but we are now talking about 2 different design objectives. I mentioned in the bit quoted above "width with respect to planing hulls"
is imax building a planing hull or a displacement hull? 10-13knots is planing hull territory in my mind.

I'm going for planing.

yup. planning hull aspect ratio is important and not the same as displacement hulls.

been lots of research into planing hulls for surfboards and boats. a guy worth reading is surfboard pioneer Simmons. his stuff is inspirational.

in more recent times Daniel Thomson has been pushing the limits.

Similar in concept to Tinho Dornella's Z2, which was sort of an early custom prototype for what ended up as the Kona Hula. Z2 was built specifically for a huge guy. Based on the success of the Z2 (which is amazing) and the dogginess of the very heavy Hula, I'd urge you to make it as light as you possibly can. Here's a vid of the Z2:

Imax1 said..
^^^^^
Does it have that huge cutout thing going on ?
Should I at least have a couple normal style cutouts ? Shallow ones ?
Keeping in mind it's only for under 15 kts and flattish water .

I'd suggest cutouts if you can handle the shaping/glassing. My 2001 Formula board doesn't have them, and you can really feel how helpful they would be in allowing trim control at higher speeds (You'll be going pretty fast even in 15. 26-28 off the wind most likely, with an efficient sail.). It won't really hurt you for early planing because you'll probably be ooching onto a plane off the long straight section behind the mastfoot, rather than pumping off the fin.

I like the idea Imax. I'm 95kg and ride a JP SLW 168 most of the time, the two issues are when there isn't enough wind it just bogs down, and when there are waves it is a harsh ride.
This is a bit unconventional, but I was wondering the other day if it would benefit to have a longer thinner nose with a wave piercing bow. Something similar to a SUP raceboard, but cut off at the back to a wide planing surface.
I think it would still have a fair bit of drag at low speed due to wide tail, but might help reduce the hump? And should be better at slicing through waves at speed?

sun fisher said..
I like the idea Imax. I'm 95kg and ride a JP SLW 168 most of the time, the two issues are when there isn't enough wind it just bogs down, and when there are waves it is a harsh ride.
This is a bit unconventional, but I was wondering the other day if it would benefit to have a longer thinner nose with a wave piercing bow. Something similar to a SUP raceboard, but cut off at the back to a wide planing surface.
I think it would still have a fair bit of drag at low speed due to wide tail, but might help reduce the hump? And should be better at slicing through waves at speed?

You're talking about the AHD Tactik: www.ahd-boards.com/fr/tactik

I've never even seen one in person but I want one BAD!

decrepit said..

Gestalt said..
yup. planning hull aspect ratio is important and not the same as displacement hulls.

But we aren't just talking planning, we are talking early planning.
Planing occurs once you are surfing your own bow wave instead of butting your head against it.
As mentioned above, the short wide boards are fantastic once on the plan, but in very light wind it takes a lot of pumping to "pop" then over their bow wave. Where as a longer narrower board has less bow wave to get over, and isn't going uphill as much to get over it. So getting onto the plane is easier, but not as efficient once there. There's also the matter with fin length, Imax won't be using a long fin, so this also looses some of the advantage of a wide board.

yup I understand that.

I guess the point is why 290 long. why not 270, 260 etc.

for eg. if we take 20cm off the length would that make any quantifiable difference to the early planning threshold of this board. I don't believe so.

but

if we added 20cm to the width I would suggest it would make a noticeable difference.
anyways i'll leave it at that.

Imax your board looks great and you're workmanship is excellent. I'm sure it will work. we are just talking ideas.
.

nice job maxie ....man you don't muck around ...

i don't know if this will matter about the cutout decision ..but I have a 115 with cutouts ,then i have a 100 without cutouts ...the 100
seems to plane through lulls easier and it will hold its own against the 115 ,the sail range between them are half a metre .115 ,6.5 -8
100 5.5 -7.5 .
both plane in the same wind strength ..which surprised me ,so not cut outs in my mind seems to plane earlier ,which i think your after .

it will be interesting to see where you put the straps ,don't ask me ... I'm just enjoying the build .i can barely build a sand castle ..lol.

