What am I doing wrong?

[simon ballantine]

I 've just spent a very frustrating day trying to set my rig up and, even after a couple of phone calls to John Murrell I'm not sure I've got things right.
N3291 is a Design 8 with a Kappa mast, which seems to be so stiff I'm wandering if its been filled with concrete.

Baically when I set it all up as the Tuning Guide with the P&B published spreader length and rake it all looks OK, except that the mast stays dead straight, or even bent forward when under lots of forestay tension.  Pre-bend only happens when the shrouds are cranked on to give 400mm of rake, and even then there is only about 10mm of bend.

I 've tried drastically increasing the rake of the spreaders, clamping them in place so they don't spring forward.  I managed to achieve 35mm of pre-bend under normal mast rake and tension, but the spreaders needed to be hinged so far back that the shrouds look knock-kneed, like they've been kicked in the nuts. ..The deflecion angles are enormous.   The spreaders are now so close together they are almost touching.  Bit of an exageration that, but the spreader rake increased from the textbook 157mm to a new value of 216mm.

It all looks horribly wrong.  Any ideas?

How do I post a photo?

[jonsue N3469]

The speaders on 3286 (for sale below, D8+ Kappa) are set at 190mm which works OK with a set of Alverbanks.
They look over raked but  are limited swing so when offwind and the l'wd shroud is off the spreader is out of the way.

[rick perkins]

Is the heel properly in the step?

If it has rocked forwards and the heel is sitting on the bolt at the front all the compression will be down the front of the mast and all the things you describe will happen ...

Rick

[marcus3292]

simon

i have 3292, and i am at the stage of trying to work this boat out as you, im going to measure mine tomorrow to see what it is, because at the moment all i do is pull bits of rope.

the only thing i am unsure of is how to measure rig tension, i suppose there must be something on the web to enlighten me..

as regarding the photo lark, i think you find the picture you want say for ex.

http://www.boat-pics.co.uk/Photos/pod/pod060215.jpg

then i think you add at the end. (it must be on the same line)



so it looks like that. i hope this is right but i may be mistaken as i am not a expert on computers, i not even at novice grade yret

[simon ballantine]

[quote by=jonsue link=Blah.cgi?b=Cool1,m=1170447510,s=1 date=1170448507]The speaders on 3286 (for sale below, D8+ Kappa) are set at 190mm which works OK with a set of Alverbanks.
They look over raked but  are limited swing so when offwind and the l'wd shroud is off the spreader is out of the way.[/quote]

Thanks for the advice, I'm particularly keen to get tips from someone with a well-sorted identical boat.  I'm going out into the garden now and will set it up to 190mm and see what it looks like.  

A couple of questions for you.... Do you know your spreader length?  and how much mast prebend do you achieve with the rig in 'normal ' mode?

Rick: thanks for the tip about the mast step.  I can see the logic.  The male fitting in the end of the mast is heavily worn away at the aft end, which will encourage it to pivot about the forwards edge.  I've just ground it down level.  Incidently half of Smalls Cove beach fell out of the mast when I took the fitting off so I've saved 1/2 kg in the process!  

Incidentally the mast foot was previously set up way forward and I have moved it back to the textbook setting, which is central on the mast step.  Perhaps the way it was when I bought the boat works better and I should set it up with the step forwards and with more rake than normal in order to get it to bend?

As for posting photos, presumably they have to be sitting on the web somewhere first?

[Tim L (Guest)]

Simon,

have you considered lengthening the spreaders to get the same effect?

For a D8 (my old boat was 3295) from memory:

9in rake measured as the distance back from the gooseneck black band to a weight hanging on the halyard - there should only be enough rig tension to hold the mast in position rather than creating any prebend when measuring this.

Then whatever spreader length and angle to achieve a) 1-2in prebend (it wasn't more than about 1.5in on the Proctor C in 3295) and b) when you sail upwind the leeward shroud doesn't go completely slack.  If you feel the main is too full for the conditions just juggle the kicker and ram settings until it looks happier.

[marcus3292]

[quote by=simon_ballantine link=Blah.cgi?b=Cool1,m=1170447510,s=4 date=1170493785]


As for posting photos, presumably they have to be sitting on the web somewhere first?

[/quote]

thats right in this instance,

measured mine 2day found my spreaders are set at the reccommended setting, played with the rig with the boat on its side and was amazed how much the sail shape changes, learnt alot by doing this aswell

[jonsue N3469]

[RogerBrisley]

Moving the mast  heel back should induce more pre bend for an otherwise given set of settings. My settings include mast stepped in the middle of the heel plate.

My D8 has a Proctor C and a Kappa.  I have never used the latter, the previous owner purchased it but did not get on with it so it is virtually brand new. Was the mast a choice with new D8's?.

Suffice to say I find that I can get a lot of (controllable) bend in the P'C and can find no good reason to use the Kappa despite being generally on the heavy side.

Roger
3334

[simon ballantine]

Thanks for all the help,everyone.  It's great to get lots of slightly different perspectives and I feel alot more confident as a result.  The mast is now starting to look like the right shape.