Large Centerboard Dilemma

[rrayfield]

I am currently refurbishing a classic 1969 bill Tripp custom 60. it has a draft of 6.5 feet and 14 feet or so with the main stainless board down. it also has a smaller bronze board aft of mizzen extending 3 feet.

the aft board is mechanical, with a winch. the forward and larger board is lifted with an electric motor and backup winch with a worm gear. the motor and worm gear are fixed to the top of the truck.

my dilemma is knowing when the board is up or down. there is no indicator that tells me what position it's in. how or what would I add to let me know if it up or down? almost like a magnetic rotation counter on the motor like a chain counter or something? throw out some ideas, I'm all ears

thanks
Ryan

[rrayfield]

here is a photo, motor on left, manual drive for handle at top and worm gear mounted and sealed atop the trunk.. the truck top is about 4 feet forward of the pin. the loaded waterline will be just under or in the worm gear. it's all sealed and bolted with at least 50 bolts. before the owner would just guess it was fully extended after counting the time to lower it at the yard, when raising it he would just hit the switch untill the breaker popped on the panel... Not the way I want to approach it. some sort of calibrated counter is the way I would like to go.... I think...

[GILow]

I feel like some kind of morse cable arrangement would be nice. Morse cable is pushed by movement of board and moves a simple dial or indicator lever. Of course not so good if there is a LOT of movement of the board, morse cables are only good for short throws.

Maybe a small line with counter weight, a bit like the simple gauge used to indicate water level in a rainwater tank. Counter weight travels up and down inside either a transparent pipe (to stop it slapping around at sea) or cut a slot in a piece of PVC pipe and paint the counterweight a contrasting colour. Weight goes down as board goes up. Zero maintenance, very reliable and very cheap. Heck, an old fishing weight, some line, a block and some pipe. Probably got most of that on board in the spares... I know I have.

If you do decide to go electronic, a simple optocouple counter that passes an infrared beam through the chain links is a neat solution. I've used such a setup in the past to measure chain speed on a rowing ergo and it was surprisingly reliable. But, it worries me that it may become uncalibrated through a power outage or something, you'd need to "zero" it in the full up or down position should it lose its memory of the board location. I have had this problem of memory loss using picaxe chips on my solar tracking, and found the only solution was for the system to swing the panels to one end of their travel in the event of a cold powerup. This triggers a microswitch which both stops the travel and resets the position counter.

Don't like it though, if the microswitch fails the tracking motor will keep trying to move the panels. Had to add a timer on that code loop as a backup. But then, if the system is running slow due to resistance the timing loop can be too short, and you don't get a proper zero calibration.

Variable resistor on an arm is all very well, but even the best quality POTS tend to change resistance over time, particularly when surrounded by salty water.

Ahh... what I guess I am saying is I don't feel electronics are great for this situation, I'd go mechanical.

How much travel do you have to measure?

Edit: Oops, just worked out you said how much travel... but is it a swing board or slot board? Swing board would work easily with morse cable, not the slot sort though...

Matt

[rrayfield]

Matt,

thanks for the reply, I would definitely go for mechanical over electronic if I can. the only real problem is accessing the board from the top. the cable configuration would have to be drilled through the worm gear and attached to the board right? how about adding in another sprocket on the chain drive and have that move the cable? the chain is going to only turn so many rotations one way and the other.

one problem with the current setup is if you let the board down to long I could see where the cable would end with the board all the way down and start to respool in the other direction and come back up..

it is a swing board, I am guessing there is probably 3 feet if travel where the cable goes down

[GILow]

I like the idea of adding a drum to the chain sprocket and using that to wind in the weighted line. As long as you started with a few extra turns on the drum with the board in the fully down position I can see no problems with overshooting. Plus, and this is a big plus, by starting from the down position you can wind the small weight up in the tube as the board goes up which feels much more intuitive to me.


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[jimbunyard]

How many revolutions does the gear or shaft that rotates the least, and that you have access to, make to go between raised and lowered?

[Reefmagnet]

I've done some similar things in industrial environments in the past and would consider the following ideas. One involved a multi-turn potentiometer connected to a voltmeter using voltage dividing resistors to make the reading on the meter correspond to the position of the board e.g. 0 for fully up to 100 for down. A potentiometer can be mounted to the drive reasonably easily using various mounting options and can measure either a rotary or linear movement. Of course if the above description sounds like Chinese to you this might not be practical.

