brsseb

My GP PT-40 is well underway in my shop now. Here are some photos of the constuction so far. If you have any tips, comments or other feedback to the photos, dont hesitate to post it here. Im glad for all the help I can get.



The kit came in a nice box, with a decent hardware package too (wih all needed linkage, screws and landinggear, etc included). Only missing fueltank, wheels and wheel collars.



Set up a small workshop in my office room. Found an old isolation plate in the garrage that was smooth to stick pins into (and, hopefully, flat enough). Aint much, but its home



As with most kits, the tail surfaces are first on the list. They were both two-pieced, so justs a dash of CA and they were all done. Havent done the hinging work yet (not looking forward to it either, I always find it hard to get them strait and smooth)

brsseb

The kit comes with prefabricated leading and trailing edge, so only light sanding to make it nice and smooth.




The wing was fun do build. One side was done in an hour or so. Best part of the construction so far.




Damn, you just got to LOVE the interlocking system on this plane. The wing was constructed with NO GLUING untill all parts were firmly inplace, all lined up.

brsseb

The fuselage is also under construction now. The two sides was made pretty quickly, as they came in 3 pieces each that was glued together with CA. Then the fuse doublers were layed out (and pinned down of course, one of the fuse doublers had a crazy bending) as accuratly as possible.



Then the two main formers were CA-ed on, with me trying to get them 90* on the side (as the pictures shows, high precision equipment were used ).



Then ive started bulding the 3-part firewall and 3-part wing-bolt support. Epoxy was used and left to dry overnight.



As the last picture shows, I used too much epoxy on the firewall assembly and it resultet in some ugly rock-hard gluebubbles on the sides. Need to sand them down (better find some 40 or 80 grit), or else the firewall wont fit in the fuselage. At leas I learned a valuable lesson about epoxyglue...(dont use to much! ).

newbieT

A few things I ran into, if I can remember them all.

On the wing, be careful to shim the R2 ribs and remember the 3/32" spacing on the leading edge for sheeting. Looks like it's a bit late for that now, but it also looks like you had it right.

With Epoxy, if some squishes out of your work, wipe it away with a paper towel. The firewall should've been clamped together which would free up your hands to do so. Sometimes a paper towel with acohol helps to thin and remove excess epoxy.

Be careful and work slowly on the wing center spars, LE and TE. Make sure they get a good fit before thinking about glueing. Do the same with the doublers and be sure to clamp them well with the spacing for sheeting.

When you get the wing joined and the trailing edge center and tip TE's glued on, be careful when you're sanding them flush with the wing. Sanding the tops down makes the very edge more like a point and brittle, causing you to have to sand that down a bit, the result: it won't fit in the wing saddle for-to-aft and the ailerons will be wider then the aileron notch

In your pic of the tail feathers, the rudder is upside-down [X(]

If they didn't include it, remember to put the triangular stock between the fuse sides at the end of the plane.

When doing the wing sheeting, careful not to sand too steep an angle on the LE sheeting to make it fit. I did, and there was subsequently a small gap near the top which I had to fill with putty (that worked out fine). The angle is really slight.

When doing the washout, follow the directions carefully, clamp and leave it clamped until you're done. It's amazing that it even works, but you'll be pleasantly surprised when you take those jigs off! I thought that was some of the most contorted and painful construction of the whole plane.

When joining the dorsal fin 1/4" square stock to the fin, be sure it's centered and not really flush with one side. I had this problem...the little tab was flush with one side and off on the other side which would push the v.stab off to one side, albeit not by much. I believe the instructions say to lay it flat when gluing, I guess I'd suggest having the fin clamped and gluing the tab on by hand and centering, perhaps using medium or thick CA to give you time to slide around to center before it's set.

When hinging, take your time and follow the guide, it works well. Cut into the TE's slowly, not too deep at first and make sure the knife is straight, it'll be fine.

Hmm, what else did I learn...

Don't be too eager to finish sand, it'll take off too much wood. Get things rough and don't finish sand until they tell you to cause there's always another piece that needs to be lined up (this might help with the root and tip TE's).

The instructions have good building tips, if you haven't read the instructions as a whole, both wing A and B, cover-to-cover, you should do so. Knowing what's next in the plan can help.

