Twisted Sticks August 2006 Newsletter

Build of the Phoenix Decathlon

       After I put my Venus 40 through a tree last month I wanted another plane. Well duh… I had planned on getting a World Models Super Stunts 40 Stick, but Theresa had other ideas. She wanted to go down to Armstrong’s to see what they had in stock instead of ordering from the Internet. Who am I to say no to my wife? Don did not have any Sticks but Theresa thought the Decathlon was beautiful. I was amazed at the $120.00 price, so in the spirit of supporting my local hobby shop I bought it. Do I have a great wife or what?

Overall construction of the bird is excellent. It is covered in Ultra Cote with a 66” wing span. The parts are laser cut and the glue joints tight. I was blown away by the apparent quality of this ARF. The covering job is good and being Ultra Cote easy to replace. Mine weighs 6 lbs 14 oz with a Magnum XLS 46A two stroke and a 4 ounce Dilbert pilot. Dale and Bob have both bought Decathlons. I do not know if theirs are from the same manufacture. There seem to be a glut of 40 sized Decathlon ARFs on the market. J Phoenix and Seagull are both based in Vietnam and are owned by two brothers. I believe that Black Horse models fits in there somewhere. These are all around the same basic size but with slightly different spans and construction techniques. Phoenix models are also carried by Tower Hobbies. Black Horse models are available from Hobby Lobby. Seagull Models are carried by Horizon. I’ll bet that Allard’s will be happy to order them too.

There are a lot of similarities between the planes but Phoenix and Black Horse both use an aluminum wing tube while Seagull uses a plywood brace. Phoenix says to epoxy the wing tube in place for a one piece wing, while the Black Horse model has a two piece wing. In looking at photographs the only apparent difference was an anti-rotation pin added. So guess what I did? I added the pin and will fly the plane as a two piece wing. The wing mounts using two ¼” dowels at the leading edge and two ¼ - 20 nylon bolts through the top of the wing at the rear. Pretty standard except there is nothing under the bolt holes for support except the ¼” edge of the fuselage. So I made a couple of balsa ramps behind the ¼ - 20 bolts to support the underside of the wing. One member of RCU actually crushed the sides of the fuse by over tightening the wing bolts!

The motor mounts at a 45 degree angle. A stock two stroke muffler fits underneath the firewall and is mounted so the cowling fits over it. No need to buy a Bisson or Slimline muffler. I used a Dubro silicon muffler extension and it is the only thing that shows! I also added a Dubro twist cap remote glow. The cowl has only three holes in it and one is for the needle valve! I closed off the left engine opening to try and force more air across the motors head.

The fuel tank uses a three hose connection so I added a fuel dot to the cowl. I plumbed my tank with two pickup clunks. I’ve used these in the past with no problem and it assures draining the tank completely. Be sure to seal the 2 rectangular holes that are under the fuel tank. I did not and while breaking in the motor had exhaust / un-burn’t fuel getting into the fuselage. When the plane is new it is quite easy to put some covering over the holes. It’s a little harder now.

This is the first plane in a long time that I’ve used wheel pants. I slotted the pants for the landing gear. The end of the gear is mounted on the inside of the wheel pant. They can’t rotate.

I used standard ball bearing servos, Futaba 3004’s in wings and Hitec HS425 BB for the elevator and rudder. Be careful of too much elevator throw. The elevator is quite large.

After doing some reading on RC Universe it was felt by some people that the stock CG of 100 mm is too far aft. The wing chord is 265mm. 25-30% of that is 66.25mm to 79.5mm. Mine with the battery behind and the receiver in front of the servo platform is at 92 mm. A lot of RC Universe users are flying at 90 mm with others at 100 mm reporting no problems. Go figure.

As to it’s flight characteristics that has to wait for another issue. I was at the field yesterday and the wind wanted to blow the plane off the table!

Next meeting is at the field August 10^th 7 PM or Dale’s if the weather is nasty.