Cracks in stern tube to hull transition General Forum Forums

avatar

Please consider registering
guest

sp_LogInOut Log In sp_Registration Register

Register | Lost password?
Advanced Search

— Forum Scope —






— Match —





— Forum Options —





Minimum search word length is 3 characters - maximum search word length is 84 characters

sp_Feed Topic RSS sp_TopicIcon
Cracks in stern tube to hull transition
avatar
mgav451
Member
Members
February 2, 2018 - 7:41 pm
Member Since: September 27, 2017
Forum Posts: 143
sp_UserOfflineSmall Offline

laughing to myself as I post yet AGAIN. thanks for all the advice thus far I’m really getting along in my refit lots and lots of work and long days as I cross things off the list.

  Took the antifouling paint off the boat and noticed some cracks in the area wher it’s faired transitioning into the stern tube( I think it’s called stern tube).the cracks aren’t in the laminate just the bit that’s fared. I chased them out with the Dremel and put a little bevel in them and drilled a hole at the end. Has any one seen what the end of these boats look like under the fairing? Is this something that’s cookie cutter or each boat is different? I was planning on filling the cracks with thickens epoxy with high density filler ( west system) and laying some biaxail cloth over the whole bit. Here’s some pics of the cracks after I chased the cracks and drilled the ends. Any advice here? I’m wondering if I should grind out all the  red fairing and refair it with high density filler and glass over that?  Do you think this is factory or a p.o. fix? I have a yanmar 3gm30f think it’s a 1991 so I assume it’s been repowered and maybe the shaft log was installed then. I’m wondering if the red fairing compound was the wrong choice of material for this?

Print Friendly
avatar
mgav451
Member
Members
February 2, 2018 - 7:43 pm
Member Since: September 27, 2017
Forum Posts: 143
sp_UserOfflineSmall Offline
avatar
mgav451
Member
Members
February 2, 2018 - 9:31 pm
Member Since: September 27, 2017
Forum Posts: 143
sp_UserOfflineSmall Offline

P.s has any one seen the seam on the very bottom of the keel on these boats?mine wasn’t sealed up very well from the factory. Don’t know if that’s a common issue but I’d definitely look into that since I’ve added a real compression post the weight of the mast (and the monster post) will be transferred to the keel now instead of the coach roof (and head door) taking most of the load. I figured I’d take a look at the keel. I’d say that was the day the shop foreman took off when they did my boat. It’s wide open exposing the lead ballast and pretty hap hazzardly joined from the ballast aft. Seems like a very venerable point of the boat to miss. I’m gonna add 3 layers of biaxail glass down there. Really makes me wonder about the decision making at the factory.i didn’t take a pic but to any one else if your out of the water I’d get your head under there and take a look at that.

Print Friendly
Avatar
Argyle38
US Northeast
Member
Members
February 3, 2018 - 5:33 pm
Member Since: October 13, 2009
Forum Posts: 70
sp_UserOfflineSmall Offline

I look at the bottom of my boat every year, scraping off flaking bottom paint, sometimes sanding a layer down, and re-painting. I'm in Connecticut so I haul out every year anyway. I've never seen any gaps between the two hull halves. That sounds pretty crazy. There is a seam there of course, but even the seam is only visible in places and not all the way fore and aft. I wonder if it was a hard strike on the bottom that caused that? Sounds like you have a good repair plan, what you're doing is what I would do.

 

Regarding the cracks near the stern tube (that is what it is called), I haven't seen that either, but I've never ground that area down to the gelcoat. That is not a particularly high load bearing area, so I'm not too concerned. From your photo's it seems that area is thickly laid up resin, which would explain the cracking since it shrinks as it cures. Is your boat a 38 or a 32? I know the 38's were for the most part only sold with Farymann engines, a 24 or a 36 hp model. Not to say that some customer couldn't have insisted on something else, they were semi-custom after all. If the engine is from '91, then of course it's a re-power, the last DE's were built around '83. If the prop shaft is larger than 1" diameter, then the stern tube was replaced with a larger one, which could be the case here. If you find that it's likely a replacement stern tube, I would hunt down all the cracks in that area that I could find, grind them out and re-fill and reinforce them with cloth as you have described. If it looks more like something the factory did, I wouldn't worry about hunting down more cracks as much, but since you've discovered the ones you have, it certainly wouldn't hurt to fill and reinforce them as well.

