i think you're playing with words there nebs,

yes cutouts reduce wetted surface area. and yes that makes you go faster.

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nebbian said...

decrepit said...


So yes cut outs CAN reduce wetted area, (sorry nebs).

We both agree Decrep, I said:
(if the angle of attack of your board is the same and the bottom is flat).
Which is different to your rationale which says that cutouts will make the nose of the board sit higher, changing the angle of attack.

The problem is that people seem to think that cutting bits out of a board will reduce the wetted surface area because there's less surface area to wet, which is just plain bollocks.

this isn't bollocks because the altered angle of attack the board has achieves less wetted surface area.

You could also reduce the wetted surface area by moving your footstraps back -- same idea as cutouts.

or by moving your mast back, or lowering your boom etc.

In the end they're another tuning tool, you want to get the optimum angle of attack of your planing surface. Too nose-low and you've got too much wetted surface area so will be slow. Too nose-high and you will be ploughing through the water, not skimming over it so will be slow. I think that cutouts first came into use with those big fat new-school boards with a wide tail -- the lift from the back of the board was making the board sit at the wrong angle so they put some cutouts in. Then the sheeple saw the cutouts and assumed that these speed holes made them go faster. *sigh*

they do make you go faster because you do have less wetted surface area. the "sheeple" assumed correct

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keef said...

i found the futura jibed like a wide board and could feel the rail;s catching,infact it felt like i was draging a house brick behind the board (maybe the cutouts) the second was a jp 108 lt 2008 slalom again it felt like a wide board jibeing, besides i allso didnt like the deck.
tell me more about the duck tail Gestalt i'm all ears ,are there any production boards that have a duct tail let me know and ill check them out,
there,s one consiation about sticking cutouts in is you can allways fill them in and play around with them after the board is made, not so easy the other way around

are you a lightweight?

I recently got an F2 SX-L with deep recesses and plates to adjust the depth. I was told by a few people, and also read on some forum, to only put in the plates when the conditions are really choppy - to help then keep the nose down. I don't know what to believe - I would have thought the shallower plates would help to get planing in lighter conditions, but I know sweet f@#k all.

Baaaaaaaaaaaaaaaaa! Baaaaaaaaaaaaaaaaaaaaaaaaaa!

i weigh 80kgs at the most and shed 5kgs by the end of the season due to no work and all play
can you post a pic of those cutouts decrepit

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decrepit said...



the rocker on my speed board has a straight section at the back 1.1m long, so when it sat flat, it had a lot of wetted area. (entry between front foot and mast) When I put the cutouts in the entry point moved back to just under the front foot, and I got better speeds.

that is interesting decrepit the rocker on the board i have in mind has 2mm of rocker at 1.2mt with 3mm tail lift and 175mm@ nose rocker

Here is my take .

Wide tailed boards generally trim flatter , nose down and can be "sticky" . Tail cuts alter the trim and allow the nose to lift freeing the board up . As discussed this can be acheived in other ways like a larger fin ,placing the straps further back , mast track further back , boom higher ect , so tail cuts are just one tool to acheive a looser and faster ride .
When designing a board it,s a balancing act around a whole list of parameters and tail cuts are just one way of acheiving the desired result . They are not a "wank", they work , but only when part of the initial design equation.

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mr love said...

Here is my take ." .. . Tail cuts alter the trim and allow the nose to lift freeing the board up . As discussed

so what your saying is, i can have a slightly flatter rockerline and the cutouts will give me more lift,or do you meen it will help the board to plane earlyer

I was loaned a Tabou Rocket with out cutouts yesterday nice board and fast but I can't wait to get my F2 Stoke back on the water as it's far more comfortable and cut's through the water better.The owner of the Tabou was impressed with the f2's ride and could see why when he thought about the cutouts.

