Page 1 of 2 12 LastLast
Results 1 to 50 of 80

Thread: Shaft Log: questions

  1. #1
    Join Date
    Aug 2004
    Location
    kirbyville texas
    Posts
    701

    Default Shaft Log: questions

    My plan was to use a two cutlass bearings-shaft log system, this will secure the 1 1/4 in SS shaft, both enternally embedded into deadwood. One at the stern post , the other attached/embedded into the frame floor. As it comes up at slight angle toward the end of shaft it would couple to a Lansdrop Gen 11 shaft seal. Lenght of shaft is short, @ 4 feet. My question is what to make the shaft log out of? They have a multitude of Duramax cutlass bearing with names like Doris and Della, these being 1 1/4 inch internal diameter for the shaft to go thru, but what type of material do you use for this bearing to insert into. Is PVC pipe a no -no, and why? The dead wood and floors are made of Long leaf pine, so I'm not really concerned with rot or sepage. Another problem I have is that my stern post is 3 inches thick, remember I made a mistake and under sized the stern post because I had this beutifull piece of old growth LL pine that fit perfectly during the build and I missed the correct thickness during build

  2. #2
    Join Date
    Dec 2008
    Location
    Bay Area, Northern California
    Posts
    619

    Default Re: Shaft Log: questions

    Chuck, Buck Algonquin ( www.buckalgonquin.com ) will sell you a bearing housing and tube made out of bronze, with this shaft length, you don't really need, or want a forward bearing, Cheers, BT

  3. #3
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
    Posts
    9,782

    Default Re: Shaft Log: questions

    A superior tube can be homemace with epoxy and FG. A resin tube is very strong and less metal to go "funny" down the road.A machine shop can turn the end to take the bearing.
    I am a bit confused about 2 cutlass bearings. An inside bearing would not be a cutlass. Cutlass is a wet bearing. Gonna use an aqua-drive?
    If your deadwood is too skinny and the shaft is only 4' long ,can you make the shaft 1"? ,cuz then you can make the tube thinner.

  4. #4
    Join Date
    Feb 2008
    Location
    Nowra NSW. A little piece of paradise
    Posts
    1,260

    Default Re: Shaft Log: questions

    I am biulding John Gardner's Garvey out of plywood. I have used a cutlass bearing at the outboard end and a normal stern bearing at the inboard end. The stern tube has been embedded in the structure of the keel/skeg assembly. The stern tube is a copper pipe with a wall thickness of about 4/5 mil. The tube has a thread cut on both ends and the bearings screw onto these threads. Before epoxying them into place I made sure they were in alignment. This has given me an assembly that will not move at all and I believe, once I have used the right sealing rope in the stern bearing. will not leak at all. I sourced these parts from the company that provided my prop.

  5. #5
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
    Posts
    31,644

    Default Re: Shaft Log: questions

    I am not sure what is meant by a normal stern bearing at the inboard end. Every normal shaft I've seen is supported only at the ends: out back by the cutless bearing and up front at the coupling. There are some boats with really really long shafts requiring some sort of pillow bearing in the middle but that's pretty rare.

    Are you perhaps, by inboard normal stern bearing meaning the stuffing box?

  6. #6
    Join Date
    Oct 2000
    Location
    Wellesley, MA USA
    Posts
    8,858

    Default Re: Shaft Log: questions

    Not everyone can make a glass-epoxy composite tube to adequate quality.
    G10 glass-epoxy tube can be bought from McMaster and other plastic suppliers.
    PVC pipe is not strong or heat tolerant enough.

  7. #7
    Join Date
    Dec 2008
    Location
    Bay Area, Northern California
    Posts
    619

    Default Re: Shaft Log: questions

    Chuck, While fiberglass tube can be done, the use and advantages of the conventional tube and bearing housing are hard to beat. Changing the cutlass bearing in a glass tube requires removing the shaft each time, depending on your situation, that may or may not be an issue. As to the metal problem, most boats I see range from 40 to 80 years old, and the shaft tube is almost never an issue...Cheers, BT

  8. #8
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
    Posts
    9,782

    Default Re: Shaft Log: questions

    A cutlass bearing can last a LONG time if the engine is in alignment. That means, being aligned WITH the bearing. ( Unless one has a jumpy motor, like a Volvo MD1) By the time a chap needs to replace a cutlass, I would think one would want to pull the shaft, just to check it and re-new the coupling bolts.
    I cannot speak to a 40-80 YO copper or bronze tube.Except I would certainly re-new it,just for kicks and giggles!

