Shaft tubes done

Hi,

That looks like a very neat install.

I have to say when I only saw the first part of your post I was asking myself how that little bit of bearing sticking out could make any difference.

I would be curious to know the condition of the running gear, bearings, wheels, bottom coating prior to the stern tube installation.

Theses are the level of percentage improvements I typically see after after a thorough bottom job which usually includes work on the engine top ends as well.

Hard to believe that 3 feet or so of stern tube located aft of a flow-damaging strut could have any significant impact on performance.

Any clarifications would be appreciated.

It cost a lot of money, it has to work!

How do the bearings get water flow? That may cause the bearings to have premature wear- and in which case brings to mind- how do you change the bearings? Will that extra work at haul out time cost more than the fuel savings?

Why not use aero tubing? In formula cars the suspension components are all made from aero tubing as used on older airplane construction and there is a measurable effect on drag and top speed. In the water, (reynolds number?) the flow separation effects and drag values may be substantially improved. Aero shrouds can also be effectively used to improve flow around round tubing known to have non-optimized flow properties.

Subscribed.

I'd be interested in seeing what the inside of that tube looks like after a season of growth in the water where a where diver won't be able to clean regularly. Additionally, how the water holes hold up to (again) growth, potential plugging, and if flow to the bearings is thereby restricted over time and use.

What flavor boat is this being done to?

Does that mean the tubes are in effect a part of the hull? Like an extension of the shaft log?

If so then the water comes from the engine raw water circuit through the log under pressure and that small hole probably doesn't even need to be there since, if the tube is sealed at the hull end, all it does is reduce flow through the strut bearing.

Given that even a zinc on the shaft too close to the strut can wreck the flow to a bearing I am curious where the water to lube the aft strut bearing is going to come from on yours.

Interesting. The tube is going to have more resistance then the smaller diameter shaft, but it also is going have less resistance because the water can flow over the rear strut much more smoothly. I'm guessing it gets good waterflow through the front strut, and the small hole is additional and it is enough to cool the rear strut.

Striker enclosed the shafts in a housing all of the way back on a few sportfish if I remember correctly......but then they never caught on. I would think one tube all of the way would be even more efficient, but who knows.

This sounds like a Wall St. analyst call I was in on many years back, when that was my gig... "I expect that if traders view today's news as good prices will strike sharply upwards. If they don't, the market will shift down. If I'm wrong, we'll know quickly."

Actually, nothing of any substance should grow inside the tube. In order for growth you need waterflow or current, and sunlight. I don't see any sunlight getting inside of the tube and while the boat is sitting at the dock, the water inside the tube should be stagnant, so I don't feel growth would be a problem.

I ran a 58' Striker for a year or two while it was for sale and it had two seachests. The port seachest only had the engine and generator drawing off of it, and with the lid off you got sunlight in there coming up from underneath the boat. It grew NO barnacles. The starboard one had the starboard engine and generator, AND A/C pickup (never plumb the a/c pickup to a seachest), it grew barnacles like wildfire and in 2 months would look like a coral reef in there because it had sunlight and plenty of waterflow in the seachest. The port side, when you took the lid off, if the boat hadn't been run in a week or longer, the water inside was stagnant and rotton smelling.

Won't the shafts have to be pulled also?

Glad you are willing to be the test case.

It constantly amazes me that builders don't plan for maintenance that they KNOW will eventually have to be performed! Must be either a case "it's not my problem" or thikning it will generate future revenue, neither reason IMHO is sufficient justification.

Shaft tubes CAN be made removeable so cutlass bearing replacement doesn't require pulling the shafts. They can be split down the middle into two halves, and have grooves are machined into them that fit two-piece collars (much like a shaft zinc) to hold them together. These collars are then flush to the outside of the tube and don't cause any additional drag or turbulence. Pulling them off for bearing replacement AND inspection is a simple matter of loosening a few screws.

When you find it's time to cut them off, send them to a machine shop and have them modified and some collars made. It only costs about $750 per tube to do all the work (around here) which should quickly be recouped at the next bearing change.

By the way, she's a pretty boat!

Is there a update of how the performance has held up over time here? Thanks.