I've been flying radio control since 1975 with my first venture into Giant Scale in the late 1970's when Byron Originals came out with their 1/3 scale Pitts(now available through Iron Bay Model Company ). This was also my first venture into gas. Gas engines have come a long way since then, and I'm still a big advocate. Due to some changes in my life I was forced to sell my 35% and 40% planes and choose one plane around 25%. I looked at everything offered in this size, and found that Dave Patrick Models (DPM) released a Extra 330L ARF that best filled my need. Along with Dave's reputation, I figured the Extra would be a good bet. I wasn't disappointed. Dave Patrick is known for great flying planes, and the Extra 330L is no exception.
The Extra 330L has a 78" wingspan and is 74" long with 1220 sq. in. of wing area. Though considered a 25% scale plane the dimensions suggest a larger model. As a comparison, the 29% Aeroworks' Edge is only 2" longer and has a bit less wing area at 1200 sq in, even though its wingspan is 84".
Although Dave does not recommend gas for this plane, it seemed an appropriate size, and Dave himself had been testing a Taurus TS-42 42cc gas engine in one of his prototypes with great success. A friend of mine is also a big proponent of the Taurus, and though I knew little about them, I figured I'd try one out. I wasn't disappointed here either. I'll give more details later.
Before I ever received the Extra 330L ARF, I had been reading some threads on online forums about a couple of problems with the Extra. First, it was coming in a good pound heavier than advertised, and second, it was building extremely tail heavy. Knowing this ahead of time I was able to make some adjustments to fix these issues.
It is quite common for ARFs to be heavier than advertised and this one is no exception. Most likely the difference is due to variance in wood densities used in the ARF. This is hard for a manufacturer to control. Dave Patrick reports that some are coming out on target, and others are coming in heavy. I had a heavy one. I weighed every little component before starting and was coming up with around 15lbs, which I knew from experience would be at least a half-pound less than the reality when finished. I was not concerned about the tail-heavy tendency since I was putting a 4lb gas motor up front so I figured I would be ok. As it turned out I was, but barely.
The ARF came well packed in a single large box, with no damage and no missing parts. I was immediately impressed with the quality of the paint, glass cowl and wheel pants and excellent covering job. This is a first class ARF. This does not mean it's perfect, as I do have a couple of nits. The two things I was not happy with is the glue used, and the color match between the painted parts and the covering. The yellow part of the covering is Ultracote Pearl Bright Yellow, not "light yellow" as the manual states. As mentioned the glue joints leave a bit to be desired and I strongly recommend going over everyone you can reach with CA.
Although the hardware package is very complete and of good quality, there were several items I changed to make sure they were up to serious stress that 3D can put on them. You can check the changes out in the Equipment List below. The manual is of excellent quality with easy-to-follow, well written instructions, with excellent quality pictures where needed. What impressed me most during the construction is how well everything fit. There was no need to tweak or adjust parts as you assembled the plane as with a lot of ARFs on the market. Everything fit perfectly.
Following are changes I made during construction. Most of them were done to lighten the plane. None of them are necessary to build the plane into a very capable, fantastic flying plane.
Weight saving modifications:
- Replaced stock firewall with 1/4" CF sandwiched (Composites available from Aerospace Composite Products )
- Removed the aluminum angle firewall braces. Pinned and epoxied in the CF firewall, then reinforced the corners inside and out with Kevlar cloth and special epoxy. It's VERY strong and much lighter than the standard setup.
- Taurus specific - I removed the stock radial mount from the engine and bolted the engine directly to the CF firewall. Taurus made a new prop hub that was 3/4" longer to clear the cowl. This was originally done to move the CG back, which as time went on turned out not to be necessary, but it still resulted in a .5 oz weight drop and moving the engine back helped keep most of it inside the cowl.
- Replaced the top cover of the engine box with 1/8" CF honeycomb composite.
- Drilled two 2" holes in the bottom of the engine box ( This appears to be structurally sound)
- TNT custom landing gear - 9.7 oz relative to the 12.4oz for the stock gear. It is thinner, but is of a stiffer aluminum. It is still springier than the stock gear, but won't break, and is plenty stiff if you can do fairly soft landings. If it does bend you can bend it back without it breaking. I also drilled two 1.5" holes between the mounting holes which took off another 0.6 oz.
