Things I wish I knew about boats.

[Cadence]

Originally Posted by zeehag

it is not the weight but the flex. boats flex while sailing. rigid rails do not. no lifelines is perfect as they are not designed to be life saving devices but edge feelers. they are there so you know where the edge is. the lifesaving device is your teakwood grabrail on coachhouse roof.

[captlloyd]

Drive shaft setups do exist for boats and they do eliminate alignment issues. However a thrust bearing is required in the setup.

[newhaul]

Originally Posted by captlloyd

Drive shaft setups do exist for boats and they do eliminate alignment issues. However a thrust bearing is required in the setup.

Lloyd more info please.

[sailorboy1]

Originally Posted by Don C L

So my wife asked me, since she does not take kindly at all to my lifelines that flop around when you grab them, "why don't more boats have railings that stay put?" In other words, rigid railings... and I could not answer that, I cannot think of a good reason why not... I don't know, aesthetics?... but I confess, I like the idea!
Secondly, after trying to help someone with adjusting a prop shaft a while back, I wondered aloud to mechanic, why don't they make prop shafts with u-joints so you don't have to be 4 feet tall with arms like Popeye to crawl back in there with a feeler gauge? (He didn't know) Or do they and I just haven't seen them yet?

I stoped reading when didn't see the answer, so if some gave the real answer sorry.


It's MONEY

[captlloyd]

Originally Posted by newhaul

Lloyd more info please.

Don't know as I can give you more info, I remember seeing an article in Yachting magazine that I used to subscribe to before they pretty much went to writing reviews on 120 ft mega yachts. There is not really much to it, a thrust bearing takes up the thrust of the prop (with stout mount as well) and then your driveshaft to transmission. It does make it nice for removal of transmission/engine as well. Normally the marine transmission takes up the thrust as they have a built in thrust bearing. Would not be difficult to do, especially on a new construction.

[seabreez]

Originally Posted by Don C L

So my wife asked me, since she does not take kindly at all to my lifelines that flop around when you grab them, "why don't more boats have railings that stay put?" In other words, rigid railings... and I could not answer that, I cannot think of a good reason why not... I don't know, aesthetics?... but I confess, I like the idea!
Secondly, after trying to help someone with adjusting a prop shaft a while back, I wondered aloud to mechanic, why don't they make prop shafts with u-joints so you don't have to be 4 feet tall with arms like Popeye to crawl back in there with a feeler gauge? (He didn't know) Or do they and I just haven't seen them yet?

The thrust from the drive shaft (in a car) is rotational torque. In an automobile this is great as the torque from the motor and transmission is transferred to the rear wheel and this thrust and torque from the rear wheels is transferred back to the body through torque arms and make the vehicle go forward. In a vessel the torque is rotational and longitudinal and is transferred through the prop shaft to the prop and this thrust is transferred back to the vessel by the prop shaft to a thrust bearing in your transmission and therefor if you did have universal joint, they would take the longitudinal torque and they are not designed to accept this thrust and would fail sooner than later. The propeller shaft(s) have to be perfectly aligned... if not aligned, the flange would try and throw the prop shaft away from center and would create vibrations. (Very hard premature wear on bearings, bushings, seals and harder on the mental state of the Captain and passengers as these vibrations are transmitted through out the whole vessel) The thrust bushing(s) or bearing(s) are heavy and built in with a very conservative safety factor of many tons. (I do not know the safety factor) Our tugs push barges the are mega tons, and the bearings are not that big (in my opinion) but they do take the load... and last a long time...

[captlloyd]

Originally Posted by seabreez

The thrust from the drive shaft (in a car) is rotational torque. In an automobile this is great as the torque from the motor and transmission is transferred to the rear wheel and this thrust and torque from the rear wheels is transferred back to the body through torque arms and make the vehicle go forward. In a vessel the torque is rotational and longitudinal and is transferred through the prop shaft to the prop and this thrust is transferred back to the vessel by the prop shaft to a thrust bearing in your transmission and therefor if you did have universal joint, they would take the longitudinal torque and they are not designed to accept this thrust and would fail sooner than later. The propeller shaft(s) have to be perfectly aligned... if not aligned, the flange would try and throw the prop shaft away from center and would create vibrations. (Very hard premature wear on bearings, bushings, seals and harder on the mental state of the Captain and passengers as these vibrations are transmitted through out the whole vessel) The thrust bushing(s) or bearing(s) are heavy and built in with a very conservative safety factor of many tons. (I do not know the safety factor) Our tugs push barges the are mega tons, and the bearings are not that big (in my opinion) but they do take the load... and last a long time...

Exactly. That is why if you run a driveshaft you need to add a thrust bearing in the mix. Another words, if you run a driveshaft, you are going to end up with two thrust bearings, one in the transmission (which you don't need anymore) and one after the prop shaft which you now need.

