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mtreble

Position of tow release

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mtreble

I am building a 4m (1:3.5 scale) Luňák and have got to the point of fitting a tow release for aero-towing. My question is how critical is the position of the tow release? 

I am fitting a standard Multiplex aero-tow coupling. The instructions say "Drill and file out a 10mm hole in the extreme nose of the fuselage, taking care to make it exactly central", however the build instructions I have for the model say to install it down 30degrees on the centre line - I don't understand how to measure this, but there are plenty of pics on the web showing full size Luňáks and show the tow release below centre.

Just wondering - should I be carefully measuring this somehow at 30degrees? or will an approximation do - what are the potential issues of getting this wrong if any? Does it even matter at all?

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SilentPilot

I'm not familiar with the Lunak, but my Ka-8 has its aerotow hook fitted under the nose by approximately 30° and there are plenty of people who report that it balloons too easily if you get a bit fast (or a bow in the line) on tow, so some have modified it for a true nose hook which made things easier.

Like I say though, I'm not familiar with the Lunak, the K8 is a lazy flier with quite a high lift wing so the two factors combined likely make things worse...

If I were you I'd forgo the scale accuracy and go for practicality. Stick the release in the nose :) 

 

Tony

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mtreble

Thanks Tony. The Luňák is quite a different beast to the Ka-8. The wing is pretty much on the centre line, and it's a quick aerobatic machine.

I would have thought that the high wing would be the main contributor to the ballooning on the Ka-8?

My fear is that if I install it too high, the opposite might happen - it will tend to nose down? 

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SilentPilot

Aye, could do...

Maybe sticking to the manufacturers spec would be best in this case!

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mtreble
3 minutes ago, SilentPilot said:

Maybe sticking to the manufacturers spec would be best in this case!

except.. these aren't the manufacturer's specs. It's just someone else's build off the internet which concludes with a successful flight on the slope!

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SilentPilot

Aerotowed onto a slope??? :popcorn:

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oipigface

Put it in the nose, and mention it to the tug pilot, so you can both be prepared.

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oipigface

Here's some advice from one who knows better than I do about such things:

Following a couple of paragraphs about the position of the tow attachment on tugs, Martin Simons writes: "At the glider end, a simple release in the extreme nose, or as close to it as possible, is all that is required very easy to arrange. (sic) It is not feasible to tow with the ordinary fixed winch launching hook." Model Aircraft Aerodynamics, 4th ed. p168.

This is clear enough, despite the poorly edited first sentence. Are you sure that the device you have described as the 'tow release' isn't for a winch tow? 

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simon_t

Having tugged and been tugged 100s of times (including tugging Stephen Spittle's Lunak), just put it where it is convenient in the nose.  It won't matter a jot to the way the model tows.  It's quite a pointy nose so you can't get it too far away from the vertical centreline.

Simon

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simon_t

Stephen's yellow Lunak - the hook is in the scale position near the front of the nose skid

Simon

IMG_4120.JPG

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mtreble
2 hours ago, oipigface said:

Are you sure that the device you have described as the 'tow release' isn't for a winch tow? 

Yes!

 

2 minutes ago, simon_t said:

Stephen's yellow Lunak - the hook is in the scale position near the front of the nose skid

Hard to see on that photo Simon, but thanks anyway!

 

if the scale position works well, then I will go with that. It's also more convenient for the install to have it below the centre line.

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simon_t

It will be perfect - the glider will naturally adopt the 'high tow' position.  If you haven't been aerotowed before, use an experienced tug pilot - it is not good to have both ends inexperienced.  If you don't have a local tug pilot let me know and we may be able to sort something out.

Simon

IMG_2925.JPG

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mtreble

Cheers Simon, I've not been aerotowed before. I will probably fly it off the slope first, and maybe come to an aero towing event over the summer (if I finish it in time!)

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simon_t

How about this...

Simon

IMG_3116.JPG

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