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SARPLT · 02-23-2015, 06:54 PM

As I did not see any info on the FlyFly MB 339 I thought I would start a build thread. Although I had looked at this ARF a few times, I had no intentions of picking one up until I saw that HK had it listed for $69 a few weeks ago during their February sale. As I have spent much more than this on 50mm EDFs, I figured for a 90 mm EDF it was pretty cheap so I ordered one to give it a try. Even with the significant shipping cost and exchange rate it arrived at the door for under $200. I was expecting it to come in a larger box but given the fact that the fuselage is in four pieces (2 front halves and 2 rear halves) they have nicely packed it in a moderate size carton. The model came undamaged which was likely due to the fact that the carton is honeycomb construction and somewhat indestructible which was demonstrated by the delivery system, lots of exterior dings and dents but fortunately no damage. As there is an in depth thread on this model on RC Groups, I will keep my comments to my own experiences with this build.

This is a rather large EPO foam 90mm EDF. As this is my first FlyFly model, my initial first impressions of the quality, detailing and finish are very good, particularly considering the price. I have a spare 100 amp Turnigy ESC and Turnigy 3553-1800KV (6S) motor sitting around so my intent is to build this model with this setup. My first step in the build was to check to see if the stock fan unit was suitable with this motor or whether or not I needed to buy another EDF unit. The fan appeared to be of lesser quality and had some burrs on the route of a few of the blades, likely from the forming process. After cleaning these up I balanced it and then mated it to the motor before running it up on a test stand. I must admit that I was expecting this thing to come apart but it ran nice and smooth for about 2 minutes producing 1.6kg thrust on a 5000 mah (6S) battery at 65 amps. The model is supposed to weigh around 2.6kg so we will see how this works out for performance.

The next task was to look at putting the wing together. This is a very unique wing style as it has a large clamshell intake located right where the wing halves are joined. There are several reported wing failures in-flight due to this design and it’s lack of supporting structure in this area. It appears that the manufacturer has tried to stiffen the wing by installing a spar along a portion of the trailing edge of the wing and adding four small plywood stiffeners to go across the bottom of the wing where the bottom clamshell cover is attached to the underside of the wing but it quickly became apparent that this would not be sufficient. I therefore decided to add a 6mm CF spar through both wing halves out to the aileron servo location. This spar is located so it comes in contact with the air scoop on the clamshell cover to help stiffen the spar from any flex. Once I glued the wing halves together I realized that an aft spar was also required. It was a little more difficult to install after the wings were attached but never the less I managed to get one in without too much problem while still preventing any twist in the wing. This aft spar does not go out as far as the forward one. All the flying services use double taped hinges. I was going to replace these but from other forums it appears these are holding up well as a hinge except for operations in high temperatures where the tape begins to lift. Also as I do not want to paint the model, if I remove the tape it will likely pull all the paint off so I will give them a try. For some reason the rudder has not been cut out of the vertical stab so that will require a little bit of cutting and carving to mount a rudder servo. The ailerons and elevators all have servo cut outs that HXT 900s fit nicely into so that is my servo of choice. I must admit that I have yet to have one of these servos fail which I cannot say the same for some of the various Turnigy and Hitec metal servos that I have used. Although there are control rods provided, I replaced them as I do not like using the wheel collar type connectors on flying services. The model comes with fixed landing gear with plastic housings and metal oleos. As I cannot image going without retracts, I will be installing the HK 514s into the wing and the matching HK nose retract into the fuselage. The 514s fit nicely in the mounting wells but do require a bit of foam to be removed to widen the hole in the clamshell. I am currently waiting for some servo extensions to be delivered so I will have to wait to join the clamshell to the bottom of the wing. I have also ordered some more robust gear struts as the ones supplied are pretty flimsy.

The front portion of the fuselage went together fairly easily. I had to modify the nose gear mounts to take the HK retracts so this included adding a couple of hardwood mounts . Contemplating whether or not to add a bulk head as well. I used 5 min epoxy to glue the halves together rather than PU glue as I did not want the glue squeezing out of the seams ruining the paint finish. I should have used a slower setting epoxy as there was not much working time to get everything lined up. Hopefully I will able to get going on the aft portion of the fuselage soon.

