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Desert Aircraft DA-50R 50cc Gasser
I thrash the gold standard 50cc engine
Text, photos and video by Tom Hintz
Flight video by Clark Ponthier
Posted – 5-11-2015
Start talking power plants for larger RC airplanes and the DA (Desert Aircraft) brand name inevitably comes up. Considering how difficult it is for one product to garner so many RC enthusiasts putting a DA engine into a FlyingRC.net aircraft just seemed like the thing to do. While I did put the DA-50R into an ill-fated Bill Hempel ¼-scale L-4 Grasshopper and it did perform perfectly in that plane, an early crash made the DA-50R available again. Enter my RedwingRC 50cc Yak 55 and the DA-50R had a more fitting platform in which to show its stuff.
One of the things I liked about the DA-50R is its compact overall length that fits the firewall to prop washer dimensions of nearly any plane in this class. With the 2-1/2” standoffs the DA-50R is 6-3/16” firewall to the prop washer which relieves many of the headaches of stuffing a motor into a cowl.
The DA-50R is a true 50cc (3.05 ci) that puts out 5.0 hp with an overall weight (including standoffs) of 3.13 lbs. (1.42 kilos). It has a 1.6771 in (42.6 mm) bore and a stroke of 1.3779 in (35 mm). They use a long rod to stroke ratio that combined with the combustion chamber shape helps the DA-50R produce the most torque in its class.
This is no re-purposed engine but an exclusive Desert Aircraft design. The motor case is CNC milled from 7075 aluminum alloy for strength, accuracy and smooth running. The quality of the design, manufacturing and components lets Desert Aircraft put a three year warranty on this motor.
Of course the DA-50R comes with the official Desert Aircraft auto advance, electronic ignition module with wiring. I don’t have much to say about this other than I didn’t have to adjust anything and it works great. I chose to install mine and then keep my hands off of it!
The permanently fractured Internet says Walbro carbs are either junk or the best there is. As of this writing, my Walbro is the best there is. Once I got gas to the carb it starts very easily. I initially richened up the top end slightly because of my ingrained fear of leaning a new motor to death. However, once I flew the DA-50R it was obvious that the factory setting was way closer than mine so I went back to their adjustment and with an hour or so flight time on it the mixture seems to have gone just a tick rich, perhaps from the compression coming in. I’m leaving it alone for a while and will let its performance guide my carburetor adjusting later on.
Another nice thing about the carb is the beveled slots in the high and low speed adjusting screws. This seems like such a small deal until you put the cowl on and reach in with a long screwdriver. Actually getting the driver in the slot is way easier and then you find that there is more tension than most have so turning the screw just a little (as we should be) is easier as well. It is becoming clear that DA has this figured out.
Making so much torque means the DA-50R can swing a bunch of props with authority. In two bladed props you can use 24x8, 23x10, 23x8, 22x12, 22x10 and a 22x8. I am going with a Vess 23B because I love these props. In a 3-blade prop you can use 22x10, 20x12 and the 20x10. Of course people will experiment with other sizes that might better fit specific planes. I always seem to wind up in the middle of the manufacturers range so I am starting out there.
Firewall Template - Not
One bizarre thing is that Dessert Aircraft does not have a firewall drilling template – anywhere as far as I can tell. In an email Desert Aircraft told me, “We don’t have a template but I can tell you the crankshaft is in the center of the mount so should be easy to make your own from measurements from the engine.” When I asked on one of the forums I was told simply “make one”. In the manual Desert Aircraft stress that the mounts have to be right or stress can be placed on the crankcase. They do have dimensioned drawings on their site so if you are comfortable making mechanical drawings you can make one. I did notice that Desert Aircraft even shows off their solid model imaging in printable pictures (not labeled as scale) but they need to cough up a drilling template! We did find a printable template on somebody else’s site at - Click Here
In the Shop
If you come from a background of die cast glow engines the solid aluminum, CNC (computer numerically controlled) carved DA-50R crankcase is quite literally a work of art. Never mind the engineering behind the design, the outside is simply pretty. The deceptively smooth outer surfaces hide the brutally tough crankshaft and bearings that make the dependability of Desert Aircraft engines legendary.
Installation of the DA-50R was as simple as it gets once I found the drilling template. The throttle arm is installed in the correct orientation so the servo is pulling it open rather than pushing for full power. This just makes sense so if the throttle linkage fails the carb goes to idle on its own.
I used a Pitt’s style muffler that combined with the side exhaust port makes a nice installation for many cowls. I like the look of the twin down tubes, plus the DA-50R sounds very cool through this muffler. As is my habit now I tossed the included gasket and used Permatex red silicone gasket maker according to label instructions. Since I have gone to this sealer I have not had a muffler loosen up.
In the Air
As cool as the DA-50R looks just hanging on the front of a plane it is in the air that you get to see the power and smooth-running that has made these motors the standard by which others are judged. Right out of the box the idle was smooth and stable. I was purposely making high approaches and chopping the throttle from wide open to idle to see if it would quit but it kept on chugging along.
During the first couple of days flying I tried several props in the range of 22-8 to 23-8. The DA-50R handles them all easily. You have to listen hard to pick out any difference in rpm in the air because the DA-50R has a surprising amount of torque.
At this writing I have several dozen flights on the DA-50R and it has yet to do anything wrong. It runs fine in the air, throttle response is clean and the idle steady and dependable. It also starts easier than any other engine I have and they all start pretty easy as well. The DA-50R is just better and modelers appreciate that.
I have to admit that I was skeptical about all of the praise that DA engines get in the modeling world but flying the DA-50R has given me a new perspective. Try as I might, I can’t find anything lacking in the DA-50R other than no drilling template (c’mon guys….) and they don’t send a technician to my shop to install it for me. I do have to put the fuel in myself but it stars so easily it is hard to consider that work.
A small negative to some will be the lack of a muffler in the box with the DA-50R. I suspect that most of us would, as I did, be using an after-market muffler anyway so why add that expense to a motor. DA does offer stock mufflers for their engines at additional cost.
On the plus side – and it is the bigger side by far – the DA-50R is one sweet motor. It has been absolutely dependable, easy starting and seems to be easier on fuel than my other engines if that is possible. I like how even at partial throttle the DA-50R pulls my 16-lb RedwingRC 50cc Yak 55 across the sky. In fact, I found it is much easier to do things like harriers and hovering with a prop with less pitch like the Vess 23A. The torque of the DA-50R just pulls harder at lower throttle settings.
Being regarded as the best there is usually means charging more because of what it takes to develop and manufacture such a product and the DA-50R does cost more than many equivalently sized motors. The $549.95 (5-6-2015) street price is less than I expected given the high-dollar praise these motors so often get. I know that is not cheap but I don’t consider it expensive either considering the rest of the market.
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