The new keel for the old boat

Hi Martin, sorry I missed this post.

Yes, there are big differences between Spencer's keels and Uffa's "Flying Series" keels as well as one or two broad similarities. I guess I chuck them together as very few other boats of the era seemed to have a longer chord at the base than at the tip. I think they are both excessively fine in section at the front end and have issues when modified to NACA-style sections because the chord variation along the span.

I seem to recall that John made a reference to the FF keel and his being similar but different but I may be wrong in that. They were both, however, quite different to the S&S/Illingworth/Payne etc keels of their day and (IMHO) also different to the keels on boats like the Van De Stadt Black Soo and Diamond, which had a much more prominent and less 'streamlined' bulb from some angles.

Re FF helm; I think that the weather helm was largely alleviated in about 1969 when Bill Shand raked the rudder post, which effectively increased the balance by moving the "hinge point" aft. A '72 FF in WA may not have had this alteration; I think many of them were by a different builder. I owned one of the early raked-rudder Shands and while still fairly heavy it wasn't too bad.

My FF experience was one reason I've got a big (second hand) rudder on my Spencer; the Serendipity is a bit shallow so I wanted to develop a lot of lift from the rudder like the FFs do.

Cheers

 

Hi CT249,
Interested to hear something was (eventually) done about the tiller loads on the ff; mind you I always thought the keel needed a small relocation as well. But Bill Shand had quite a history/reputation in the ff15s if memory serves correctly so he would be better qualified than me on a ff re-design.

Re the Diamond and Black Soo keels, yes they were just crude(?) flat plates with large slabs of lead bolted on. I recall being told that the ply (about 32mm ?) for the Diamond's keel was specially made with all the plies running in one direction to get the necessary strength/stiffness but still a mighty crude arrangement. However with so much power above (more so after trapeezes were allowed) and such straight planing lines and in a one design class who cares about less than optimum keel shape when you can cream past almost anything.

At RPYC there was an interesting chine 28'er or thereabouts which looked rather like a Black Soo but with a fuller bow section; she has a huge slab of steel about 32mm thick and 2 very rectangular slabe of lead bolted-on and on the rare occasions she sailed she did not do well at all. In fact I tried to buy her (before buying the Scimitar) without success. The owners took the "gas axe" to the steel slab and carved a chunk out of the leading edge and a huge scallop out of the aft edge until it looked like the Scimitar keel in side view before my keel mods which would have been standing on the hard nearby the not-quite-Soo. The discarded pieces of steel lay against the fence at RPYC for a long time and I was never tempted to try to move/lift them; they must have removed 300kg of steel!
The leading and aft edges of the revised keel were left plain square edged blunt. No real performance improvement but she was a lovely little yacht and very well built but do not know the designer. And it was 40 years ago.

Have you launched into any keel mods for your Spencer yet?

 

DEAR SIRS thank you for your message.
1.You mentioned yacht keels - Van De Stadt Black Soo and Diamond, there is Diamond? Where can I find a drawing?
2.If on the keels Uffa Fox on flying and 15-25 on the keel Australia apply a profile NACA fashionable today is whether it will make effective?
3. What effect does a sweep of the fins? As for the keels of this form to find the center of lateral resistance? Center application of lift?
Thank you.

 

What better NACA 0012 or 836 Epler?

 

It depends on what you want from the foil section. What speed are you expecting, drag bucket targets, Reynolds number range?

 

6.3 Max Node speed. 90 degrees between tacks to windward.

 

The 00 series seems the best for your application as you're not going fast enough with other sectional shapes, to take advantage of their benefits.

 

What are the with other sectional shapes, to take advantage of their benefits.
My Yacht waterline length 7.2m or 23.6 ft
What section will reach the speed of 7-7.5-8 nodes. Is that possible?

 

I have a half-tone yacht. It has 23.6 ft. LWL, 7.2 ft. WWL and displacement of 6620 pounds.
The keel has a trapezoidal shape. I would like to reduce drag. Which profile is better for this,
NACA 0012 or Eppler 836?

 

Alexander, you're getting into an area of understanding that can become quite complex and also one that will technically offer some improvement, but these improvements may only be measured in fractions of a knot. Considering the weight and LWL of your boat, you will have fairly limited results with a significant plan form and section change to your appendage.

The NACA or Eppler sections you've listed have absolutely nothing to do with the "profile" (plan form). These are sectional shapes and can be used on any appropriate plan form.

Simply put, if your boat is sailing in the4 - 7 knot range that most do, very little difference will be noticed between a rounded leading edge, with a tapered trailing edge and a NACA or other type of section. So, unless racing against identically shaped and equipped boats, any changes you make will be nearly meaningless.

 

How it changes the yacht behavior on downwind and windward courses if I reshape the leading edge of the keel to ogive. http://en.wikipedia.org/wiki/Ogive

 

So you want to employ a leading edge section intended for use on ballistic speed objects? Why use such a disparaging speed differential shape? If you use this shape, the foil section will stall at low angles of incidence. A much better choice would be is the elliptical ogive leading edge, though sticking with thew previous recommendations would be a wiser choice for your appendages, in comparison to using the nose shaped employed on rockets, bombs and missiles. It's really easy to over think this thing and end up with a foil that doesn't do anything you'd like.

 

My friend has an old Soling. No sails. Where in the U.S. can buy used sails? Mainsail, genoa, spinnaker.