  9. #9
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    The two-shaft bearing system is workable. Sometimes the second bearing is a second cutless bearing in the shaft tube, sometimes it's a carrier bearing located forward of the stuffing box. I've worked on boats that had as many as four carrier bearings. That was a 110' salmon tender with the engineroom right forward, and the shaft running under the fish hold.
    This approach works better in boats that are quite rigid. It doesn't work very well with a soft-mounted engine, because the shaft is quite rigid, while the engine is all over the place.
    For a wooden boat of moderate size, the approach I like is a single cutless bearing just forward of the propeller, a shaft tube running through the stern post and deadwood, an inside-mounted stuffing box that's mounted on a length of rubber hose, and a soft-mounted engine.
    I've installed many of the urethane "drivesaver" couplling buffers, but have come to the opinion that they're an added expense that doesn't do anything useful.
    In this system the engine can move around, the stuffing box goes with it, and the cutless bearing is far enough aft that it can accept the little bit of angular deflection that the engine mounts allow.
    One additional point that's quite important...
    If your boat currently has a four cylinder gasoline engine, like an Atomic Four, Palmer P-60, or Greymarine, it may have a hard mounted stuffing box. If you repower with a diesel, and if you soft-mount the diesel to cut down on vibration, you may have trouble with the old stuffing box. Simply put, the engine movement generates a lot of side-loading on the stuffing box, because it can't move around as the engine and shaft do. The problem most often appears as the stuffing box working loose, or breaking mounting bolts, or pulling the bolts out of the timbers, or wearing the packing nut into an eccentric shape.
    The solutions to this problem are to: A) hard-mount the engine. B) Switch the stuffing box to a soft-mounted type with a rubber hose.

  10. #10
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    RE: shaft tubes. High-strength plastic or FRP can work fine as a shaft tube, preventing leaking through checks in a wooden shaft log. One good thing is that they're cheaper than bronze, and because they are electrically inert, they won't interact with the wood. A good thing about bronze is that you can have the outboard end of the tube threaded, and then bore and tap the inside of the stern bearing, so that the two are very firmly joined with a water-tight thread joint. A good thing. Also, on the inboard side the shaft tube can be allowed to protrude a few inches, and then a piece of rubber hose clamped over that, and the stuffing box clamped to the inboard end of the hose.
    It is possible to retrofit a shaft tube into a boat that has always had a simple hole bored through the sternpost, deadwood, shaft log, etc. It requires using a couple of stuffing boxes as bearings fore and aft, a piece of old shafting set up with a cutter, and a very powerful drill motor. It works, but takes a long time. It's a good way to break your wrist, when the cutter snags a bolt in the deadwood, and the Milwaukee Hole Hawg quits spinning the cutter shaft, and instead spins you.
    All this is a good argument for offset shafts, which use a simple tube sticking through the hull planking, the tube welded to a plate that's been shaped to fit the inside of the planking. The stern bearing is usually mounted in a strut, although it's possible to bore out the tube so that a cutless bearing can be pushed into it. On the inboard end a rubber hose can be slid over the tube, with a stuffing box clamped on the forward end of the hose.
    This arrangement is pretty simple, and in many cases cheaper than the conventional arrangement.

  11. #11
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    The olde-timey solution to a checked and leaking shaft log is to dry out the crack (I use a wet-dry shop vac. Not exactly olde-timey...) and then pour hot tallow into the crack It runs into the crack until it hits cool water, where it congeals and hardens. Fill the cracks right up full. It works fine, if you can get at the checks. Also possible to drill holes into inaccessible checks.

  12. #12
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
    Posts
    31,644

    Default Re: Shaft Log: questions

    Which brings up another thought - why would a shaft tube be hot? One important purpose of the cutless (when not totally exterior on a strut) is to let water in and out of the shaft tube. Obviously it will be well below boiling. Sometimes, by the way, you'll see a grease fitting tapped to the tube just abaft the stuffing box and a little line run from the cooling water exhaust (just before it enters the exhaust or muffler) to force water into the tube and flush back out through the cutless.

    I must say, I've never seen a boat with a normal length shaft (under 20 feet or so) where the shaft was supported in three places, never seen a forward cutless, and even for a pretty rigid boat it makes no sense to me. For any normal wooden boat, even the tightest mount and couple and most perfect allignment has vibration that will shred the forward cutless. I should think.

    But then, different boats, different longsplices.

    G'luck

  13. #13
    Join Date
    Aug 2004
    Location
    kirbyville texas
    Posts
    701

    Default Re: Shaft Log: questions

    Thanks all: But that was my thinking entirely, to prevent any wiggling with a 2 cyc Kabota diesel with soft mounts; by securing the shaft log with two cutlass bearing , prop end, the other attached to interior floor. The Landrop Gen 11 shaft seal, is only a shaft seal, my limited mechanical thinking was that one cutlass bearing will have a wiggle at the prop end. And if I can engineer a CV joint right below the Hurth tranny, It should be overkilled. Since I have a skinny deadwood keel, my mistake, perhaps a thin outer shaft log made of metal would be better than a hard plastic or FG log, just matching all components and then making a jig for the bore out of @ 2 inches. It's a 1 1/4 SS shaft.
    Again it's difficult around here, as no one builds WB's down here, up NE I could come visit a shop or shipyard.

