Hi all,
Im just starting to get back into flat water sailing and I've been dusting off some very old kit so my wife and I can sail flat water during winter.

We have a old fibreglass era, speed/slalom board that has approximately a (0.5mm depth) negative hollow in its rocker line.

Its located in the centre stringer area in front of the fin box and is about 300mm long.

Was this some old design thing from the 80's ? or 90's. ?
Or
Is negative rocker a speed thing ?

It's difficult to photograph but I've tried to show what I mean in the pics, with the camera pointing forward from the fin box towards the front of the board, I have used a aluminium straight edge and some paper to try and show the gap clearance.




PS The Aussie guy that shaped this board, who I believe is still around today.

This is most probably due to sailing at speed into chop, the core foam has compressed. -ve rocker just in front of the fin will slow you down.
Fangy had that in one of his ancient boards, he bogged it up straight and he went faster. -ve rocker under you back foot will create lift behind you, pushing the nose down and increasing wetted area.

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decrepit said..
This is most probably due to sailing at speed into chop, the core foam has compressed. -ve rocker just in front of the fin will slow you down.
Fangy had that in one of his ancient boards, he bogged it up straight and he went faster. -ve rocker under you back foot will create lift behind you, pushing the nose down and increasing wetted area.

Ah ok I didn't know what it was all about, I figured it was built into it. From memory it was always like that.

Cheers Thanks

I have a Wind Action slalom board with a flat tail on one side and a V on the other side?! or its twisted or it's on the piss!? Who knows anymore. I can't believe that I didn't see it before I bought it and that it was shaped like that. Its now hanging up on show.

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BSN101 said..
I have a Wind Action slalom board with a flat tail on one side and a V on the other side?! or its twisted or it's on the piss!? Who knows anymore. I can't believe that I didn't see it before I bought it and that it was shaped like that. Its now hanging up on show.

Wow not good, what did it go like ?

Im might do the same with mine or nail it to the wall in the shed.

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getsum said..

BSN101 said..
I have a Wind Action slalom board with a flat tail on one side and a V on the other side?! or its twisted or it's on the piss!? Who knows anymore. I can't believe that I didn't see it before I bought it and that it was shaped like that. Its now hanging up on show.

Wow not good, what did it go like ?

Im might do the same with mine or nail it to the wall in the shed.

You could fill the 0.5mm gap with filler

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John340 said..

getsum said..

BSN101 said..
I have a Wind Action slalom board with a flat tail on one side and a V on the other side?! or its twisted or it's on the piss!? Who knows anymore. I can't believe that I didn't see it before I bought it and that it was shaped like that. Its now hanging up on show.

Wow not good, what did it go like ?

Im might do the same with mine or nail it to the wall in the shed.

You could fill the 0.5mm gap with filler

Good idea !

I've seen some guys do that to make small rocker changes.

But I don't think I will muck around with mine, there's a lot of good memories attached to it the way it is.

I've got a few other old crusty boards I can dust off and try.

They have a more rounded style of rail for off the wind sailing and the mast track position is probably more suited.

In the boating industry what you talk about is called 'hook'. Kind of inbuilt trimtab to level hull at speed.
My 380 Starboard Phantom RB actually has 1mm hook from rear of CB case to tail. With moderate V laterally.. Planes early but not the best top end speed. I was surprised to see the 'hook' on a modern board.

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olskool said..
In the boating industry what you talk about is called 'hook'. Kind of inbuilt trimtab to level hull at speed.
My 380 Starboard Phantom RB actually has 1mm hook from rear of CB case to tail. With moderate V laterally.. Planes early but not the best top end speed. I was surprised to see the 'hook' on a modern board.

Thanks olskool
that's Interesting.

Im way out of touch with models of boards to know what is good nowadays.

Im going to try out some of my other old narrow 52cm wide epoxy boards at my local spot on lake Illawarra.

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getsum said.. >>> Im going to try out some of my other old narrow 22cm wide epoxy boards at my local spot on lake Illawarra.

Are sure you aren't talking about a water ski?

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decrepit said..

getsum said.. >>> Im going to try out some of my other old narrow 22cm wide epoxy boards at my local spot on lake Illawarra.

Are sure you aren't talking about a water ski?

Ops thanks now edited.
I meant 52cm wide.

Slow, you need to fill it. I always put a hint of rocker in my tails to make sure it does not go negative ,

At only 0.5mm it is probably well worth trying. It will probably still sail very well. But if it is too severe it can have a drastic negative effect on performance. I have a 49cm wide Polyester board I made around 2000 that went hollow in front of the fin. It really affected performance.( I had done a 44 kt peak on it before it distorted. I was struggling to get past 40 with it later on). I took it to my local surfboard craftsman and had him put another layer of glass on the rear section. They I had him sand it again, checking with a straight edge as we went. He has a much better eye and touch with the sander than I ever had and it come out perfect. It made a massive difference to the performance and feel of the board . But that was about the time I got my first even narrower epoxy speed boards so it has not had much use since then.

This technique is well worth a try. If the glasser and sander is highly skilled, it should be virtually impossible to notice when done well. Oh, and rather than dead straight, I would leave it 0.5mm high, just to allow for more compression settling, just as Mr Love says above.

I can see that a tiny bit of negative rocker may not be a bad thing .... if ... your going from a flat cross section into a V in a narrowing tail . My old Mistral OD does it a bit also.
Probably not a good thing for an all out speed design .
Is it a thing on some long boards , so you can have some V without the tail sinking too much ???

