Skeg construction

[first wind]

hi. i am in the middle of refitting a 1971 cal 27 pop top. one thing i do not like about the boat, that i am having difficulties finding out how to change, is the spade rudder. i would feel much better if it was skeg hung.

in theory, that shouldn't be hard to achieve. build another rudder...that part there is a ton of info on the web about...and build and attach the skeg....that part, no matter how hard i look, i can't find out anything about. so, here i am.

i have read that skegs are very hard to do as a part of a one piece mold and that many companies add the skeg afterwards. so, here are my questions:

on a solid hull boat (as compared to a cored boat) how is the skeg built? is it cored, solid, or hollow?

secondly, how s it attached? by this i mean how is it glassed on? i guess to explain, it's like this: if you plug a thru hull you glass on the inside and outside. the hull around the hull has to be tapered back inside and outside 12X the thickness of the hull. so, if your hull was half an inch thick, each side would have to be tapered back 3". that's the proper way to glass a through hull shut. so, with that in mind how do they glass the skeg onto the finished hull?

any information would be a big help. it really shouldn't be that terrible a job but, finding out any information on how to do it is neigh on impossible.

thanks

[barnakiel]

I have seen skegs both molded and added on. The added on were added in the production process, not post production (grp boats).

The ones I have seen were some solid some filled with foam. The full long ones were (foam ?) filled. Half skegs on some quality scandinavian designs were solid grp. Heavy but strong.

I would not add a skeg to any design that has a spade rudder. This changes the hydro of the hull and can create more trouble than benefit.

Buy a new rudder, replace the bearings and (optionally) strengthen the bearing/tube area.

A well designed and build spade is as strong as anything else.

b.

[GordMay]

Here's one example ➥ WEST SYSTEM | Skeg Construction For Sparks

[neilpride]

Most skegs i see in my life are Split in half in the intial hull construction , that mean 2 halfs joined together and FG tabed inside, later filled with a mush of resin and FG the top, filled with foam and in some cheaps boats with crap,, and agree with Barnakiel if is a spade rudder keep it like that ... there is a bunch of ways to improve a existing spade rudder....Cheers.

[noelex 77]

Bob Perry once suggested many skegs are held on by the rudder, not the other way around .

I think you are going to find it hard to easily retrofit something strong. If the skeg is deformed it will likely jam the rudder so you will need to be careful that you will not put in a lot of work and end up with something worse, especially when the other drawbacks of a skeg rudder are considered.

[GordMay]

Originally Posted by noelex 77

Bob Perry once suggested many skegs are held on by the rudder, not the other way around ...

Indeed.
“... For me, a spade rudder should be engineered to be just as strong as a skeg-hung rudder. A good knock at the heel fitting of a skeg-hung rudder can easily jam the stock up into the hull, causing damage. The common geometry of most skegs make them very difficult to laminate and I am very confident that there are a lot of skegs out there being held on by the rudders ...”
From A Bob Perry Design Review ➥ Perry Design Review: Morris 32 - boats.com

[goat]

Originally Posted by first wind

hi. i am in the middle of refitting a 1971 cal 27 pop top. one thing i do not like about the boat, that i am having difficulties finding out how to change, is the spade rudder. i would feel much better if it was skeg hung.

in theory, that shouldn't be hard to achieve. build another rudder...that part there is a ton of info on the web about...and build and attach the skeg....that part, no matter how hard i look, i can't find out anything about. so, here i am.

i have read that skegs are very hard to do as a part of a one piece mold and that many companies add the skeg afterwards. so, here are my questions:

on a solid hull boat (as compared to a cored boat) how is the skeg built? is it cored, solid, or hollow?

secondly, how s it attached? by this i mean how is it glassed on? i guess to explain, it's like this: if you plug a thru hull you glass on the inside and outside. the hull around the hull has to be tapered back inside and outside 12X the thickness of the hull. so, if your hull was half an inch thick, each side would have to be tapered back 3". that's the proper way to glass a through hull shut. so, with that in mind how do they glass the skeg onto the finished hull?

any information would be a big help. it really shouldn't be that terrible a job but, finding out any information on how to do it is neigh on impossible.

thanks

In the last 47 years of your boat's life, how often was the spade rudder lost? If the answer is zero, I'd look for other things to worry about.

goat

[a64pilot]

Would it not be very likely that you would lose quite a lot of maneuverability?
And as how spade rudders are usually balanced as in they have a lot of surface area ahead of the pivot point, are you not likely to end up with a very hard steering boat?

Likely best to sell this boat and buy one that has a skeg rudder?

[Suijin]

You're going to have to redesign the whole rudder on that boat to hang it with a skeg. Not only is it currently swept, but the pivot is not vertical. It's going to change how the boat handles, and you'll be adding a bit of weight that the boat was not designed for.

