Slow speed wander

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oldtimer
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Slow speed wander

Post by oldtimer » Sun Jul 23, 2017 10:29 pm

Hi guys. I have a 36' Tricabin, 1974, 280hp Chryslers. It's a great boat in all regards except one. We have to travel a few miles up a narrow channel to get out to open water. It's speed restricted and we usually travel along at 1600/1700 rpm which gives us a 7.kt cruise speed. At this speed it's like steering a barge, wander left, correct; then wander right and correct again. It's a constant battle with the wheel and we must be leaving a wake like a snake. Can't speed up anymore due to wake control. Has anyone tried running at this speed with trim tabs down, or even one tab down to create a drag to minimize the wander. Any other Tricabin owners experience this condition, any advice passed on would be helpful. Hull is clean & props are good, and at 1950 rpm she cruises along @ 8kts as shown on GPS. Steering is tight and the proper offsets are in place. Thank you.
1974 Trojan Tri Cabin

rickalan35
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Re: Slow speed wander

Post by rickalan35 » Mon Jul 24, 2017 8:43 am

I had a 1974 TriCabin for sixteen years. It had different engines. Sold it three years ago.

One thing that comes to mind is that one engine may be reading the same rpm at just above idle, but in actuality be slightly different.

Secondly, the trim tabs may indeed both indicate (via you pushing the trim tab buttons for several seconds) that both tabs are equally up, yet one may be actually slightly lower than the other.

Difficult to believe that the rudders wouldn't be matched up, but that could be another cause. All I can think of here is the possibility of a bent rudder (because the rudders are indeed the lowest part of your boat.)

Great boat though, solid fiberglass and great hull design. Our tricabins are usually undervalued and under respected, even by other Trojan owners. No boat was essentially designed to still be alive after 43 years - yet here you are.

Good luck, Oldtimer.

Rick
Trojan 1994 370 Express, 502 Bluewaters

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prowlersfish
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Re: Slow speed wander

Post by prowlersfish » Mon Jul 24, 2017 1:00 pm

Look for play in the steering , rudder damage . And check the rudder alignment . The Rudders should be toed in at the front no toe or toe out can cause a wander .
TROJAN F36 Conv.
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captainmaniac
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Re: Slow speed wander

Post by captainmaniac » Mon Jul 24, 2017 2:30 pm

Would also give a +1 on confirming the engines are really in synch. If one is pushing harder you will be constantly fighting it.

If you don't have an engine synch gauge, listen for a 'droning' sound - if you hear it that's a harmonic difference between the engines, telling you one is running faster.

Also you could test things out in your slip by putting a separate tach on each engine, idling up until the dash tach shows your typical rpm, and seeing what the external tach says is really going on. If far enough off, you may need to calibrate the tachs on the dash. Also note that getting them calibrated at a single rpm doesn't mean they will be fully calibrated for all rpms.... ideally you should calibrate at the rpm range you normally run in, and figure out and log or remember what the calibration error is at other common rpms.

oldtimer
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Re: Slow speed wander

Post by oldtimer » Mon Jul 24, 2017 4:05 pm

Thanks for your replies guys. It's possible that Rikalan has a solution with the tabs, that one is down further than the other when in the fully up position. I will try and play with light taps on each tab next time out to see if things improve. Capt I believe the engines are in synch, I do have a digital synchronizer on dash, showing rpm of each engine, and when they are both in synch. Prowlerfish, the rudders were set up a few years ago to the specs in my owners manual with a friend of mine. Admittedly they could be out due to wear and tear. And the steering system as you know is by the chain, shaft, and steering box (that always looks like it came out of an old pickup prior to the power steering era). I wont be going out again for a few weeks due to other commitments, but will keep following the thread and will post when I go out again. Thanks guys.
1974 Trojan Tri Cabin

mikeandanne
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Re: Slow speed wander

Post by mikeandanne » Mon Jul 24, 2017 6:41 pm

I fought the same thing with the f32 ,darn small rudders ( they are referred to as high speed rudders,lol ) and with mine there was a fair bit of play in the components, it got better after getting the play out and tightening the rudder packing.One question, is it worse going downstream with the current than returning??
78 F 32

oldtimer
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Re: Slow speed wander

Post by oldtimer » Thu Jul 27, 2017 11:03 am

Hi Mikeandanne, seems to be the same coming or going. Only thing different is with a following sea, and like all semi planing hulls it take a lot of wheel work to hold a straight course if you cant get up to speed. That I can live with. As I said in my reply above, I will be going back out the channel in about another week or so, and will double check out everything the guys above brought to my attention. A friend of mine, not related to the Trojan net, mentioned a phenomenon about water pressure feedback related to boats traveling in shallow water. The area I am running in is about 6' only, and less in some areas. It could be a possibility, I dont know. Will have to read up on this one. Thank you for your feedback.

