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Toe-in or out on the hard link?

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Initially Posted - 07/03/2007 : 10:51:39

I'm almost finished with my hard link. Thanks to Steve & everyone else for blazing the trail. I don't know if you'd call it 3rd generation, but hopefully I've learned from your mistakes & end up with a reliable system.

My question is, are you setting any "toe-in" when you calculate the distance between the rudder & engine so as to counteract the asymmetric thrust from the prop? Has anyone bothered with this, and if so can you tell me how you did your calculation? This is the last thing I need to do, the rest of the rig is built. I deliberately made the connecting bar in two pieces so I can adjust for this, but it's a one time adjustment (or I drill another two holes).

It would seem like you'd want the rudder & prop to be slightly crow-footed (further apart at the aft than at the fore) so the prop would push the stern slightly to port which should slew the bow to starboard, counteracting the offset when the rudder is amidships.

Thoughts? Or is this over-engineering it (which I know I'm prone to).

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

Edited by - on

Steve Blackburn
Master Marine Consultant

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Canada
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Response Posted - 07/03/2007 : 13:03:42

David, Yes I did do a slight adjustment for the "toe-in". However I only eyed it. I don't feel any pulling on either side under power. In any case the rudder would compensate and you wouldn't feel anything even if perfectly parallel. What you loose is a bit of power efficiency, but the % should be very small.

What you can do is to run unlinked and get the boat to go full straight without touching the tiller (just by the engine). Then mark it off on your link and connect them.

Please send pictures when you can. Last weekend I broke my rod that connects engine and rudder (stupid mistake). So I had to go back to the old school of doing things, man did I ever hate it! You'll love your link.

Edited by - Steve Blackburn on 07/03/2007 13:06:31

delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 07/03/2007 : 14:08:04

Steve,
I'll take pictures tonight so I can post them. The problem with taking the boat out & testing is that it's not in the water, and the next time I put it in the water, I have to manage to get it into it's new slip. Here's a [url="http://maps.google.com/maps/ms?ie=UTF8&t=k&om=1&hl=en&msa=0&msid=113410289865331465424.000001136417780cb2a5c&z=19"]link[/url] to what I'm up against. The river flows north in this picture, trying to push me into the 40' Formosa. I've only got about six feet of clearance between him & me, so I expect the first few times to be exciting. The mid-ship cleats I ordered to make it easier should arrive today or Thursday.

I made my connecting rods out of 3/4" box aluminum with 1/2" bronze sleeves for a 1/2" SS clevis pin. I've got the sleeves epoxied in place and plan on expoxying a 5/8" wooden dowel inside each of the rods (they stack on top of each other) for additional strength. Once I have the measurement figured out, I'll drill oversize holes in the box beams, fill with epoxy putty, and redrill for the 1/4-20 bolts that'll hold it together.

My turning point attachments to the rudder & engine are very similar to yours, I just used 1/2" bronze bearing sleeves & SS clevis pins instead of bolts, and expoxied them (the bearings) to a piece of 1/8" aluminum L bar like yours. Looking at yours, it looked like the aluminum would wear on the SS bolt threads and I wanted to avoid having to do this again.

The clevis pins are just long enough to get a keeper pin in the upper & lower retaining holes while they're in the bearings, so (presuming I've got the keepers tied off) I'll be able to insert the clevis pin while it's still tethered at the top, push it most of the way in, insert a second keeper pin (I bought a spare), pull the upper keeper & push the clevis home. A bit complex, but I wanted to be able to handle the pins in gloves, so I made everything oversized.

Edited by - delliottg on 07/03/2007 14:20:33

Steve Blackburn
Master Marine Consultant

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1091 Posts

Response Posted - 07/03/2007 : 21:05:32

David,

You are right that my aluminium will wear on the SS bolt threads. I will change this someday, but a link is better than no link at all. I think you will be able to back into your slip, or back out of it pretty easily with the engine at idle and go real slow.