- Servos - I chose the servos, by speed, power and weight ( They're listed below in the equipment list )
- Spinner - purchased with lightened backplate
- Replaced the rudder servo and receiver mounting plate with 1/8" CF honeycomb and made it about a third narrower too.
- Didn't put a tiller on the pull-pull rudder. This isn't the best way to do it, but it appears to be working fine.
- I used another piece of about 1.5" X 5 in CF 1/4" composite, as used in the firewall, to make a mount for the gas tank at the center of gravity. I epoxied and screwed the composite to the top framework at the rear opening into the cockpit area.
- The only mod I could make in the tail(where it needs it the most), besides light servos and control rods, was to open the covering on the side and cut off about half of the huge tail wheel mount. Unfortunately that didn't result in much gain.
- I also did one silly thing that was just kind of cool, though the weight savings are barely measurable; I replaced all the 4-40 screws with aluminum round head hex screws. Even though the lightness isn't very important, they do look a lot better than the standard allen head screws.
- The Zinger Pro props were chosen because they perform well and are about the lightest out there at about 3-3.5 oz in the sizes I'm using
Non-weight saving modifications:
- I replaced the screws for the canopy to #2 round head hex screws. They go on and off in about a 10th the time as the screws that come with the kit....assuming you're using a hex driver.
- Covered all the open bulkheads in the cockpits with 1/32" texture painted balsa.
- Put floors in the front and back cockpits made out of 1/32" texture painted balsa.
- Added two photographic quality instrument panels
- Added "profile" photographic quality pilot
- Replaced the landing gear mounting method by drilling and tapping the mounting holes for 3/8" inserts that have 10-24 centers.
15lb 1oz including the two instrument panels, painted bulkhead covers and floors, and profile pilot. I could lose another ounce by replacing my 2oz syn receiver with a 1oz 148DP receiver, which I will probably do at some point. The instrument panels, bulkhead covers, floors and pilots added about 1.6 oz. I've decided not to use the forward floor at least for now so I can have easier access to the wing bolts and so I can easily see the fuel level through the canopy.
Total weight savings over other average building methods is probably around 3/4 to a pound. You can extrapolate to some other savings (some that I would not do), such as removing the wheel pants (4 oz - not worth it to me), removing all the pilot stuff(1.6 - I'm happy with this weight), put a lighter receiver in, and say putting a BME 44 or FPE in saving another 5 to 7 oz (though I wouldn't trade the weight for the Taurus) and you're down right at 14lbs.
CG came out without adjustment at 6 1/4". See comments below in the flight report section on CG.
- Futaba 9ZAP WC2 with Futaba 309 receiver
- Taurus 2.6 with Pitts-style muffler
- Zinger Pro 22X8 @ 7200RPM
- 24 oz Dubro tank
- TruTurn 3 1/2 spinner with lightened backplate
- TNT Custom landing gear
- Rudder uses Rocket City horns, Nelson 3" control arm on servo and Nelson cable ends
- Stock horns on elevators and ailerons
- Central Hobbies' carbon fiber rods and titanium ends with Hanger 9 ball links
- Dual Horizons NZ instrument panel graphics mounted on 1/32" balsa
- Profile pilot figure I made
- Elevators(in tail) 2x JR DS9411 - 1.36oz , .15 sec, 82 in/oz at 4.8v
- Rudder (stock location) 1x Hitec 5945 - 1.97 oz, .14 sec, 158 in/oz at 6.0v
- Ailerons 2x Airtronics 94358 - 1.8 oz, .10 sec, 200 in/oz at 6.0v
- Throttle 1x Multiplex MC/v2 Micro Speed - .99 oz, .07 sec, 41 in/oz at 6.0v
- Receiver - Tadiran(Duralite clone) 1600 mah - mounted front-left outside of engine box.
- Ignition - Tadiran(Duralite clone) 800 mah - mounted front-right outside of engine box.
- Fromeco regulated switch on ignition and unregulated on receiver
....continued in next post...