Oldtimer
1974 Trojan Tri Cabin

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WayWeGo
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Re: Slow speed wander

Post by WayWeGo » Thu Jul 27, 2017 6:02 pm

Our F36 Convertible doesn't wander at all unless there is a following sea. I think Paul is on the right track -- look at the rudder alignment and slop in the steering. I doubt it is engine speed unless the RPMs won't stay constant.

Our last boat was a single stern drive. Talk about wander -- if you looked away, the boat would be 30 degrees off course in a moment. :roll:
1975 F-36 Convertible
Twin Chrysler 440's

oil&water
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Re: Slow speed wander

Post by oil&water » Fri Jul 28, 2017 9:58 pm

Both my prior 32' Chris Craft and my neighbor's F32 will wander when coming off plane due to water pressure. There is also a decent amount of wander on the F32 if you don't tweak the throttle just right. Those small rudders aren't much for steering at low speed.
1980 Trojan F32 / 323 (sans lower helm - wet bar in its place)
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WayWeGo
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Re: Slow speed wander

Post by WayWeGo » Sat Jul 29, 2017 1:50 pm

At 7 knots, you are almost at hull speed and perhaps starting to generate some lift. That could be complicated by the squat effect if you are in shallow water which would tend to pull the boat down.

Also, if you are near the bank, it will tend to push the bow away from the bank and pull the stern towards it.

If you can't find any problems with the steering, it might be worth it to slow down to 6 knots and see if that helps.
1975 F-36 Convertible
Twin Chrysler 440's

oldtimer
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Re: Slow speed wander

Post by oldtimer » Fri Aug 04, 2017 9:56 pm

Hi Guys, I was back to my boat for a few days this past week. I did go and recheck a few things that were mentioned above. First off, I checked the alignment of the rudders with a straight edge and a large square. Both the rudder quadrant arms are toed in between 1 1/2' to 1 3/4" so this is almost as per spec in my owners manual. Both engines are in sync, and run at idle smoothly. The only thing I have found so far was a difference in my tabs. When both are in he full up position, the starboard tab is about 1 1/2 in higher than Port side. I measured this by using a pc of dowel resting on top of each tab, marked at swim step level in the fully down position. Then raising to full up and marking down travel. I suspect that the Port tab may be 1 1/2" down and dragging in the full up position. I tried working the tabs on my last trip, but being summertime, boat traffic was a little heavy. (Imagine everyone in a hurry coming and going) But I will check next trip out in better conditions. My tabs are InstaTrims, and I believe there is some adjustment at the bottom of the cylinders to the tabs. Also speed over bottom in shallow water also may contribute. I will try a slower rpm to see if it makes a difference. Thanks everyone for your ideas, gave me some options to still try out.

Oldtimer
1974 Trojan Tri Cabin

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prowlersfish
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Re: Slow speed wander

Post by prowlersfish » Sat Aug 05, 2017 6:40 am

The rudder alignment still needs to be checked . The arms maybe in spec but don't assume the rudders are . I have seen he arms in spec and the rudders off . arm alignment won't cause wander , rudder alignment will . Did you check for play in the linkage ?
TROJAN F36 Conv.
6BTA Cummins diesels
Life is to short for a ugly boat :D
2009 TROJAN RENDEZVOUS
Port Kinsale 2010 & 2011. Solomons get together 2011.

mikeandanne
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Re: Slow speed wander

Post by mikeandanne » Sat Aug 05, 2017 8:50 am

prowlersfish wrote:The rudder alignment still needs to be checked . The arms maybe in spec but don't assume the rudders are . I have seen he arms in spec and the rudders off . arm alignment won't cause wander , rudder alignment will . Did you check for play in the linkage ?
+1

To add.IMO , one tab down a bit may cause the boat to pull one way ,but you would only correct one way and you said you steer one way then steer the other which would be overcorrection.Not sure what is causing that, but one engine or one tab would be one direction only I would think.Do you have a completely mechanical steering ( no hydraulics )?
Mike
78 F 32

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jimbo36
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Re: Slow speed wander

Post by jimbo36 » Sat Aug 05, 2017 9:21 am

As mentioned above, did you check for ANY steering play? Takes two people, one at the rudder posts and one at the helm,..and some shouting,..

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