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Old 03-02-2016, 06:16 PM   #1
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Adding a skeg

Any merit to adding a skeg here?
Would replacing the spade require engineering?
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Old 03-02-2016, 06:53 PM   #2
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Not an overly complicated job and something I really like to have to protect my prop. Just don't do it like this guy .....
Somewhere in my files I have close up of the cavitation (caused by proximity of prop & shoe) eating his propeller.

PS what you call a skeg, I call a shoe.
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Old 03-02-2016, 07:10 PM   #3
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Yes a shoe.

But to put a shoe on this boat an extended keel must be built on and a new rudder made to be able to carry a vertical load of a considerable portion of the weight of the boat.
Probably the most dificult part will be to get the stern bearing very firmly attached in exactly the right place and aligned perfectly w the existing propeller shaft. Not a small job at all.
What do you expect to gain from the added keel and shoe?
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Old 03-02-2016, 07:27 PM   #4
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Greetings,
Mr. mb. "...new rudder made to be able to carry a vertical load of a considerable portion of the weight of the boat." I don't think so unless when one chocks the boat, a support is placed under the new skeg/shoe portion or one hits something in which case the OP is probably screwed anyway. Otherwise, the rudder is still just hanging there, albeit with a post going into the end of the new skeg.
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Old 03-02-2016, 07:42 PM   #5
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Thanks bp & mb.
Eric, I like it for the reasons bp said, protection.
Plenty of junk the size of a man's arm around here to spoil a good cruise.

Skeg vs shoe; I'll defer to the two of you although it is odd, I cannot find "shoe" but "skeg" as I used it, is frequently defined as such.
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Old 03-02-2016, 07:48 PM   #6
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So, part two of the question then; if one is going to go to the trouble of adding a shoe and new rudder, would there be any benefit to making the rudder larger?
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Old 03-02-2016, 07:52 PM   #7
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So, part two of the question then; if one is going to go to the trouble of adding a shoe and new rudder, would there be any benefit to making the rudder larger?
Depends on the boat. My boat is a pig to turn in tight quarters and I will be adding fish tails to the rudder at next haulout. Some times a horizontal wing on the rudder helps steering too ..... it depends. You need to consult with someone experienced in this area.
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Old 03-02-2016, 07:57 PM   #8
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RTF,
IT's all about prop protection. Well that would involve contacting the bottom and frequently that results in the boat being stuck .. as in won't move. Could be mud and could be rock. But when the tide goes out the boat w all it's weight will settle on the bottom. And there's a good chance the bottom of the rudder will come to rest on the bottom where there is not a depression. It's not unlikely that 50% of the boat weight will come to rest on the rudder.

My rudder is 3/8ths" thick and solid bronze. The shoe is also but way over 3/8".

Went to the computer to post this picture. That shoe is cast bronze.
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Old 03-02-2016, 08:36 PM   #9
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IIRC, Gerr's book goes into detail about this.
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Old 03-02-2016, 10:03 PM   #10
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I think it would be well worth adding a skeg bar under the propeller. It should be quite easy IF you have access to the inside of the keel to run your bolts up through. You will need a new. full depth rudder. 1-1/4 stock should be plenty and yes make it full height. You want the propeller to clear the bar by 10%D. I made my bar of stainless, drilled the aft end for a piece of cutlass to form the gudgeon. and the forward end for 3 5/8" bolts which go up through the keel. Grind a taper at the front of the bar.
The major question is, based on the length of your bar, is the bottom of your keel strong enough to take the force or do you need to reinforce it and can you reinforce it.
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Old 03-02-2016, 11:35 PM   #11
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One of several "must haves."

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Old 03-02-2016, 11:52 PM   #12
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One of several "must haves."
+1

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Old 03-02-2016, 11:54 PM   #13
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Any merit to adding a skeg here?
Would replacing the spade require engineering?
IMO - Everything takes engineering!

It's said to be fact that somewhere near a billion neutrons fire in the brain with each step taken while running. Now, I call that Engineering!!
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Old 03-03-2016, 12:15 AM   #14
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You and Mark have opposite rotation. What is your power? Be interesting to know how many different single motor, transmission combos and prop rotations there are. Follow me?
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Old 03-03-2016, 01:46 AM   #15
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The Coot has a "left-handed" propeller (goes counter clockwise in forward gear), which means the prop-walk is to starboard. Works great with a starboard helm position. Right-handed prop is just the opposite. The 80-hp JD engine provides plenty of power for the boat's heavy-displacement hull/weight combination while not expecting a speed faster than 7.3 knots.
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Old 03-03-2016, 06:52 AM   #16
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Why not consider a basket to keep junk out of the prop?

Have one made where the commercial fish guys do and bolt it on.

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Old 03-03-2016, 08:54 AM   #17
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Refugio has a Volvo TMD100A (225hp), Twin Disc MG509 (with trolling valve), 3" shaft, and 40x23 RH prop. FWIW my bronze shoe extends all the way forward to above the waterline.

I know it's too much power but what can I say, I'm an acceleration junkie.
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Old 03-03-2016, 09:12 AM   #18
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IMO and experience, a deep keel ahead of the props takes care of 80% of the needed protection. A skeg is very nice, no doubt about it , but the cost to properly retrofit one (as noted in a few posts above) is not insignificant.
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Old 03-03-2016, 09:53 AM   #19
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Two things.

1. Re caltex's post above he may get what he wants just by adding to the keel.

2. Me thinks Hawgwash should just go buy a trawler.
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Old 03-03-2016, 10:52 AM   #20
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2. Me thinks Hawgwash should just go buy a trawler.
If you only saw that underbody picture of the Monk 36, I don't think anyone would think its from a "trawler". That all around lack of protection would concern me in the PNW. I'd still take it cruising if that's what I had, but I would always be a bit on edge and ready with anchor and diving gear. Maybe an outboard on an OMC transom lift? Probably better to retrofit some underbody protection like he's considering.


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