Another A4 to join the fleet....
02-14-2015, 11:26 AM
#1
Another A4 to join the fleet....
Here is my SM-BVM A4 Skyhawk which I have finally finished assembly and detailing. Now I hope she flies as good as the others I have seen. My only real modification is the nose gear. I could not get the cylinders to operate and give me enough throw, so I built a bracket for the lower portion and attached a metal gear digital servo. I hope it holds up, as she is about to be sent for test flights as soon as I replace a leaking door cylinder on the front gear door. I keep getting blow back thru to the electronic valve and it is driving me crazy. Finally figured out that it looks like a bad cylinder seal, so I will replace it and hope that fixes the last of my problems.. It is powered by a Kingtech 140 and a Spektrum DX18.
02-14-2015, 11:44 AM
#2
She looks good amigo!!! Good luck with initial flights, I look forward to hearing your impressions of handling characteristics. One of my favorite airplanes but I'm leery of the ground handling and nose steering etc.
any chance you will be attending Mississippi afterburner?
any chance you will be attending Mississippi afterburner?
02-14-2015, 12:15 PM
#3
I can't get off very much right now, and my off days are scheduled for Top Gun and a few days during Kentucky Jets. I am hoping the new mod I made for the steering helps with this, but I know with the close mains she will be a bear in a cross wind. Thanks for the compliment, and I will report back when I get a chance to fly it. Right now looks like mid March before the maiden.
02-15-2015, 06:51 AM
#7
Well my steering now is quite sufficient, if it holds up to the flight testing. I made a bracket which attaches to the lower trunion unit. Found a digital servo that I could adjust for direction and throw, which had metal gears and enough strength for the job. She will now turn in tight circles at full throw and runs straight and true. The steering is very tight now with no slop. The mod takes up no more room than the previous cylinder and sits right behind the wheel much like the original. Taxi tests so far are successful and the gear retracts with no problems. IF not for the leaking gear door cylinder she would be ready to fly, but I have to replace it before I feel comfortable enough to put it in the air. BTW, this is the perfect size A$, 1/6 scale, I now have a complement of ground crew to take care of her. Now I have to finish the bomb cart and crew ladder.
02-15-2015, 08:09 AM
#8
Hey Doc would you mind taking a pix of the nose steering arrangement you are talking about.
Good of luck with the maiden.
Btw does SM have drop tanks for it as they will certainly help minimize wingtip scraping in a crosswind ? I haven't looked on the site in a while.
Good of luck with the maiden.
Btw does SM have drop tanks for it as they will certainly help minimize wingtip scraping in a crosswind ? I haven't looked on the site in a while.
02-15-2015, 05:41 PM
#11
WooHoo!!! Woody, looking forward to it.
Thanks Oli.
And yes, they have wing tanks for it. They are on my plane, but in the picture they had been removed because I keep banging into them and am afraid I will damage the pylon. THey are big and extend in front f and behind the wing. They are nicely detailed as well. The missiles were scratch built from an old BVM Electra missile set I won as a door prize at Georgia Jets many years ago. I finally found a use for them.
I will take a pic of my modification I made to the nose gear. If you can zoom in on the front gear you can see it in the pic. It looks almost scale...haha
Thanks Oli.
And yes, they have wing tanks for it. They are on my plane, but in the picture they had been removed because I keep banging into them and am afraid I will damage the pylon. THey are big and extend in front f and behind the wing. They are nicely detailed as well. The missiles were scratch built from an old BVM Electra missile set I won as a door prize at Georgia Jets many years ago. I finally found a use for them.
I will take a pic of my modification I made to the nose gear. If you can zoom in on the front gear you can see it in the pic. It looks almost scale...haha
02-20-2015, 04:39 AM
#16
Doc,
Can you elaborate on the rudder control linkage? I just received my A-4 and there is no hardware or instructions other than on Skymaster website of how they want it done, not too clear even there.
Thanks,
Bill
Can you elaborate on the rudder control linkage? I just received my A-4 and there is no hardware or instructions other than on Skymaster website of how they want it done, not too clear even there.
Thanks,
Bill
02-20-2015, 05:02 AM
#17
Bill,
The servo mounts in the hole under the rudder. You have to remove the rudder in order to do this, just pull the wire out and slightly turn it to the side. I used a heavy duty servo ar and in the outermost hole I put a 4-40 screw about 3/4 inch long up from the bottom of the arm. I then secured it with a nut from the top. Using a sanding disk I slightly rounded the tip of the bolt., centered the servo and then attached the arm. The bolt will be at the rear most position. With the servo powered off, you can slightly turn it to the side and remount the rudder with the bolt passing up thru the slot in the bottom of the rudder. When you power it up the rudder should center. It took a little playing with it to get it right, and I used a servo tester on the bench to do it, but it works good now and has minimal slop. The key is finding the right length of the servo arm and the right length of the screw which protrubes from the top of the arm.
The servo mounts in the hole under the rudder. You have to remove the rudder in order to do this, just pull the wire out and slightly turn it to the side. I used a heavy duty servo ar and in the outermost hole I put a 4-40 screw about 3/4 inch long up from the bottom of the arm. I then secured it with a nut from the top. Using a sanding disk I slightly rounded the tip of the bolt., centered the servo and then attached the arm. The bolt will be at the rear most position. With the servo powered off, you can slightly turn it to the side and remount the rudder with the bolt passing up thru the slot in the bottom of the rudder. When you power it up the rudder should center. It took a little playing with it to get it right, and I used a servo tester on the bench to do it, but it works good now and has minimal slop. The key is finding the right length of the servo arm and the right length of the screw which protrubes from the top of the arm.
02-20-2015, 05:11 AM
#18
Great thanks,
I think a sleeve of brass tubing over the bolt threads would keep the slot from wearing and maybe be a little less friction. I am into good and accurate rudder throw, I will work with this system before punting and mounting the servo in the fin with external pushrod.
Thanks again for your input.
Bill
I think a sleeve of brass tubing over the bolt threads would keep the slot from wearing and maybe be a little less friction. I am into good and accurate rudder throw, I will work with this system before punting and mounting the servo in the fin with external pushrod.
Thanks again for your input.
Bill