  14. #14
    Join Date
    Mar 2005
    Location
    Cruising on Strider
    Posts
    1,852

    Default Re: Shaft Log: questions

    Quote Originally Posted by chuckm View Post
    But that was my thinking entirely, to prevent any wiggling with a 2 cyc Kabota diesel with soft mounts; by securing the shaft log with two cutlass bearing...
    You're over your head here. Having designed a lot of marine drive trains over the years, I'm getting a bit concerned about the amount of home brewing going on here and on other forums. These are some expensive components and hard to modify later. There are a lot of pitfalls. This is an area where people need to either do what a competent designer drew on the plans or obtain professional advice.
    Roger Long

  15. #15
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    If you want to stop the shaft from "wiggling" you have to stop the engine from wiggling it. Which means hard-mount the engine. If you want the engine to be able to wiggle (vibration damping), then the shaft has to wiggle with it, at least at the engine end. If you draw this out with chalk on your floor, you'll see that 1/4" of wiggle doesn't change the angle of the shaft very much if the beaaring is six feet away, but it changes it a lot if the bearing is eight inches away. That simple fact of geometry is what makes the system I described above work.
    If you want to go another way, you can install an Aquadrive or Evolution shaft system with roller bearings, lip seals, thrust bearings, yadayada. At the forward end of that system you can go to a drive shaft with no thrust on it, universal joints, slide couplings, just like a rear wheel drive car's drive shaft. But that's a VERY expensive approach.

  16. #16
    Join Date
    Aug 2004
    Location
    kirbyville texas
    Posts
    701

    Default Re: Shaft Log: questions

    Yes, over my head and going down for the 3 rd time. Which is why I have'nt done any real bulding or drilling yet, instinctively I believe in " make mistake slowly". But do not be to alarmed: as The Kabota diesel came out of a sunk fiber glass sailboat from one of the hurricaines, paid 150$. The Lansdrop Gen 11 seal I found on ebay for a pitance, The SS shaft I traded extra lead for, and the Hurth tranny also found on Craig list for @ 250$. So far wife is still clueless to above expenses, thats the real danger. I did see two Cutlass bearing on E-bay, Doris or debie, any way 1 1/4 inch for 49$ apiece so all is still in real of mad money. Mad as in crazy being the pretence statement.

  17. #17
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    Ian,
    I was a little surprised just a week ago when talking with the head engine installation guy at Billings Diesel, in Stonington, ME. If you look at their website
    http://billingsmarine.com/
    I think you'll agree that they do all kinds of work on a remarkable variety of vessels.
    Anyway, his preferred shaft installation in a lobsterboat or dragger is a cutless bearing at each end of the shaft tube, hard-mounted stuffing box, hard-mounted engine. I inspect lots of small commercial vessels on the Maine coast, and see that arrangement some. It's certainly how it was done on every single large commercial vessel (research, cargo, towing, tanker) that I've worked on or inspected.
    Which doesn't mean that I'd recommend that approach, but if that's what a guy wants, it can be made to work. There isn't a lot of room for error.
    Day before yesterday I was talking to Glen Holland at his boat shop:
    http://www.maineboats.com/boat-launchings/muskrat
    asking him about how he does boat installations. He's a soft mount engine & stuffing box guy.
    I've personally had good luck with this approach, particularly in sailboats. All of my professional training was acquired while growing up on a farm in Minnesota, but over the last 30 years I've installed, operated, repaired, owned, and surveyed a lot of machinery installations. So I try to keep it as simple as possible.
    As far as the boat under discussion in this thread, I must admit I don't know what a John Gardner "Garvey" looks like, and the one very small picture isn't very informative.

  18. #18
    Join Date
    Dec 2008
    Location
    Bay Area, Northern California
    Posts
    619

    Default Re: Shaft Log: questions

    Chuck, Have you found the Buck Algonquin website/catalog? They have some tubes, and I'm sure if you speak with them live they can help you navigate the challenges of your build. You really dont want to build some swiss watch system here, one stern bearing, a stuffing box to keep the water on the outside. Align your engine to the face of the shaft coupling, and you are off to the races, soft mounts work just fine, it will outlast us all... Cheers, BT

  19. #19
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    There are four specifications that the "Debbie," "Dinah," nomenclature covers:
    1) Shaft size
    2) Outside diameter (inside diameter of any bearing carrier you have)
    3) Length
    4) Material. The outer tube can be brass or FRP
    I don't think $49.00 is a bargain for a cutless bearing...

  20. #20
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
    Posts
    31,644

    Default Re: Shaft Log: questions

    seo, Billings is certainly tops. I'm not a mechanic, just a sailor and aside from tug boating (and not in the engin room), driving launches and a season of charter fishing, I've little power boat time. Perhaps it's that sail boats have such different problems. It would be interesting to see if they treat the relatively light engins and light loading of an auxillary, where the engin might be called on to work at 45 degrees heel, differently.

    I'd not thought to ask chuckm what sort of boat - just projected on the basis of my mechanically limited but in the rhelm of auxillary sail to 20 tons pretty extensive experience. Goes to show the limitations of not having a systematic and broad training.