I checked out Simmons n Thomsons shapes. Great to see someone thinking outside the square as there's always room for development to find the magic shape. But theyre mostly developed to run on a curved sloped surface, the wave. Guessing thered be some similarities though.
Imax1 cool keep the pics coming. Wish i could get there to see the build first hand.

Surfboard design is extremely interesting in it's own right, but as a long time surfer and windsurfer (slalom/speed), I have to say that the planing shape of the two types is designed around COMPLETELY different parameters. (probable exception is for Wave sailing). For one thing, slalom windsurfers go twice as fast as surfboards an a flat, not curved surface!

Imax, you shape reminds me of my very early 1990's AHD slalom boards. I still have a AHD 295 in my museum that was my go to very light wind slalom racing board in those days. (I seem to remeber it was about 26 inches wide at the very far forward wide point). Of interest, is that it is not actuall a typical sandwich construction, but rather it was built with Glass fiber directly over a EPS core but with a foaming resin in a closed mould. This makes a light, resonably stiff, but relatively thick laminate compared with straight laminated firberglass, but no where near as thick as PVC foam sandwich.

I will see if I can get it out in the sunlight and post some photos of it.

It may be also interesting that in those days we actually had speedo's. (No not talking about the Bugie Smullers) Not GPS speedo's , but the SpeedWatch. It had a very small magnetic prop hanging off the fin sending pulses to an electronic (solar) display for an instant speed readout.

With this device we found that our best VMG upwind was at a board speed of around 13-14 knots. that seems very slow now, as I am hearing 21-22 knots on GPS-logit now when getting my best upwind VMG on modern slalom boards.

But there is no doubt that we could get planing in very light winds on those old boards, even though they were not nearly as fast as the modern boards in top speed.

When I was building hollow wave skis back in the early 80's, I did some with PVC sandwich bottoms. Not wanting to use vacuum bags, I made a male mould plate to clamp down in the female mould over the foam. I certainly worked, but even with my best efforts I could not eliminate some air bubbles between the foam and bottom glass. Cant be too bad though, as I was out surfing a couple of days ago on a 30 year old one I had made for my Miss's way back then.

I dont think that will work for you but it may highlight the difficulty in getting rid of trapped air, even with quite high positive pressure very evenly applied. I think one needs Vacuum to draw the air out.

sun fisher said..
I like the idea Imax. I'm 95kg and ride a JP SLW 168 most of the time, the two issues are when there isn't enough wind it just bogs down, and when there are waves it is a harsh ride.
This is a bit unconventional, but I was wondering the other day if it would benefit to have a longer thinner nose with a wave piercing bow. Something similar to a SUP raceboard, but cut off at the back to a wide planing surface.
I think it would still have a fair bit of drag at low speed due to wide tail, but might help reduce the hump? And should be better at slicing through waves at speed?

Add a foil.

Gestalt said..
for eg. if we take 20cm off the length would that make any quantifiable difference to the early planning threshold of this board. I don't believe so.

but

if we added 20cm to the width I would suggest it would make a noticeable difference.
anyways i'll leave it at that.

Imax your board looks great and you're workmanship is excellent. I'm sure it will work. we are just talking ideas.

Agreed just ideas, what we need are graphs of lift drag ratio of short wide and long narrow, around the planning threshold.
We know wide will be better after it gets planning, but what happens just before?
Wide will have more lift but also more drag, does this greater drag give long narrow the advantage? Without the data it's academic.
Here's where you need the boffins

4 oz glass strip along stringer , carbon inergra patches on nose mast track and fin box . Covered in 4 oz glass all over . Ill do the same on the bottom. ( minus a couple patches ). Ill save you the pain of those pics.
Wetted out on bench and slight tint added so i can see better wetting . Had to add a bit extra over the patches to wet through .
It has used a lot less resin this way but you can see millions of tiny areas ( in the foam bubbles ) , that haven't stuck to the foam . If i wetted on the blank it would have filled all those tiny pin holes , but used at least one third more resin . I wonder if there is any strength or any bond to foam difference ??