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rudder blade mould that will suit the 8.5 - old thread


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Rental

Posted: Sun Nov 30, 2008 7:31 pm Post subject: 8.5 Rudders?

 

Does anyone have a rudder blade mould that will suit the 8.5?

 

Went out for test sail number 4 this weekend and blasting along by Browns Island when bang went the rudder. The bottom gudgeon on the case failed and after closer inspection the other side was about to go, also one of the blades had split and was full of water

 

They were the original frozen snot variety so I am not at all suprised, just need to get something sort quick smart for Christmas. I understand this is a standard issue problem with GBE rudders?

 

 

Ant.

 

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samin

Posted: Sun Nov 30, 2008 7:46 pm

 

 

Rental wrote:

I understand this is a standard issue problem with GBE rudders?

 

Ant.

 

 

I think rudders are a problem on all Multihulls! im on number 6...

 

2nd one broke 20 mins into my first race...

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The Saint

Posted: Sun Nov 30, 2008 8:24 pm

 

Give "JT" John Tez???? a call, he made us a new c/board and rudder for the tri from the GBE moulds,

 

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ScottiE

Posted: Mon Dec 01, 2008 7:56 am

 

yup - I'm on iteration 3. Decided not to muck about and got Wolfy to build them. They're awesome - no f/glass that I can see - just lots and lots and lots of black stuff. The cases will surely give way some time soon though.

 

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MrWolf

Posted: Mon Dec 01, 2008 9:28 am

 

The fastest way is to get the JT mould (Which Jason currently has).

That way the new blades will fit in your existing case.

 

My moulds require a new (or at least modified) stock.

 

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Rental

Posted: Mon Dec 01, 2008 5:05 pm

 

Any chance you have a number for Jason?

 

MrWolf wrote:

The fastest way is to get the JT mould (Which Jason currently has).

That way the new blades will fit in your existing case.

 

My moulds require a new (or at least modified) stock.

 

 

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catabatic

Posted: Mon Dec 01, 2008 8:09 pm

 

Here's my too sents worth. It looks like a case of 'peel' on the cassette gudgeon - something composites are notorious for if they aren't detailed well. I'd recommend a couple bits of horizontal quasi-iso c-plate or e-plate at each end of the gudgeon tube with a bit of edge clearance on the tube and a bit of wrap on the cassette sides, then tape over it all with uni's. A standard chainplate style detail doesn't work with gudgeons because of the much higher side loads (much higher than the fore/aft loads).

 

As Wolfy says, the stock in the rudder is also important. It's what takes the bulk of the sideways shear load which the outside skin is not good at taking, no matter how much black stuff you throw at the outside. The stock needs double-bias (45's) on the front and aft faces to take the sideways shear. Snot (expanded polyurethane) ain't very good at doing that. Cedar is not too bad if you make it thick enough, although, I feel dirty talking about wood here.

 

We all know the loads are much higher on multi's. Going from 10Kts to 20Kts puts 4 times the load on the rudder (same angle of attack, etc). I think all rudders should be designed for loads up to stall near top speed - for all those moments we live for.

 

(p.s. I love wood...I must be dirty??)

 

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Rental

Posted: Mon Dec 01, 2008 9:25 pm

 

Hey catabatic thanks for your input, when I cut down the stocks from the original GBE height I beefed up the fore and aft edges with carbon DB and ran some uni's at 45 across the case to try and stabilise the sides, when I looked at the general glass work I was not real happy with the gudgeons but it was a matter of "not broken".......

 

As it happens I have some carbon Q-plate about 8mm thick so that might do for the job. I think I understand what you are suggesting with the Q-plate, a piece at the top and the bottom of the tube, what do you suggest as a former between the two pieces of Q-plate?

 

And there is nothing wrong wood !!

 

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catabatic

Posted: Tue Dec 02, 2008 11:34 am

 

I'm know eggspurt...but anyway... I used plywad between the carbon Q-plates on Catabatic as a former for the cover straps. You could use HD foam if the plates are up to taking all the side load. I think a lot of the gudgeons we see work simply because there's enough glue area around the tube to take the side load - but the uni straps are still susceptible to peel.

 

By the way... my definition of a stock is the bit that goes inside the rudder. I call the thingy that holds the rudder on the outside the cassette....but hey, it could be called a widget, just as long as it works.

 

cheers, Bryce

 

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MrWolf

Posted: Tue Dec 02, 2008 12:15 pm

 

Bryce

 

that mumbo jumbo you speaking ?

 

My Gudgeons are actually turned orkot. (Orkot is a type of reinforced plastic containing glass fibres, it sticks when glued with Epoxy really well).

the orkot is glued in the correct position with a small spacer of solid carbon or I have successfully used High density foam).

 

So then you have the ability to line up the pin and get the rudder straight and at the correct forward rake).

 

To hold the Orkot "bushes" on to the stock It is mostly Uni, but I also include DB as well as 2 covering layers of Carbon cloth.

 

Any time is suits come take a look. I make lots of foils and cases and stocks (bloody things don't always fit), they are very strong and can't think of any that broke ? Ok except Positive touch, but there in lies a different story as you will be using the cassette stock to take all the load rather than a fixed rudder.

