Sticking hook release

[Davross]

Have just finished and test flown my Hot Avia Trio full house glider:
http://www.f3-modellbau.de/drupal/page_trio_en?PHPSESSID=aa4ebe08755d952c6a7628653b9 792b1

It's flying nicely, but has a nasty tendency on the winch; the hook wont come off properly on the ping.

Two of us have these, and both has experienced the same problem... nothing but the most aggressive of pings will make the line come off.

The hook provided with the kit is a cast item and its rather square in cross-section. It doesn't appear to have any burrs or excessive moulding marks, but nonetheless, it doesn't let that line go easily.

Does anyone have any suggestions for improving the release; dremel the hook to be more round perhaps, or seen similar problems as this related to hook position (both of us have our hook at about CG position, possibly slightly behind it)?

Thanks for any information in advance.

Kev

[Mark Miller]

I have used that same hook on many planes with out a problem. I am not sure what to suggest. They are CNC cut from aluminum stock.

Mark

[OVSS Boss]

A file might be called for, you can work them.

[Davross]

I have used that same hook on many planes with out a problem. I am not sure what to suggest. They are CNC cut from aluminum stock.

Mark

Do you have a Trio (I know you're the USA dealer for Hot Avia) and if so could you give me the position of your hook please.

We cut our hook slot with its centre on the recommended CG (given in post on this group) and 5mm adjustment fore and aft. We've tried the hook at both extremes and neither releases.

I agree, the hook is a quality item, albeit squarer than the usual bent wire arrangements. If it was on one model, I'd think it was a quirk... 2 identical problems suggests we've got something wrong in the set-up.

Kev

[jrgospod]

Kev,

You may want to skip the file and use very fine sandpaper (600g) followed with a rubbing compound to smooth out the surface. Then polish with a good hard wax and add a drop of WD40. In your case smoother may be better.

John

[rogerflies]

Is this the hook you're using? http://www.isthmusmodels.com/images/CNCHook.jpg

If so, try filing the hook so it's tapered top and bottom toward the aft end and has rounded edges. Removing this material won't affect the strength of the hook, which is limited by the cross-section under the front of the slot.

Roger

[mlee8249]

Kev,

The aluminum hook you are using is simply junk for two reasons. The shape is wrong, being squared off and the fact that it is aluminum. This is a soft metal and the ring will dig into the metal, making it stick. Switch to a hardened steel hook that has a round profile and this will cure the problem. Beleive me, I have been exactly where you are at, and I know what you are talking about. Change the hook and I can guarantee you it will not happen like this again. Even if you round off that hook you have, it will still stick..maybe not as often, but it will. I rounded mine, curved it, sanded it, and then it got too thin and snapped it. Change it out and be happier.

Mike Lee

[Mark Miller]

Gee...I have been using that same hook for years and sold about 100 of them so far. Never a problem with release, breaking or wear. It is a 7000 series hardened aluminum. What size ring are you using on the winch line?

Mark

[bobby legue]

Mark may have something there. One of my highstarts had a small 3/4 inch ring on it and I had lots of trouble with it, pop offs and wedging on the hook. I hammered the ring to an egg shape oval and it solved all problems.

[Mark Miller]

Kev,

I have flown Trios, Sopranos, Pipers, Duets and many other sailplanes of all construction types with the same hook. I like it's simplicity of install and adjustment. Can be used in a rounded fuselage using the inner plate with the curved side down or a flat bottomed fuselage with the inner plate flat side down. I have the inner part of the hook (where the ring pulls) just about on or slightly forward of the CG. The CG of the Trio is usually around 83 to 84 mm from the leading edge.

On the Trio it is a tight fit because the ballast tube is right above the tow hook plate. This is one of the lowest form factor hooks out there so you may not be able to fit something else in there.Also be careful not to use screws that are to long as they could push up into the ballast tube.

Is there tow ring free to slide back and forth on the hook? I have not seen a ring to large for this hook. This is not to say they are not out there but it's just a thought.

Mark

[Davross]

Thanks for all the input... shall do a little bit of filing and polishing, and check the ring on the winch tomorrow.

Slightly off topic, but any recommendations for flying the Trio Mark? Coupled rudder seems to be a must to coordinate the turns nicely (can normally do it manually). Useful hints for my first competition with it on Sunday please :)

Thanks
Kev

[Mark Miller]

Kev,

There is not to much unusual with the Trio. I do not couple the rudder but it is persoanl preference. Learn to fly with both hands is a good thing. Aileron differential is a good thing. Just fly it and have fun. It is a nice, reasonably priced full house plane that will launch well. I just got two in stock with the Soprano type tips. It adds a but more dihedral that will make it a bit more stable in the turns. If you have more questions please feel free to ask.

Mark

[mlee8249]

Hi Mark,

Please do not get me wrong, I am not making comment to insult or degrade the aluminum towhook. When I first saw one of them things, I thought they were the cat's meow. I fly competition and F3J, and so the planes take a lot of stress, along with everything else. Most of the time, we have no choice on the ring being used on the tow line when at a field where the host provides the winch or launch equipment. So, I have seen welded steel rings, cheap split rings, and even outer ball bearing races used for the towing ring. I used to think it may have been small size rings that were hanging me up, and then I thought maybe I'm not putting enough elevator into the launch when I ping off the line. This all came to a head when I started flying F3J style competition and one of the guys who helped me was Larry Jolly and Ben Clerx. Ben told me to get rid of the aluminum hook if you want to launch consistently. Larry agreed. I changed and have not had a problem since. Several of my club members had the same experience. They changed, and problem solved. You would think that a hard anodized aluminum hook would be equal to or batter than heavy piano wire steel. Guess not, in my experience. Oh, BTW, Mark, I have nothing but the highest respect for you, as you have assisted more than your share of model pilots in your time with solid and timely advise. I applaud you for that.

Mike Lee