ive noticed they dont have tail rescesses on lower volume boards. do they work and what do they do,

I think the more recess the deeper the tail of the board will ride in the water giving u more nose out of the water and I suppose that will make u go a little quicker. No recess and the board rides a little higher and may go over chop better and more control. I would say small speed boards would have the cutouts but not wave boards. Someone will have a better explanation than me Im sure

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Jman said...

I think the more recess the deeper the tail of the board will ride in the water giving u more nose out of the water and I suppose that will make u go a little quicker.

thank's for your thoughts on this one jman, are we talking about tail rocker,the way i see it is that if the board is, flat or has tail lift, the overall water line length wouldn't change where the recess's are, quote me if i'm wrong, what i want to know is what do they do, or maybe they do shorten the waterline length at the front of the fin

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Jman said...

I think the more recess the deeper the tail of the board will ride in the water giving u more nose out of the water...

I thought it was the other way around, tail recesses make the nose trim closer to the water/flatter???

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Pugwash said...

Jman said...

I think the more recess the deeper the tail of the board will ride in the water giving u more nose out of the water...

I thought it was the other way around, tail recesses make the nose trim closer to the water/flatter???

You might be right there, I realy have no idea

Im Not sure that cutout do anymore than reduce weted surface area and attract weed. Some of the F2 boards have trim plates in the cutouts that can trim the board I never tried one though.

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vando said...

Im Not sure that cutout do anymore than reduce weted surface area and weed.

That was what I understood. Supposed to give you the gybing capability of a narrow tailed board.

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vando said...

Im Not sure that cutout do anymore than reduce weted surface area and attract weed

I don't care how "cutout" you get vando, but really you shouldn't being doing weed while in control of a high speed transportation device

Oh and I'd heard that the cutouts can give a bigger range of fin suitability though I couldn't vouch for that. The new futura etc seem to promote keeping a quiver of fins to enhance the boards usage range.
As far as low volume boards go I suspect they already have a lower wetted surface at the tail so maybe not really needed on them?

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sailpilot said...

vando said...

Im Not sure that cutout do anymore than reduce weted surface area and attract weed

I don't care how "cutout" you get vando, but really you shouldn't being doing weed while in control of a high speed transportation device

Hey man nothing like floating on air

How can a cutout reduce wetted surface area? What a load of bollocks.

I suppose the reasoning goes like this:
"If I cut some bits out of the tail then those bits won't be wetted anymore so I'll have reduced wetted surface area". OK then let's carry this on further, and skim 2mm off the entire bottom of the board. Wow we'll have no wetted surface area so will have unlimited top speed!

What rubbish.

If you stop a certain portion of your board from touching the water and therefore giving you dynamic lift then the board will sit lower. This will mean another part of the board that wasn't touching before is now touching. So your wetted surface area will be the same (if the angle of attack of your board is the same and the bottom is flat).

I think the cutouts make the board less 'bouncy' in chop by allowing you to have effectively a narrower tail but with more leverage 'cos your foot is further outboard. Personally I prefer not to have them but each to their own.

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nebbian said...

How can a cutout reduce wetted surface area? What a load of bollocks.

I suppose the reasoning goes like this:
"If I cut some bits out of the tail then those bits won't be wetted anymore so I'll have reduced wetted surface area". OK then let's carry this on further, and skim 2mm off the entire bottom of the board. Wow we'll have no wetted surface area so will have unlimited top speed!

What rubbish.

If you stop a certain portion of your board from touching the water and therefore giving you dynamic lift then the board will sit lower. This will mean another part of the board that wasn't touching before is now touching. So your wetted surface area will be the same (if the angle of attack of your board is the same and the bottom is flat).

I think the cutouts make the board less 'bouncy' in chop by allowing you to have effectively a narrower tail but with more leverage 'cos your foot is further outboard. Personally I prefer not to have them but each to their own.

But...but...but...not wanting to make the foolish mistake of contradicting Nebbian in a scientific argument, buuuuuuut...

Once a board is planing, it's not "sitting in" the water any more, is it? It's skimming the surface, and the tail cutouts should reduce the amount of board surface which comes into contact with the water, shouldn't they? Reducing the wetted area and thus lowering drag?

How about asking someone whose board has cutouts to actually look down behind them as they are planing? What do they see? Does the tail "sit lower in the water" while planing, or are there visible gaps between board and water surface at the back of the board, where the cutouts are? Maybe there's a bit of spray coming out the gaps, but the board couldn't be said to be in contact with the surface at that point?

You will notice I'm not venturing any strong opinions here; I'm just posing questions. That way, I can't be proven wrong, 'cos I'm not saying anything!!


Shouldn't I be working now?

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nebbian said...

How can a cutout reduce wetted surface area? What a load of bollocks.

I dont know about reducing wetted area, but isn't it like bringing the rail closer to the fin at higher speed, i.e. the cuttout edge becomes the rail, giving you more control
<shrugs shoulders> who knows?

Nebs et al.

I have sailed 2 boards with cut out and own one of those small speed thingy's with no cut out.

The cut out boards I have also have the "air pipes"

Vando - happy to give you a run on the F2 SX S when we next sail together. (btw: Manly was crap yesterday!).

Nebs - you can feel the difference when the boards start to go fast (and I'm talking 27 knots+ - less than than and I can't tell the difference) - the tail feels like it is sort of 'levitating' you can feel lift from the tail of the board. - This feeling takes a bit to get used to and you need to have a bot of faith -especially in the fin. Are the designs any faster - I don't really know. When I swap from my F2SX to my Warp Speed In say 20-22 knots, the Warpy only seems to be about 0.5 knot faster on average - and sometimes slower.