 

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catabatic

Posted: Tue Dec 02, 2008 6:29 pm

 

Yeah, I used orkot for the bearings also. I housed them in glass tube but didn't think about laminating directly onto the orkot... nice idea. I take it the epoxy sticks OK. It's builders innovations that usually create the best developments rather than techy stuff.

 

Positive Touch was a bit of a weird one? It's not like they got up to Timberwolf speeds.

 

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Shayne Y

Posted: Wed Dec 03, 2008 3:51 pm

 

This is a classic rudder box failing! After distroying I dont know how many of them in the skiffs over the years I have finaly figgured out how to stop it properly.

I will do a simply drawing and post it at www.syasperformance.com for you.

one of the biggest problems is gatting the bush as close as possible to the front of the case.

Send me some piccys of the boat i'm keen to see how it turned out.

 

Cheers Shayne

 

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oldsailor7

Posted: Mon Dec 22, 2008 9:21 pm

 

Sam, have you thought of trying Crowthers alternate spade rudder on Capricorn. ?

 

Cheers, Paddy.

 

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samin

Posted: Tue Dec 23, 2008 6:28 pm

 

Actually no, dont have the original plans so didnt know it was an option... My latest one has lasted a while but is pretty industrial.

 

What do you know about the spade option?

 

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oldsailor7

Posted: Tue Dec 23, 2008 6:38 pm

 

SAM.

If you PM me your postal address I will mail you the plan of Crowthers alternate spade rudder for the B24.

 

It frees up the transom so you can hang the outboard motor off the stern, out of the way of all the waves etc:

 

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Marshy

Posted: Tue Dec 23, 2008 7:48 pm Post subject:

 

Wow that means we can get rid of that outboard bracket that slaps and causes the hobby horsing! lol

 

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oldsailor7

Posted: Tue Jan 06, 2009 3:54 pm

 

SAM.

Did you get the spade rudder plan I sent you???

_________________

Cheers, Paddy.

 

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samin

Posted: Fri Jan 09, 2009 7:25 pm Post subject:

 

Yes I did thanks! Its very interesting! Im still not happy with my outboard arrangement! I wonder how well a small spade rudder and very small rudders on the floats would work?

 

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oldsailor7

Posted: Fri Jan 09, 2009 9:53 pm

 

Because the B24 comes upright as soon as it gets head to wind whilst tacking and spins around the daggerboard, I suspect the rudders on the floats would not be doing much work, and may not be worth the extra complication. If you were flying the main hull that would be another matter, but you would need 200% displacement floats to do that

 

I would suggest a bigger (longer) main rudder with two or even three fences on it to help resist air entrainment.

12mm aluminium right angle strips work very well I found.

_________________

Cheers, Paddy.

 

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samin

Posted: Thu Feb 26, 2009 7:55 pm

 

Shayne is it ok to exchange the QL plate for epoxy glue/filler? Where do I get QL plate and how do you cut it to shape?

 

Also how different is the design of the case for a kick up rudder rather than a lifting rudder? Gudgeons are the same I take it?

 

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MrWolf

Posted: Sat Feb 28, 2009 2:49 pm

 

I'm not sure if Shayne is around at the mo'.

 

But the QL plate really refers to a solid Carbon or even glass former that is used to attach the gudgeon tube to the stock. The QL really refers to the fibres being in all different directions, that is because the loads can be so random.

 

The reason so many stocks fail is that the strap laminate around the pin will peel off from one side, so connecting the pin to the stock must be by something that is strong in all directions which rules out your epoxy glue idea.

 

You can laminate Carbon plate either side of high density foam, or plywood, or even wood.

The part behind the pin and in front of the stock (the spacer) is the part where a failure will start.

 

to shape the q plate we cut it out with a carbon cutting bandsaw, then use a face sander to shape the outside and a bobbin sander for the inside.

 

if you want to do this job properly so it will last for ever you are welcome to come up one weekend and use our facilities to make up your gudgeons.

 

I even recommend vacuum bagging on the strap laminates using rubber Toughened Epoxy, as it is much stronger.

 

Also I have an unpainted stock at home which i can show you as to how they all go together.

 

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samin

Posted: Sat Feb 28, 2009 3:54 pm

 

Thanks Tim

 

So If I make some 10mm thick QL plate and have 20mm of high denistity foam beween it (looking from side on) for a 40mm gudgeon it should do the trick? I just cant imagine trying to cut 40mm thick carbon plate with my little jigsaw...

 

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MrWolf

Posted: Sat Feb 28, 2009 4:23 pm

 

Yep that will work out great.

So your 40mm will be made with 10mm plate on top then 20mm hd foam, then 10mm plate.

You can get special blades for your jigsaw called T141HM specially for cutting glass and carbon plate.

 

I didn't answer your other question about daggerboard rudder vs pivoting ones.

when the Rudder is down and the blade is pinned down (which you need to do with a pivoting one), then the loads on the two sets of gudgeons are the same.

 

But when the pivoting rudder is half down then the loads on both the blade and the gudgeons are absolutely huge, a great big lever trying to snap everything off.

So if you go pivoting then you need to keep speed right down until blade is locked in the down position.

 

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