|Jun 04, 2011, 01:46 PM|
Building a Decathlon - part 2
Once the part one steps are done, I then go to the tail, graphite epoxy the wheel mount, and the interior of the plane...
Step 5: Tail Assembly, time - 30-60 minutes
The PZ Decathlon tail comes with control horns, rudder, elevator, and a mounting block. I use CA on the block to affix to the horizotal stabilizer - the block has 2 slots and 4 pegs/posts which puncture the elevator section to eventually mount the rudder. Once attached, use CA on the rudder where it mates to the slot on top. Ensure that the empennage is SQUARE at this time. It is important to get the tail properly aligned to the fuselage so that the plane not only looks good, but flies true. Much less trim req'd if done right.
Step 6: Tail installation time - 30 minutes
Once the CA is dry, Check the slots where the tail fits into the fuse, and test fit it to make sure that it will mate well. I often have to cut a small slot on top of the fuse where the rudder tab mates into the unit or else it won't go on right. I use a hobby knife to check that the tail can split at the rear a touch to fit the tabs properly, just tane care not to rip the tapes on both the upper and lower sections (other than the cut if needed to mate the vertical stabilizer front to the fuselage).
Use 1:1:1 [hardener:resin:graphite] 6-minute graphite epoxy (GE) to mate the tail to the rear of the fuselage. I use powdered lock graphite - available at many hardware outlets. It goes a LONG way, and it changes the rheology (flow and setting characteristics) of the epoxy. It flows nicely for about 3 minutes, filling in cracks and gaps, and ends up smooth. It also makes the material VERY sticky even on smoother surfaces, it is VERY strong, yet pliable. It can handle flex better if required, and highly reduces embrittlement over long periods, and works better when operating in colder weather.
Mix well for 30 seconds, then apply to the fuselage top section, covering the holes and apply to the tabe portions as well carefully. Insert the tail slowly, pressing the assembly into the slots and holes as per the test fit. Adjust for squareness, and use a Qtip to remove excess before curing. This stuff is much runnier than epoxy itself, so watch for any drip runs to avoid a mess. Allow 20 minutes for strength cure - the 1:1:1 GE will start to tack around 4.5 minute and get stringy. It stops flowing after this point and gets very gummy. During cure, the material will warm a bit, this s normal. Any excess can also be removed by using a Qtip or wipe with isopropyl (rubbing) alcohol. Take care not to rub too hard or the finish on the plane will marr. The GE comes off pretty easily during cure, similar to rubber cement - it balls up a bit.
Step 7: Tail wheel mount installation - 10 minutes.
As with the tail, Use GE to affix the wheel mount to the underside of the fuselage. Invert th efuselage on a small box or convernient location, being mindful of the tail. Apply GE just over the edge of the tape on the fuse, and I use masking tape to shape the epoxy cleanly along the underside of the fuse to avoid flow over and make a better job. Apply GE to the underside of the fuse, and a tiny bit on the posts of the mount. Insert into the holes, and avoid pressing too hard during initial install to avoid squeezing the GE out.
Once inserted, adjust to match the shape of the fuse sides and square it to the fuselage underside. Before allowing setting up of the GE, peel the tape off the fuselage where the excess GE has flowed. Leave intered and permit the GE to flow smoothy to shape, watching for excess drips, or runs. Once set, the tail wheel mount should be aligned with the rudder hinge, just below the control horn position, and square and central to the underside of the fuselage. See pix below.
Step 8: tint matching, and control horns - 10 to 12 minutes
Apply some CA to the control horns and insert into slots. After assembly, re-coat the GE sections as needed to match tint best. (GE is black and usually requires 2 coats to cover properly). Insert control rods, and control arms on servos after powering them up to make sure they are neutral and aligned.
On to part 3!
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