Slocum`s Spray

Discussion in 'Sailboats' started by Elmo, Dec 19, 2009.

  1. sharpii2
    Joined: May 2004
    Posts: 1,863
    Likes: 86, Points: 48, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    Great story, as usual.

    One thing I noticed about engines is the engine weight per hp seems to go down, as the as rpm goes up and the crankshaft torque goes down. this rule seems to be consistent all the way from reciprocating steam engines to gas turbines (jet engines).

    One of the things I learned in school is that for a displacement type boat to be efficient, it needs to have a large propeller. and the large propeller needs high torque to turn it.

    to get that high torque, a high rpm engine needs to be geared down, so the propeller shaft is turning at as little as one fourth the speed of the crank shaft.

    This is as big a problem with airplanes as it is with boats. I read a horrifying story about an builder/pilot who's engine was geared down with belts. He was doing a sharp climb when the belts failed on him. The plane stalled immediately and nosed into the ground from about 400 ft.

    The 8 hp outboard would do better if it had a more displacement speed prop on it. I can anticipate sometime in the future someone making displacement speed props for older outboards. The amount of improvement would be limited, as the propeller diameter will be fixed by the shaft speed. But the pitch and the number of blades can be changed. It would be interesting to see how much improvement is possible.
     
  2. troy2000
    Joined: Nov 2009
    Posts: 1,743
    Likes: 170, Points: 63, Legacy Rep: 2078
    Location: California

    troy2000 Senior Member

    That 'bang...pause, bang...pause,' reminds me of the old 225 V6 in my Jeep. It's a cut-off version of the Buick Dauntless V8, which means the banks are angled at 90 degrees instead of 120 degrees -- like a Harley engine. And since the firing order is 1-6-5-4-3-2, it has the same 'potato, potato, potato' rhythm as the Harley when idling. The cylinders fire in pairs 90 degrees apart from back to front, with a pause of 270 degrees between each pair. Combined with a heavy flywheel, that double bang seems to be why the engine has an unreasonably high amount of low-end torque for its size....

    I had just replaced the carburetor on it one afternoon and was test-firing it, when a neighbor who fancies himself a mechanic walked over with a 12-pack in his hand and said, "hey, why don't you let me tune that lope out of your engine?" Since he brought beer, I didn't argue. We went through most of the 12-pack before he gave up, and I never did tell him that's the way it's supposed to sound.:)

    Addendum: most of the parts for a Jeep Dauntless V6 are exactly the same as those on a Buick Dauntless V8. Knowing that can save you big bucks at the auto parts store.... for example, the last time I checked I could get pistons marked 'Buick' for about half the price of those marked 'Jeep.'
     
  3. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 96, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    All that matters to the water/boat relationship is propeller RPM and blade area.
    A big prop with lots of area will push against more water, giving more effect, or in this case thrust.
    To twist the shaft and make this happen requires torque, either from a big slow engine without reduction or a fast engine geared down to give the same effect at prop.
    A steam engine develops maximum torque at stall, totally unlike an internal combustion engine, and watching a steam tug accelerate silently is awesome.
    BERTIE has a 2:1 reduction and a 2 blade prop setup intended for a lighter boat.
    The proper SABB factory gear would have been the 3:1 reduction and the 3 blade controllable pitch wheel but that would have cost much more.
    What this means is we had no prop pitch sweet spot initially and the engine could not be run at a proper RPM because the blade area to load ratio was too large for available torque with the 2:1 reduction.
    There was either too much pitch or not enough and I couldn't get proper HP into the water....
    So the only thing I could do was reduce blade area, which was accomplished by using the boat as a lathe bed, setting a scribe pointer on the hull and revolving the prop by hand to mark 1/2" off the tips, then making a metal template with the right curve, scribing it on both blades, then cutting the half moons of metal off with an electric saber saw.
    This was finished by leaving the prop in place then filing both to the template till they were the same to the pointer when the prop turned. Then I disassembled the prop and weighed the two blades. They were very close so were filed on the thickness of the heavy one a little to get them closer and called it good.
    Putting the boat back in the water the difference was large. Now we have a pretty wide range of usable pitch for different conditions and all the power goes in the water.
     

    Attached Files:

  4. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 96, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    BERTIE's mast is back in the boat and I've been stretching the new lanyards and now the stick is wedged, coated and stayed slightly raking forward, the big change to the rig to move CE a little forward and make the sail hang outboard in light airs. Camera died so I don't have photos yet but plan to get one soon. The boom operator snagged the masthead on the crane and broke the cross fitting that carries the lights and wind vane so next is unbolt the thing and get it on deck, repair or replace and move on. Wind is howling so maybe not today. Doing much reading about the trip around Vancouver Island and all the hundreds of nooks and crannies on that beautiful BC coast. We leave in May. Here's a photo from a couple years ago.
     

    Attached Files:

  5. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 96, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    Mast wedges and more taken with iPhone.
     

    Attached Files:

  6. goodwilltoall
    Joined: Jul 2010
    Posts: 814
    Likes: 20, Points: 18, Legacy Rep: 31
    Location: nation of Ohio

    goodwilltoall Senior Member

    How thick is the deck where it comes through?
     
