Pitch, for obsessives

[bigpuddles]

I have just gone through setting up a scull from scratch, and worked out a couple of tricks for people who a little obsessive about getting pitch just right. I am sure these are known about, but someone might find them useful.

For pitch and lateral pitch at the pin, I think that the digital levels are now much easier, and more accurate than bubble levels. You need a digital pipe level, which will have a groove that sits against the pin. The boat needs to be dead steady, otherwise the display will flicker between readings, and be useless. I tied one rigger onto the upright of a heavy bench press with bungee cord, which worked well.

The other trick gets you out of this problem: what do do if you end up with half a degree difference in pitch out at the blades, if you are sure that both pins are set accurately. You can get around this by using a mismatched pair of inserts for one gate. In other words, using a 7-1 and a 6-2 will give half a degree more pitch than a 6-2 and a 6-2. This is not recommended by Concept2! But it works. I have had this set-up for a month now, and it has'nt given a problem yet. If the inserts wear out, they are cheap to replace.

[KiwiCanuck]

(snip)
The other trick gets you out of this problem: what do do if you end up with half a degree difference in pitch out at the blades, if you are sure that both pins are set accurately. You can get around this by using a mismatched pair of inserts for one gate. In other words, using a 7-1 and a 6-2 will give half a degree more pitch than a 6-2 and a 6-2. This is not recommended by Concept2! But it works. I have had this set-up for a month now, and it has'nt given a problem yet. If the inserts wear out, they are cheap to replace.

Another solution is to carefully fix the pitch on the sleeve of the blade... This depends a little on how the manufacturer defines "zero" pitch, but for Croker it's straightforward. Place the blade, tip down on a level. The shaft needs to be perpendicular to the level, and the level is placed 60 mm away from a peg/vertical pin, which is in line with the shaft. (that ensures that the level is aligned where Croker defines their blade pitch - 60 mm from the tip of the blade along the projection from the shaft, and perpendicular to the shaft). Place a level on the sleeve. carefully file or scrape down the high side.

Howard Croker suggested to me that if it's more than 1/2 degree off, replace the sleeve.
Then you're not monkeying around with mixing and matching pitch inserts, your blades are zero pitched..
Cheers,
WM

[bigpuddles]

Yes, sure, you can file down the sleeve, and screw up the way the sleeve sits in the gate. Or, you can change the gate inserts. The point I am making is that the inserts don't just allow one degree increment changes, you can also quite easily make half degree increment changes. Your choice.

[SwagRowerYOLO]

Yes, sure, you can file down the sleeve, and screw up the way the sleeve sits in the gate. Or, you can change the gate inserts. The point I am making is that the inserts don't just allow one degree increment changes, you can also quite easily make half degree increment changes. Your choice.

To get the gate back onto the pin with mismatching inserts, you must have to force something.

Assuming your pin is straight, you're putting two inserts that don't line up onto it. I reckon your half degree is in either in your head or in your pitchmeter.

[bigpuddles]

Honestly, I don't think so. I think it is pretty accurate. If the gate explodes or the sky falls in, I'll let you know. However, as the inserts are soft(ish) plastic, and the pin is a bloody great piece of steel, I suspect that the inserts will just deform a bit and deal with the slight misalignment.

[SwagRowerYOLO]

Honestly, I don't think so. I think it is pretty accurate. If the gate explodes or the sky falls in, I'll let you know. However, as the inserts are soft(ish) plastic, and the pin is a bloody great piece of steel, I suspect that the inserts will just deform a bit and deal with the slight misalignment.

That's sort of my point if you're into correcting half degree imbalances, doing it by mashing the edges off inserts is probably not the best way.

[BitchinCamaro]

Honestly, I don't think so. I think it is pretty accurate. If the gate explodes or the sky falls in, I'll let you know. However, as the inserts are soft(ish) plastic, and the pin is a bloody great piece of steel, I suspect that the inserts will just deform a bit and deal with the slight misalignment.

That's sort of my point if you're into correcting half degree imbalances, doing it by mashing the edges off inserts is probably not the best way.

You'll be wearing down the corners of the bushings and greatly lessening their useful life since they are designed to sit evenly on the pin. You're going to end up with a sloppy oarlock pretty quickly.
As was suggested earlier, any discrepancy between the blade and the oarlock must be in the oar itself (assuming you are measuring correctly), I've always corrected this on the oar, this would be especially true in any club situation where oars and boats are often interchangeable.

[KiwiCanuck]

Yes, sure, you can file down the sleeve, and screw up the way the sleeve sits in the gate.

Did you miss the bit about if it's more than 1/2 degree off, replace the sleeve? Or send it back to the manufacturer and have them fix it.

I have, in the past, used two "5/3" inserts facing the same way to render a "net" 4 degree gate, but it did require a bit of force and ruined the inserts (yes, they're sacrificial parts).

How about "if you can feel this much difference, we're glad you're that skilled and sensitive - could you stop fussing over little things, and push on the foot stretcher"

It's more important that the pitch be the same on both blades in the water, less important how they sit in the gate unless it's a long way off.

[bigpuddles]

Hi KiwiCanuck

I guess we have exhausted this topic! Yes, I agree, there are quite a few ways of going about things. I mentioned it as a quick and accurate fix to make a small adjustment, but it does seem counter-intuitive in engineering terms. So far, the only odd squeaks and groans are coming from me, not the gate, its working fine.