Thread: Jib on A PD Racer? Gennikers or "Code 0"

Originally Posted by nickpullen

Whats a gennicker? Anyone got pics? I assume its similar to a Spinnacker.

It's a cross between a genoa and a spinnaker made of lighter material than a normal headsail used when the heading is too shy or close hauled for a spinnaker. Sometimes called drifters when spinnaker material is used. The spinnaker on the 18' skiffs could be called a genniker as they are cut to work very shy rather than a traditional radial cut spinnaker for true downwind.

Someone want to draw up an add on plan for the OZ PDR? Will the standard mast be up to the task?

Over to Mik

Howdy Guys,

The OZ PDR was basically designed as a platform to play with. I have drawn up two rigs that are as efficient and simple as I know how to do. Also have done one retrofitted rig stolen from the Sunfish (which is a hugely popular class in the USA)

But that is it for the moment.

If you want to go for it ... its up to you.

Feel free to keep going in this thread and I am happy to contribute to make it work as well as possible ... but time for you guys to start doing a bit of sail designing I reckon!

Any tech stuff I can help you with .... just ask.

And note that I have changed the topic of this thread even.

Best wishes

Michael

OK I think Mik has pointed us in the right direction a Code O would be easier to make no seams and panels and probably work better than a genniker using tarp material.

I'm thinking on a lug rig as long as it is only used in light breezes the mast may take the loads when reaching.

Some quick measuring and I'm thinking the following
1. Bowsprit 750mm 500 outboard and supported by 250 on the foredeck. Bout 40mm wide x 30mm high going out to 60 at the mounting points. Might laminate with a slight downward curve a la Gwen 12, cool. Mount using some alloy strap screwed to mast support cleats and bow transom. Maybe an alloy bracket screwed to bottom edge of the bow transom would hold a wire strop bracing the sprit. Tape the end to stop splitting and bolt a saddle for a pulley to run a tweaker attached to the tack for hoisting this would need a jam cleat and could be mounted on the side of the mast just above the deck.
2. The foot would be 2200 long so the clew would roughly be in line with the middle of the centre case when set. Endless sheet would run through pulleys attached by loops tied in the traveller just above the side deck. The mainsheet will need a swivelled jammer mounted on the back end of the Ccase might be a bit tight when tacking.
3. Luff length equals mast top to sprit end and some VB chord sewn in to control stretch although given the halyard is eased on these sails to get a good shape reaching, a chord may not be necessary.
Foot curve gradually increasing from tack to clew so clew lines up at about 40% up the luff. Perhaps 100mm of positive roach in the leech at the 75% point? I think the halyard could run through the mainsail eye and made fast on the main halyard cleat (save on fittings).

I will do a drawing and post soon. Thoughts so far?

Cheers
Mike

Sounds impressive. But, I did not understand 90% of what you said, I'm very novice!!! Drawings will help...
Thanks though...

Originally Posted by nickpullen

Sounds impressive. But, I did not understand 90% of what you said, I'm very novice!!! Drawings will help...
Thanks though...

Hi Nick, may be a while before I post a drawing as I don't have access to a scanner at the moment.

I've been searching for some info on code 0 heres some sites explaining the concept.

http://www.ukhalsey.com/sails/CodeZero/
http://www.northsails.com/north_amer...sails/G0QA.htm
http://en.wikipedia.org/wiki/Spinnaker

Mike

Originally Posted by nickpullen

Sounds impressive. But, I did not understand 90% of what you said, I'm very novice!!! Drawings will help...
Thanks though...

Me neither. Got bow-sprit, Gwen 12, sheets & halyard ok.
Tweaker ? I thought a tweaker's a person who thinks they can make their car go faster by adding spot-lights, roof-racks, GT stripes & etc.

I like the concept though.

Would you be able to get by with a straight luff, or would it need some concave to compensate for the wind blowing? The other thing is that I have doubts about polytarp's ability to be doused into a chute. Blimmin stuff seems to snag on nuffink at all at the slightest excuse. Totally unlike lightweight ripstop or whatever.

