Keel and skeg OK?

[treeclimber@xtr]

I bought this hull a little while back and I'm gearing up to start building her next year. I was hopeing to get some feed back on the keel and skeg design as this hull has quite an interesting history of being passed on through several owners.... two actually I'm the third time lucky. Anyway please note how the keel extends towards the skeg and leads into it so to speak. Looking at other boats I've noticed they seem to cut back away from the skeg (or spade rudder) much like a surfboard fin. I note there is plenty of room for diesel and lead in this keel I'd just like to get a heads up on how she will perform in general. Now is the time for minor alterations if required.
Comments?

not sure what you want us to say here
last time we pm,d you were going to contact Mummery?
keel skeg fine, as per those days, this design is old , if indeed it is the earlier vs of the one in my gallery
and anyways you are set in concrete now without major and waste time surgeory
design a rudder for you , if you want, no charge, and that includes the gland and brg detail

[PAR]

Assuming the appendages have some reasonable sections and considering the relatively shoal nature, those will work as well as most anything on a moderately burdened hull like that.

[schakel]

Hi,

Looks like a conventional Sparkman & Stephens underwatership. Which is al right! They turn fast enough and you have plenty room for the prop to be placed before the rudder which gives a lot of manouvrability when docking.
Very nice... You already bought it; one very important question: are the keel and skeg aligned with the rest of the hull?

If not: It is nice boat to circle around with. (that is not very funny) But I am sure you bought it allright.

[daiquiri]

I would call it an old design, en-vogue in the 70's. It has pros and cons, but overall you can't expect a great performance with this one.

The leeway angle during the navigation will be high because this keel's aspect-ratio is low.
The drag will also be relatively high for the same reason.
Same for the yaht heel angle, because even if you fill it up with lead it will still have a small lever arm and thus will create a smaller rightening moment.

On the pro side, you will have a cruiser which will be able to access shallow waters and you will also need to be less worried if you hit something underwater. The eventual impact loads will, just like the ballast weight, have a smaller lever arm and will interact with the hull through a bigger surface, thus causing less strain in the structure.

At the end, it's all matter of compromise. This yacht is not a racer, so it has a keel which is in line with requisites for cruising boats.

Ted Brewer has written a short but informative article on various types of keels and their pros and cons - you can read it here:
http://www.boatus.com/goodoldboat/keeldesign.asp

[PAR]

Leeward slip will not be excessive with that much lateral area. She may not "hang on" with the big boys, when close hauled, but she shouldn't have a lot of side skid.

Ballast percentage is only one way of increasing righting leverage. Since she's a steel, cruising hull, intended for shoal waters, she'll carry enough beam to "shoulder" along fine, in spite of having a low ballast/displacement ratio then other appendage/building material configurations.

Originally Posted by PAR

Leeward slip will not be excessive with that much lateral area. She may not "hang on" with the big boys, when close hauled, but she shouldn't have a lot of side skid.

Ballast percentage is only one way of increasing righting leverage. Since she's a steel, cruising hull, intended for shoal waters, she'll carry enough beam to "shoulder" along fine, in spite of having a low ballast/displacement ratio then other appendage/building material configurations.

I built two of these , later models same hull without skeg, if the original builder stuck to the keel sections she will sail well
i am abt to call the designer, to see if it is actually his

[treeclimber@xtr]

Thanks for the reponses I really appreciate it. I'm just trying to get a feel for how this configeration will perform. I don't want to race but I do want to cross oceans. In response to the allignment question yes it is alligned with the rest of the hull. Lazy jack, whether or not the builder stuck to the keel sections I don't know.
I did call Alan Mummery. To be honest he wasn't much help. He identified the hull as one of his and well built at that, but when I alluded to purchaseing plans and more to the point that I don't have any at the moment then he polished the idea of redesigning the keel and skeg ie, fin keel and
spade rudder. As to the performance of the current configeration he would not give out to much information. none actually.

Originally Posted by treeclimber@xtr

Thanks for the reponses I really appreciate it. I'm just trying to get a feel for how this configeration will perform. I don't want to race but I do want to cross oceans. In response to the allignment question yes it is alligned with the rest of the hull. Lazy jack, whether or not the builder stuck to the keel sections I don't know.
I did call Alan Mummery. To be honest he wasn't much help. He identified the hull as one of his and well built at that, but when I alluded to purchaseing plans and more to the point that I don't have any at the moment then he polished the idea of redesigning the keel and skeg ie, fin keel and
spade rudder. As to the performance of the current configeration he would not give out to much information. none actually.

guess he has his reasons, leave it as is, cos there is a sort of bustle leading up to the skeg, he is dead against skegs last 15 years, as am I

[Brent Swain]

Looks great . I design boats with a similar underwater shape , no problems. They all make great passage times, upwind and down.That skeg will shed lines that would foul so called "Modern " rudders.It will also give the rudder far more strength than any spade rudder would ever be capable of.
Brent

[treeclimber@xtr]

Thanks Daiquiri for the interesting read on keel design It seems for my purposes I'm onto a winner.

Sorry, Lazyjack, What is a "bustle leading up to the skeg? " and could you tell me why you are against skegs in general.

[rwatson]

Treeclimber - check out

comment on rudder

for a recent full discussion on skegs. Very informative

[Brent Swain]

I like to put a piece of 1/2 inch plate between the skeg and the back of the keel , about 4 inches deep in the middle and turing into gussets onto the keel and skeg at each end. Ths carries the weight of the keel right to the transom and stops the crossover flow between the keel and skeg , reducing the tendency to broach.
Brent

[treeclimber@xtr]

I'm not sure if you can see this in the photo but there is a peice of half inch plate running between the keel and the skeg. Is this what you mean?

[treeclimber@xtr]

You can see how the top of the keel feeds into the skeg. This material between the keel and skeg is halfinch in thickness at the leading edge and is formed with the hull