Print Friendly
S/V Argyle Downeaster 38 #40 Long Island Sound
avatar
mgav451
Member
Members
February 3, 2018 - 6:59 pm
Member Since: September 27, 2017
Forum Posts: 143
sp_UserOfflineSmall Offline

I’ve heard people who know better then me say this isn’t structual? I  would have thought that was an area under high load ( not per say structural)from the prop drag when sailing pulling slightly side to side.  And from vibration when motoring,But I guess if the shaft is aligned properly it’s not? I  should know the year of my motor but I don’t. And the shaft isn’t greater then 1”. It’s a 77 de32.. hmm strange thing about the seam in the bottom. It’s dead center and straight down the middle. I’ll take a pic of it tommorrow. If the bilge was full  while up on the hard and froze....doubt that would rupture like that. I don’t know what could be going on down there. To be honest nothing surprises me any more with this boat. While I was down there I did notice the bottom rudder connection that’s supposed to be glassed into the keel (?) wasn’t so glassed in. Rather it was just faired in with that red filler. Mine was flaking off so I took it off.. it’s one very solid chunk of bronze.

Print Friendly
Avatar
Scott Carle
Admin
February 4, 2018 - 8:43 am
Member Since: October 10, 2009
Forum Posts: 1480
sp_UserOfflineSmall Offline

My 2 cents worth..

 

I would go with the first thought of fill cracks and put some cloth over it.. Should be good.

 

our bronze shoe also was just covered with fairing material. when we hauled last time and they recovered the rudder he also ground off all the fairing around the shoe becuase of small cracks and re-faired it and covered with glass. I don't think is was structurally necessary, but since he tacked it on and didn't charge me I was like "that would be cool" lol. It was about 10 minutes worth of work for him. It is a solid chunk of bronze!

 

That is crazy that you can see the lead in the core. I don't think I have heard of that with one of our boats before.

Print Friendly
Scott Carle DE38 Cutter s/v Valkyr
Avatar
Argyle38
US Northeast
Member
Members
February 4, 2018 - 11:57 am
Member Since: October 13, 2009
Forum Posts: 70
sp_UserOfflineSmall Offline

I should have probably said that this area isn't "significantly" structural. There's not going to be much side loading on the stern tube at all. If you look at fin keel boats, they often have a prop shaft strut that contains the cutlass bearing. This strut extends from the hull straight down some length, generally connected to the hull with a few bolts. There's very little lateral support of the shaft with that design, and it works fine. These shaft struts do offer some vertical shaft support. Since the prop is at an angle with respect to boat, there will be some load on the bottom of the shaft when motoring forward. Most of the load from the prop gets transferred from the shaft, to the transmission and ultimately to the engine mounts, which are what actually push the boat forward. The amount of downward load on the cutlass bearing seems like it would be roughly the tangent to the angle of the shaft with respect to the axis of the boat (or the waterline) times the total propeller load.

So there will be some up and down load on the stern tube area, but the geometry of the hull at that location can take a lot of force, even with some cracks in there. (Just like the skinny prop struts on fin keelers.) Side to side load, I can't see very much there. Vibration will certainly be present to some extent. In any case, when you find cracks in the hull, you fix them of course! I can't say for sure whether adding cloth to the area is necessary, but it certainly can't hurt. I'd probably do it even though I don't think the area is under much stress. It isn't like the extra ounce of weight in that area is going to hurt performance! 🙂

Since your boat is a 32, I really don't know what the stock shaft was. Might be 1" like the 38, but could have been 7/8", I think that was common too. Might find it in the "Boats" section of this site. I know all about the 38's because that's what I have and I considered upgrading my shaft diameter when I put my Perkins 4.108 in there. Didn't end up doing it so I'm slightly under-shafted for a 50 hp engine.

The Bronze piece under the rudder is called the "Rudder Heel" or "Keel heel" for obvious reasons. It's secured through the aft bottom of the keel with either two or four long bronze bolts. I tried like hell to remove mine. Took the bolts out (that was fun) and hammered away at the end of the thing with a mallet and eventually a small sledge hammer (on a piece of wood wedged against the back end, did NOT want to break the heel). It absolutely would not budge. Figured it was well secured and wasn't going to fall off, so I put new bolts in, covered it in thickened epoxy, faired and painted it and that was that.

Print Friendly
S/V Argyle Downeaster 38 #40 Long Island Sound
avatar
mgav451
Member
Members
February 5, 2018 - 8:20 am
Member Since: September 27, 2017
Forum Posts: 143
sp_UserOfflineSmall Offline

Thank you.

Print Friendly
Forum Timezone: America/New_York

Most Users Ever Online: 120

Currently Online:
8 Guest(s)

Currently Browsing this Page:
1 Guest(s)

Members Birthdays
sp_BirthdayIcon
Today None
Upcoming None

Top Posters:

Jonathan Oasis: 174

bobmcd625: 165

CAE: 150

mgav451: 143

Rick: 94

svbodhran: 84

Member Stats:

Guest Posters: 7

Members: 364

Moderators: 1

Admins: 1

Forum Stats:

Groups: 3

Forums: 13

Topics: 744

Posts: 3833

Newest Members:

Spirare, BradHartliep, Duncan, MistyDawn, realitysailing, Kwally@sbmn

Moderators: Patrick Twohig: 134

Administrators: Scott Carle: 1480