Wednesday, March 07, 2007

The Repowering Project Day 13

Fort Pierce

Why is 13 an unlucky number?

This morning we finished off the second coat of bottom paint. It looks sharp, but the black color still looks strange to us.

While Libby painted, I fiddled with the gear shift control cable. I still don’t have it right.

After that, we decided to take a break. We drove to Vero to check our mail and to have a brunch at Panera Bread.

After lunch I decided that we would remount the Max Prop propeller. That’s where we ran into trouble. The propeller doesn’t fit onto the new propeller shaft.

Here’s the deal. The back end of the propeller shaft is tapered and then threaded, and a small hole is drilled through near the very end. The propeller hub is similarly tapered. One puts a key into the keyway on the shaft, then slides the hub over the shaft and the key. Then a special nut (part of the prop) screws onto the shaft and butts against the hub. Holes in the nut line up with the hole in the shaft. A small pin locks the nut into place.

In our case the hub would not slide far enough onto the shaft to let the nut screw down.

I called Fred at Max Prop support and described the problem. He said, “You can’t do that. The hub has to be fitted on to the taper before cutting the threads and before cutting off the end of the shaft.” He suggested turning the hub on a lathe to shave a thousandth of an inch or so from the tapered hole. I called Bud Taplin. Bud is the one who commissioned the shaft to be made. Bud said that it was supposed to be machined to the exact specs for a Max Prop. Bud suggested a simpler alternative -- machine some material from the forward end of the nut.

I called Fred back with Bud’s suggestion. He said that if we did that, the nut would be so deep in the hub that the pin could not reach the holes. He was right.

I asked the marina for the name of a machine shop. They said Turner Machine Shop on Orange Avenue. I drove over there with the hub and explained what I needed. They said that because the hub’s hole was tapered that it would be nearly impossible to do without having the shaft. They said that it would be easier to machine the shaft.

So I went back to Tarwathie and removed the shaft. Oh no! After all that work to put it in. Fortunately, I did not have to undo all my work. I unbolted the coupler from the engine, and removed the coupler from the shaft on the engine end. Then I removed the stuffing box. After that, Libby and I were able to go outside and pull the whole shaft off from the rear. Without the propeller hub on it cleared the rudder barely. It actually rubbed on the rudder the whole way out.

Tomorrow morning I’ll take the shaft and the hub and the nut and the pin over to the machine shop.

At the end of the day Bud called back with some more ideas. While talking he said that he realized that most customers buy a new prop with the new shaft, and that the shop can custom fit the hub to the shaft while still in the shop. That agrees with what Fred said about cutting the threads after fitting the hub.

Sigh. If there was ever a time when the saying “we got shafted” was appropriate, this is it. This will cost us a day. Now I’m worried about meeting our self imposed deadline for launching on Friday. Don't get me wrong thouth. I'm not mad at anybody. These things are terribly complex and technical. It’s easy to understand how a new circumstance, like buying a new shaft without a new prop, can cause a misstep.

In the software world we always assume that when doing complicated things that we will have to make several attempts and testing cycles before everything can be expected to work. Indeed, it would be foolish to expect it to work right on the first test. This time we are dealing with hardware, not software. Can we expect everything to work first time without retries or prior fit tests?

I also bought a set of metric wrenches today. I found that none of my wrenches work on the new Beta engine from England. Of course, I’ll have to keep the old wrenches too for everything else on the boat.

Repowering day 14

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