  7. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 96, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    Deck thickness is 2" old growth fir deck on top of 4" partner timbers bolted fore and aft through 4x6 beams. Very typical 1900 setup copied directly from a San Francisco oyster sloop of that date, the GOV MBM (photo) which was rebuilt as a schooner in 1974 or so. These boats had their masts far forward, more so even than SPRAY and BERTIE, so the partner had to be absolutely fool proof as the mast staying triangle was quite narrow being way in the bow, and the resultant timbering was used as the method for BERTIE. If maintained well, it seems to last for many many years of hard sailing, so far. Photos of B in build show the deck, but it's hard to see the 4" partner blocking where the mast cut out will be. The massive pawl bitt is the mast step for the bowsprit, and is bolted to the deck beam and stepped in a mortise in the stem knee. Bowsprit is 10" at gammon, same as mast diameter at deck. Steel hanging knee P&S on beam just forward of mast to give more stiffness. All the deck frame and plank was old growth, very tight grain Douglas Fir. The quality of wood in this boat would cost $200k today yet at the time I spent $15k on the build, hull and deck.
     

    Attached Files:

  8. troy2000
    Joined: Nov 2009
    Posts: 1,743
    Likes: 170, Points: 63, Legacy Rep: 2078
    Location: California

    troy2000 Senior Member

    People who buy plantation-growth Douglas fir at Home Depot today have no idea how strong the genuine old-growth stuff was.

    I'm sure it's been mentioned before, maybe even by me. But I'll say it again: the old lumber schooners were framed, planked, decked and sparred in old-growth Douglas fir.
     
  9. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 96, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    Had to cut end grain with a chisel in altering mast rake and it was like white oak.
     
  10. goodwilltoall
    Joined: Jul 2010
    Posts: 814
    Likes: 20, Points: 18, Legacy Rep: 31
    Location: nation of Ohio

    goodwilltoall Senior Member

    Those photos help alot.
     
  11. sharpii2
    Joined: May 2004
    Posts: 1,863
    Likes: 86, Points: 48, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    A very interesting but dis-heartening statistic. If you were born, say, 36 years later and wanted a boat like BERTIE, how would you build her?
     
  12. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 96, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    If building another BERTIE I'd still prefer heavy sawn frame construction over steel or a cold-molded boat since it's well insulated and massively strong, easy to repair and simple to build. A wood boat should be built with what wood is available locally. The original SPRAY was oak and yellow pine, like most East coast work boats.
    If looking for the same stuff I used then, here on the West coast, I'd go to the woods, buy standing trees for the fir backbone and deck, saw it with a portable mill and sticker it to dry.
    BERTIE's keel, stem and deadwood was green when it was cut out and set up, then doused with red lead to dry slowly since the boat took 8 years to launch (kids, life, paying for it, etc).
    A few months in the Oregon mountains getting to know locals should turn up enough standing dead hillside stumps of PO cedar for the curved frames.
    PO cedar planking is harder to find, but available.
    If on the East coast, I'd be finding all the little sawmills that saw one or two trees at a time and asking them for white oak, locust and pine, there are many guys who do this part time.
    As always, substituting personal effort for money will usually pay off. It just takes longer.
    Small wooden ships like BERTIE have always been built in the open by the waterside on the cheap and it is still possible if you have the right attitude towards the job by keeping it simple and researching how it was done in the past and not trying to 'improve' on that out of ignorance of the past and arrogance in thinking we're smarter than the old timers were about this job.
    Remember, the Laughlin McKay yard in Boston built four, 400 ton packet ships per year (one every 90 days) in the late 1840s with no power tools and a work force of about 30-40, so it's possible to build a 20-some ton ship like BERTIE with the same technology (crude) in a short time with one or two people who know what heavy physical work is all about.
    Maybe $200k is too high and one could purchase the wood outright for $100k or less, now that I think more carefully about it, and less than $30k if you went around finding and cutting it yourself. Spikes, cotton and oakum are all available and not much more is needed.
    A big bandsaw and a planer are the only necessary stationary machinery needed. All the rest is a moderate amount of skill and a large amount of commitment because you can't build a thing like this working evenings and weekends. I put in 10 hour days 6-7 days a week for the first two years, and regularly work at least 4 weeks a year on it now just keeping up.
    The mast overhaul has gone on about 6 weeks and cost $1500 this year and I'm close to bending the main back on. The investment never ends. Two years ago it was a big stem repair, next year hopefully just a paint job.
     
  13. troy2000
    Joined: Nov 2009
    Posts: 1,743
    Likes: 170, Points: 63, Legacy Rep: 2078
    Location: California

    troy2000 Senior Member

    You have my respect twofold: once for building Bertie, and again for managing to take proper care of her all these years.

    What do you envision for Bertie in the future? Will your children care for her as you have? If not, will you sell her, donate her to an organization, or....?

    Once upon a time her working ancestors were sailed until they wore out, then unceremoniously discarded and replaced. But I'd hate to think of that being her fate.
     
  14. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 96, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    Troy, good question! My younger son says he wants her but he's a guitar repairman, not a shipwright, and poverty stricken, so I don't know. When I get too old she'll probably be sold....
    But first, lots of sailing! I often flirt with the charter idea but never do it because it's just the hotel business in a cramped space with no shower.
    Around Vancouver Island next summer. Personally I want to sail around the world and make a film just for the hell of it, but wifey is much more practical, so not today.
     

  15. sharpii2
    Joined: May 2004
    Posts: 1,863
    Likes: 86, Points: 48, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    In other words, it would not cost $200,000 to build today. It would only cost that much if you bought all the lumber from a lumber yard. Harvesting and cutting it yourself (with help of a sympathetic sub contractor or two) is a way around that, which apparently you used when you built BERTIE.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.