-RCAEROSPORT-Reviews-DPM Extra 330L

Dave Patrick Models(DPM) "Extra 330L ARF" Build Report by Bill Pryor

Contents:

Introduction
Construction
Modifications
Setup - Equipment Listing
Flight Performance
Conclusion

Introduction
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. 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.

Construction
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.

Something that speaks to Dave Patrick's excellent customer service is how he is dealing with the unexpected tail-heavy nature of the plane. Dave has come up with a kit (free of charge to Extra owners) that will change over the two elevator servos in the tail setup, to a single servo up front using pull-pull. I did not have to do this modification to my plane due to the gas engine, but it does appear to have helped solve the problem for people using lighter glow motors, though they still need to at least move their receiver battery as far forward as possible.(More information on Dave Patrick Models website)

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.

Results

15lb 0oz 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 8 to 9 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.

Setup

Futaba 9ZAP WC2 with Futaba 309 receiver
Taurus 2.6 with Pitts-style muffler
Zinger Pro 22X8
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 - Email: Greg
Profile pilot figure I made
Servos:
Elevators(in tail) 2x JR DS9411 - 1.36oz , .15 sec, 82 in/oz at 4.8v
Rudder (stock location) 1x Hitec 59455 - 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
Batteries:
Receiver - Duralite 1600 mah - mounted front-left outside of engine box.
Ignition - Duralite 800 mah - mounted front-right outside of engine box.
Fromeco regulated switch on ignition and unregulated on receiver

Flight Performance
Firstly, the Taurus is a spectacular engine. It is the best quality gas engine I have owned (and I've owned most of them), starts easily, runs smoother than any single I've ever had, and the power is impressive for a 2.6, pulling numbers equivalent (7140RPM on a Zinger Pro 22X8) to a Brison 3.2 even though it only had 30 minutes on it.

I set the control rates, high and low, as recommended by the manual. The CG was slightly less than 6" after substituting a 1200 Nimh for the Duralite on the receiver. The rearward recommendation for CG is 5 ¾". What numerous people have reported is that the recommended CG range is on the conservative side. Some people have reported running the CG at 7" for serious 3D work, but I would recommend you only do this if you are a very experienced pilot. At 6" the Extra is a pussycat. It's very stable, has no tendency to tip stall, and will land at a crawl. The only side affect I did notice was the elevator is very sensitive even in low rates.

Take off was uneventful, but spectacular. Advancing the throttle to about a 1/3 the Extra virtually leapt forward, requiring only the lightest touch of rudder to keep it straight, not that it mattered as it was off the ground in about 30 feet. The plane only needed a couple of clicks of aileron and elevator to trim out perfectly. I flew the plane for two 10-minute flights, landing and checking out the plane thoroughly between flights. I was fairly conservative during the flights, and left low rates on.

Snaps (in and out) were easy to initiate and stopped immediately with neutral controls. Aileron rolls were axial, fairly fast for low rates, and also stopped on a dime. Spins (upright and inverted) were easy to initiate and also would stop immediately on release of controls. Loops (in and out) were easy to make round and big with only half throttle required to complete them. Inverted flight required the lightest touch of elevator to maintain level flight. Vertical was out of site and a hover could be maintained at 1/3 throttle. Landings are a non-event and even a beginner could land this plane. On low rates, trimmed for level flight, all you do is chop the power to idle and the Extra settles into a perfect glide and easily controllable sink rate. As I mentioned, it slows down to a crawl and has no tendency to tip stall at these low speeds.

I am not a 3D expert, but I can get through most maneuvers, only they're not very pretty. It was my plan to turn on high-rates on the third flight and try out the Extra's 3D capabilities, which have been reported to be stellar by other pilots, but I had some bad luck. Shortly into the third flight during a low inverted pass down the runway, I had just pushed up and the engine quit. I was able to roll upright, but didn't have time to flare completely and took out the cowl, landing gear and supporting structure. I also bent the wing tube. It was a pretty hard crash and the plane held up very well. I was surprised how little damage there was. The only part I had to order was the wing tube and Dave Patrick had it in stock and in my hands in two days. Impressive. It turned out that a wire had broken that went to the ignition sensor. I have the plane fixed now, but haven't had weather decent enough to fly again to further try out the Extra's capabilities.

Overall
What I can tell you is what I've heard several other experienced pilots report, this plane flies BIG. The Extra 330L ARF flies and reacts much more like a 33-35% plane than a 25% plane. This is a real winner and I'd recommend it to anyone from advanced beginner to expert. If you like glow, it appears the OS 1.60 is the best match. Anything smaller would not have the vertical necessary for good 3D. The BME 44/50, ZDZ40, FPE 2.4, Brison 3.2 would all be great gas motors for this plane. With the BME and FPE being the lightest(3lbs 5oz -8oz w/muffler, mount and ignition - no battery), the ZDZ in the middle (3lbs 12oz), and the Brison and Taurus being the heaviest(4lbs 1oz) and the most powerful. I would recommend gas (even though Dave Patrick doesn't publicly), though I have seen a couple of glowing(no pun intended) reports from people running the OS 1.60. So if glow is what you like, go for it. - Bill Pryor

Many thanks to Bill Pryor for this excellent and comprehensive review. We appreciate if you or anyone else could contribute pictures and a short write-up for a review. Make Rcaerosport a success!!!

Relevant Link : Dave Patrick Models.
Relevant Link : Review of Dave Patrick Models's Ultimate.