I was going to order a few Bluebird BMS-380MAX, but did a little research to see if there is anything new since it came out. What I found was the 380MAX will overheat and melt itself or even catch fire. :scared:
Can anyone corroborate this on Footies, or is it just an airplane problem? I still have some concern because sometimes the sailwinch is loaded for a long time, like upwind beats on windy days, so I wouldn’t want a meltdown in my wood-hulled Footy.
The sail servo will not be highly loaded when winched in with a Stollery Power Lever.
An elastic boom return will also unload the servo.
A lanyard will prevent straining fully winched out.
I sailed today in solid 10 knots, gusting 15 with a balanced Unarig using a classic Tower Pro SG90/HXT900 sail servo with no problems, using a Power Lever.
I have not had any problems so far using the 380MG in my K2. I think the 380MG is an analog servo, so it works fine, and the digitals (like the 380MAX) have the problem.
My thoughts about the people reporting the meltdowns is that there is something (binding or inappropriate use of servo) causing an overload and the servo burns itself out. Putting in a new servo isn’t the cure; it just perpetuates the situation.
My Power Lever is a straight 40mm long 16 gauge ss wire with a normal servo throw and lots of adjustment potential on the rear boom with the Unarig.
Roger uses a 9 gm servo and a balanced swing rig.
Is there any information on the Power Lever, like a description of how it’s constructed, or how it’s rigged, adjusted and used? Roger used a loop of the wire for the sliding ring, but RustyNail uses just a straight piece. What’s the difference?
Tomo, I haven’t found any other information on the Power Lever other than the above annotated photo and drawings off the Bug plans sheet.
I tend to re-think, re-engineer and simplify so tried the straight arm solution without problems and no need for a jig. Sure beats making a long servo arm for simplicity alone.
I imagine that the curved front face of the loop that does the work is intended to assist the ring to slide.
I wanted the ring to be able to get as close to the servo shaft as possible - it has little leverage there but maximum torque and holding power.
It has to be past 90 degrees to the hull centre line to allow the ring to slide down. If the servo is located near the centre line of the hull the boom will be centred winched in and slightly out of centre winched out 60-odd degrees.
The ring on the above photo is a nylon washer- hole size not critical. In my application the kevlar line is not tied to the ring as Roger did, but is sheeted through it and tied off with a Stollery bowsie on the hull and the boom to get a 2 to 1 purchase. The bowsie is on the hull tie off rather than the boom to avoid tangles.
The bead is just an end stop and is retained on the Lever with a bent up (down to avoid tangling with the boom) wire end. The far end is bent down into the end hole for the small servo arm. A bicycle spoke serves as good material for the Lever - it needs to be strong enough not to bend too much, (but some bending might assist saving the nylon gears from stripping in a gust) but capable of making a tight bend around a nail for the long servo horn retaining screw and washer.
Appended is a full-size servo version showing the sheeting arrangement.
Let us know how your experiments work out.
When using the power lever, does it pull the sheet in a smooth, predictable way, like a regular arm winch, or does the boom jump when the ring slides in toward the servo horn or out to the bead?
found the rest of your boat Rusty, interested in your bow detail on the bottle? and how you achieve it.
nice rig BTW:)
good to see there is some NZL activity going on…interested in registering your boats?
edit…its ok rusty,found your videos,nice job btw…we should really work together promoting this class