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Hitec HS 785 HB Sail Servo


Old 10-09-2013, 11:53 PM
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Default Hitec HS 785 HB Sail Servo

Hi guys
I recently got a new HS785 HB sail servo for a 1m sailboat.
The problem is that if there is any tension on the sheets it does not reach its end points.
It seems to run fine in the middle.
I've tried 4,8 and 6v packs with the same result.
I've also tried two different radio systems (Spektrum and Turnigy) and no difference.
Is this normal ?
Any help will be appreciated.
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Old 10-18-2013, 07:21 AM
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What make/model boat are we talking about? It would be helpful to have you post a few pictures of your boat including the servo installation. Is this original servo or did you install it? If so was the original sail servo a drum or standard arm style servo? There are some difference in the geometry involved when a change is made from one style to another.

Let's take a look at the performance specifications for this particular "winch" style servo. Here is a link to a data page from Servo City that provides those details.

This winch should produce 3.5 rotations according to the specifications. Suggest you confirm you are getting the full 3.5 rotations the specs call for as the first step. If you have a table fan you can simulate the wind and sail load using a fan. Make sure you have the boat secured so the fan's force doesn't knock the boat over on it's stand.
You can also check to see if your sheets (lines that control the sails) are the correct length to permit full extension and retraction. Do you have any tensioning devise to keep the sheets from becoming slack - which can result in the lines fouling inside the drum -

I will wait to here back once you determine if the winch actually rotating per specs.


Last edited by boomer1; 10-18-2013 at 07:24 AM.
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