  21. #21
    Join Date
    Mar 2005
    Location
    Cruising on Strider
    Posts
    1,852

    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    I was talking to Glen Holland at his boat shop... He's a soft mount engine & stuffing box guy. I've personally had good luck with this approach..
    So have I. These three boats, starting at 1200 horsepower, all have a single bearing in the strut with the engine waggling around on soft mounts. No flexible couplings, just a standard hard coupling at the transmission and a flexible stuffing box. The first is going on two decades of service and being repowered, last I heard, at Billings. These boats are remarkably smooth. I have a video of one somewhere with a cup of coffee sitting on a quarter bit while running at 20 knots and there aren't even any ripples on the surface of the coffee.







    Same set up as most sailboats including my own and hard to beat. Boats like lobsterboats with their engines well forward can't do it because there is a limit to how much shaft you can have between bearings. Once you've put that second bearing in, you have to either hard mount the engine or go to complex flexible couplings and Aquadrive like setups if you want to prevent transmission of any but just the highest frequencies. I've often gone up on shaft diameter just to be able to retain this simple shaftline arrangement. A larger shaft is way cheaper than all the other stuff involved in a two bearing set up. However, with a forward engine location, the shaft gets too large.
    Roger Long

  22. #22
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
    Posts
    9,782

    Default Re: Shaft Log: questions

    Seo, How does it work with a cutlass bearing forward of the SB? It would be dry!

  23. #23
    Join Date
    Dec 2008
    Location
    Bay Area, Northern California
    Posts
    619

    Default Re: Shaft Log: questions

    Wiz, If a boat has a long section of unsupported shaft, think fishboat, down in the shaft alley, etc it can have intermediate bearings, sometimes called pillow bearings, the ones I've seen and worked on are iron or steel housings that is shimmed and bolted to floors, with greased roller bearing insert. The whole thing obviosly needs to be aligned well. I have seen one or two water cooled bearings at the forward end of shaft tubes, and they have been trouble in those few instances, not enough water flow in this area in my estimation... Certainly not needed in a boat with a 4' shaft length... Cheers, BT

  24. #24
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    Boattruck has it right. They're often called carrier, or intermediate, bearings. Babbit pillow blocks were pretty standard, replaced with self-aligning ball bearings. The virtue of the babbit pillow blocks is that they were in two pieces, so could be replaced (or new babbit metal poured in situ), without sliding a new bearing the length of the shaft. Now then have two-piece roller bearings that can have a two piece housing, so easy to replace. Absolutely not needed for a 4' shaft.
    Here's a picture of a typical shaft installation in a lobsterboat. Soft mounts, FRP shaft tube. The stuffing box will be a self-aligning box on a rubber hose, not yet installed. B-model Cummins, ZF gear. The open mount hole on the back of the gear is for the power steering pump, I think.
    SEO
    http://s1191.photobucket.com/albums/...t=IMG_0100.jpg

  25. #25
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    Nice looking boats, Roger. Are those alu hulls?
    Mainly I'm fooling around with pasting pictures right now, but here's a kind of interesting picture.

    http://s1191.photobucket.com/albums/...t=IMG_0062.jpg

    I'm not having much luck with this attaching pictures business. In the post above it linked all right, but didn't display the picture, even though I selected WYSIWYG. This is even worse, but if you past the url above into a new window it ought to display.

    This is a picture of the stern bearing and prop of a sistership of the Holland 32 pictured in post #24 above. You'll notice that there isn't a stern bearing housing bolted to the back of the keel (sternpost, whatever you'd like to call it...) Instead, Holland simply takes the FRP stern tube, and glasses the stern bearing to the back of it, then installs the tube and bearing into the hole bored through into the hull, and builds up a strong FRP laminate around the bearing. There are a couple of set screws threaded into the FRP, and nosing into the bearing liner. The drill for replacing the bearing is to pull the shaft, put some dry ice into the bearing, and warm the outside. That gets it out. To install the new bearing, put it in the freezer overnight, warm the housing with hot water, and slide it in.
    This is a pretty aggressive approach to reducing the turbulence around the prop. The rather elaborate 5-blade prop in the picture is turned by a 425 hp Cat 3126, and will go over 30 kt.

  26. #26
    Join Date
    Mar 2005
    Location
    Cruising on Strider
    Posts
    1,852

    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    I'm not having much luck with this attaching pictures business.
    It's dead simple. Just type "[img]" in front of the link and "[/img]" directly after it. You have it right in your post but typed "url" where you should have typed "img". Either that or you clicked the link button instead of the image button. Easier just to type directly.



    Yes, those are aluminum boats, part of my 80-90% market share in additions to the coastal research vessel fleet over the last two decades. They also have 5 blade props and single struts. I'm with Glen on clean flow to the props. These two boats that you've probably seen have their skegs offset outboard of the props with single struts so you won't have all that structure slowing down the water to the wheel. The smaller one went a knot faster than predicted. It also makes them more likely to shed pot warps.