Cheers
Marty

02-23-2015, 06:54 PM	#1
SARPLT RCC Senior Contributor I am: MartyZ Join Date: Jan 2013 Location: Brighton ON Radio of choice: Spectrum # of RCs: 8 Feedback: 10 / 100% Posts: 561 Total Props: 1	FlyFly MB 339 Build As I did not see any info on the FlyFly MB 339 I thought I would start a build thread. Although I had looked at this ARF a few times, I had no intentions of picking one up until I saw that HK had it listed for $69 a few weeks ago during their February sale. As I have spent much more than this on 50mm EDFs, I figured for a 90 mm EDF it was pretty cheap so I ordered one to give it a try. Even with the significant shipping cost and exchange rate it arrived at the door for under $200. I was expecting it to come in a larger box but given the fact that the fuselage is in four pieces (2 front halves and 2 rear halves) they have nicely packed it in a moderate size carton. The model came undamaged which was likely due to the fact that the carton is honeycomb construction and somewhat indestructible which was demonstrated by the delivery system, lots of exterior dings and dents but fortunately no damage. As there is an in depth thread on this model on RC Groups, I will keep my comments to my own experiences with this build. This is a rather large EPO foam 90mm EDF. As this is my first FlyFly model, my initial first impressions of the quality, detailing and finish are very good, particularly considering the price. I have a spare 100 amp Turnigy ESC and Turnigy 3553-1800KV (6S) motor sitting around so my intent is to build this model with this setup. My first step in the build was to check to see if the stock fan unit was suitable with this motor or whether or not I needed to buy another EDF unit. The fan appeared to be of lesser quality and had some burrs on the route of a few of the blades, likely from the forming process. After cleaning these up I balanced it and then mated it to the motor before running it up on a test stand. I must admit that I was expecting this thing to come apart but it ran nice and smooth for about 2 minutes producing 1.6kg thrust on a 5000 mah (6S) battery at 65 amps. The model is supposed to weigh around 2.6kg so we will see how this works out for performance. The next task was to look at putting the wing together. This is a very unique wing style as it has a large clamshell intake located right where the wing halves are joined. There are several reported wing failures in-flight due to this design and it’s lack of supporting structure in this area. It appears that the manufacturer has tried to stiffen the wing by installing a spar along a portion of the trailing edge of the wing and adding four small plywood stiffeners to go across the bottom of the wing where the bottom clamshell cover is attached to the underside of the wing but it quickly became apparent that this would not be sufficient. I therefore decided to add a 6mm CF spar through both wing halves out to the aileron servo location. This spar is located so it comes in contact with the air scoop on the clamshell cover to help stiffen the spar from any flex. Once I glued the wing halves together I realized that an aft spar was also required. It was a little more difficult to install after the wings were attached but never the less I managed to get one in without too much problem while still preventing any twist in the wing. This aft spar does not go out as far as the forward one. All the flying services use double taped hinges. I was going to replace these but from other forums it appears these are holding up well as a hinge except for operations in high temperatures where the tape begins to lift. Also as I do not want to paint the model, if I remove the tape it will likely pull all the paint off so I will give them a try. For some reason the rudder has not been cut out of the vertical stab so that will require a little bit of cutting and carving to mount a rudder servo. The ailerons and elevators all have servo cut outs that HXT 900s fit nicely into so that is my servo of choice. I must admit that I have yet to have one of these servos fail which I cannot say the same for some of the various Turnigy and Hitec metal servos that I have used. Although there are control rods provided, I replaced them as I do not like using the wheel collar type connectors on flying services. The model comes with fixed landing gear with plastic housings and metal oleos. As I cannot image going without retracts, I will be installing the HK 514s into the wing and the matching HK nose retract into the fuselage. The 514s fit nicely in the mounting wells but do require a bit of foam to be removed to widen the hole in the clamshell. I am currently waiting for some servo extensions to be delivered so I will have to wait to join the clamshell to the bottom of the wing. I have also ordered some more robust gear struts as the ones supplied are pretty flimsy. The front portion of the fuselage went together fairly easily. I had to modify the nose gear mounts to take the HK retracts so this included adding a couple of hardwood mounts . Contemplating whether or not to add a bulk head as well. I used 5 min epoxy to glue the halves together rather than PU glue as I did not want the glue squeezing out of the seams ruining the paint finish. I should have used a slower setting epoxy as there was not much working time to get everything lined up. Hopefully I will able to get going on the aft portion of the fuselage soon. Cheers Marty Attached Thumbnails Last edited by SARPLT; 02-24-2015 at 08:03 AM.