Jib without the camberspar

Bill
Posts: 18
Joined: Wed Aug 05, 2020 6:57 pm

Jib without the camberspar

Post by Bill »

Removing the camberspar and replacing it with a batton
My forestay is getting damaged by the camberspar fitting the stay is being forced forward and rubbing on the pulpit crossbar
Has anyone removed the spar do I need a batton

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mike cunningham
Posts: 489
Joined: Sat Dec 20, 2008 11:21 am
Location: Jacqueline, F30 #3, Discovery Bay, California

Re: Jib without the camberspar

Post by mike cunningham »

Sounds like maybe the fore stay is too loose? Should not be rubbing on the pupit unless the pulpit has been modified.

The camberspar imparts sail shape at all points of sail (I just recently figured out how it works after 23 years of ownership). A batten is not going to hack it. Having said that, no idea what kind of shape you'll get without the spar. Probably not great.

I would try to fix the rig and, coincidentally, I am fixing my camberspar as I write. I bent the thing, I have straightened it (for the second time) and intend to wrap it with some carbon to resist future bending.

However, if you do decide do remove it, I will buy the spar forthwith so please keep me in mind if you go that route.
Mike Cunningham
Freedom 30 (Mull) Hull #3
Build date...June, 1986 . Freedom Yachts USA, sloop, shoal keel
Gun Mount and pole retrofitted (purchased from a Hoyt Freedom 32)
Yanmar 2gm20F , 1600 hrs fixed two blade prop
e-rud and ocean racing equipment

Bill
Posts: 18
Joined: Wed Aug 05, 2020 6:57 pm

Re: Jib without the camberspar

Post by Bill »

Thanks for your advice ,don't really want to discard the spar as it does work
Recently tightened the forestay as it was very loose .it is still not as taut as a stayed rig , after which I got the damage
Stay seems to rub when the main is bending pulling the stay backwards
When sailing the jib luff bends at the camberspar forming a trapezoid shape in the jib, is this an indication that the stay is too loose or am I sailing it wrong
I am going to replace the stay but I would like to resolve this as I don't want to damage the new one

Pearce
Posts: 65
Joined: Sat Feb 22, 2020 10:28 am

Re: Jib without the camberspar

Post by Pearce »

Hi,

Agree that the Forestay could need tightening. I had a problem with a loose forestay and Camberspar end banging against the mast and forestay rubbing pulpit.

Two things helped:

1) Paul Dennis advice is to add tension until just before the mast starts to deflect. It’s much easier with another person there, so they can watch the mast from a distance and call out the moment it starts to bend.

2) Steve Lee’s advice is to tie the tack ring to forestay to keep jib forward.

Hope this helps.
Pat
Schoodic - F36
Beverly MA

SunnyIsleMark
Posts: 60
Joined: Sun Oct 17, 2021 8:42 am

Re: Jib without the camberspar

Post by SunnyIsleMark »

It is hard to get used to, but there is supposed to be some forestay deflection when things are set up properly. It is quite a clever design and adds fullness when sheeted out, ands also acts as a whisker pole in light air. I think you ma be disappointed if you get rid of it, other than perhaps upwind.
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Bill
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Joined: Wed Aug 05, 2020 6:57 pm

Re: Jib without the camberspar

Post by Bill »

Thank you all for your posts very helpful
I'm sticking with the spar replacing the damaged forestay , adjusting it as explained
and checking the pulpit .Also adding a Nylon rubbing strip to the pulpit cross brace to ensure no rubbing of the stay if it slackens when the mast isn't bent
Anyone needs a drawing or photograph of the spar I will take them
Bill

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mike cunningham
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Joined: Sat Dec 20, 2008 11:21 am
Location: Jacqueline, F30 #3, Discovery Bay, California

Re: Jib without the camberspar

Post by mike cunningham »

Bill, One thing you could do for me if you happen to have the spar off the boat.