Take your time! Make sure everything's a good fit before gluing, never just glue...someone has a signature on their posts that says something to the effect of:
'Murphy's law says that if you glue without a dry fit, it's not going to fit at all'

When covering, be prepared! On RCU is a review about the p-38, within that there are how-to videos to help you do covering. Watch them! I learned a lot just watching those videos and it helped me a lot. Take your time and read the directions for your iron and covering to get specs about temperatures and what-not.

When mounting the engine, be sure to mark the holes carefully and accurately. There isn't a lot of room for error since the mount holes in the engine won't give if the screw holes aren't perpendicular or correctly spaced.

When putting in the control wire guide tubes, before you join the sides completely make sure the guide tubes don't turn too much and cause binding.

When clamping pieces, use scrap balsa under the clamp heads to spread the pressure and not damage the balsa being clamped.

When putting in the firewall, clamp carefully and firmly. Be sure to wipe away ALL excess epox from the joints. When you put in the nose tripplers they won't sit flush with the firewall if you don't wipe away that epoxy!

Last thing, I guess...when doing the fuel proofing I used 5 minute epoxy with denatured alcohol mixed in to get a thinner, more redily 'painted' viscosity. It worked very well, but I would suggest either using 30 minute epoxy or expecting to cover small parts at a time (5 minute sets at 5 minutes, regardless of thinning).

Hope that helps! There are a handful of pics in [link=http://www.rcuniverse.com/forum/MonoKote%2C_problems_taken_care_of%3F/m_1882404/tm.htm]this thread[/link] from me with my PT-40 if you're interested.

-Dave

iflyrc24

My Feedback: (5)

Use the lowest dihedral angle. I have seen PT40's show up at the field with a LOT of dihedral which makes them a bear to fly in any wind. Use the 1" or 2" setting and it will fly great.

DEG

brsseb

Lovely set of tips for me to digest there. Thanks .

Yeah, i saw the upside-down rudder. Dont worry, i know the right way. Just me photoshooting in a hurry

Ill make sure the piano wire tubes are firmly secured in their holes with CA on the outside so they dont start moving.

Im making the B-wing (sport version, less angle), since lots of ppl says this thing is a b**** to fly land in crosswind with the A-wing.

Learned my lesson with epoxy now after the firewall "indicent". Went all fine though, sanded off the extra dry glue in 10 min with 100grit sandpaper.

Ill check out the covering videos. Nice tip .

brsseb

Joined the two sides now with CA. The formers went into the sides pretty smooth, just minor sanding needed to get the to fit just right. Then weightet down with something heavy (and again im using the expensive Epoxy for all its worth..).



Half an hour later it sits nicely togeter. Looks like the fuselage is pretty strait and even. Added some extra CA on the joints to make sure they are secure.



The sanded firewall was up next. Drill its holes and fit the hardware for it. Hammered them down and secured them with some CA on the outside rings. Hope the fuelline-holes are big enough. Havent got the engine yet, so didnt have a fuelline to test. The holes for the throttle and front wheel steering tubes fits just nicely, though.



Last ting for today; Epoxy on the firewall and secure it with lots of rubberbands. It fit nicely, with the fueltankfloor in place (abit drawn back and secured with a strap, so it dont come close to the epoxy. Gonna slide it down after its dry and secure with CA as instructed).

Gonna do the main front floor, rear floor and some more formers at the back tomorrow.

newbieT

oh yea, and if you're doing the dowel wing (highly suggested by instructions and others here on RCU), don't forget the dowel doublers under the windshield before gluing the windshield in place! [X(] Oh it sux fixing a mess like that [:@]

brsseb

Yeah, im making the rubber band version. Bet its gonna get some beating on landings. Having a thick ugly bolt though the balsa wing and fuselage dont sound like a good idea for a beginner (can imagine the damage it can do if the wingtips hit the ground on landing ).

flyboy2610

My Feedback: (1)

Do not glue the "windshield" into place. Use some #2 x 3/8 screws and make it a removable hatch. Ditto for the horizontal plywood piece behind the engine. That will give you a 2 piece hatch and make it much easier to get to the fuel tank.