AJ

Originally Posted by b.o.a.t.

Me neither. Got bow-sprit, Gwen 12, sheets & halyard ok.
Tweaker ? I thought a tweaker's a person who thinks they can make their car go faster by adding spot-lights, roof-racks, GT stripes & etc.

Sorry actually called a tack line, allows the tack to be hauled back into cockpit. A tweaker is used to trim a spinnaker ie similiar

Would you be able to get by with a straight luff, or would it need some concave to compensate for the wind blowing?

Yep I think for tarp stuff the luff could be straight cut the round is induced by freeing the halyard slightly. The leech has positive roach to increase area and I'm guessing because of the cut the sail makers can eliminate flap for our purposes a straight leech would maybe work better. Need to see what Mik thinks.

The other thing is that I have doubts about polytarp's ability to be doused into a chute. Blimmin stuff seems to snag on nuffink at all at the slightest excuse. Totally unlike lightweight ripstop or whatever.

AJ

Hmmmm......I agree, need to find really light weight tarp stuff still a problem but I reckon you drop the halyard and just stuff it into the space in front of the front centre case brace then release the tack line and stuff the tack in after it.

Mike

Go for it guys! I am very impressed already!

MIK

MIK, Do you think the normal hollow 5m mast could handle this extra strain?

I think holding the mast up could be quite tricky once the wind got going. There is one trick that can be tried though .... and that is to have a figure of 8 knot in the halyard about a 8 inches from the spinnaker head. when hoisted the knot will jam against the halyard block. The halyard can then be belayed to a cleat on the windward quarter to help stay the mast.

Don't expect to gybe in a hurry though.

Temporary sidestays going from about 3/4 up the mast to the back of the foredeck might stop the whole thing from disappearing over the bow in a gust.

MIK

If one were to increase the the lug mast diameter from 62mm to say, 70mm,
(still in 12mm thick staves) I'm guessing that it would add significant stiffness
& strength - probably more than the 10% dimensional increase. With a
*little* extra beef around the partner & step, it might be possible to avoid
the complications of stays & etc altogether. Would be a smaller maximum
size sail than a leg o' mutton masthead rig, but one that can still be carried
when the wind picks up a bit.

Howdy AJ,

I think the additional staying makes better sense than extra mast diameter.

Extra diameter is with you forever so will be slowing the boat on all points.

Whereas stays add negligible weight and can be left off completely if desired too.

A couple of low stretch ropes would be all that is required for the sprit rig.

Lug is a bit more tricky as the yard and boom end will want to catch the stays sometimes (which is why I think lug rigs with stayed masts (ie lug rigs with jibs) a bit strange. But can be done.

MIK

Originally Posted by Boatmik

Howdy AJ,

Lug is a bit more tricky as the yard and boom end will want to catch the stays sometimes (which is why I think lug rigs with stayed masts (ie lug rigs with jibs) a bit strange. But can be done.

MIK

The yard end is the one I was thinking of regarding stays.
And snagging the foresail too. Jib / reacher #2 on Teal was somewhat abbreviated
based on experiences with jib #1... Gennaker would probably need a gathering/furling
line from luff to leach at yard height to pull it clear of yard when tacking / gybing /
swimming.

Readings on adding stays to free-standing flexible masts suggest not great idea.
Divert stresses from strong tension in mast to weaker compression.
(The vector diagrammes made sense that way, anyway.) So stronger, stiffer mast
made sense in that context.

cheers
AJ

This thread very promising. Should be some great pictures, if you can keep the hulls in the water that is! Best ever sailing I have had was blasting across the Solent under Gennaker in force 5 winds. Great stuff.

I would guess a PDR, with a big rig, will plane very early, say 10 to 15 knots of breeze. Once on the plane the wind will go so far ahead with a fullish sail you will have to keep bearing away to keep the apparent wind correct, so a fairly flat gennaker might be good.

When it's made, stick it on the Goat!

Brian