Thread Tools
Jun 26, 2018, 12:54 AM
Zen in the art of foam
djacob7's Avatar
Thread OP
Question

Is it tail heavy, nose heavy, or what?


Was testing a chuck glider to find the CG of a Robara - a swan-like bird.
It either zoomed straight into the sky, or plowed its nose into the ground.
I couldn't find a sweet spot.
What's the verdict?

Robara glider CG test (0 min 50 sec)
Sign up now
to remove ads between posts
Jun 26, 2018, 02:24 AM
Build straight - Fly twisty
Whiskers's Avatar
Impossible to tell from those tests, although the very last flight looked nose heavy.
Try launching it level at roughly its gliding speed and see if it (a) dives in = nose heavy or (b) goes nose up, stalls and drops its nose = tail heavy. Or (d) glides nicely and makes a smooth landing.
Jun 26, 2018, 02:42 AM
Zen in the art of foam
djacob7's Avatar
Thread OP
Good suggestion, Whiskers! Will do asap.
Jun 26, 2018, 05:13 AM
An itch?. Scratch build.
eflightray's Avatar
What about the incidence angle ?, is it fixed ?, adjustable ?

Chuck gliders tend to have one fixed speed to fly stable with good duration, and the trim should be adjusted to suit that flight style.

A good hand chuck glider needed to turn, (part roll), on the way up to stop them looping.

For a catapult launch free flight glider, we used to use a 'blow-back' elevator to compensate for the high speed launch otherwise they would just loop.

You really need two states of trim, one for the stable gentle glide, requiring some incidence, and one for the high speed catapult launch, with reduced incidence. Or change the catapult design.

.
Last edited by eflightray; Jun 26, 2018 at 05:27 AM.
Jun 26, 2018, 05:27 AM
An itch?. Scratch build.
eflightray's Avatar
Found this video ---

How to fly chuck gliders and catapult gliders! (15 min 52 sec)


Hope it helps.

.
Jun 26, 2018, 04:27 PM
Zen in the art of foam
djacob7's Avatar
Thread OP
Thanks, Ray.
AOI is zero as seen in the pic.
I made the glider to be approximately the weight of the model. Should chuck gliders be lighter than the model?
Jun 27, 2018, 02:25 AM
An itch?. Scratch build.
eflightray's Avatar
That zero incidence is your main problem.

Unless you are considering rc and an elevator, zero incidence doesn't work with free flight chuck giders. To get a stable glide there needs to be some positive incidence between wing and tail, or wing reflex if a flying wing.

It is possible to get a 'glide' with no incidence, but it would be super critical in pitch. Sometime it will glide if you get the launch speed just right, other times it may dive or stall.

Add a 'gnats whisker' of positive incidence. Too much and it will be 'loopy'.


Ray.
Jun 27, 2018, 03:08 AM
Zen in the art of foam
djacob7's Avatar
Thread OP
Gotcha, Ray. Thanks.
Jun 27, 2018, 04:07 AM
An itch?. Scratch build.
eflightray's Avatar
Robara ?

Is it like this ---

https://www.rofalconry.com/robara-3/

Ray.
Jun 27, 2018, 04:18 PM
Zen in the art of foam
djacob7's Avatar
Thread OP
Yup, that's the birdie :-)


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion tail heavy, nose heavy or just on the mark? vil64 High Performance 11 May 23, 2013 09:23 PM
Discussion when a plane porpoises is it tail or nose heavy? stemo99 Electric Plane Talk 35 May 10, 2012 05:36 PM
Question pica 1/8 Corsair kit tail or nose heavy? ululi1970 Fuel Warbirds 3 Feb 11, 2012 09:03 PM
Poll SU-26m; nose or tail heavy? jrb Micro Ready-to-Fly 6 Nov 18, 2009 08:59 PM