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New Keel For a Ross 930


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redlinekeel 011Small.jpgWell IVe taken the plunge and took a grinder to my keel last week, its now lying on the floor next to the boat.

 

Have to say Im impressed with how this thing was attached, taking off keel-bolt nuts does nothing. As Studs are epoxied into the keel, as well as the boat itself, then heaps of glass over the top of the lot, made for a good watertight fit. Just impossible to take apart, unless you use a big grinder and a sabre saw to cut thru the whole thing, which was the onyl way I colud get it off.

 

Will be melting down the old one after getting the rest of the bog from it, into a new torpedo. Same keel as used on Pepe, Animal Farm etc.

 

First q I have relates to fore/aft positioning of new keel. The current advice is that new foil leading edge needs to be at approx the 1/2 height position of the leading edge of the old sloped keel foil. But if I transpose that onto the boat my mock up of the new keel top plate bolting pattern would mostly hit the existing floor frames.

So id like to slide the attachment point back 60-90mm aft, so the boltng pattern would fit, and I wouldnt then have to cur and replace too many existing frames. But im not certian what effect that might have on the trim of the boat. eg exaclty how much will lthis trim the stern by. It cant be worse that 3 guys in the cockpit?

smallKeelTemplate.jpg

The boats stats are LOA 9.3M LWL 8.1M Beam 2.81 Old Draft =1.92M Displacement = 2200kGs

 

) Im replacing the solid lead fin & small bulb (120kg) total weight around 950kgs max draft 1.92M

 

2) with a new Foil and 760kg Torpedo Bulb. Total Weight around 870kgs, max draft 2.4M.

 

Any thoughts on this?

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Sounds like it's all on Stu, nice work.

 

Don't suppose if you get a quick minute you can roughly sketch where the lead was sitting in your keel. I'm getting conflicting reports on where it's positioned. Some say it goes nearly to the top and most of the std keel shape is only bog. Some say the bottom 1/2 is all lead with something filling in the top bit.

 

Very interested to see what you said about getting it off. That sure isn't the case many seem to think is with them.

 

Positioning wise, don't ask me. Try having a chat to Murray ex-Animal Farm, he did some work on that when he tweaked her up.

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Hi KM

 

You cant see from the photo, but basically the whole thing is made of lead, prob the top 6 inches is solid iroko shaped to fit the hull. Then mine has about a solid 10mm or so of bog, and a total wrap of glass. I'll try to post a photo when all of it is gorund off. Theres no steel can on this keel.

 

Positioning wise Ive already got Murrays advice on where he fitted it. But when I work it out on my boat, it clashes with the existing floor frames. So Im going to shift the whole thing about 60mm, and hope it doesnt cause the boat to sail on its arse so all the crew have to be on the foredeck!! Just though some mathematical genius would be able to say its the same as adding a 50lb load 4 inches back from the mast, or that it will alter trim by 0.0025 degrees!!

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Hi KM

 

You cant see from the photo, but basically the whole thing is made of lead, prob the top 6 inches is solid iroko shaped to fit the hull. Then mine has about a solid 10mm or so of bog, and a total wrap of glass. I'll try to post a photo when all of it is gorund off. Theres no steel can on this keel.

 

Positioning wise Ive already got Murrays advice on where he fitted it. But when I work it out on my boat, it clashes with the existing floor frames. So Im going to shift the whole thing about 60mm, and hope it doesnt cause the boat to sail on its arse so all the crew have to be on the foredeck!! Just though some mathematical genius would be able to say its the same as adding a 50lb load 4 inches back from the mast, or that it will alter trim by 0.0025 degrees!!

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Could you not change the top plate hole spacings? So that the fin can stay in the same place but the bolt holes are 60mm moved either side of the keel floors?

If you are moving the fin aft then you could always keep the bulb further forward so it stays where it is meant to be too?

 

Although watching the other 930's sail upwind in the simrad with the helms around their necks as they try reach upwind we did come to the conclusion the keel fins could be a touch more aft to keep the balance a little nicer on the stern hung rudders!

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Having hung the old keel from a Hiab, and worked out its C of G, I have a more accurate idea of where the new keel plate will fit longitudanlly on the hull. So the keel bolt pattern will lay out ont the existing keel floors without having to demolish them all. Ive attached a mock up of what Im planning on doing to the keel floor frames to support the extra load. Am also beefing up chain plates to cope with the extra loads by doubling up the existing ones with ply and glass and extending them thru the shelves further down the hull. See cardboard template passing thru shelf to use full extent of already glassed in stringer.

CPlateKnees.jpg

keelflrs.jpg

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Big weekend, got lots of glassing done on the new keel floors, no pics of glasswork but will stick one in when its finally done, but u can see the pic of the new floor framing I'm putting in. Also the new 780KG Bulb came together with the new strut last Fri. So the project is moving along nicely. Have seen the odd photo of other 930's with new Keels and they dont seem to have done much in the way of frames to take the loads over and above the original frames. I think with 2.4 draft, and that size torpedo, you'll rip the bottom out of the boat eventually if you didnt do too much. So have prob gone overboard, but better to make it too strong rather than have it fail the fisrt time you hit the putty.

 

Also beefed up the Chain plates, and doubled the length of hull attachment, and replaced all the stainless hardware.

 

Still lots to do, but hope to be back sailing in time for Spring Racing.

frames.jpg

keel.jpg

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ok after nearly 3 months of solid work the baot hit the water last Tue with a shiny new keel & foil. Wouldnt do this agin though as it took twice as long and twice as much money as i thought it would. Std boat project I guess.

 

Had the boat planning at 18kts last weekend and beating into 25-30 kts with full main and blade. So its transformed it into a beast!!

20121023_115532.jpg

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Glad you have been rewarded for all your efforts. :thumbup: And if it's any consolation, it looks like a job that took twice as much.

 

Very enjoyable thread, I will miss it, what/who's next?

 

Think Royale is overdue for a confession, seems to be lots of new items being quietly investigated...

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Bit late now... but I've only just seen the thread.

Anyway the thoughts on the affect on trim by moving the fin aft 60mm I think were missing a key consideration.

The function of the fin (other than a means of attaching the bulb) is to provide lateral resistance (and even better lift) to stop the boat going sideways. It's position is important to ensure a balanced boat. My thoughts would be to position it in the best possible place in this regard and then adjust the trim by shifting the bulb either fore or aft on the bottom of the fin.

Anyway, hopefully it's all worked out well.

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The can Mike did for my 930 was an adapted take on one he does for 1050's from a structural point of view. I just then chose a conservative NACA profile which was faired and glassed on to the outside (inside it's basically a diamond sort of shape). The bulb was cast. The can is the same whetted surface as the original 930 design. It was situated in the same place from a CLR point of view as the one it replaced. I think the bulb was just attached at it's point of balance.

 

I've got some sketches if you want to PM me.

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