Can a Tuttle or Powerbox fin be modified to suit old US box? Pointer style fin no bigger than 40cm.Whats involved guys? Milling machine territory? Or can it be done with linisher n hand tools etc?

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olskool said..
Can a Tuttle or Powerbox fin be modified to suit old US box? Pointer style fin no bigger than 40cm.Whats involved guys? Milling machine territory? Or can it be done with linisher n hand tools etc?

i have changed tuttle to power box by using a large cut of saw and grinding very carefully,if u grind i down to us box spec you will end up with a very short fitting which will pries your box apart with the extra leverage .probably better to get a old glass us fin and ad to it,but all said and done i do not think you will get any real gain for all the work .i have changed my eliminator to power box and the only difference is it will stay on the plain on a tight up reach better.but using a bit of center board will do the same.remember the boards are skinny and don,t require a lot of fin and can over power quickly

^^^ I agree with grich, if you really need to go with a large fin I would investigate this route, I've used them in the past to convert a couple of lightnings ;

www.surfsailaustralia.com.au/product/chinook-power-fin-box#surf-sail-clothing-hardware

Hi Greg, just looking at all options. I feel my IMCO goes better with Finworks 393 pointer shape than standard 34cm fin. So was looking for similar fins to suit US box for Speed formula one.Its either muck with fin or muck with finbox upgrade. Will finbox change make board illegal to compete at raceboard comps?

you won't find the Speed on the list of registered boards but that would not be an issue at any club races. I am guessing even at nationals they would be pleased to have you turn up with that board, even so, the finbox could be considered a repair, was not an issue years ago with my F2's

www.sailing.org/41157.php

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olskool said..
Hi Greg, just looking at all options. I feel my IMCO goes better with Finworks 393 pointer shape than standard 34cm fin. So was looking for similar fins to suit US box for Speed formula one.Its either muck with fin or muck with finbox upgrade. Will finbox change make board illegal to compete at raceboard comps?

it will only become an issue if you beat them ha ha. try the board first,remember they have bigger rails than the imco .if you still feel it needs a bigger fin and want to change the box , go for a tuttle box from chinook,you will have better fin options.remember that short fat fins work as well

skip through this a bit to about the 305 minute mark and you will see the board tracks well any way.this was light winds with a 9.5 and small fin they are not as loose as a imco in the back end and the rails really help.

I posted a while back on a similar discussion about fins for raceboards in this thread

www.seabreeze.com.au/forums/Windsurfing/Victoria/longboarding-where-did-wwwlbwindsurfingcom-go#765273

I also have done done an upgrade on eliminator from US to Tuttle and completely agree with observation of grich above.

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jonesmb said..
I posted a while back on a similar discussion about fins for raceboards in this thread

www.seabreeze.com.au/forums/Windsurfing/Victoria/longboarding-where-did-wwwlbwindsurfingcom-go#765273

I also have done done an upgrade on eliminator from US to Tuttle and completely agree with observation of grich above.

you made the same mistake as me and put the box in the middle of the old fin position,probably should have gone back a bit for better rear strap access and balance. can you post a photo of your board,and what mast track do you use.(now i feel stupid just seen the photos,looks like the standard track i think they were tyronseas tracks. if your track are jamming mine was packed on the sides with batten material which distorted the track ,i end up using a bic track which is great to move)

I don't have the eliminator anymore, I cut it into many pieces and took to the tip. Instead I now use a raceboard I designed and built. But back to the eliminator, below are some photos. I also changed the most rear footstrap positions to have two side by side, rather than the single centre strap it came with. I found this really helped the balance. You can see from the photo the relative position of rear footstrap to fin, this seemed to work. The mastrack is Tyronsea, by re-positioning the location of the retaining pin I could mount a chinook base into this but the track never really slid easily.

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olskool said..
Can a Tuttle or Powerbox fin be modified to suit old US box? Pointer style fin no bigger than 40cm.Whats involved guys? Milling machine territory? Or can it be done with linisher n hand tools etc?

G'day Andrew,
I butchered a good Tectonics Talon 50cm on the rock's, and used it.
I cut it down enough to take out the damage and re-shaped it.
I have good steel layout benches so I tacked some bits of scrap to bench top to secure the fin.
I then tacked a piece of 20mm Square hollow section to the bench parallel with the top of the fin base. I then cut a piece out of another 20mm SHS to fit over the fin parallel to the bottom of the base.
The square hollow section pieces served as a support for the router.
Was surprisingly easy and perfectly accurate. Photo coming.

