30 SEP 08

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Update for 

CAVU 

and other AALmps 30" Mini-XL Old Timers

The CAVU is a really neat old timer model. Making it available as a laser cut kit made it even neater. Now, with some equipment upgrades, it has become kind of fantastic!

Imagine, if you will, a 30" span stick&tissue mini-old timer that flies for 15 minutes, can climb to "which way is it really headed?" altitudes at least 3 times, can ROG and shoot touch and goes from pavement or smooth dirt, flies in winds that cause free flighters to put their models away, and can penetrate that wind so that a downwind flight is not a real problem! 

Last week, I decided to see just what could be done to update these models  with currently available items. These are not expensive pieces made from the finest unobtanium - some are probably as close as your hobby shop, while others are easily available through the internet or by phone.

The CAVU initially was set up with a FOCUS IIIss AM, a Hobby Club Puma 050n motor and 8 NICADs of 80 to 110 mah. This arrangement worked OK and can still be recommended if that's the equipment that you have. With this set-up, the CAVU could make a couple of long, slow climbs and cruise around for about 5 minutes. Looking to save some weight, the receiver was changed to an FMA dual conversion Extreme 5, which weighs about 11 grams [the FOCUS III receiver is about 31 grams]. 

Seeing a display of the GWS motors in a local hobby shop, I looked for one with a gear ratio close to the original VL motor and the Puma, finally choosing one with a gear ratio of 4.14. The GWS motor/gears appear to be sold by a number of companies - mine came from MAX Products, with a stock number of EPU4. The recommended prop is a 9047, which is 9" in diameter, with a pitch of 4.7 inches. The CAVU landing gear/wheel combination, as drawn/built, will clear the 9" prop quite easily. It also appears that the GWS items are all actually based upon a single motor, but with a number of optional gear ratios. I'd guess that slightly higher or lower gear ratios GWS  items would work as well.

The NICADS originally recommended for the CAVU, and all of the my other 30" models, were based on GE/SANYO 9 volt rechargeable battery at about US $10. Inside that battery, we find 6 individual cells. Those batteries were cut apart [razor saw through the plastic case] and combined to make 8 cell flight packs [8 cell packs are not all that easy to charge, BTW]. Looking for something a little easier to work with, I found 280 mah NiMh cells at BatterySpace, for $15.95 for 12 cells with solder tabs, so I ordered 24 cells. The cells were quickly/easily assembled in 7 cell packs for this project. 

So, there we have it: a VERY practical equipment setup for these 30" models. Here's a summary of the equipment now installed in the prototype AALmps  CAVU: [note the underlined links to many of the sources]

Motor MAX Products, (GWS), EPU4, with 4.14 gear ratio. This is also called IPS-S1 (IPS-DX2BB-1XCS) at Officeshops.

 

Prop 9047: 9" dia. X 4.7" pitch: a rather ridiculous looking, kind of large, orange plastic prop,  that is recommended for the selected motor.

 

BEC / ESC Mine is a GFS by SIRIUS, and it works really well. You can also use any BEC/ESC that can work with 5 amps or less.

 

Battery I'm using seven 1/3AA  280 mah Ni-MH cells, with solder tabs from BatterySpace.

 

Receiver FMA Direct Extreme 5.  The replacement for it is the M5 at .3 ounces. You will need to order the crystal separately.

 

Servos CS-10: not the smallest, but not very expensive either! Look for servos that weigh 10 grams or less.

 

Connectors Mine are 2 pin  Deans. Any small connectors will work, and you'll need 1 set for each battery pack plus another for the charger.

So - there we are - I usually resist the urge to brag about my plans /kits, but this setup works really well! 

Here's the CAVU kit info, as presented on the website:

CAVU

 Our First Laser cut

Mini-XL Kit for Free Flight or RC

 

CAVU [a 1930-50s pilot's term: Ceiling And Visibility Unlimited] is scaled-down 1938 free flight design from Ken Willard. The original CAVU was powered by an Elf Single, one of the very early model gas engines available for modelers. Ken was probably better known for published and kit sport and amphibian RC models in the 1950-80 era. This model is a classic parasol, with the wing supported on body-mounted struts. As are all of these mini-XL models, the 30" wingspan CAVU is suitable for the free flight FAC electric old timer replica event [power by HiLine Mini-6 or equivalent] or larger CO2 motors [GM 120 or bigger], and for RC flying with the VL HY50B or Hobby Club's Puma 050N motor. 

As drawn, the top portion of the body from the cockpit forward is easily removable for access to flight batteries, servos or the CO2 tank. On my prototype model, the top hatch is secured by a pair of those tiny Radio Shack magnets, operating in shear, at the rear of the cockpit. One could easily install a rubber band or wire latch instead, if desired. The few body stringers are 3/32" sq. and are easy to handle.

CAVU is supplied as a complete kit: plans, instructions, laser cut balsa and hand cut ply, sticks, LG and wing strut wire, windshield plastic, balsa headrest and noseblock, bamboo wing supports, and 4 sheets of very nice Esaki Japanese tissue. The cut balsa includes laminated wheels, but you could also use SIG's 1 7/16" light plastic wheels, real Trexler air wheels, or turned balsa wheels from Aerodyne [as on the prototype] which look just like Trexlers, but can never go flat! Plywood includes control horns for rudder and elevator plus 2 motor mounts - one for VL or CO2 motors, plus another for the Puma that is located about 1/2" farther back. The price is $30.95 plus postage. See 'Order Info' for shipping costs.

There you have it - I'm very pleased with the latest development for these small replicas of old timer models, and I hope you might be too!

See the CAVU listing at the:

Catalog

where you can order direct using PayPal.