i allso had a 105 rocket, and replaced it with a carbon art 55.(because the c/arts smoke to windward) the board is fautless no cutouts sails sizes 5.0 to a 7.3 with eaze, thats the board im tooling up for, dropping the rockerline and adding a bit of tail lift and hopefully come up with about 80lts, the only thing i'm not sure on is these cutouts, but at the end of the day if there not working i can fill them in without adding hardly any extra weight
i was looking at the f2 web site and all there boards look great(i noticed they have a mini stringer), when ive finnished this board i'm going to make a freestyle board like the chille but wider and thinner, but ill have to have a look at one so i can see the tail sliders . or if someone has a closeup pic i'm sure it wont be a problem on this site everyone is so helpful

My 2 bobs - (what do you call twins with no arms or legs in a swimming pool)

Wetted area is a function of 1) All up weight, 2) board speed, 3) width (aspect ratio)
4) angle of attack (pitch). I think that's all.

So cutouts allow the use of wide tails that provide high aspect ratio planing surfaces which provide higher lift to area ratio hence - less wetted area. According to that theory they should be faster. I think they would be but for 3 things 1) windage, 2) The planing patch required at high speed is so small that pitch control becomes an issue for wide tails. 3) They require more fin.

The cutouts just allow the fin to be positioned appropriately vis a vis the planing surface. IMHO. FWIW. dont quote me. why did i open my ignorant mouth to bore you all with such vacuous drivel. kill me now. no dont bother. I'm not worth the exertion. Stewie I need an acronym for utter self abasement.

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keef said what do you through a drowning bass player" his amp" NotWal said...

NotWal said...

My 2 bobs - (what do you call twins with no arms or legs in a swimming pool)

hey notwal are you going to finnish the joke,the picture im getting is that on a low volume board with cutouts you wont plane as early but once on the plane they help to keep the nose up and keep you on the plane longer, and on a wider board with more volume they reduce the wetted surface around the fin base so maybe you can use a smaller fin and the help wider tailed boards jibe, hows that have i got it rite

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keef said...

keef said what do you through a drowning bass player" his amp" NotWal said...

NotWal said...

My 2 bobs - (what do you call twins with no arms or legs in a swimming pool)

hey notwal are you going to finnish the joke,the picture im getting is that on a low volume board with cutouts you wont plane as early but once on the plane they help to keep the nose up and keep you on the plane longer, and on a wider board with more volume they reduce the wetted surface around the fin base so maybe you can use a smaller fin and the help wider tailed boards jibe, hows that have i got it rite

i don't see why you would want to copy what is arguably the fastest production board in existance and alter it's design??????? trouble looms ahead.

as for the *board and the JP, both are very good boards. your gybing issues could be technique based. i thought you may have been a lightweight and therefore not liking the wider tails but at 80kg this shouldn't be an issue.

to help wide boards gybe, either, add more rocker or cut away the rail.

to answer your previous question, the kona tanker is a ducktailed production board.

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keef said...

keef said what do you through a drowning bass player" his amp" NotWal said...

NotWal said...

My 2 bobs - (what do you call twins with no arms or legs in a swimming pool)

hey notwal are you going to finnish the joke,the picture im getting is that on a low volume board with cutouts you wont plane as early but once on the plane they help to keep the nose up and keep you on the plane longer, and on a wider board with more volume they reduce the wetted surface around the fin base so maybe you can use a smaller fin and the help wider tailed boards jibe, hows that have i got it rite

2 Bobs of course, unless they are good lookin girls. Then you would call them corkers.

Wider boards need deeper fins regardless of cutouts unless of course you mount the footstraps inboard.

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Gestalt said...
[br

Gestalt said...
[bri don't see why you would want to copy what is arguably the fastest production board in existance and alter it's design??????? trouble looms ahead.

as for the *board and the JP, both are very good boards. your gybing issues could be technique based. i thought you may have been a lightweight and therefore not liking the wider tails but at 80kg this shouldn't be an issue

to answer your previous question, the kona tanker is a ducktailed production board.

ok Gestalt at what point did i say i was copying a carbonart what i said was

did i say im changeing or copying the rocker, does a carbon art have tailrocker NO NO NO ,

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thats the board im tooling up for, dropping the rockerline and adding a bit of tail lift and hopefully come up with about 80lts, the only thing i'm not sure on is these cutouts

did i say im copying the deck NO(i wouldnt do that because i like the deck on the tabou's)does a carbon art have cutouts NO NO NO, this board wont look anything like a carbonart,tell me whats the point in copying a board you allready have,and you have got it wrong carbonart boards are custom not production every board is hand made
now these cutouts were designed by say f2 i don't know who came up with the idea, are you saying that all of the other boards out there with cutouts were'nt copied, and how about fins say the tuttle does that meen no other company can use that design
your right about my jibeing technique i do need to improve its taken me 30 years to get this fare and theres allways room for improvement

[b]Gestalt said...

to answer your previous question, the kona tanker is a ducktailed production board.

i hope your not going to copy that ducktailed production board gestalt


.

jeez mate,

get a grip,

p.s. you should have left your original response up rather than editing it into the garbled mess it is now.

I wonder about tail rocker. I have always thought it would create drag by sucking water upwards. However as the water has already been pushed down then it will be under a bit of pressure. I guess if the rocker is just right it can allow the water to accelerate upwards under this pressure without actually doing any sucking work. The result would be less lift on the tail with no extra drag due to sucking. However you end up with more wetted area than the minimum required to provide lift.

How about using actual sharks' fins?

yeah and waveboards could be shaped like flying fish and speed boards like barracuda (oh wait, they are)

Having built my current speedboard without cutouts and then adding them at a latter date I can offer these points.
The cutout cured a bad rocker line (too much flat)
Reduced the wetted area but increased drag at lower speeds
Reduced its ability to point upwind
Increased its stability in chop or rough conditions
Allowed the board to "fly" much more off the fin

Would i do it again No ,complacates the design

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kato said...


The cutout cured a bad rocker line (too much flat)

what do you call to much flat, do you know the rocker depth at 200, im looking at flat plannining 35mm from tail too 900, then 75mm at 2.00 then 175 nose rocker with 2mm tailrocker,all you guys out there makeing flat water slalom boards i would appriciate you input, im looking at 80lt
im defernately going to use the cutouts mainly to see how they work, then im going to fill them in and see the difference, curiosity killed the cat

Nebs said

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I think that cutouts first came into use with those big fat new-school boards with a wide tail

Tried temporarily filling in the cutouts- they definitely make a big board more stable as soon as you get into fifth gear. Must be due to lengthening the contact patch, maybe with the same wetted area in both cases. Dunno about top speed but i'm thinking that they wouldn't be needed on a speed board if the shape is right.

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oldie said...

Nebs said

i'm thinking that they wouldn't be needed on a speed board if the shape is right.

had a look on the f2 site and the missile "s"has them

While I was talking with slowy about my cutouts, I think he said that the carbon arts don't hace cutouts because they have tail rocker instead.
So I'd think if you increase the amount of tail rocker the carbon art has, and put in cutouts, you may end up overcooking it.
Too much angle of attack and slow the board down, but it will be nice and loose.

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keef said...

oldie said...

Nebs said

i'm thinking that they wouldn't be needed on a speed board if the shape is right.

had a look on the f2 site and the missile "s"has them

Does the missile S also have pipes to connect the cutouts to the deck? One of the missiles did.

Reminds me of the old saying about fly fishing:
The fly doesn't have to catch the fish, it just has to catch the angler

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decrepit said...

While I was talking with slowy about my cutouts, I think he said that the carbon arts don't hace cutouts because they have tail rocker instead.

well if c/arts have tail rocker they for got mine it has strait planning from the tail to 800,the way i see tailrocker is like a primary and secondry, if your rocker was to flat, say strait from tail to 100 it would have a earlyer maximim top end speed than if you had a secondry rocker say 2mm to 3mm 35mm from tail as you put more pressure on your back foot you can feel the tailrocker kick in and your sailing off your fin.
now were talking 2mmto3mm if it doesnt work with the cutouts bet some foam and muck around with some different depths(fill them in)
anyway guys you have all been a great help i dont think we can cover to much more on this subject thanks for your help maybe Gestalt can do a post on
the kona tanker he's makeing, by the pic's i couldnt get the drift or the concept but it is interesting ,if anyone has seen one maybe you could do a post

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keef said...


well if c/arts have tail rocker they for got mine it has strait planning from the tail to 800

Remembered that slowy also said the back of his board was a narrow pintail whereas mine is a wider square tail.