    Note in the second picture that can be clicked to at your photobucket site that the coupling is a plain steel coupling. No flex coupling or even a Drivesaver. That's the way you do it folks.
    Last edited by Roger Long; 12-03-2010 at 07:54 AM.
    Roger Long

  27. #27
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    Thanks for the link tips, Roger. Still practicing. Here's another photo of the Holland boat:

    [img="http://s1191.photobucket.com/albums/z477/se02/?action=view&current=IMG_0107.jpg/img]

    Some other good things about this installation are:
    1) Use of a split shaft flange. Also sometimes called a "Kahlenburg" coupling, because that was the company that made them. In this design, the shaft is clamped into the coupling by the pair of heavy bolts that run perpendicular to the shaft. By loosening the clamp bolts the flange can be taken off without needing a three-jaw gear puller, which can be very hard to use in the space often found around the back of a marine reverse gear.
    2) The use of welded aluminum angle brackets that are bolted to the inside of the engine beds, instead of just fitting the mounts to the top of the beds. This has several good results:
    a) The brackets can be easily adjusted up and down by drilling new holes, which can be very useful when repowering a boat.
    b) The beds can be deeper, which adds longitudinal rigidity to the hull right where it's needed, under the heaviest item in thos (engine).
    c) The beds are set wider, which makes access better. When the beds are set in right under the engine mount brackets they impinge on the starter, and often on various pumps and coolers that are often mounted down low on the engine.

    OK, now we'll see if the link works...
    SEO

  28. #28
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    Try that again...
    [IMG][/IMG]

  29. #29
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Lightbulb Re: Shaft Log: questions

    EUREKA!!
    High fives! Pats on the back!! Senility postponed!!

  30. #30
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    "Kahlenburg" couplings are an extra cost option, but unless you have really good access to the back of the engine they're worth the price.

  31. #31
    Join Date
    Mar 2005
    Location
    Cruising on Strider
    Posts
    1,852

    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    Some other good things about this installation are:
    One that I would question though is how high the engine appears to be jacked up on the mount screws. Some adjustment is required but going all the way to the top puts a lot of leverage strain on the mounts in a high power installation. I would put some shims under those mounts.

    When I lived in Friday Harbor WA, one of the fast gillnetters did a show off departure opening up suddenly to WOT in front of the fuel dock. There were loud rumblings and clashing noises and it sagged back in the water and limped back to the dock. It's engine had been cranked up right to the top of the coupling bolts and it had simply bent them over!
    Roger Long

  32. #32
    Join Date
    Mar 2005
    Location
    Cruising on Strider
    Posts
    1,852

    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    Try that again...
    Almost. You've got the img tags in twice which is why it says "[img]" on each side of your picture. Just put them in once and you're there.
    Roger Long

  33. #33
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    With the bracket arrangement as pictured above it's easy enough to put in a spacer block between the bed brackets and the soft mounts if one wanted to bring down the height on the bolts. From the fact that there's no exhaust hooked up, no steering pump, and no couple bolts, as well as no cockpit platform, I don't think the boat is quite finished.
    In the picture attached below (I'm gonna get my 40 hours in on this photobucket stuff...):



    The boat in the foreground is the one with the stern gear that's pictured above. The boat in the background is the infamous "Red Baron," which belongs to Glen Holland's father, Corliss Holland.

    Before retiring from racing, the Red Baron held the title of "World's Fastest Lobsterboat" for several years, with a record speed of 57 knots. It's powered with a bored and stroked 460 Ford with a supercharger, probably producing around 600hp.
    In the time I've known the Hollands, the Baron has had a straight-drive engine, a vee-drive, and a remote-mounted vee-drive that allowed putting the engine right in the stern.
    The point is that if Glen figures those mounts will hold up, my guess is that they will.
    Aside from that, the boat with the Cat engine only has a 1.8:1 reduction gear, so I doubt it will have the hole shot that a gillnetter with a big prop might have.

  34. #34
    Join Date
    Mar 2007
    Location
    East Quogue,NY
    Posts
    6,945

    Default Re: Shaft Log: questions

    Great thread guys. Thanks for sharing your expertise! I hope you don't mind me to try and wring another tidbit out of all this. In this picture, are the prop nuts on the shaft in the proper order? or should the half-height nut bear against the prop hub?


    Thanks
    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  35. #35
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    Here's what I get from this source:
    http://www.boltscience.com/pages/glossary.htm
    2. The term is sometimes used for thin (or jam) nuts used to lock a thicker nut. When used in this way the thin nut should be adjacent to the joint surface and tightened against the thick nut. If placed on top of the thick nut the thin nut would sustain loads it was not designed to sustain.
    I can't say that description is completely clear to me.
    In my somewhat anti-technical experience, any two nuts, thin or thick, will do okay, If you put nut #1 on first, and tighten it to the correct torque value, then put on nut #2, and tighten it snug against nut #1. Then Get a good wrench on nut #1, and hold it in place, and the get a wrench on #2 and yarn it against #1.
    Aside from this profound theory, it's noted that in this picture it also look like there's a cotter pin through the shaft behind Nut #2. All things being equal, I'd rather it was a castle nut.
    But all things are not equal.
    And as the man said:
    "The perfect is the enemy of the good."
    Or something like that.
    SEO

