Can’t stop tinkering!

Can’t stop tinkering!

 

With my improving flight skills and a reasonable stable of planes, I haven’t found the need to build a new plane for a while. But that doesn’t mean I haven’t been busy. This is my second ‘season’ of flying, and over the year I’ve moved-on to more interesting models and challenges. Flaps, flaperons, flight stabilisation, etc. plus working on existing models to fine tune their performance.

The Morphocoupe, which started life as the 1927 Velie Monocoupe, still sports the same main wing and wing bracing, power system, servos and the undercarriage assembly as the original plane  – everything else has been replaced!

Current specs;

Wingspan - 1000 mm / 39 inches

Length - 680 mm / 26.5 inches

AUW - 1080 grams / 38 ozs with 2 x 1000mah LiPo batteries

D2380 1000KV 21A motor with 9 x 4.7 prop

The addition of flaps to the Morphocoupe gave me a wider flight envelope, but flight times were limited, about 6 minutes with the 1000mah batteries I favour. (It’s a weight per mah per $/£ thing – basically, bang per buck!) Plus, when the battery alarm went off I had to get the plane down fast as there wasn’t much reserve in the battery. It was OK, but I began thinking about ways to get a larger battery on board.

Here’s the battery compartment. The single battery is a nice fit.

All sealed-up and ready to fly. Note the extra fitting on the battery balance lead – see my other article on “battery mods” for an explanation of this.

In fact I already had the answer. I’d been flying a couple of other planes on dual battery packs running in parallel, but I didn’t think there would be enough room to double-up batteries in the morphocoupe battery compartment.

Then I had one of those; AHH-HAA! Moments – put the batteries on edge! I tried it, and the gods of small spaces must have been smiling, because 2 x 1000mah batteries fit so snugly in the battery compartment, you would think I designed it that way.

Ready to fly… OK, not very pretty once the cables are all connected, but enough to get me in the air. I can work on tidying the connectors and build a hollow lid for the battery compartment later.

The addition of an extra battery meant I could remove a pile of nose weight. Again the gods of airplane balance were smiling – I was able to remove every single bit of dead weight – 63 grams/2.2 ozs – to get the C.G. back to where it was before.

The extra battery weighs 94 grams/3.3 ozs, so for a net increase of 31 grams/1 oz I’ve doubled the battery capacity.

I immediately did a static test, to see what kind of flight times to expect, and came up with about 14 minutes. I was a bit sceptical that pairing the 1000mah batteries would add 2 minutes more to the expected flight time, but even if I just got the 12 minutes in the air that was more than respectable.

Tinkerer that I am, I also stuck on an Orange flight stabiliser, and mixed in a little rudder to act with the ailerons.

So how did the flight go? According to my internet weather site, winds were supposed to be around 4-6 mph but they were stronger on the field 8-10 mph with a few even stronger gusts and a bit of turbulence coming over the trees. With the addition of flight stabilisation, I reckoned the plane would have no problem, and I was right.

I got my 14 minutes in the air, and that was using aggressive throttle settings to keep the speed up for the stronger winds – no coasting around the field with the flaps down. I’m thinking I might get even longer flights in light winds. There was a lot less stress at the end of the flight too, with a good amount of time to get the plane down after the battery alarm went off. I can usually tell how the battery is doing when the alarm sounds. If I back-off the throttle and the alarm stops, it means there’s a reasonable bit in reserve. If the alarm keeps sounding it’s definitely time to land.

In theory these batteries can push-out 35A which was fine for the (max) 21 amp motor, but running in parallel the theoretical output is 70A. Bottom line, the batteries are ‘coasting’ compared to how they were being used before. This probably accounts for the longer than expected flight times. Next stage is to tidy-up the dual lead system and make a new lid for the battery compartment.

UPDATE 28/03/2015 - I've been collecting and updating all my articles, planes and plans on my own website on this page; RCplanes It's still a work in progress, but there's a few extras and beta-stage projects that don't appear here on the Flite Test website yet.

All the best, alibopo.