Testing Explorer before maiden flight

[gpetty]

I have just about finished the FT Explorer -- my first RC build ever -- and am looking forward to taking it to the RC park for its maiden flight (and mine). Before I do, I'd like to know whether there's anything I can do to make sure there are no aerodynamic surprises before launching it. In particular, I built the 3-channel version, so I don't have aileron control to correct for any subtle twist in the wing that might send it rolling over into the ground as soon as it's released. And it does look to my eye like there might be a slightly higher angle of attack on one end than the other.

Maybe I'm overestimating the danger (again, I'm an RC newbie), but is there a simple way to verify that there is not any strong rolling moment short of actually risking a crash? I'm not worried about pitch and yaw, because those controls are clearly working well enough to correct for any imbalances. One approach that comes to mind is to launch it at the minimum power required to stay airborne so that the wing dihedral has a better chance of overcoming any rolling tendency.

If I do discover a tendency to roll in one direction, should I try to remove the twist? Or is it easier to create an aileron-like tab with fixed deflection on the trailing edge of one or both wings?

 

[kdobson83]

Do u have landing gear on it? I HATE maidens (lol) but landing gear makes it a little easier. Especially if u have a decent area to play with. Take it to a highschool parking lot if u have landing gear and put around on the ground. Try to get a few feet off the ground. If it seems good, then pull the trigger and take it to the park. Other wise, I say your only real option is to just have at it. I heard the 3 channel explorer is a lazy easy flyer.
Good luck and have fun. Building/repairing is half the fun. Post your results too!

 

[Hai-Lee]

When in doubt check it! For asymmetry measurement I use a simple $2 spirit level and check the angles of each flat section in turn making sure they are roughly the same at the same point in each wing. Only takes about 5 minutes or so.

Failing that the old hand launched test glide into the tall grass is always a good guide as to how equal each wing's lift really is.

 

[RCman50]

I was gonna mention the same thing, set it up as you were ready to fly with battery installed, check cg and with no power applied, throw,(test glide) the craft into the wind into a hay or tall grown field to "catch it" so no damage is done if it does not track straight or corkscrews one way or another. I use this method all the time. After a few test glides you will have a good idea of what to expect on maiden. The test hop method is good too mentioned above if you have gear of course and it also gives you the chance to adjust your gear if it doesn't roll straight.
Good Luck on your maiden and let us know how it goes
Dustin

 

[gpetty]

Thanks for the advice. Test glide into tall grass sounds like a good idea. No landing gear on the Explorer, so I can't do the short hops.

Still wondering what the best corrective action is if it turns out there is an asymmetry in the wing. It seems a correction tab would be easier to implement but could have undesirable side effects.

 

[Hai-Lee]

To correct any incidence or warp issue you will need to identify it!

Sometimes the issue is a poor dihedral joint alignment which you can simply cut apart and rejoin.

With the FB I use here I can often get rid of a warp by applying force to "Un-warp" it and hitting it with a little heat from a hairdrier.

If the FB has not been covered or sealed then it can be reverse warped with a coating of white glue which seems to want to shrink the paper as it dries.

As for temporary landing gear I have a set of standard type bent wire gear which I stick onto my aircraft I wish to maiden by using a simple single layer of packing tape. A bit of scrap ply is fitted between the gear and the fuselage to reduce impact damage on the fuselage. I also use a similar set when teaching my students to take off using their Tiny Trainers. The packing tape makes it effectively a "Knock Off" set of landing gear

 

[gpetty]

Followup: I went for the maiden flight today and, just as I feared, it immediately rolled sharply to the right and dove into the ground. Fortunately no significant damage except for a broken rubber band. Careful examination of the wing revealed that there was indeed a bit of a twist to the outermost wing surface on the left wing. Using a blow drier to soften the glue and try to realign things proved more or less fruitless, so I cut an aileron and permanently deflected it upward with a strip of tape to hold it. On the second try (and with the help of some experienced aeromodelers who happened to be on the scene), the Explorer flew perfectly, and I managed to keep it aloft for 8 minutes and then land it successfully -- my first real RC flight ever, so a red letter day.

 

[Hai-Lee]

Congratulations!

Now that it flies you can set your sights on building either a replacement wing or your next full plane!