Easier Keel Case Construction/Cassette?

[Warren Nethercote]

I was looking at a Melges 20 at the sailing club last night and saw that it used an oversized keel box and fillers around the keel itself. I thought I'd seen a note somewhere that the pdx guys do something like this too. Seems a reasonable alternative to the tight cassette insert which requires dimensional control on the keel section that might challenge a builder in a hurry. I am not advocating 'poor' keel dimensional control, but when is better the enemy of good enough?

[Chad]

Most guys build their keels early on, then splash a sleeve from the (nearly) completed keel itself. This can work well, if the keel is padded with a generous amount of plastic sheeting first, and the trailing edge of the keel not made too fine.

My keel happens to look about like the one in your pic, and yes the delrin shims are nice in that they allow some tuning of the fit. Another builder oriented the delrins vertically, with some taper, to fit into corresponding tapered pads inside the trunk- all to allow some give in the event of a brisk grounding.

[admin]

I sorta wish I had done that with mine, Warren. My fit into the sleeve is pretty darn tight and when I life the keel, the angle of the lift point is critical or the whole foil binds on the sleeve. I think this would be less likely to happen with:

1) a bit more slop and
2) just two areas of contact instead of an entire section of the foil (e.g., less surface area making contact)

In fact, the notorious PRoss once emailed me saying I should consider this....did I? DID I???

nope....

[micah202]

....In fact, the notorious PRoss once emailed me saying I should consider this....did I? DID I???

....err, he's not the only one, I've been tooting that horn for 3 years or so.
A big concern for me is what happens to those 'fits-like-glove' keel trunks when a boat hits bottom


https://www.flickr.com/photos/59103003@ ... 034413213/
...in the pic, the delrin blocks bolt to the top of the keel.,pour-foam in plastic bags fills the extra space nicely.

[Big_Dog]

I had a photos of the viper keel box repair part, but I think it is on a dead hard drive. From memory it only held the keel in a few small areas. The trailing edge was in a relief so the back contact was an inch or so forward. The sides were cut out like the Swift Solo ruder cassette.

IMG_20140228_171743.jpg

IMG_20140228_171836.jpg

http://www.rondarboats.com/us/viper-640 ... mprovement

Concept from the Swift Solo dagger board that only contact top and bottom.
http://www.single-handedskiffs.com/imag ... sion_2.pdf

[Dan]

Hi All,

Have completed foil and bulb all to painted level, and am think of the above options.

Will probably use a combination of the above keel box designs as although I like the ease of rectangular keel box I would like the keel to have support in any position (motoring in shallows), so will be making a keel 'sleeve'.

How has everyone installed sleeve into area in boat, and what reinforcements have you done other than ply doubling. Cant seem to find much detail on this and am concerned about loads.

Thanks
Dan

[i550sailor@aol.com]

Hi All,

Have completed foil and bulb all to painted level, and am think of the above options.

Will probably use a combination of the above keel box designs as although I like the ease of rectangular keel box I would like the keel to have support in any position (motoring in shallows), so will be making a keel 'sleeve'.

How has everyone installed sleeve into area in boat, and what reinforcements have you done other than ply doubling. Cant seem to find much detail on this and am concerned about loads.

Thanks
Dan

Mine may be overkill, I built a plywood/fiberglass reinforced outer box, with a sleeve suspended inside the box with expanding foam, the idea was to have a sacrificial crush box,, (we have stumps in the lake I sail in).

[Dan]

Hi i550sailor,

Thanks for photo. I have done similar with doubling and timber reinforcements around box and hull.

From what you say your sleeve is filleted and glassed in at top and bottom, and void filled with foam?

It get pretty rough here in Cape Town and most sails will see 20 kts, so wonder if I will not need a little more?

Anyone else sailing in rough coastal water?

[ryderp]

Because I sometimes sail in a very rocky lake, I grossly overbuilt the center of my boat. The three center bulkheads (89, 110, and 124) are all 1/2", The floor between 110 and 124 is 3/4" thick, as are the walls of keel-box. Lots of longitudinal support is built in and I used a bunch of carbon fiber cloth to reinforce everything. Some of this is described on 381.blogspot.com

I have hit rocks hard a couple of times resulting in a fattened nose on my keel bulb and some damage to the trailing edge of the keel foil. No hint of damage to the boat or keel sleeve however.

Phil