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Old Jul 09, 2014, 11:56 PM
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Ed's Great Planes PT40

After going through the process of uncovering, examining, "repairing", engine tuning, and maidening of a Hangar9 Alpha40 I have decided to give it another go, this time with a full build from a kit....ground up.
I got a great deal on a GP PT40 from my lhs who has had it in his store for quite some time. I am assuming at this point that due to newer versions and differing manufacturers of the same type plane have led to decreased sales of this particular plane. I am willing to give it a go....and so I have.
Let me first say a few things..of course...I know I'm long winded.
I have all the electronics and engine (once repaired) for this plane, so it will just be a matter of building, coating , mounting the engine, and rollin' out to the field.
About the kit:
This will be my first kit build and introduction into how these things really work. When I repaired the Alpha40 I had no idea what I was doing or what I was getting into. As stated in that plane"s build thread, I certainly bit off more than I could chew. In spite of all things against me, I thought it went as most expected, but better than I personally thought it would. True, in the end it happened to be a pile of wood and broken aluminum on the engine....for what I learned and experienced, though, it was worth it to me.
But, I digress. I am impressed with the full sized plans and the detailed instruction book. I really don't see how, unless I don't follow the directions, I shouldn't be able to complete the build and eventually fly this thing. THe problem is that I am my own worst enemy and this will be an exercise in patience as much as anything. I have all the initial items to start including thin and medium CA, square, hobby knife, blades, sharpened pencils, scissors, wax paper, rubbing alcohol, q-tips, and 30 minute epoxy.
So far I have glued the stab/elevator and rudder/fin, beveled the leading edge of the elevator and rudder, cut the hinge slits and hinge material, fitted them, and drawn the center line to round the leading edges of the stab and fin. I have not glued the hinges yet.
Ever since the Alpha 40, I have been wondering how they were hinged...pretty neat technique with the hinge material.
I was really nervous to start gluing anything together because I want to get it right and didn't want my first time to go wrong or end up misaligned and full of glue all over the place. Eventually I said you have to start somewhere and better it be with a piece of wood that can easily be replaced and shaped to try again and not a fuselage former or something complicated like that.
I'm happy with the results thus far, but know it could be better. I'm glad that first gluing is over and feel good about moving on.
I wasn't happy with the working time of the medium CA and thought about using the thick next time instead. I could have used the extra few moments to make a final alignment before setting. I'd rather just be patient and let it dry overnight rather than end up with a jacked up plane.
So currently I am through Step 9 of "Build The Tail Surfaces" in the instruction book. Some pics and a quick video coming.
What does wicking the hinge material mean? Or is that just what the material does on its own once the CA is applied? If there is only a tiny gap between the two hinge surfaces and I am supposed to use thin CA, how will/can be sure it wicks all the way through the material? I don't want one of these things flying off during flight, that's for sure.
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Old Jul 10, 2014, 12:00 AM
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PT40 Stab and Elevator (2 min 42 sec)
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Old Jul 10, 2014, 09:33 AM
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My suggestion, for what it's worth, is to buy a bottle of Titebond II and use it on most of the wood gluing, especially the wing. CA has it's use but wood glue is best for general building. I'm sure you'll get a bunch of "I only use CA when building" replies but I've always had better results using Titebond.

Use 30 minute epoxy on all critical areas, firewalls, LG mounts, wing hold downs, attaching tail pieces or any place there will be added stress. Also coat your engine area and fuel tank compartment with a thin film of epoxy for fuel proofing.

Hinges: I also always pin the outboard and inboard hinges on ailerons and the outboards on elevators. I have seen CA hinges come loose. Probably not as critical on a trainer but I still do it on all planes.

Patience: You must have some, and an eye for straight and level. If you become frustrated with something just set it down for a while. Don't build something crooked or misaligned that you'll regret later on, because you got in a hurry.

Don't expect your first build to be Top Gun quality. Just do the best you can, ask questions and take your time making sure everything is flat, straight and properly glued in place. Every model you build after your first will be better than the previous.

Happy Building,
Rick
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Old Jul 10, 2014, 10:03 AM
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Thanks for the encouraging words. What do you mean when you say "pinning the inboard/outboard hinges"?
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Old Jul 10, 2014, 10:38 AM
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Cool Ed - looks like you've already made some progress on the new plane. Like you said - patience is key. Don't put a deadline on finishing the plane, just do it step by step and you'll eventually get it finished. I'm just finishing up my first kit and it's taken me much longer than I thought - I wanted to maiden this thing over a month ago and I'm still putting on the finishing touches - in fact I just attached the ailerons last night.