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 07/04/2007 : 14:41:08

Here are some pictures:

The as-yet-unbolted link arm:

The stacked arrangement was a happy discovery. Even with a HDPE wedge between the engine cowling and the aluminum angle attachment to better align them, the wooden link arm I made my measurements with would try to pivot out of the rudder attachment when I went all the way to starboard (port turn). The wedge is sort of visible in the engine attachment picture below. In order to make an adjustable arm to get the best angle, I stacked two pieces of scrap wood together and clamped them. The fact that the pivot out was nearly eliminated was pure serendipity.

The rudder attachment:

The engine attachment:

The link arm attached:

All the way to port (starboard turn):

This misses geometric lock (I love that term) by maybe 10° or less. I deliberately shortened up the throw on the link arm so that when you're all the way to starboard (next picture), the tiller won't quite touch the catbird seat upright. There was no way to easily prevent this when all the way to port because you nearly completely lose the strength of triangle as the link arm, engine & rudder attachments approach 180°. However, even with the tiller all the way to port, it still won't go into lock, there's still a bit of an angle.

All the way to starboard (port turn):

In the upper left of the photo, notice the 3" or so gap between the tiller & the catbird seat upright. This was deliberate. I lose a tiny bit of turning ability, but I don't whack either my tiller or engine against stops either.

I'll take some more after I've epoxied & bolted up the link arm. I've made it so when it's not attached, it folds back onto the rear of the engine and is held in place with one of the keeper pins. I had to shorten up the upper bar to accommodate opening the cowl on the engine, but I think this will be OK. The link arm is a bit shorter now than when I took the pictures.

Edited by - on

Steve Blackburn
Master Marine Consultant

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1091 Posts

Response Posted - 07/04/2007 : 22:18:54

Very nice. I guess those red clamps are temporary? So you say you expoxied those pins and bronze sleeves. I don't know much about expoying alumimum with other materials, how is it?

I'm eager to hear your report after using this for real. I bet you will have the same conclusion that I did and will never want to go back.

I think the Formosa has it worse than you. Does he have to backup the whole way?

Edited by - Steve Blackburn on 07/04/2007 22:21:05

delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 07/04/2007 : 23:25:50

I epoxyied the bronze to the aluminum, the SS clevis pins are free to move inside the bronze bearings, they're designed to slip right out when you don't want to use the link. I have no idea how well the epoxy bond will work between dissimilar metals. I chose bronze, aluminum & stainless because they're all good marine materials (just ask Randy...). But I don't have experience with bonding them, we'll see how it goes. The epoxy is there to keep everything together, but if the bond fails, there's still metal encircling metal, so they'll stay in place.

Yes, the clamps are temporary, I just used them to get the distance right with easy adjustment till I was happy. I've got the link arm pieces (which were clamped together in the photos) with their reinforcing dowels in them standing upright while the epoxy filling the voids sets. Tomorrow I'll drill oversize holes in them where the bolts will go, fill with epoxy putty, then drill 1/4" holes for the bolts that hold them together when that's set.

As far as the Formosa, the manager of the marina says he backs all the way down the fairway on the way out. One of my best friends is in the marina immediately next door, and watched him go out and come back last weekend, says he's pretty good at it, and does it alone, which is impressive. I'm looking forward to meeting him, he sounds like quite the seaman.

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Nautiduck
Master Marine Consultant

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Response Posted - 07/05/2007 : 11:25:26

It's a kick watching the evolution of the link starting from Arlyn's classic soft-link design and then the hard link spinoffs. Some major advances in the past few months from Steve, Paul and David including a movement to all marine components and some excellent building techniques. The idea of the clamps for working out the measurements is very clever. Good work all!

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Steve Blackburn
Master Marine Consultant

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Response Posted - 07/05/2007 : 22:55:35

David,

If you ask Randy, he's not very partial to anything but stainless. Randy keeps pimping up his ride with stainless. The boat will probably be too heavy to do anything else, but man will it ever look good! LOL.

But seriously, I really like the clevis pin idea. I think a good move would be one of those stainless quick disconnect ball joints I posted a while back.

Keep pimpin up y'all.

Edited by - Steve Blackburn on 07/05/2007 22:59:22

Steve Blackburn
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Response Posted - 07/10/2007 : 15:56:26

David, you tried it yet?