The other idea is to use proximity sensors placed to sense the up and down position of the board. Proximity sensors are non contact and will work in hostile environments meaning they could be rigged to sense the actual board pretty easily. These would only be able to be used to indicate the extreme positions of the board, but they could be wired into the drive arrangement to prevent "over-running" by deactivating the drive when the limits were reached. And proximity sensors are not that much more complex than switches to work with for those with limited electrical knowledge.

[barnakiel]

I would add a wire driven revolutions counter. You want one working both ways.

Say at all zeroes you will be fully up. Any number will indicate you are out. The actual number will indicate how far out.

The driving part can be contained in the manual drive/handle socket.

Cheers,
b.

[rrayfield]

Originally Posted by GILow

I like the idea of adding a drum to the chain sprocket and using that to wind in the weighted line. As long as you started with a few extra turns on the drum with the board in the fully down position I can see no problems with overshooting. Plus, and this is a big plus, by starting from the down position you can wind the small weight up in the tube as the board goes up which feels much more intuitive to me.


Sent from my iPhone using Cruisers Sailing Forum

Thanks for everyone's replies, I too am leaning towards fully mechanical with a spool attached to the worm gear sprocket. Like this Scubamax Stainless Steel Finger Spool Reel with Clip (Yellow, 100):Amazon:Sports & Outdoors


using a weight in a clear solid pipe mounted somewhere hopefully in view on the companion way. I'm not sure how many rotations there are yet. I know the smaller the spool the less the weight will travel. with is what I want.

[rrayfield]

Originally Posted by barnakiel

I would add a wire driven revolutions counter. You want one working both ways.

Say at all zeroes you will be fully up. Any number will indicate you are out. The actual number will indicate how far out.

The driving part can be contained in the manual drive/handle socket.

Cheers,
b.

could you provide a link to this product? could the counter ever be unsycronized?

I'd like a counter that I could mount somewhere.

[tankersteve]

The extended shaft with winding spindle is fairly elegant for a mechanical solution. I was wondering how much the chain moves during a lowering. If you could mark a link (paint?) and note its position when raised or lowered, that would serve your purpose. Not terribly elegant, but very simple. You probably would have to touch it up regularly.

Tankersteve

[barnakiel]

Revolution Counter | Products & Suppliers on GlobalSpec

Gives you an idea. Next thing you walk into your local hobby shop and see what they stock.

You can get an industrial grade too from local machinery suppliers. Beware very sound mechanical units cost money.

b.

[rrayfield]

Originally Posted by tankersteve

The extended shaft with winding spindle is fairly elegant for a mechanical solution. I was wondering how much the chain moves during a lowering. If you could mark a link (paint?) and note its position when raised or lowered, that would serve your purpose. Not terribly elegant, but very simple. You probably would have to touch it up regularly.

Tankersteve

it probably does somewhere in the area of 30 complete chain revolutions, so chain marks wouldn't work. unless you counted them going around. Remember, to get the torque need to raise this 2000 plus pound board it uses the worm drive. so the motor spins @ 60 rpm and the worm gear drive is about twice the size. I won't be able to test it again until I get my new switch wired up.

on that note. it has a 4 wire 32 volt motor... Anyone know how to hook that up to a 2 way momentary switch?

[GILow]

Now I have thought about it some more... I think there's a problem with my suggestion.

There's just going to be way too many revolutions of the spindle if it is driven by the sproket on the worm drive. It is going to haul in many meters of line, no matter how small the drum. So either you then have to add some small blocks to "gear down" the travel of the counter weight, or you are going to need the sight tube for the counter weight to be about 5 meters tall. (That's 15 feet for our non metric cousins.)

A block arrangement is just going to be a pain sooner or later..

So, after all that I am favouring the revolution counter suggest by Barnakiel, I'd prefer a mechanical one, to avoid the electronics problems. But, I am having problems finding one that rewinds. Plenty that reset, but that's just a pain, having to reset at the end of each action.

Hmmm... maybe an electronic counter after all, with a timer reset is not so silly. i.e. it always starts off at zero, you push the down button and it counts the revolutions till you know the board is fully down, you let go of the power button and the unit resets the counter to zero again, after say... 10 or 15 seconds. Then when you hit the up button, again you just watch the counter...?

Matt

[jimbunyard]

Maybe a homemade linear actuator consisting of a sprocket-driven threaded rod, mounted parallel to the worm gear in the centerboard winch, actuating an indicator at the helm via a Morse cable?

If you're handy with tools, you can do it yourself with off the shelf components, for probably less than 200.00 in parts and materials.

Simple and robust.