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Couple things I've learned that you talked about. 1) Thick CA doesn't give you a whole lot more time than medium or thin. While thin is pretty much instant, Thick will just give you a few seconds - really not enough time to adjust much at all (although I guess it's better than none). What I did with my build was use the glues that were recommended in the instructions (mostly thin or thick CA) to do the initial bond, then I went back over with wood glue (as suggested above) to add extra strength at the joints.

CA is going to run and drip down between joints like you experienced, so building over wax paper or another smooth surface is important. I had my plans laminated before I started and that helped a lot.

As for the hinges, you apply a bit of CA to the slot with the hinge in place and it wicks into the wood and up the hinge itself to glue it in place. For my model I wasn't supposed to do this step until after the covering job was done - but maybe yours is different... Pinning the hinges (as shootnstarz mentioned) refers to actually drilling a small hole through the wing and aileron (for example), right through the hinge, then put a pin through the hole so it physically can't pull out. I've seen some people use tooth picks for this purpose. Then you have to cut off the excess and sand it flush. I didn't do this on my plane, so hopefully my hinges stay in place!
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Old Jul 10, 2014, 11:11 AM
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I used toothpicks to pin mine as Nitroroo says, just in case in the event the glue joint on the hinges were to fail its certainly not going to break multiple toothpicks out and the hinge will remain in place. I did it because it was a relatively small thing to do for added piece of mind.
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Old Jul 10, 2014, 09:35 PM
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Gonna pick me up some of that titebond. I wish I had it or used epoxy on the fuse sides. They didnt line up flush and even though I can sand out the difference I would rather have set it right and left it over night. Next time.
I have the upper fuse doublers compressed between some boards and 30 minute epoxy right now. The instructions say this is an important step and again, I'd rather wait an hour or so and know it's right than not.

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Old Jul 10, 2014, 11:52 PM
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Fuse sides and doublers, firewall, and wing bolt plate.

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Old Jul 11, 2014, 09:26 AM
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Fuselage formers tacked in place. Still have to drill firewall engine mount holes and pushrod tube guide holes before finalizing placement and permanent glue down.

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Old Jul 11, 2014, 09:27 AM
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Off to work for 12 hours. ..
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Old Jul 12, 2014, 12:43 PM
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Picked a few goodies. Titebond, differing grit sandpaper, clamps, various drill bits. Off at 5 and back to the building bench.
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Old Jul 13, 2014, 01:25 PM
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Coming along.
Fuse formers and sides glued up. Tank floor, firewall, and bottom fuse on as well. Gonna go back through and hit all the joints again before adding the top fuse side and hatch.
I certainly can already see what I'll be doing differently on the next build.
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Old Jul 14, 2014, 08:27 AM
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For film covered planes I pin the hinges with regular sewing pins. I just shove them in with needle nose pliers until the point just goes through the hinge. Then I clip the pin off and push it the rest of the way in with a nail set type tool. Do this from the bottom so there won't be any holes on top. If the pin is too long and sticks out either side pull it back out and start over. You don't want any part of it sticking out. Toothpicks also work but you have to predrill for them.

Tools I use a lot are my assortment of straightedges. You can get the metal ones from box stores fairly cheap. I have them from 2 to 5 foot and use them to insure everything is straight.

Example, when first pinning your spar to the plans pin the ends first then the rest holding the spar against the straightedge. Don't trust the plan lines for this. Also check it for waviness.

Same goes for the upper spar. Once glued in place lay a straightedge along it's length and make sure it nice and uniform from root to tip. If you find a high or low spot you can adjust it before the glue dries, with Titebond that is, not with CA.

Use this straightedge for gluing the leading and trailing edges on too, make sure they're nice and straight.

I also use a good assortment of clamps, both small C clamps and small bar clamps, both cheap at Harbor Freight and are fine for this work. I use lead ingots to weigh down pieces while they dry, a nail gun that shoots 23 gauge pin nails for pinning ply to ply to hold it in place until I can clamp the part.

Once you get something glued up check it and check it again for straight, square and in the proper position. It's much easier to rectify a problem before the glue sets.

You also might want to lightly thin some 30 minute and paint your tank compartment before you button it up. It will be much easier to get to.

You also shouldn't need to "go back and hit the joints" (if you were actually talking about hitting wood joints and not the other kind) if they were properly glued to begin with. You are just adding extra weight and not adding much strength. You are gluing, not welding.

Sounds like you're really fired up Ed, building is exciting and very rewarding. A properly built plane with good fuel proofing will last many years, not like the cheapo ARFs that are basically a bunch of wood parts flying together in loose formation from the get go.

Have you learned the "X-acto dance" yet?

Rick
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Old Jul 15, 2014, 12:22 AM
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A bit more progress.......

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Old Jul 17, 2014, 09:07 AM
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Stab being epoxied. Looks straight to me...

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