  36. #36

    Default Re: Shaft Log: questions

    My biggest concern would be the dia. of hole you bore thru the sternpost. If as you say you require a 2in. dia. hole and thats about what i would guess, that leaves you with only 1/2 of wood either side, i'm no engineer but thats not much wood. As prev suggested reduce the shaft dia. as much as possible to gain wood. I'd use the smallest shaft possible that will safely take the torque of your engine. Then go with the standard set up, shaft tube(well secured on the inboard end) cutlass bearing , and some sort of flexiable seal on the inboard end, I use "Last Drop" seals on my builds and have found them excellent. I also use expensive Aqua Drive couplings but thats not really necessary with your H.P.Give some thought to, installing good stiff motor mounts as a way to reduce engine movement. Be sure to allow the shaft tube to extend far enought out the stern to facilitate good flow for the lubricating/flush holes for the cutlass bearing. If this is not possible use an inboard seal that has a water intake connection to help cutlass lubrication. And as mentioned above if you have any safety concerns consult a hands on pro. A few dollars could save alot of headaches on your next insurance survey.
    Last edited by viking north; 12-03-2010 at 11:27 PM.

  37. #37
    Join Date
    Mar 2005
    Location
    Cruising on Strider
    Posts
    1,852

    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    the thin nut should be adjacent to the joint surface and tightened against the thick nut. If placed on top of the thick nut the thin nut would sustain loads it was not designed to sustain.
    I used to do some steam engine modeling and the books said it was always done this way on steam equipment and pressure vessels. Steam engine models being judged in shows have points deducted for the jam nuts being on top.

    There is always some microscopic slop in straight threads. If you put the jam nut on top, it will push the big nut down and take up all the slack towards the pressure vessel. When the bolt is stressed, this slack will have to come out before the big nut takes any load. The thin nut will then be holding everything. It may crack and back off leaving you without a jam nut. A prop is not a pressure vessel however and anyone who has tried to remove one knows that there isn't likely to be a significant load against the threads after installation. A pressure vessel is put together with no load and then the nuts and studs are stressed. The main thread stress on a prop is during installation when the nut is pushing it up the taper. You want a big nut for that and those forces will push the thread slop in the other direction. In service, the primary forces are in the opposite direction of a pressure vessel. The jam nut is not going to take any significant loads and should go on last.
    Last edited by Roger Long; 12-04-2010 at 06:19 AM.
    Roger Long

  38. #38
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    Roger, that's the clearest explanation of locking nuts that I've ever read. Thanks.
    Viking, how much does an Aquadrive cost? I know you're not recommending it for this application but I'm curious.
    The issue of a thin sternpost is an argument for an offset shaft.
    It's not too hard to find a used strut. Lots of old powerboats that are currently moldering away in the back of a boatyard have them. Think Scrap price.
    SEO

  39. #39

    Default Re: Shaft Log: questions

    Seo, He'll be fine going with a smaller shaft just needs to gain a little more wood on either side of the tube. Worst case senerio he can fasten a couple of 1/4 metal plates say 6 to 8 in. long on either side of the stern post and thru bolt them above and below the shaft tube . The idea is to prevent a split occuring in the sternpost. If that happens there'll be hell to pay with the structure, mucho repair work. My stomach churns at the thought of offsetting and struts on a nice clean hull. Getting off the subject a little, I see from your ad. you're from the Ireland on the east side of the pond, I'm from the Ireland on the west side, Newfoundland, The Newfoundland Irish are more Irish than the Irish, visit the pubs on George street, St. Johns and you'll know what i mean. And while i'm off the subject, Roger i think we might have crossed paths in Boothbay, spent a week or so there passing thru on the Windigo back in 74/75. the two old schooner wrecks were still there, the Hesper and ?. Oops missed answering you question, Aqua Drive possibly the best coupling you can install costs from $5oo to $2000 for most size boats a regular Joe would own. (30 to 50) "A Yacht is not defined by the vessel but the love and care of her owner"
    Last edited by viking north; 12-04-2010 at 01:03 PM.

  40. #40
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
    Posts
    9,782

    Default Re: Shaft Log: questions

    A FG /epoxy tube is stronger than a conventional bronze one. If it was glued in, it would add some strength to the skinny wood wall.
    Also, once the FG tube is glued in, one only needs to bore a 1/2" hole on each side, through the wood and into the tube,a few inches fwd of the cutlass ,to keep the tube full of water. One would not want to bore into a conventional tube like this.

  41. #41
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    I'm actually from the Belfast in Maine.

    My enthusiasm for offset shafts comes from having owned a Herreshoff H-28, and looking at a lot of LF Herreshoff plans. I have no proof of this, but my observation is that an H-28 with an offset and angled shaft running in a one-legged strut, and a solid rudder (no aperture) Is a faster sailboat and all around better boat. It makes sense to me, considering the turbulence and drag caused by the aperture. Construction is simpler as well.
    I think a boat with a solid rudder goes to windward better, and absolutely steers a lot better running off in a lot of wind on a quartering reach, where the top third of the rudder is sucking air, and the middle third has a big hole cut in it, and is operating in a mass of dirty water behind the prop. So that leaves you steering with the bottom one third of your rudder.
    The only disadvantage I know of for the H-28's offset shaft is a greater tendency to wind up lobster pot warp.
    One arrangement that never made a lot of sense to me was the twin-screw/single rudder arrangement found on some big sail yachts. Then a few years ago I spend several months driving a schooner called "Amistad," which shares that arrangement with her big sister, the Pride of Baltimore 2. We went to lots of places that required fairly tricky handling, and I actually found it to work pretty well. You can't walk her stern much, and the long keel of that design keeps you from twisting her, but she springs on and off docks as well as any vessel with a 28' bowsprit/jibboom and an overhanging boom is likely to do. Aside from springing, you just handle her like a sailboat.
    We also carried a Zodiac that served as our own private docking tug, so the lack of a bow thruster was not a big deal. Pictured below is the Amistad's crack pushboat crew, standing by. Any resemblance between the guy at the controls and my 14 year old son is strictly coincidental.