[a64pilot]

The Sigma drive I linked to is a universal joint that will take a thrust load, it's the only universal joint that I am aware of that will. About an hour to install. Will allow up to a 3 degree misalignment, which is huge, I don't think a three degree misalignment is even possible on my boat
Thin wall steel tubing attached to a stanchion every few feet, will flex way more than a hull does, although I know there are some flexible hulls out there, I've had riggers tell me they adjust rigging to the doors, meaning they never get the tension and mast prebend they should as they doors inside of the boat jam first.

I'm with Sailor boy, I know what I paid to put rails on the cockpit and every now and again consider doing it on the rest of the boat, until I realize the cost.

http://www.katomarine.com/lifeline.htm

Real quality product, check the price though.

[TrentePieds]

Quote: "Exactly. That is why if you run a driveshaft you need to add a thrust bearing in the mix. Another words, if you run a driveshaft, you are going to end up with two thrust bearings, one in the transmission (which you don't need anymore) and one after the prop shaft which you now need."

Yes, but these things are really "old hat". A year or so ago a discussion of Hundested props came up. The "fiskekutter"s that I grew up with had semi-diesels driving Hundested reversible pitch props. The actuating mechanism for the prop was a rod within a hollow shaft. The shaft transmitted the thrust via two conical ball bearings (back to back, so to speak). The housing for these was fixed to the structural members of the keelson/deadwood, floors. Such a "thrust box" with a short shaft with CV joints ahead of it would be the cat's pajamas, but Hurth and Twin Disc are doing alright, so I doubt that we'll see anything like that in toy boats.

These days the Hundesteds are hydraulically activated, but the mechanical engineers among you will soon divine how, exactly, the fore'n'aft motion of the actuating rod within a rotating tube was accomplished from a non-rotating actuating lever connected to the control wheel in the wheel-house.

These days a Hundested is expensive beyond what most yotties would pay, but remember that in my benighted boyhood in Darkest Denmark the fisherfolk were poor in a manner that it is difficult to comprehend today. The Hundested VPP installations were MUCH cheaper than the sort of reversing tranny we use today :-)

Smaller motorboats were often driven by Ford "A" "salvaged" engines and trannys. Prop 'em for forward in low gear and astern in reverse. Don't forget to keep the clutch. And don't forget to fit thrust bearings! You do what you gotta do, eh :-)?

Talk about CE category "D"!

TP

[NevisDog]

Originally Posted by a64pilot

... Thin wall steel tubing attached to a stanchion every few feet, will flex way more than a hull does...

Sure, but remember hull bends somewhere around the waterline level (depending on rigidity of keel/deck) whereas fixed rail is way above deck level so must endure proportionally greater bending. I've seen oil tankers rip their piping apart, just because the piping was raised above main deck level.

[Tetepare]

You can't hang laundry on tube. That's what lifelines are truly for.

[newhaul]

Originally Posted by NevisDog

Sure, but remember hull bends somewhere around the waterline level (depending on rigidity of keel/deck) whereas fixed rail is way above deck level so must endure proportionally greater bending. I've seen oil tankers rip their piping apart, just because the piping was raised above main deck level.

True but thin wall tubing will flex many times more than schedule 80 steel pipe will.
Also the pipe railing on them big cruise ships seem to do just fine.

[bailsout]

Don, as soon as I bought my Columbia 29 I removed the lifelines. I've done the same to my wooden H28 ketch. My first boat, a wooden 28' Kingscruiser never had them. I don't like 'em.

[Don C L]

Originally Posted by bailsout

Don, as soon as I bought my Columbia 29 I removed the lifelines. I've done the same to my wooden H28 ketch. My first boat, a wooden 28' Kingscruiser never had them. I don't like 'em.

Yes, my first boat did not have them either and I added them because I thought boats were supposed to have 'em, but I am not sure they made me any safer. In fact one could argue they offer a false sense of security. Also, the idea of falling on a stanchion has never appealed to me. Now if I have to have a railing, and I have to fall, I'd rather fall on the "T" of a rigid tubular railing rather than the T of a stanchion and lines... And yet.. there my lifelines sit... I am reticent to rip them off the boat...with kids on the boat I want all the lines I can get...
I can see that racers, who want less windage and don't want the hassle of working around the boat while clipped on with a harness, would prefer lifelines... at least you have something to grab on your way off the boat...
Now all here have me pondering other options... hybrids perhaps...

[Elie]

Originally Posted by Don C L

Secondly, after trying to help someone with adjusting a prop shaft a while back, I wondered aloud to mechanic, why don't they make prop shafts with u-joints so you don't have to be 4 feet tall with arms like Popeye to crawl back in there with a feeler gauge? (He didn't know) Or do they and I just haven't seen them yet?

I agree completly on this one. After trying unsucessfully to adjust for a couple of years the rigid coupling I resorted to install a CV joint system with a strong stainless steel bulkhead to absorbe the compression from the propeller. What a big difference!. It was a significant work, but since I simply forget all about this ridicule problem, and the ridicule engine compartment construction made for ourangoutangs arms and radiographics vision... These sailboat builders don't seems to care much of the future maintenance of their products. A CVJ eliminate all vibration, some noise, transmission bearings problems, and let the engine danse the diesel rumba as much as it likes. A joy!