If you're cruising in the Chesapeake I don't understand why you'd be so set on a skeg hung rudder anyway. The keel on that boat is considerably deeper than the rudder, and the Bay is not exactly filled with rocks.

It's one thing if you're headed way offshore, then there would be an argument to be made about it's benefits (and it would be an argument, as there are lots who believe otherwise, with valid reasons). But you're not. I doubt you'll ever be out of VHF/SeaTow range in that boat so why go spending hundreds of dollars and hours adding something you'll probably never need and which will alter the boat's already fine sailing characteristics?

[Stumble]

So I wrote out a long post on how to get started, but really the only way Tom convert from a spade to a skeg and do it right is to cut off everything you have and go to a designer and have them design you something. Then build and install whatever they suggest. It's a massive addition involving removing a lot of glass from the hull to bond the new skeg to, likely installing a new skeg sump and bolts in the boat, a completely new rudder, and a lot of engineering that is beyond my ability.

All of this will gain you absolutly nothing btw. The boat will be slower, no more safe, and the rudder just as prone to damage as before, it just changes the failure method. If you really have doubts about the rudder strength then ask a NA to design a stronger rudder for you and shop it out to Phils Foils. For a couple of grand you can drop in a newlyweds designed rudder that is X amount stronger than what you have. X being whatever number makes you feel good. Because if a rudder has lived for 45+ years it was probably engineered right the first time.

[noelex 77]

Originally Posted by GordMay

I am very confident that there are a lot of skegs out there being held on by the rudders

Thanks for finding the exact quote Gord .

[Paul L]

Lots of work for less than no gain.

[first wind]

in response, in another interview, Bob Perry states he thinks the best compromise is a rudder with a short skeg as this allows a bit of rudder before the pivot point and keeps the bearing away from the very bottom of the rudder where it is likely to get struck.

everyone who likes spade rudders swears they are as safe as skeg hung rudders. it's kind of like everyone that loves fin keels swears they are just as seaworthy as full keel boats ( a point that C.A. Marchaj's book on seaworthiness totally debunks).

spade rudders do break off and they do fall off. they are supposed to be designed to break off before they crowbar a huge hole in the hull. make one strong enough not to break off and you eradicate the designed in failure point. it would be like running electricity without a breaker or a fuse.

yes, if i never leave the bay i will be within a call away if it does break off and then i can figure out how to pay for the tow-in. as far as the bay having a soft bottom, spade rudders are vulnerable to other things besides groundings. logs and other unseen obstructions can damage them, too.

i realize i would have to make a completely different rudder. i believe i included that in my original post.

boats have been sailing for a long time without spade rudders. skeg hung rudders and even full keel vessels have maneuverability to sail. the biggest loss in maneuverability is backing under power, maneuvering around the marina, or racing around the buoys. i intend to cruise not race. i chose my slip at the marina just for it's ease of setting off and returning. i won't have to be maneuvering around a tight marina all the time. if you talk to cruisers with skeg hung rudders, you don't here a lot of depressed sailors trapped with a boat that just won't steer.

i don't see the skeg as being a useless thing that won't add rudder protection. there are enough people out there whose skegs took a grounding and protected the rudder for me to believe they do work. just like there are more than enough spade rudder failures for me to believe they are not as safe/strong as a skeg hung rudder. just because some people make it over Niagara Falls in a barrel and live, that doesn't mean that's a safe mode of transportation over the falls. plenty of other people in barrels didn't make it.

finally, thanks for posting the link to that article. i have actually seen that. the problem is that it doesn't go into detail about attaching the skeg and i doubt that skeg is under the same stresses as one on a sailboat. but, i do appreciate you trying to answer the question i asked.

[first wind]

Originally Posted by Stumble

Because if a rudder has lived for 45+ years it was probably engineered right the first time.

i am not doubting that Lapworth designed the rudder well, for it's intended purpose. however one point about the above statement:

the brass gate valves the boat was built with, instead of bronze seacocks, have held up for 45+ years. perhaps brass gate valves are just as good for the purpose as bronze seacocks. not trying to be a butthole. just pointing out the flaw in that logic.

(and, no, i'm not leaving the gate valves in place. i'm actually glassing over all of the thru hulls as the only one i might have used would be the one for the galley sink but, there are better ways to handle the sink than to have a hole in the bottom of your boat. my relationship with murphy being what it is, i try to leave less to go wrong, if i can.)

[Stumble]

In that case you need to hire a NA to design a new rudder and skeg. Figure you will need to remove 2 or 3 layers of glass within a foot or so of the new rudder post in order to bond the new skeg on, and likely reinforce the inside of the hull where the new skeg will be located.

The upside is you can likely go to a much thinner rudder post since the skeg will be carrying part of the load so you won't need the post to be as stiff.