    [IMG][/IMG]

    Here's another picture of the pushboat being useful, this time when it provided a convenient work platform for installing a new dolphin striker. We were tied up in London, waiting for a gale to go through so we could go to Portugal.



    These pictures actually have nothing to do with shaft logs. I'm just practicing with pasting photobucket images. Today's thing is to see how caption work.

  42. #42
    Join Date
    Mar 2007
    Location
    East Quogue,NY
    Posts
    6,945

    Default Re: Shaft Log: questions

    You want a big nut for that and those forces will push the thread slop in the other direction. In service, the primary forces are in the opposite direction of a pressure vessel. The jam nut is not going to take any significant loads and should go on last.
    Thank You Roger and Seo
    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  43. #43
    Join Date
    Mar 2005
    Location
    Cruising on Strider
    Posts
    1,852

    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    It makes sense to me, considering the turbulence and drag caused by the aperture.
    This is a greatly underestimated effect. There is a large pressure differential on the two sides of a hull and keel when a boat is going to windward. The total force is about the same as produced by the wind on the sails. Otherwise, the boat would be making a lot of leeway. Local pressure created by rudder angle adds to this. The result is a major flow of water sideways through an aperture. Think of the kind of flow you would get through a similar sized hole in the middle of your mainsail.

    The rudder on a long keel boat acts much like the aileron on an airplane wing. It creates a zone of pressure difference which extends forward of the rudder so that the deadwood actually exerts turning force on the hull. Punch a hole in this critical area and you will need more rudder angle to hold the same close hauled course or turn at the same rate. This increases drag after you are already paying a drag penalty for setting up all this sideways flow over the prop. A large enough aperture will also shift the center of pressure of the rudder foil aft so that the rudder has more leverage which creates more apparent weather helm.

    A reason many traditional boats got by with so much sail area aft is that few of them had prop apertures so their rudders were more effective.

    An off center prop seems like the perfect solution for someone who has made their deadwood too small. The boat won't work quite as well as a powerboat but it will sail faster on the wind and steer better. It will have more drag off the wind since the prop and shaft will be more exposed and in cleaner water flow so a folding prop would be important.
    Roger Long

  44. #44

    Default Re: Shaft Log: questions

    Jasus Boys ( thats me Irish coming out). Whats with all the tech. stuff, I have no doubt there are pros and cons on offsettin the shaft. I did it once by 3 in. to prevent cuttin the aluminium backbone on a lifeboat conversion and i offset it on the side that would counteract the the paddlewheel effect of the big 3 blade prop, knew nothing about all those other theories. However logic says drag is drag and regardless wheather its behind the keel or off on the exit side of the hulls water flow pattern it's still drag. On one tack there is less drag on the other more, depending on how deep the appendage is emerged. Is there less drag overall, could be, but in the long run this is not the Lipton Cup, this is one of the boys trying to solve a problem and no disrespect to him but i don't think he is about to take on boring holes thru his hull at some ungodly known angle and installing a shaft tube ,cutlass bearing, and strut that all have to be mounted on angular cut supports , hey maybe he will take it on but i certainly wouldn't when the alternative is much less complicated. Seo so who told them they could have a Belfast on this side of the pond, actually know your neck of the woods well, had a friend there who ran a motel and whose great grandfather was from St. Johns N.F.L.D. as was some 50% of New Englanders from N.F.L.D. in the 1600's i mean. Roger,checked back in my 74/75 notes, the guy was James Long and he was working on a Friendship Sloop, got to talking to him as his father was stationed where i grew up, U.S.A.F. SAC. Base Harmon Field, Stephenville N.F.L.D. Maybe a LONG lost relative. Top of the evenin ta ya, George
    Last edited by viking north; 12-04-2010 at 09:56 PM.

  45. #45
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    My H-28 had a two-blade folding prop, a Michigan clone of a Martec, except that it had magnets inset into the blade that were strong enough to hold the blades folded in. I once actually won a cash money bet by backing her up in a figure eight. It was really not hard to do, by backing off power as you get the turn started toward the off side.
    She was also the only sailboat I've ever been on board when she went fast enough to pull her stern wave over the transom. The log showed over 10 kt at the time.