As mentioned, I have bent my camberspar...several times...I would really like to get a sense for the original "chord" of the spar and its shape.

I have contacted Paul Dennis at Warren Isle BW and he indicates he built one (for an F30) a while back with a max chord to camber distance of 11 inches. But it would be really useful to have that confirmed with measurements of an original article. Would be useful for the board records too. One can extrapolate dimensions from the drawings in the camberspar documents on FYI but I have not found reference to the precise chord length or camber shape.

What I have done is laid the spar on my messy garage floor. I then used a sharpie to copy the spar shape on the floor.

I then took a straight edge and connected the ends of the arc (minus any fittings, just the spar). Looks like a strung bow with chord line running tip to tip.

Then I measured the MAXIMUM distance between the chord line and the spar camber + the distance from this point to the forestay sheave.. I also took a measurement from spar to chord line every 24 inches along the spar. My spar is approx 8.5 feet long so I wound up with five measurements. The longest distance (max camber) and the four additional measurements which help ID the overall camber shape.

I realize this sounds like a lot of work but it is actually pretty simple if the spar is free and clear of the rig and sail.

As an aside, I had spent some time looking at wing shapes when I was contemplating building my own emergency rudder. I finally decided to have an experienced builder fabricate the rudder but I did discover there are a large number of standard wing profiles with specific, scalable, dimensions. I have often wondered if the camberspar shape reflects one of these models. If so, I wish I knew which profile it was.

And if this process looks wrong to anyone, I am all ears. My objective is to understand what the original camberspar shape was and to get my bent spar as close to that original shape as possible.
Mike Cunningham
Freedom 30 (Mull) Hull #3
Build date...June, 1986 . Freedom Yachts USA, sloop, shoal keel
Gun Mount and pole retrofitted (purchased from a Hoyt Freedom 32)
Yanmar 2gm20F , 1600 hrs fixed two blade prop
e-rud and ocean racing equipment

SunnyIsleMark
Posts: 60
Joined: Sun Oct 17, 2021 8:42 am

Re: Jib without the camberspar

Post by SunnyIsleMark »

Mike- I think the drawing I posted above has pretty much what you are looking for. The camber pocket would have to match the spar, and the drawing is scalable to different size sails. It looks like max depth is 13% of the length from clew to front of spar, and the space is defined by a couple of other points as well. This could also be confirmed by your sailmaker, as the pocket would have to match the spar to work properly.
Mark

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newt2u
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Location: UK

Re: Jib without the camberspar

Post by newt2u »

Mike,

the camber profile of the spar is probably related to a NACA aerofoil profile. The simplest are the 4 digit profiles, e.g. NACAxxxx. The symetric profiles have 00 in the first two digits, the next 2 give the thickness as a percentage. I have used NACA0010 as a rudder profile to good effect. It might be useful therefore to check out NACA00xx data against your measurements.

This is a useful site to view and generate data for various profiles. The link is for NACA 4 digit but there are other profiles there you can check.
http://airfoiltools.com/airfoil/naca4digit
Because you are dealing with a sail and not a complete profile I suspect the spar data is a truncated aerofoil, i.e. you will have to add a fixed amount to each of your chord-to-camber measurements, to allow for the rounded leading edge. I hope you understand what I mean

Anyway, have fun with the site,

Chris
Rockin - F21 twin drop keels - located Whitehaven, Cumbria, UK

Stephen_H
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Joined: Fri Apr 13, 2018 6:35 pm
Location: Port Washington, NY

Re: Jib without the camberspar

Post by Stephen_H »

I measured the curve from my camberspar when it was off the F30 I previously owned, and had the attached made by a machinist shop. I had it made from Sch 80 aluminum pipe with the theory to increase strength, but that was a mistake because it ended up too heavy. I would stick with Sch 40 if I did it again.
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1985 F39 Express (Hull #44)
S/Y OXYGEN
Port Washington, NY

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