I have found the 'cut out' trim/adjustable plates in the F2SX S - nothing but a pain in the proverbial - for me they were making the board spin out - I took them out and the board just behaves a lot nicer (smoother air-flow under the board?).

Can you carry a bigger fin than normal - probably yes, and my experience is that with the cut out board with the wider tail and greater lever moment cos your feet are closer to the edge of the board I usually need to go +2cm than for a narrower board of the same volume.

As or the wetted surface area argument - I'll brush off my considerable scientific talent and think about this some more.

Dr J

i've been using cutout tails for a long time now.

i find they give better response in higher winds on wide boards because there is less tail of the board lifting (railing up)

they have less drag because of the higher aspect drag ratio,

turn better due to an effective shorter water length,

make the boards trim more effectively,

allow a greater fin range to be used.

cutout boards usually work best with slightly bigger fins.

oh, and reduced wetted surface area....

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Gestalt said...

.....

oh, and reduced wetted surface area....

See? SEE????

its great to get the response on this one as im tooling up to make a board, and i'm tossing up on wether to use them,ive only ridden two boards with cutout's both were very popular boards and i didnt like either of them, so i appreciate any comments fore or against

When I look back at the cutouts whilst planeing (futura 122) they are well clear of the water so there has to be less wetted surface area hence less resistance which should equall more speed, but then again I'm just a baggy arse plumber so that might be crap too.

well that was one of the boards i tryed futura 115 i think thats the volume,but i must add i didnt use my gear eveyone sets there gear different, to be honest i couldnt wait to get off, but getting my board back was a different story

Tails cut outs to my understanding are to reduce the area at the back of the board, from what I understand these where introduced as boards got wider. Smaller boards generally aren't very wide hence they don't really need cutout outs

I have read somewhere that deep cutouts as well as reducing the wetted surface area allow the tail of the board to dig in when the nose of the board hits chop thus making the board handle chop better, if wide tail was flat the nose of the board would take a bit more to lift up.

The wetted area aspect, in sub planing circumstances deep cutouts by dramatically reducing area at the back of the board can make the board harder to get on the plane, boards with shallower cutouts are not affect that to much (this is why some Board manufacturers have inserts).

Size shape and all the rest of it is way beyond me, Kato (I thunk) played around with all different shapes of cutouts trying to get his most efficient set up for him.

At the end of the day, you either believe they work or you don't, some people like them some don't

Just watched Plug and play 2 this F2 dude says put the cutouts inserts in and the board gets higher out of the water and is easier to control in chop. He has inserts to change the depth, so shallower cutout will make board sits higher, deeper cutout and the board sits lower. Deep cutouts makes rear of board sits lower and nose higher giving you a more free feel most suited to flat water. Thats what he says anyway

is that a play station or can you send me a link

I'm so proud of myself for posting something intelligent for a change.

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keef said...

is that a play station or can you send me a link

Its a DVD, I was going to put the clip on youtube but Im worried about that copywrite thingo

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keef said...

its great to get the response on this one as im tooling up to make a board, and i'm tossing up on wether to use them,ive only ridden two boards with cutout's both were very popular boards and i didnt like either of them, so i appreciate any comments fore or against

i'd be interested to know what you didn't like about them. it may not have been the cutout that you didn't like.

maybe the rocker or the front rail shape was what you were feeling wasn't right.

at the end of the day cutouts or not the rocker is the most important thing.

a board with a very flat rocker is still going to drive into chop regardless of cutouts. granted you can get away with less nose lift with cutouts in the tail but this is also relevant with shorter boards too.

i am looking to start to play around with duck tails. they don't have the drag shape that wide style boards have but also achieve some of the positive outcomes like turning improvements and reduced wetted surface area.

as a few have already mentioned. it is a system that is being desiged. effectively a grab bag of compromise.

forgot to say, i sit in the deep cutout camp.

good onya willy, now dont wet your self tell me jman what f2 are we talking about, ill have a look at the f2 site

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

One day slowboat explained it to me while I was trying to figure out how to improve the trim on my speed board.

Any lift behind the rider will tend to flatten the trim of the board, (force the nose down).

So if your board is riding too flat, you may have more wetted surface area than you need.
So yes cut outs CAN reduce wetted area, (sorry nebs).
It's all about optimum angle of attack, if the angle is too great that will slow you down, (pushes water).
If it's too small that can also slow you down (too much wetted area).

Tail rocker can have the same effect as cutouts, a bit of tail rocker reduces lift behind the rider, helping to get the nose up.

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.

Thanks Slowboat!!!!

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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.

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

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*

Yep, agree nebs.
My back strap is already directly over the fin, didn't like the idea of it going any further back!

Think this was discussed before, and it was mentioned that the US navy found an angle of 7deg was optimum for their planning hull boats, lets the wetted area reduce with speed increase.

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nebbian said...

How can a cutout reduce wetted surface area? What a load of bollocks.

I suppose the reasoning goes like this:
"If I cut some bits out of the tail then those bits won't be wetted anymore so I'll have reduced wetted surface area". OK then let's carry this on further, and skim 2mm off the entire bottom of the board. Wow we'll have no wetted surface area so will have unlimited top speed!

Nebs Surely if you take mat from each side of the fin box your reducing the area that will touch the water.
Going abit further what about channels arnt they also suppose to reduce wetted surface or am i missing the point somewhere