  46. #46
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    I think the work of installing an offset/angled shaft is no more complicated. I'd certainly rather bore a hole out through a plank's thickness, then through a sternpost, deadwood, shaft log, etc. The idea of bolting metal scabs to the side of the sternpost to reinforce it makes sense to me, as does Wizbang's point that a strong FRP tube can be glued in place strongly enough to add to the strength of the sternpost.

  47. #47

    Default Re: Shaft Log: questions

    Now don't forget with an offset shaft, he also has to modify his engine beds and mounts if he can't get enought adjustment on his present mounts althought i suspect it might be a matter of re aligning his engine (offset) and re positioning his mounts. Still touchy work if you don't have the experience. When i bore thru the sternpost and deadwood i have a jig that i make up where the drill is held in a cage and slides on two rails that are set on the pre determined angle and inset equally but parallel with the run of the keel. The only problem is the time to weld it up and it is usually only compatable with that particular job at the time, which by the way i might never have to do again, however it worked for me. Wisbangs idea is certainly a good one and why not combine the two, reduce shaft/tube size and go with an FRP tube epoxied in, that should alleviate any concerns of weakness.
    Chuckm, you following all these words of wisdom? (how do you attach those smiley faces, teach me computer skills and i'll fly out and drill that shaft tube hole for ya.) ( Visit my brother in law at the same time , he is in Huston)Geo.

  48. #48
    Join Date
    Oct 2005
    Location
    Belfast and Marshall Cove, Islesboro, Maine
    Posts
    1,877

    Default Re: Shaft Log: questions

    I don't know how far along in the project Chuck M. has gotten. Except for one thumbnail picture in post #1, I don't know either what the hull is like, or how close to completion it is. It does take a bit more figuring to lay out and build engine beds for an angled engine, because you're not just putting them in square to the floor timbers. But it's not exactly rocket science. The same is true of the hull flange that the shaft tube is welded to. It could be shaped to fit tight to the curve of the planking, or it could be made of flat material then set down in epoxy putty.
    But is this a flat-bottom garvey, or a vee-hull? Is it a sailboat? I think of a "garvey" as being an inshore fishing boat with a flat or nearly-flat hull. But that doesn't mean there aren't "garvey" types that are radically different from that. As an example, as a kid I did some sailing on a type of boat called an "E class scow," which was a 28' very lightweight racing boat. In later years I worked towing garbage scows, which were hopper barges with no hatches. Later I worked towing "dump scows", which are used for carrying dredged material out to a dump site. They were also hopper barges, but have opening clamshell hatches in their bottoms that allow them to dump their cargo out through the bottom.
    The point being that all three of these hulls are scows, but they are very different. Without knowing anything about the garvey being discussed here other than that it's:
    A) designed by "Gardner." John Gardner?
    B) It has a 2-cyl diesel diesel engine. Horsepower?
    C) It has a Hurth gear. Reduction ratio?
    D) It has a 1.25" SS shaft. Why so big? As an example, my present sailboat is 40' long, about 22,000 Lbs actual weight. Its engine is a 4-107 Perkins, which produces about 27 continuous horsepower, probably an intermittent peak power of 40. The gear is a Hurth with 1.8:1 reduction. The shaft is 1 1/8 " bronze. I guess that a 1 1/4" stainless steel shaft is about twice as strong. So, if my boat has at least twice as much power as yours, and your shaft is twice as strong as mine, it suggests that your shaft is four times stronger than it needs to be.
    My old H-28, which was set up for a Universal "Blue Jacket Twin" of about 12 hp, 1;1 gear, used a 1" shaft, which never caused trouble.
    I've installed shafts as small as 3/4", but that was in a small antique launch.
    But anyway, that's the sum total of what I know about the boat in question.
    SEO

  49. #49
    Join Date
    Mar 2005
    Location
    Cruising on Strider
    Posts
    1,852

    Default Re: Shaft Log: questions

    Quote Originally Posted by seo View Post
    the sum total of what I know about the boat in question.
    Which is the problem with this thread. It's turned into a nice opportunity to discuss some interesting issues but I fear Chuck is headed for another wooden boat disaster in which a lot of nice woodwork is spoiled. It's hard enough to design your own mechanical systems through a forum discussion even when providing full information. One comment somewhere above leads me to believe that salvaged parts are a driving force behind the drivetrain considerations which further puts the time and money invested in the woodwork at risk. It would be an unusual 2-cylinder diesel that needs a shaft that large. If he hasn't thought ahead to the prop yet, he could get all this stuff done and find that the appropriate prop doesn't have a large enough hub for a shaft that size. Chuck, you admitted you were over your head and all I see right now is a couple fingertips waving weakly above the water.
    Roger Long

  50. #50

    Default Re: Shaft Log: questions

    Ditto and now have to tackle a wee bit of a challenge myself, today taking the lines off my hull in my latest and hope to be last big boat build (conversion). Now if people would only stop tempting me with money i just might hang on to it. Once i get this done and learn how to post her lines along with photos maybe some kind people out there will ignore the fact the hull is glass but appreciate the fact the superstructure will be composite (wood/epoxy)the interior just pure fine woods, and help me confirm those magic numbers. Geo.
    Last edited by viking north; 12-05-2010 at 10:25 AM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •