Shaft Tube Discussion

[El Mar]

some of us dont have shaft tubes

Time for a retrofit if you ask me

Welcome to the 21st Century

Here is a topic that I have seen thrown around many different boards, but never really discussed in detatil. I know Capt. Larry has some good info and pics about the retrofit on his 31 JC and have seen Ken Flowers artfully install them on his builds here, and I'm sure First Team as well as others know plenty about them.

With all the info here, fill a novice like me in about the finer points of shaft tubes, pros and cons, installs, etc.

 

[jerseysportfisher]

Here is a topic that I have seen thrown around many different boards, but never really discussed in detatil. I know Capt. Larry has some good info and pics about the retrofit on his 31 JC and have seen Ken Flowers artfully install them on his builds here, and I'm sure First Team as well as others know plenty about them.

With all the info here, fill a novice like me in about the finer points of shaft tubes, pros and cons, installs, etc.

according to conventional wisdom, and i would presum experimentation. The rotation of a shaft creates more frictional drag, it has been said that adding a shaft tube even though its larger in diameter, helps alleviate the extra drag caused by the shaft rotation. Thus picking up speed

 

[tunaorlater]

In a downeast no part of the tube is in the water it's all in the keel so I don't understand how it would reduce drag?

No need for a keel full of water and a big chunk of brass inside and out of hull. Thus reducing weight by a lot. Also you can taper the keel back for better water flow to prop.

 

[jerseysportfisher]

In a downeast no part of the tube is in the water it's all in the keel so I don't understand how it would reduce drag?

I dont have a DE i have exposed shafts, but your right in a keel boat, i don't know what the benefits would be ?

 

[Helen L]

All I know is mine has a pin hole leak. It's exposed and easy to get to. I was planning on sealing it by glassing over the tube using epoxy when I haul out in a few months. Previous owner tried 5200 before I picked it up but it was in the water and didn't seal it up.

Anyone that's attempted something along these lines before please chime in.

 

[F/V First Team]

Currently in the process of tearing out the old stuffing box method with a wet keel and replacing with a shaft tube, I'll try to take as many photos as I can.

 

[petrel]

Since you brought that up, my 31 BHM, interestingly enough documented as an Otis boat from 1980, has a wet keel. I'm curious to know how many other models of downeasters have wet keels by design.

 

[Blitzen]

I wonder more about cost and speed of building a downeast boat that influenced whether or not the boat got a shaft tube. Let’s face it, it requires a lot less work and money to go without. I am sure boat design and purpose of use may benefit from having all that water in the keel in some cases.
My Repco had a wet keel and I can't imagine all the old marine life that ended up inside over the years and it was a bit too snappy for me on the drift.

 

[BillD]

I wonder more about cost and speed of building a downeast boat that influenced whether or not the boat got a shaft tube. Let’s face it, it requires a lot less work and money to go without. I am sure boat design and purpose of use may benefit from having all that water in the keel in some cases.
My Repco had a wet keel and I can't imagine all the old marine life that ended up inside over the years and it was a bit too snappy for me on the drift.

Help me out here.

Does a shaft tube require a separate cooling water source (engine) same as a dripless shaft seal?

Or does the shaft tube "fill with water" through the cutless bearing?

Curious?

 

[Helen L]

Mines just filled with seawater through the cutlass. I think that's how they all are.

Maybe First Team can help me out. Small pinhole leak in the tube. Easy enough to get to, it's above the normal water level in the keel. Fiberglass over the tube out of the water with epoxy? Maybe 5200 smeared all over?

 

[Blitzen]

Help me out here.

Does a shaft tube require a separate cooling water source (engine) same as a dripless shaft seal?

Or does the shaft tube "fill with water" through the cutless bearing?

Curious?

Bill,

If there is a bearing on the engine side of the shaft tube it will require a water feed to make sure it is kept cool and wet. There are some installs where the tranny is too close to the stuffing box and will prevent the use of a bearing at the upper end of the tube, in this case no water feed is necessary.

 

[BillD]

Bill,

If there is a bearing on the engine side of the shaft tube it will require a water feed to make sure it is kept cool and wet. There are some installs where the tranny is too close to the stuffing box and will prevent the use of a bearing at the upper end of the tube, in this case no water feed is necessary.

John,

If I understand your 36's shaft install correctly it has a "traditional" flax pack bearing/tube/cutless. Correct?

The bearing aft of the tranny??? Is it water fed from the engine??

Thanks,

Bill

 

[Blitzen]

John,

If I understand your 36's shaft install correctly it has a "traditional" flax pack bearing/tube/cutless. Correct?

The bearing aft of the tranny??? Is it water fed from the engine??

Thanks,

Bill

Correct with water feed from the engine and I took out the traditional flax and changed it out with DuraMax.

There is a cutless bearing inside the upper end of the tube before the stuffing box.

 

[F/V First Team]

Since you brought that up, my 31 BHM, interestingly enough documented as an Otis boat from 1980, has a wet keel. I'm curious to know how many other models of downeasters have wet keels by design.

which boat? what is the documentation #?

 

[petrel]

Was called Shadow for many years, I don't know if that was the first name. Official number is 630047. I think at least four other people have owned her previously down here in NC.

 

[F/V First Team]

Was called Shadow for many years, I don't know if that was the first name. Official number is 630047. I think at least four other people have owned her previously down here in NC.

I think that was her original name
any current photos of her?

 

[petrel]

My first post here had a photo:

Lets see em - Page 8 - Downeast Boat Forum

The previous owners didn't give her much love, so we took out all the old wet balsa core (cabin top and washboards) replaced it w/ Nidacore and in the process, we extended the cabin.

Still got the wet keel- no tube.

 

[F/V First Team]

I always thought Shadow's hull was grey, has she had a facelift?

 

[petrel]

She hasn't been gray for a long time. And she's had a major facelift after many years of neglect to the topsides.

 

[captainlarry84]

Wet Tubes

In a downeast no part of the tube is in the water it's all in the keel so I don't understand how it would reduce drag?

No need for a keel full of water and a big chunk of brass inside and out of hull. Thus reducing weight by a lot. Also you can taper the keel back for better water flow to prop.

Tunalater is correct on his assessment I agree on all he states. The shaft tube should be fed by water off the engine. In doing so it not only lubes the cutlass bearing but is also feeds the stuffing box. On my install I also added two feed hole in the keel just in front of the cutlass bear. This way should the feed clog at least the cutlass bearing is getting some water fromn the additional feed holes. You can see the feed holes in the photo attached.
In a wet keeled boat in addition to carrying a keel full of water the shaft is always spinning with full water contact. Unlike the wet tube which is just forcing water down the shaft to feed the cutlass bearing.
It is true that wet tubes are only used on keeled New England boats, However I did see a beautiful custom twin screw Carolina boat at Cape May sporting wet tubes all the way back and into the struts. The boat had a cruise speed of 28 knots and the owner swears by them, which agrees with the theory stated by Jersysportfisher. I would image that the custom struts to hold the wet tubes must be very expensive.
As far as the pin hole does I would just chanter the hole and fill it with Hull & Deck Puddy or Marine Tex. Both are like iron.