After having received the Xplorer a few weeks prior I finished up the build. In the last post I finished up the servo install in the wings. I was in a bit of a hurry to make a FSS event in May. It would be the last one until October. In the end I was unable to finish up the build before the event. I decided it was much more important to have a completely built plane that I was 100% confident in flying than putting a plane on a winch for the first time with epoxy barely hardened.
The last items on the to-do list were to get the elevator and rudder servos installed and get the servo bays on the wings covered up. I also needed to run servo extensions from the servos to the inner section of the tips so they could connect to the center panel.
Jody talked me out of the MKS 9767 for the elevator and to the much more cost effective MKS 6125e. It is designed for v-tail use. The main advantage is that it is much smaller and lighter than the 9767. This ended up working in my favor since I had a heavier setup in the fuse. Being that it is small it didn’t fit into the pre-made mounts. I ended up getting some basswood and fabricating a mount. Ideally some 1mm carbon fiber plate would have been nicer.
Something that I thought wouldn’t be so hard ended up trying my patience a bit. I didn’t realize that the only difference between the MKS 6110 and MKS 6100 is that the 6110 is made for a horizontal mount and the 6100 is a vertical mount. On my original order I just got three of the 6110s thinking that I could use two on the ailerons and a third for the rudder. In the end I had to order a 6100 for the rudder. Now I have a backup 6110.
Cutting the slot at a 45 degree angle ended up being harder than I want to admit. It was hard getting a cutting wheel in there. Also the material that the tray is made out of doesn’t take nicely to filing. It took me an evening and morning of fiddling to get it to accept the servo correctly.
I also finished up with the battery. I decided to keep the staggered setup that Paul Naton used in his F3X build clinic. I have materials and batteries to do a second 2s pack where the cells butt up on each other. I’ll see if I really need to shave some weight in the nose.
This shows the completed elevator and rudder setup. NAN didn’t send me brass adjustment ends for the clevises. I ended up just cutting them to length and using some JB Weld to secure them. It should be fine since adjustments should be really fine. I also want the best resolution and holding on the elevator. Having no slop there is critical.
The wings only took a bit of final touches in order to call them complete. For the center panel I just needed to install the bracing and cover the bay. In the picture above you can see some flat carbon fiber. It’s about 1/4″ by 1/16″. I cut one piece to span the servo bay, another piece to span the servo and then got a small piece of basswood to put under the rear side. The piece of basswood is necessary because the way the top skin is angled compared to the bottom. Doing this transfers the servos load across the whole piece of carbon fiber and ties the last bit of the bottom skin into the supporting structure.
I ended up doing something very similar on the ailerons. Since that area of the wing is much thinner I only needed the carbon fiber piece. The center panel’s setup was glued using thin CA. The ailerons are held in place with Shoe Goo.
The center panel’s flap bays are covered using some plastic from the MKS servo boxes. This lets me look in and evaluate the linkage setup without having to take off a bunch of tape and going through the hassle of removing the cover. The aileron tips required a bubble to accomodate the servo arm. Since I didn’t have any way to make the clear plastic have this feature I used the covers supplied by NAN. At some point in the future I’ll try to put clear covers on those bays as well.
Now that everything was put built out it was time to put the model completely together and then see where the CG worked out to be located. I was really hoping to get the CG at 135mm. However, after doing a lot of reading it seemed like my component choices in the nose would make this harder to achieve. I put the model on the Great Planes CG Machine and immediately found that it was too nose heavy at 135mm. Sliding the plane further back on the machine, or moving the CG forward, I found that I wasn’t too far from where I want to be. I’m right in the 130-131mm range. I didn’t get an exact measurement on it since I didn’t re-adjust the rulers but it was a small nudge back.
Once the CG was established I knew I could actually work on the transmitter program for the Xplorer. I started with a template from rc-soar.com. I’ve used it on a couple of other full house sailplanes and I’ve grown fond of it. Since I took a good amount of time getting each linkage matching the other the work required to have all the surfaces match each other was very minimal. The perfectionist in me knows there are probably a few more basic adjustments that could be done at the hardware level, but don’t seem to be such an issue as of yet.
By the time I was able to get all this ready it was late in the afternoon. My wife had just taken the girls out and I decided that I only had a few minutes before they were back from the store and it was dinner time. I decided to tape up the wings and go out to the field behind our development for a few hand tosses.
I was instantly surprised how the model just floated along. Putting in very little control input seemed to make the model react. In fact, I had to change off of medium trim adjustments to extra-fine because the MKS servos are so sensitive to adjustment. After a few hand tosses at the bottom of the field area I went to the surrounding berm. This put my start at 10ft off the ground at the lower level. Here I was able to give it a good throw and still have time to make a few trim adjustments. By the time a half hour had gone by I was reasonably confident with the cruise/normal flight mode.
This past Saturday I finally had a chance to get out and try a few launches off the high start. Man is that a tough deal! I don’t think I can pull it back more than 40 or 50 feet! To make a long story short,on the 5th or 6th launch I got a good bump from some activity in the air. I stuck it out at tree top height and ended up working the air till the bubble broke free. I rode the lift till the model started getting hard to see!
I guess that is one disadvantage to this model. With my older built-up sailplanes I could give up around 150ft in the air knowing that there would be very little chance of lift strong enough to ride me out. With this model I have to make sure I work everything since the smallest of lift is usable!
I’m really happy with this model. It’s a world class setup that hopefully I’ll get to enjoy for some time to come. It flies beautifully. I also think it’s going to make me look better than my skills are presently!
I do need to make sure that I’ve thanked everyone who provided helpful input on this build. This project would have never gotten started without Jody Miller. His skills as a pilot make me constantly want to improve mine. He’s the one who lead me in the direction to buy this model. He also provided excellent support when I built it. There were times where I felt that I just couldn’t do something, for example, cutting the wing skins for the pushrod exits. He made sure to talk me through each step and provide much needed guidance, constructive criticism, and assurances.
Also, a big thank you to Jeff Duval, John Graves, and David Web. Jeff was another great resource during the build. He’s built so many of these Xplorers he probably knows them just as good as the guys joining the molds at NAN. John gave me great pointers and tips during the final stages of the build. He’s also another one of those guys that will do next to anything to see someone else succeed in the hobby. I met David when discussing my radio options. He convinced me that the Taranis would be a suitable choice for the radio system. David also gave me a ton of information around the FrSky system that I know I’ll find invaluable as time goes by.
Finally a big thanks to the posters on the X3 thread at RCGroups.com. They provided a ton of feedback and help with the build. They’re also a good humored bunch that put up with several tricks on my part.
This isn’t the end of my posts on the X3. In my upcoming follow up to this I’m going to explain the highstart setup that I got from Graves Hobbies. I’ll also be posting some flight and contest reports as soon as I get some time on the model.