Question for engineering types...

Ed hit my opinion on the head. I think over time that style of turnbuckle will not react the way you want. The pressure, heat, cold and "step" purpose you are going to use it for will make it work loose. Have you seen you seen many "rope" turnbuckles being used on boats? I haven’t. Look closely at Craig’s pic. Those connections are static, they are not held by a coupler that moves like the Key in your pic. That component alone will add a lot more movement and friction possibly leading to fail.

Sure you idea could and might work, and not being an engineer I cant without a doubt say what will happen. My proposal was pilfer the huge amounts of trashed boats for something that has been engineered and tested for trim tabs – and at a cheap cost. I can go to the place local and see what they have if you want. Let me know.
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Derek,

I'm not an engineer either, that is why I was asking for input form folks like Scott and John who are. That is the beauty of this place created by Eric.

T
 
First of all I want to tell you that I admire your diagram as a sort of neo-Harkeresque variation but I would have thought that, as Lee suggested, you might have personalized it with an Osier-like representation...something that would allow us as viewers, to view the situation virtually thru the eyes of the poster. Whenever I see a Harker stick figure post, I stop reading, go up in the kitchen and get a big saucepan to wear while I finish reading the post...maybe its just personal preference, I don't know.

Anyway, I am an engineer too and a lazy one at that. I agree with Mr. Z that hydraulic pressure all by itself is a mean and relentless thing that is always trying to break your stuff. Add to that, the changing angles and intensity of that exerted force (like a turning and accelerating/deaccelerating boat with a trim tab dangling in the water) and you get the gist behind the design of that trim tab assembly. By the way, those pictures above really illustrated the problem well...and maybe the solution too. You can see that those components are designed precisely to support that tab...theres obviously not going to be a hell of alot of "rattle" and they are also made of the correct material with the correct backing plates and fasteners etc.

So back to me being lazy...why not just find a junked boat and scavenge all of the necessary pieces...there would still be the challenge of modifying them to fit "just right" but at least you would have started a little closer to the bullseye with maybe a little better chance of avoiding a hosed up condition on opening day, when you want to go hunting and not swimming.

Just my humble two cents...(and remember what I said about the Osier stick figure thing...I really think it will enhance the overall experience)
 
Stick figures on the DHBP are my intellectual property. I charge a quarter to anyone wanting to use them and it is payable to Sutton for site support. There, that being said...a boat boneyard might be a good place to spend a few hours. I think right now with metal being precious...that a bunch of these are probably immediately hacked off and sold as scrap.
 
Scott,

I like the lazy engineer statement...;-).....Well....me too. I have to say I was a little bored yesterday and started to make a layout then thought I'd run it though Cosmos....But the fluid dynamics threw me so I deleted the whole thing and went to lunch! Besides Craigs photos show it clearly and Tod, all the parts are available on line. If Craig went an measured the thread on his turn buckle I wouldn't be surprised if they weren't 1/2-13 threads which I believe I mentioned...BTW, I see the pontoon is forsale. Are you building something else?

Ed L.
 
on Ebay to the ones for "large gas boat" are for a large gas model boat as in remote controlled model boat. Come to think of it maybe Ed can use these on the boat he brought to the Lacrosse gathering. What about it Ed, any porpoising problems?
 
Hehehe....porpoising isn't a problem. Lack of capacity is holding me back though!
 
for now anyway, unless I build one of those little blind/boats in the new Wildfowl magazine...just for fun.

I am just "rotating my stock" so to speak. I have as much fun building or refitting duck hunting stuff and painting E. Allens anymore as I do actually going out and sitting in ice water up to my butt. Maybe once I sell it and replenish my stash of duck related funds, I'll see something that catches my eye

Sorry about the model parts too...I wasn't reading the whole things. Like I said...I'm lazy; I read the headlines, I look at the pictures

;-)
 
Ed If porpoising becomes a problem. You can always put a marble in the bow. Duck tape it down so it doesn't roll around. hee hee

Any boat that I had if you put enough weight in the back it will porpoise. I always solved it by adjusting the weight forward. Either a bigger anchor or moving the gas can. Decoys and a dog help.
 
I am an engineer, but my answers like everyone elses is just opinion. and you know opinions are like .......

The answer to your original question about the mounting part is: "pivot bracket" or "clevis bracket". I did a quick search on McMaster Carr and didn't see them listed, but I'm sure they sell them, you just need to figure out what they call them.

Addressing the concerns others have voiced:
  • Ed is right you should up size your components to 3/8" - 1/2"
  • Don't be concerned about the force pushing on the turnbuckle instead of pulling on it like a cable would. When you pull on the turnbuckle the components are in tension, and when you push on it the components are in tension which means a buckling becomes a concern. however if you use large enough components the buckling concern should be minimized.
  • Instead of buying a turnbuckle you can buy 2 clevises and a "connecting rod" of proper length. That will give you a setup that nearly matches the pics.
  • Use jam nuts to lock the components in place. This will eliminate concerns from vibration.
I like the idea of doing it yourself. That way you get exactly what you want for your application.
 
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