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delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 07/10/2007 : 16:20:23

Not yet, we're planning on putting the boat in the water on Sunday. We still don't have the name on the side of the boat, but it's been ordered, and the sign shop says they'll have it by Friday. Rita's been researching the proper de-naming ceremony so we can properly christen her on the weekend.

I did manage to get the link painted a nice shade of blue. I keep telling myself it was to provide UV protection for the epoxy, but in truth, I like the color. I'll post a picture tonight.

We still need to get the mast back down in it's trailering position, straighten the VHF antenna (caught on some branches on the way up the drive, it's got about a 20° bend right now). And sundry other stuff. I want to get some caulk into the hardware I discovered unbedded over the weekend when installing my mid-ship's cleats. Then in the fall do it properly with oversized epoxy holes & drill through.

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Nautiduck
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Response Posted - 07/10/2007 : 22:13:30

Whatever happened to the fellow with the EZ-Link setup? He was going to post his experiences after sailing for a couple of weeks.

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delliottg
Former Mainsheet C250 Tech Editor

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Response Posted - 07/10/2007 : 22:55:45

Here's a few pictures of the finished product:

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Steve Blackburn
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Response Posted - 07/11/2007 : 19:52:12

Nice! You can definetly call that version 3!

David can you post a close up picture of the way you attached the link to the motor with a hitch pin? That's your version of a quick disconnect I imagine.

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delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 07/12/2007 : 09:16:21

Actually Steve, it's attached to the engine with two 1/4-20 bolts, using an existing set of holes for the rubber bumpers (you can see the right side bumper in several of the pictures). To remove it, I pull the 1/2" SS pin. The retaining pin on the engine attachment is there as a combo spare and retainer. When I'm not using the link it can be folded back across the back of the engine. I suspect that it'll rattle & drive me nuts so I'll probably take the whole thing off & store it in one of the lockers when I'm not using it.

The two 1/2" SS pins are through bronze bushings in both ends of the link arm & the two attachment points (rudder & engine).

I like the fact that I can remove all vestiges of the hard link and there will be no evidence that it was ever there. I didn't have to drill any holes into my boat or engine, I was able to use all existing stuff.

Edited by - on

Steve Blackburn
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Response Posted - 07/12/2007 : 18:59:40

David, your link will not rattle when under sail.

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delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 07/16/2007 : 13:33:56

So here's the report. The hard link performed admirably over the course of the day yesterday. Allowing me pretty good control over the boat even when going in reverse.

After an afternoon of puttering around on Elliott bay off of Seattle, we headed to our new marina. I headed down the fairway at dead slow, with the engine simply idling in forward. We managed to snag the cleat at the end of my dock with little fuss, and with the rudder attached to the engine, it was easy to maneuver the boat around on it's mid-ship's cleat. We made several quick in and out trips to test our docking & backing proficiency, especially since we'd passed the Formosa 40 on it's way out, and had plenty of room to work with.

Backing down the fairway takes concentration as the boat handles completely differently than you expect, plus it turns oppositely of when you're going forward. You basically have to learn to point the back of the rudder in the direction you want to go. We backed it all the way down the fairway and out into the river, then oozed back down to the slip again to do another tie up. Backing is tricky with the link, if you let your attention waver, the torque of the engine will decide where the boat's going and quickly take you there. I learned that if the tiller got more than maybe 10° away from centered up, the torque would snap the tiller to that side, so you have to keep an eye (and hand) on it.

As far as the docking goes we want to make up one of the plastic hose covered lines like Randy's to make snagging the cleat easier. I swung a bit wide on my third approach, and it was only the presence of my friend on the bow keeping us from hitting the dock, Rita simply couldn't reach far enough to get the line over the cleat, even with a boat hook. This was my fault, and I'm glad the Formosa wasn't there, as we'd have been fending off. But it was a really long day, I'd been up since 0430 & it was approaching 2230 when we were doing this, so I don't feel too bad about missing one approach.

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Steve Blackburn
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Response Posted - 07/16/2007 : 23:34:59

David,

Glad to hear about it. When backing up I only go idle (or close to it), that's probably why I don't feel the torque you are talking about? I love backing up my boat with the link, it almost feels like driving a car where the back end just follows through.

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