Swing Arm make over

[John Ebell]

I am in the process of bringing a couple old Ozmun hulls back to sailing condition for loaner boats for new people. As such I want to keep costs down and just get the things working again. One boat has original ozmun winch with a U shaped swing arm with eyes at the end. And it is working! That type of set up was mentioned briefly in the EC12 man. but there are also several other types mentioned in both manuals. The other boat has a broken ozmun winch and no swing arm. I have to get the ozmun winch working again and also create a swing arm. Given this boat is going to stay a swing arm winch (costs) what are peoples suggestions for a swing arm? I know there are some still out there. What works for people?

Thanks for your help!

[bigfoot55]

I have a 30 + year old original Probar after 20 years in mothballs still works well.
Tom P

[Rick West]

I have always been an advocate of the swing arm sail unit for those that want a simple easily maintained system. The Ozmun Designs units has good resolution, are dependable and have plenty of power for the EC12.

The best arm I have seen is the one depicted in the EC12 Manual, as it compensates the sheeting rates of the jib and the main with added minor adjustments for tweaking your preferences.

Otherwise, a simple straight arm the width of the beam where it will be mounted will work just fine. You can see this set up on the building site in the Electronics section.

...94

[kahle67]

John,

Congrats on the top spot at the NOOD's. I had an Ozmun swing arm in my boat up 'till about seven years ago. I agree with Rick that this configuration is simple and easy to maintain and is perfect for those just getting in to the hobby. My Ozmun had problems striping gears. After sending it back to have the gear replaced and replacing the gears myself once after stripping it again, it has remained in the closet. It appears that the main gear axle is slightly out of alignment. If you would like to have it for parts to help get your down winch back up, you are welcome to it. Email me at kahle67@comcast.net.



Reichard Kahle
Charleston, SC

[John Ebell]

Wow what a class! It is so nice to have a question and get an immediate answer about something. Thanks! Reichard thanks much, I will email you seperately. This does bring up another question for Rick. I have looked in the EC 12 manuals and they both depict an offset type of swing arm. One offsets the main sheet the other offsets the jib sheet. I believe the one in the Optimizing the EC12 is the one that references off setting the jib. Since this manual is still a little dated, is this the latest and final tweek? Is this what you would reccommend Rick?

Thanks again for your help and input.

Best regards,

John Ebell # 1659

[s vernon]

John,

Take another look at the offsets in Manual and Optimizing. They are both effectively the same. In one case the main lags (Carr), and in the other case the jib leads (Wells). (Main sheet block on same side as main fairlead Carr / jib sheet block on opposite side from jib fairlead Wells.)

So they are just different ways of getting "main trim" which can be beneficial in heavy air. You get to sheet the main in and out a bit while the jib stays trimmed pretty much the same.

A recent AMYA magazine showed both (actual) setups on an Odom (I believe). Jib trim for light air and main trim for heavy air.

Scott

[Rick West]

Scott is correct but the questions is if one cares to go that far in crafting an arm. If you want to have the flexibility for all conditions and understand the needed trim complications, this is a good design. Most don't care to get into it that deep.

All of the national competitors use a drum winch and aside from sheet vanging don't complicate the sheeting more. There is some consideration to systems that require thought in use and judgements as to when. This meaning is that most of the time the conditions and maneuvering changes so rapidly that one could over think the situation and make the wrong decision on the water. In A fleet this is fatal.

It is rare in model racing to have the wonderful luxury of a long tack and tinker with trimming and main sheeting at close haul and the effects of sheet vanging. Most will develope reflexes to what we see and keep it a simple control input.

I once ask a good competitor how much jib trim did he have. His response was, "Only what I need."

...94

[John Ebell]

Gentlemen thank you! Rick is also very right about over complicating something if for the intended purpose it doesn't need to be. I think I will crank out a simple swing arm and try it out before I put a lot of time and effort into the offset one. However, now after Scott's input I might have to rethink the swing arm in my ODOM.
Thanks again,

John Ebell

[s vernon]

John,

I was looking at Windpower discussion group and noticed that you put a Hitec 815 (converted to 180 degree rotation) in an EC12. It will be interesting to see if this will work and if the servo will have a long life in a breeze. It is certainly a "different" way to go.

I doubt that you could find anyone who who would recommend it. By the way, the 815 is listed at about 160 oz in of torque while I recently found a paper copy of an old Larry Robinson webpage that listed the Ozmun W-12 proportional swing arm winch "with 180 oz. in. of stall torque."

Scott

[John Ebell]

Hi and thanks again for your info on the swing arm options. Regarding the Hitec 815, actually it is going in this http://www.robotzone.com/customer/produ ... =51&page=1 This is their servo gearbox. It gears down the servo to 5 to 1. I just received it and after assembly it still only gave me 140 degree throw. I needed 180 to make the swing arm work properly thats what my posting was about. I have since added the resistors and it works well. It is listed at over 1700 oz in of torque and feels much stronger than the old Ozmun that came with the boat. I was also concerned about the speed but it transits in under 2 seconds, just a little faster in fact than the Ozmun. Since I already had the 815 left over from my ODOM upgrade to the 5995 servo, it hopefully only cost me $50 to create a replacement swing arm winch. So I think the strength is there. I too am curious if it works. I will let you know. BTW I did get a reply from a guy with a Santa Barbera who said he tried this a couple years ago and he said his has been working flawlessly. I may try different gearsets in it, possibly reducing it to maybe 3 to 1 and see if the trade off in power is worth better trimming speed. I too think the RMG is the way to go but if you have to go cheap this might be a good option.

[Larry Ludwig]

Hi John,
I will be most interested to learn how this works out for you. I thought that this was going to be a very nifty alternative particularly for larger models that are not intending to be competitive. However, much to my dismay I have spoken with a guy that used this setup in a boat and his plight became obvious. He doubled the size of the arm to get the amount of sheet travel needed, and then put blocks on the arm's ends and doubled again. Unfortunately, what also was doubled was the torque requirements. He claimed he suffered gear failures and other problems from excessive loads. I would ask you to please keep us in the loop on how the system works out for you. I need to get one and test it myself, but just have not had the time, so I will be watching with keen interest for your evaluation.

Thanks
Larry