If doing it manually a tip:

Dags method is great! But for that last little bit of finish...
Get it real close as above (or sanding) then use a milling cutter in a drill press. Set it to right height (10mm I think for US base) .
Have somebody hold the drill press handles so it can't pull itself downward into the material like a drill bit does. YOU DO need to think about that part, a mill will try and bury downwards.
Then slide the fin base around on the table so you are milling just a fraction - under 0.5mm - off.

This is a good way to get it nice an even thickness as you will never hand sand it properly flat.
Don't try and mill down more than about 0.5mm it will bite and take bits of you off also.

If too thick, put a piece of paper or two under it then repeat. That way you are taking off a paper thickness each time.

Just remember fingers and mill = bad. Well, any body parts vs milling cutter is bad. Wear leather gloves and be farkennnn careful.

Hi Darren, so theres enough material in a tuttle to cut down to US box shape? Awesome thats what i wanted to know. Now the hunt for a suitable donor fin. What length did it end up as?

It's now 43cm's. Don't know how the box is going to hold up, but if it goes, it will only speed up the tuttle conversion, in which case I will then re-box the fin as a weedy. Something else I want to do anyway, and it seems like it would be perfect for it.

So tuttle suits mods? Have heard PB too shallow at 100mm & 85mm depth fore n aft. What about Trimbox fins? Suitable to mod to US?

Not sure there. I think it's been covered on a previous thread though.

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olskool said..
So tuttle suits mods? Have heard PB too shallow at 100mm & 85mm depth fore n aft. What about Trimbox fins? Suitable to mod to US?

PowerBox is good also, like this one I did recently with a belt sander

So PB fins can be used. Sweet that makes finding a donor fin easier.

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olskool said..
So PB fins can be used. Sweet that makes finding a donor fin easier.

what color is your fin box ,if it is white its probably made of plastic and easily cracked down in side, if it is black it might be glass nylon mix they still have a habit of rolling the box if you put in to big a fin and can do quite a lot of damage to the back of the board.if they crack you will get water in the core and cause more issues.try it with a standard fin and if you don,t like it then change the fin box to your preference ,it will save you wreaking and loosing a good fin

Black US finbox. Looks ok, slight gelcoat chipping midway down one edge.

Looks like your gonna get busy oldskol.got a grinder .?
i know my long board is different to yours .i have a mistral escape .190 litre 11.3 foot.
i found a 36 and 38 pointer the best size .
my mate had the equipe carbon 2 it came with a 38 pointer ...you could use a 40 -42 .?light wind .

we mainly where planing and in the straps .
And never used the centre boards much
just thought I'd mention a favourable size ..

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Tardy said..
Looks like your gonna get busy oldskol.got a grinder .?
i know my long board is different to yours .i have a mistral escape .190 litre 11.3 foot.
i found a 36 and 38 pointer the best size .
my mate had the equipe carbon 2 it came with a 38 pointer ...you could use a 40 -42 .?light wind .

we mainly where planing and in the straps .
And never used the centre boards much
just thought I'd mention a favourable size ..

Hi Phil, yep a bit of work coming up. Why do the repairs always coincide with good wind forecast? Guess itll be repairs in the morn sail in the arvo. The thought of being consumed by sailboardin 24/7 is Bliss! Bring it on. Hows island time looking?

The conversions are great.

iMO , absolute Theory opinion, the US box was never designed for fins this large, as none come that long.
around 32 is about it.

i would like to hear I'm wrong.

I don't think you are wrong.
Maybe there is less pressure (and requirement in the first place for a larger fin) on a race board though. Especially compared to a wide slalom board with outboard straps. That's when the Tuttle boxes are really required.

The main reason for fin mods is to get a modern profile fin. Rarely is there a pointer fin available in US box.So its modify fin or put a new tuttle box in board.NOT MANY REPAIRERS WILL CHANGE FINBOX. They all seem to run for cover. (Board made 1991).Raceboard doesnt need a massive fin. Between 34cm -39cm is plenty. Wouldnt think itd stress box at that length. Standard fin 34 wide chord style.So modify a new fin chuck it in US box n go sail.

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olskool said..
The main reason for fin mods is to get a modern profile fin. Rarely is there a pointer fin available in US box.So its modify fin or put a new tuttle box in board.NOT MANY REPAIRERS WILL CHANGE FINBOX. They all seem to run for cover. (Board made 1991).Raceboard doesnt need a massive fin. Between 34cm -39cm is plenty. Wouldnt think itd stress box at that length. Standard fin 34 wide chord style.So modify a new fin chuck it in US box n go sail.

Spot on oldskool, stay with the US box and IF you happen to roll out the box then worry about putting in a PB OR TB