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sailquik said..
At only 0.5mm it is probably well worth trying. It will probably still sail very well. But if it is too severe it can have a drastic negative effect on performance. I have a 49cm wide Polyester board I made around 2000 that went hollow in front of the fin. It really affected performance.( I had done a 44 kt peak on it before it distorted. I was struggling to get past 40 with it later on). I took it to my local surfboard craftsman and had him put another layer of glass on the rear section. They I had him sand it again, checking with a straight edge as we went. He has a much better eye and touch with the sander than I ever had and it come out perfect. It made a massive difference to the performance and feel of the board . But that was about the time I got my first even narrower epoxy speed boards so it has not had much use since then.

This technique is well worth a try. If the glasser and sander is highly skilled, it should be virtually impossible to notice when done well. Oh, and rather than dead straight, I would leave it 0.5mm high, just to allow for more compression settling, just as Mr Love says above.

Thanks very interesting.

I got thinking and I wonder if it's not actually compression in front of the fin , but a high spot at the fin area.

I remember rolling the standard fin box in the very early 90's , not long after I brought it new, from the fire station shop in Sydney , the box
was replaced with a Tuttle at a pro surf shop in Cronulla.

Maybe during the process of glassing the new box, a very slight amount of excessive glass was added which affected the rocker slightly and lifted it around the fin , creating a negative in front of it and behind at the tail.

I don't know..

Anyway it still sails great so decided Im not going to bother with it I think I will retire it to the shed wall.

or as one forum member here recently suggested seeing a pic of one of my boards....

"that's old sh1t mate throw it on the bon fire"

so maybe I should do that with it next time at the Primbee car park.

It has seen some epic action (see my profile pic) and had a huge amount of use as it was my number 1 board , and freaky quick.

It wasn't in my ownership from about 1998 , until now.
I only got the board back about 5 months ago.

Which revived our interest in sailing flat water again as We normally just wave sail.

It is absolutely ancient by today's design trends and standards.

Anyway I sailed it again recently , Primbee , 18cm Delta fin, big westerly easy 35kn + of wind, 5.2 sail.

I don't own a gps but I would not describe this board as...slow.

But then again I wouldn't expect it to be, which is credit to the guy that shaped it. See pics below.

Ahhh, Fin box replacement., that could well be the issue!
If that is the case, it should be easy to sand a bit of glass back over the box.

Just enjoy sailing it occasionally. Dont leave it hanging on a wall all the time.

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sailquik said..
Ahhh, Fin box replacement., that could well be the issue!
If that is the case, it should be easy to sand a bit of glass back over the box.

Just enjoy sailing it occasionally. Dont leave it hanging on a wall all the time.

It honestly has been like it for as long as I remember and I've never questioned it before because it's always been freaky quick.

I will bring it down one day you can have a few runs on it if you want to.

I don't know how many 8ft8" x 20.5" wide boards he made but I would guess not many as the others I saw at the shops were dedicated speed needles.

It was by far the largest of his boards available on display when I brought it at the fire station shop.

Mal knew what he was doing,
Time Machines Rule

Here's another vintage pic of it, in Mal Wright mode - no hands and with the pedal to the metal, on my 4.6

Sailing at Kurnell in Sydney during a big southerly. Way back in about 1996

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decrepit said..
This is most probably due to sailing at speed into chop, the core foam has compressed. -ve rocker just in front of the fin will slow you down.
Fangy had that in one of his ancient boards, he bogged it up straight and he went faster. -ve rocker under you back foot will create lift behind you, pushing the nose down and increasing wetted area.

Or not - Phil McGain slalom boards had this same little "pocket" just before the box (even when brand new - and his own personal race boards*)

These boards had no vee at all (dead flat nose to tail) and about 1200mm (IIRC) of dead flat rocker from the tail towards the nose

* His personal boards seen first hand on Maui and my own "Phil McGain" boards made by Andrew Reagan

If a board has vee / concaves / rocker / etc - probably no good???

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ausbinny said..

decrepit said..
This is most probably due to sailing at speed into chop, the core foam has compressed. -ve rocker just in front of the fin will slow you down.
Fangy had that in one of his ancient boards, he bogged it up straight and he went faster. -ve rocker under you back foot will create lift behind you, pushing the nose down and increasing wetted area.

Or not - Phil McGain slalom boards had this same little "pocket" just before the box (even when brand new - and his own personal race boards*)

These boards had no vee at all (dead flat nose to tail) and about 1200mm (IIRC) of dead flat rocker from the tail towards the nose

* His personal boards seen first hand on Maui and my own "Phil McGain" boards made by Andrew Reagan

If a board has vee / concaves / rocker / etc - probably no good???

^^^
It's truly a mystery to me, all I know is how amazing it is to sail.

The guy that fitted my Tuttle box was a highly experienced board builder and I would doubt he left the fin high but who knows.

In all these years, I've only ever had one other negative rocker board,and it also was blistering quick.

It was built for me by
Luke Hargreaves from Cronulla, from memory I went directly from Mal's Board to Luke's, Epoxy, Warboard.

I think Luke also raced on the world circuit at a similar time to McGain. ?

Heres a old pic of it with a mate of mine on it at Dolls Point.


From memory Luke got his board design experience from Maui and the world tour way back in the day.

My wife liked Luke's wave warboards.

Hi Getsum , Has been a very Long time , Hope you are good Would be cool too see you And the Time machine again, Im sure
that board would be well suited at primbee I remember sailing that day at Bonna pt with you was a fantastic spot to sail in back then
Catch up soon.

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Bazz2231 said..
Hi Getsum , Has been a very Long time , Hope you are good Would be cool too see you And the Time machine again, Im sure
that board would be well suited at primbee I remember sailing that day at Bonna pt with you was a fantastic spot to sail in back then
Catch up soon.

Baz !
Bro it's been over 20 years.

I hope you're well. Yes it would be cool to catch up.

I just sent you a message mate.

cheers
G