One other tip. It's too late for the PT40, but helpful for your next plane. Before installing the firewall, mount the engine mount to the blind nuts and trim the bolts flush with the back of the nuts. Then remove the engine mount and install the firewall. You want the bolts flush so they don't puncture the fuel tank, and it is easier to trim them off outside the plane.

newbieT

two things...

1. I think it'd be a tight fit to get those screws in on the windshield. There's very little material behind the windshield to screw into, it'd be really hard to get it right, and without splitting the fuse sides. Personal call...

2. The other way around the protruding screws would be to mount the engine mount and mark where the screws protrude, then saw them off at the line so you're not trying to saw inside the plane. Just gonna be a PITA to get a good hold on the screws while trying to saw them [:@]

brsseb

Some more work on the fuselage today:



First off was to let the fueltankfloor slide into place, and secured with CA. Went pretty smooth, except I had to sand it on the edges (some leftover epoxy from the firewall blocking a few milimeters). No problems.





Glued the front bottom fuse into place, then testfitted the rear fuse bottom and secured it temporarily with masking tape. Then added the last two formers with ease.



Wasnt too happy about the rear fuse floor at the back, it didnt fit very well (didnt go all the way down). Some CA slipped from the two formers while the floor was just temporarily secured, so no way back anyway. It just pops up 2 mm. or so from the back, so some sanding at the edges will fix it i think.

All in all, i think the fuselage looks pretty strait and solid.

brsseb

When you say puncturing the fueltank, you mean in a crash right?

Well, i got a Dremel tool with some stuff to round of metal and stuff. Perhaps that will smoothen the bolts. If nothing else, i can place some rubber hats on them (pieces from a rubber tube) so they wont be too sharp. Or did i misunderstood ?

brsseb

- Perhaps if i use smaller screws, and add strong masking tape to the material to avoid splitting when i drill the holes?

- Or, glue the front hatch and windscreen together as one piece, with a scrap piece enforcing the join. And make it a bigger hatch instead.

[:-]


Well, that time, that sorrow .

Right now i got to secure the two elevator/rudder-pushrodtubes and the antenna tube. The instruction says i can choose to lay hte antenna in a tube poking out the end of the fuselage, or strap it up as a external wire from the rear end of the main wing to a T-pin on the top of the fin. Does it matter (in terms of signal strength) what i choose? I really like the internal version, so the fragile antennacord is secure from any crashes or so.

bryris

Judging by the dates on your camera...YOU'RE BLAZING FAST! I have been working on my LT-40 for 1.5 months and haven't put the ailerons yet. But I only work on it about a night or two a week. I am jealous of your time spent. Wish mine was flyable. The time will come.....prolly aug or sept at this rate.

brsseb

Yeah, having my holiday now so pretty much working on it a few hours a day. Must get as much as I can done before holiday trip and university starts up again. Then the time will be limited.

newbieT

The PT-40 goes together quickly, and if you stagger work on different parts of the plane you can get a lot done in a night. I, too, moved quickly with my construction. I pretty much finished the plane in a week of nightly working. Now that I'm on the covering it's taken another few weeks, one to wait for parts, another to wait for covering and now this week which has been spent actually covering. Last night over a few hours I managed to hinge, bevel and cover my ailerons which was the last actual construction I had to do. Past this I have to cover the fuse (sides/top) and bottom of the h.stab then mount all the hardware. I expect to be done this weekend, time granted of course.

Then it'll be back to waiting. My wife and I just bought a house and I won't have a radio or AMA until at least the end of July. If I'm lucky, I might get enough money together this flying season.

What could've been only a few weeks construction and off to the flying field may not see the skies until next year

Not that I'm complaining, the wife has allowed me some unfair funding to my hobby. I hope the last expenses won't slow me down too much.

brsseb, good luck on the remaining construction!

brsseb

newBieT: Sure hope you get your baby up in the skies this year. Think its gonna be great fun to fly this thing. Getting my radio sometime next week, and the engine sometime in july. If i keep it up, i might get it done late july/august. But who knows with this hobby .

Anyway, here is the latest work:



The engine doublers were installed with epoxy overnight.



And the wing bolt plate (used even if im going for the rubberband version) is there adding strength to the fuselage. Just snapped right into its place, almost making the epoxy it was secured with seem like a waste .