But I'm sure slowy said his board had 2mm tail rocker, so maybe they're different years, or models.

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,the way i see tailrocker is like a primary and secondry, if your rocker was to flat, say strait from tail to 100 it would have a earlyer maximim top end speed than if you had a secondry rocker say 2mm to 3mm 35mm from tail as you put more pressure on your back foot you can feel the tailrocker kick in and your sailing off your fin.
>>>>>>

This is where angle of attack comes in. If the board sits flat you're right, but if the board sits at an angle, it will climb higher out of the water the faster it goes.
You're secondary rocker, isn't really needed if you get board angle optimum.
That's the reason I added cutouts to my board, to increase the angle the board sits at.
As I said mine is flat for 1100mm but with the cutouts I can sit it on the fin.

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decrepit said...As I said mine is flat for 1100mm but with the cutouts I can sit it on the fin.

wow those cutouts must be working overtime decrepit with that rocker, it must be a fully blown speed board its good to know they work
believe me theres no tail rocker in the c/art, the c/art is a great board and i love sailing it but i need an 80lt
if i got james dennise to make me another board designed by phil mcgain id have to grow about 8" change my shoe sizefrom 7 1/2 to about a 14 and stick on about 25kgs, now i dont know how tall, or phils weight or shoe sizs but i had to change the foot straps, "maybe they use boots over there" there is only one possition on them and i would have liked them futher back, the back ones 20mm and the front back 45mm theres allso heeps of volume on the tail with me being 5'7 and 75kgs naturally i need less volume and shoten the straps, but haveing said that the board will carry a 7.3 sail with a 32 fin so that could be the reasoning not bad for a 94lt board
sorry for the dribble but i will stick the tail rocker in and if i dont like it ill take it out "you know if you use a blender to mix your balloons they blow up much better and by useing the blender too mix you wont get any pinholes in your filler coat"
2mm of balloons weigh buggar all but i think 1100 strait plainning for me even with cutouts is a tad to much im looking at a high wind slalom

I certainly wasn't recommending 1100 straight, my speed board is a modified wave board, I ripped the old d'cell layer off, added more low density foam and re-d'celled it, to get rid of the old wave rocker.
I really wanted about 1m straight but it was very hard to measure what was going on, so I ended up overcooking it.

Saying that, I'm not disappointed with that long straight, it means in light winds, I have more fast planning area available, so although it's only 50cm wide it planes fairly early.

Your CA is definitely a different model to slowys speed boards.

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decrepit said...

my speed board is a modified wave board, I ripped the old d'cell layer off, added more low density foam and re-d'celled it, to get rid of the old wave rocker.

hey desrepit its pleasing to know that i'm not the only one out there revamping our old wave boards' i did a post months back on my" chopped rrd" (youve seen it its in my pics)
and i copped heeps of bagging from the experts , the post was aimed at guys wanting to make there own board but wasn't tooled up to do the job or the expirence, and i still believe to start with its the only way to go
1mt straight is great, i did a slalom once with 3 1/2" of rocker nose to tale(not easy to jibe) thats back early 80's because you couldn't buy them
i think i missled you about my c/a its a 55 slalom not a speed "sorry"
i got an email from james dennis yesterday, hes is in maui testing his 0'9s and hes soooooooooooo stoked on the improvements, so i emailed back and said don't forget about us lighter guys and bring the straps back or attlest some holes for the opption
i got a reply this morrning, all 0'9s the front straps are back 40ml with multi inserts, now i don't know what he meens by multi, have to waite & see ( now this is between me and you decrepit, i dont know if he wants it to be made public yet) if you haven't sailed one have a go you'll be supprised they look sooo basic with boxy rails and smoke to windward, and if he,s improved them WOW
and dont forget these boards are custom if you have a favorite decal or a minor change i'm sure he will be happy to talk to you (try that with a production board)