Supra and Sort-of-Supra Outy’s (Outside the fuse) the Simple Way
Okay credit to all the guys who’s came up with the bits and pieces of ideas and effort from doing their Inny’s (Inside the fuse).
The goal of doing Inny pushrods is to make a nicer looking sailplane.
The critical thing with either is that there is no pushrod flex from the servo arm to the Tipper belcrank.
And NO pushrod drag to slowly burn out your servo motor (on elevator it’s would ruin your pretty install! Remember when you grunt with a tough load, your face turns red, when a servo grunts to move a pushrod, its brushes turn red, and it chars the commutator plates they touch…centering and operation suffer)
Don Richmond (www.hilaunch.com/) (with a little help from Larry Jolly) came up with nice Inny installs. He used foam plugs in the tail boom to support the pushrods to their exits.
I’m always interested in trying some thing new and my World’s Heaviest Carbon Supra had Outy’s so decided to try Inny’s this time on my Carbon Lite Supra.
I had some .125 (pn 020020) and .188 (pn 020019) O.D. Carbon tubing in 48” lengths laying around the shop which I used for the pushrod runs in my AVA and Supra from the firewall to the pod exits for the Outy installs (See link below). I just cut the tubing to length so that they extended over the pushrods and Teflon housings to about an inch from the exits, starting at the firewall. I always put my servos as close to the firewall as possible so that there is very little unsupported pushrod between the arm and the firewall.
I situated my servos flat instead of vertical the usual way, (as shown on Jojo’s Website) this solved the ballast tube access challenge; I can use full length rods instead of ballast slugs.
I lined up the fire wall exit holes and drilled them out for the .125 carbon tubes instead of the .188. The .188 fits over the Teflon housings but figured I’d save some weight and add some fit room in the run back (specially now that the new Fuse has rings to receive the ballast tube in the back). But both sizes seem to fit just fine.
However I went with the .125 OD, running the .060-ish pushrod naked inside the tube to about a inch before the rear exits, then switching to the Teflon for the exit hole areas.
Neither seem to need any securing on their way back to the exits, but will
likely use a dab of goop at the tubing’s end so that the exit load is not just
on the pushrod carbon inside…and maybe at the boom pod joint.
Both size tubes do make the bend over their length pretty nicely without restricting movement.
The .175 tubes fit the Teflon housing inside and makes it a really nice run and will likely extend the wear life of the pushrods from 5years to 10years J.
Yes there is added weight to the plane and the tail, just balancing the fuse assembly with thumb and forefinger, it changes the balance point by about a ¼ to ½ ounce in the nose.
Of course if you don’t have the carbon tubing in the long lengths there is the wait for a supplier to get them to you. I found a kite supplier with excellent prices on tubing (http://www.goodwindskites.com/goodwindskites/merch/list.shtml?cat=framework.pultrudedcarbon).
The red is where the carbon tubes exit the firewall.
There is 3/16” x 3/8’w ply strips under the servo mounting screws to stiffen
the deck and for the screws J.
(These photos are from www.hilaunch.com photo site.)
Elevator push rod exits the boom about 3 inches forward of the elevator bracket. A slot about 1 inch long and the diameter of the push rod and sheath was cut in the top of the boom. After final adjustment was made, the sheaths were anchored with epoxy.
The rudder push rod exits the boom about an inch forward of the forward rudder mount. This location was determined to provide the shortest unsupported push rod length and the least binding. The slot in the boom is about 1 inch long and the sheath was anchored with epoxy after the final location was determined.
Removable Rudder
It’s a must if you travel, and simple.
I split a piece of DLG tail boom that fit inside the back of
the boom under the rudder to use a support for two 4/40 aluminum nuts.
After twist fitting the rudder onto the boom pretty snugly, (don’t forget the
horizontal stab will have to be aligned with the rudder last.) I center drilled the rudder mount rings for
the 4/40 screw access and into the boom.
Then I slid the piece of DLG boom that would hold my nuts in place, and
drilled thru both holes to get the alignment.
Then I glued the nuts in place, slid it back into the boom with some
epoxy under it, made sure the screws lined up, and….removable rudder.
I then slid the Tipper into place, marked where it would be glued in place, roughened up the boom there and the inside of the ring, and epoxied it, aligned with square to the vertical. The boom is not on the pod at this point.
I then cut the slots per Don’s photos and measurements using a Dremel cutting
wheel, the elevator slot dead in line with the belcrank and the rudder one
lined up slightly high on the tube so that the pushrod made a straight run to
the rudder horn.