Then the front dowel triplers were CA-ed and clamped down. Give you a nice stable surface to install the next part:



I didnt find a good way to make the windscreen detatchable, so I just obeyed the instruction manual (read: "gave up" ), and glued it into place. I dont feel it is that much in the way since the front hatch seems large enough for operating the fueltank.

Havent glued the rear top roof on it yet, since im having some trouble with the pushrodtubes for the rudder and elevator. They seemes to have a too sharp bend in the end, making it abit hard to pull and push the pushrods I think. Fixed one so far by drilling the hole in the last fuse former abit lower, but the other one seems to be too hard still. Also, i need to get some balsa-filler for the holes tomorrow or so.

brsseb

Fixed up the main landing gear rail and support blocks. Drilled one of the holes abit angeled, so I had to do some minor bending on the main landinggear pianowire. The railslot wasnt roomy enough for both of the wires sidebyside, so i had to cut the rail slot abit wider. But it looked good in the end.



The hood looks damn cool. The holes were somewhat bigger than what they should be for the small screws that came with the kit, so i had ot find me some bigger onces. Looks damn cool, i think. Do they sell miniature hood figures like Merscedes and Jaguar have to replace the middle screw ?

brsseb

Finally got the rear fuselage roof on it after much hassle with the damn pushrod tubes. Had do redrill the holes since the produciton marks for the holes wasnt properly aligned, and it made the tubes bend too much, causing the pushrods to be hard to move. Was gonna use the in-fuselage antennatube, but gave up after the weared antenna was too tricky to push in, even in a big wide tube. Gonna put it on the outside, exiting from the rear of the main wing and pinned to the top of the fin.



Glued the stab base on and JUST remembered to add the little easy-to-miss triangle at the very end.




Sanded the tubes so the glue would stick on them. Also got some balsa filler to secure the tube exits, and sanded them off for a clean exit. Looks good. Havent got the engine yet, so work on the fuselag is halted. Next up is probably to slot the hinges and final sanding on the fin and stab.

One question..the manual tells me to glue the stab and fin to the fuselage BEFORE COVERING. I find that strange, since it must be tricky to cover the model with them installed, wouldnt it? Never heard of this way before, but the idiot-proof manual is pretty clear on this point. What should I do?

carrellh

I recommend covering the plane before you glue on the stabilizer and fin. I've only built one kit, a GP PT-60, and I deviated from the manual on that part. Several experienced builders said it would be much easier to cover before assembling the tail to the fuselage. The plane in my avatar is my PT-60.

brsseb

Noted [8D]

newbieT

I agree whole heartedly. It's just too easy to remove the covering where you'll be gluing and much, much harder to glue then cover. I really wish I had known this before I glued mine down, I finished covering the tail feathers, but geez it wasn't easy when they're already glued on...

brsseb

Yeah. Most other kits dont do this. Very strange for such a (so far) great manual to tell me to glue the stab and fin. Someone outh to send the GP folks a note on this.

Btw, got myself together and faced my biggest construction fear....hinge slotting....[:@]..damn i hate that. The hinges on my two minor sailplanes are a real $£€[:@][:'(] piece of work. Nomatter how much i try, I still manage to get them abit wrong, so the surfaces are bend and not good looking. After cutting one slot, i gave up the idea, even with hte good backing from the manual. (And it doesnt help that the elevator surface that came with the kit got a nasty bend in it either)

So now im gonna order myself one of those [link=http://www.dubro.com/DU-BRO/DUB_CAT/DUB37.html]Dubro Hinge Slotter Kits [/link] to do the job for me. That kit looks just lovely, even if it if does cost $15 here in norway. I want that included center/parallell-guide REALLY bad. Also getting dubro pinned hinges that fits the kit nicely.

Bax

My Feedback: (11)

If you cover the tail pieces first and then trim away the covering so that you can glue wood-to-wood, be careful that you do not score the balsawood under the covering. It's all to easy to get a small knife cut in the wood, and this makes a lovely place for failure because the small slices weaken the wood.

If the surfaces are glued before covering, you use small 4-5mm strips in the intersections. They are easy to apply and you can then add the full-size covering over the surface and have no visible gaps where the surfaces come out of the fuselage.