Kyosho P40-50 Series Build and Modifications - RC Groups
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Mar 25, 2009, 10:06 PM
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Build Log

Kyosho P40-50 Series Build and Modifications

Having built 3 previous Kyosho P40s-40 series, I will be pointing out any known or experienced problems encountered in the past airframes and the remedies I applied. It appears after close inspection that although there are differences like flaps, new fuse design (EP & GP), covering, etc. that this plane is really close to the old Kyosho P40. The cowl, plastics, canopy, stab, vertical fin, elevators, and even the wings entire shape is the same. I will test a old wing on the new fuse but it appears that it will fit. That means anyone with a old P40 can buy a new wing kit and get flaps with little effort. I have looked at the problem areas on the older version and it appears they still exist on the new version. The new version has some other issues that will need to be addressed for reliability of the airframe.
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Mar 25, 2009, 10:24 PM
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Stab and Vertical Fin:
The stab and vertical fin on the 50 series is built exactly like the second generation of the 40 series. The first issue P40s (shelf paper covering) had serious problems with stab failures so it was redesigned for the second issue arfs. Holding the new stab up to my work light the framework is of the same construction as the second issue arfs (plastic film). Unfortunately, even these second issue stabs were subject to some failures. It appears that sometimes hard balsa was used and others, just soft balsa. These stabs can fail at the leading edge just to the outside of the triangle brace on the first rib. If you hold the stab up to a light you can see this brace. I recommend trying to flex your stab's leading edge and determine if it is of hard balsa construction or not. If you find it to flex too much I would get a needled syringe and inject CA into the leading edge balsa. This would hold true if you intend on putting a larger than called for engine. If you don't like the checkerboard covering like me, this would be a good time to strip the covering and skin the stab with 1/64 ply. I have done this in the past to two other P40s and never had a failure again. You can then recover with what ever you like. I would use a cloth type covering. Same goes for the fin. I have had one owner have the glue joints part on his fin. Inject CA here also.
Mar 25, 2009, 10:55 PM
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Wing and installed retracts: If you are not using the installed mechanicals you can just pass this step. The retracts in this plane are the Hobbico/Hanger 9 type and have proven to be very reliable even on uneven, rough grass fields. Issues I have had in the past have not been with the retracts themselves but the accompanying parts. The wood block holding the bellcrank spans two ribs and will need to be epoxied! Put a liberal amount on both ends and fill the gap underneath to the wing sheeting. IF YOU DON'T DO THIS, IT WILL BREAK FREE. The bell cranks need to be set up correctly and blue Loctite used. The retracts in this arf were not adjusted or set up correctly. First thing to adjust is the pushrod from the bell crank to the retract. Make sure the retract is in the fully retracted and locked position. The lock block pins can be seen on the side of the retract body and they need to be all the way to the front of the retract toward the leading edge. With the retract locked, loosen the Ez connector to the pushrod on the bell crank. Pivot the bell crank until the pushrod is exactly parrarell to the retract's strut. Tighten the set screw and actuate the retract until it is in the fully down and locked position. Again, check the lock block pins, they should be at the opposite end of the slot. The Ez connector should now be just at the edge of the plastic wheel well and not be any further under it. If you do not do this adjustment you could have the other Ez connector come in contact with the inner rib and not allow your retracts to fully cycle and lock properly. My retract would not lock down properly as the adjustment set screw located at the front of the retract was screwed in too far. Just because it is new and untouched doesn't mean it is correct or OK. Cycle the pushrods by hand and look into the retract bay from the wing root and make sure the Ez connector does not contact anything like mentioned earlier. Once everything is working smooth and in aligment,remove one screw at a time and apply blue Loctite. Do not forget to Loctite the bell crank screw itself. This screw can also come loose. CAUTION: When applying Loctite for the bell crank, do not apply it to the screw. The Loctite can get into the aluminum bearing and lock it up. Lift up the bell crank and apply the Loctite to the T-nut in the ply mounting plate. You can tighten this screw fairly tight as it has it's own bearing and is designed to be put in tightly.
The rest of the wing is pretty straight forward and no other issues were experienced. We'll have to see how it is with the flaps.
Mar 25, 2009, 11:56 PM
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Fuse: Third time trying to post this tonight. There seems to be some problem. The fuse needs lots of attention in the motorbox area. All recent issue Kyosho warbirds have been having the same problems. The motor boxes have been breaking free even with the application of epoxy. There seems to be some sort of waxy type coating on the ply that is preventing good penetration of the epoxy. All the ply needs to be sanded in side the fuse/motor box area before applying the epoxy. I will be adding 1/8th ply to the inside of the motor box side frames to help strenghten the lazer cut sections. I will also add triangle stock anywhere I can get it in.
Last edited by chistech; Mar 26, 2009 at 12:07 AM.
Mar 26, 2009, 12:16 AM
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Some other items of interest: Canopy, although painted on the 50 series, is identical to my old 40 series. Hardware is only so so. 50 series has the new clevis' that need to be thrown away. The 40 series had the nice aluminum ones with the grub screws. I used those things for all kinds of things, sometimes even as clevis'. The control horns have seemed to hold up well so far. Pushrods on the 50 series are the new carbon rods unlike the old dowels of the 40 series. I would still put shrink tubing over the ends of the carbon rods to prevent splitting. Motor mounts and fuel tank are exactly the same. The 260cc fuel tank has always provided me with flights of 12+ minutes with my OS 52s and my Saito 62. It is large enough for most power plants. Big stuff being the exception. I believe I will be putting a double pushrod on the elevator to help prevent higher speed flutter because of the Saito 65 I will be installing.
Last edited by chistech; Mar 26, 2009 at 12:22 AM.
Mar 26, 2009, 05:46 AM
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Ldm's Avatar
While I am impressed with there intent to keep the plane light , I can see your concerns over the lack of glue .
Mar 26, 2009, 09:58 AM
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mike early's Avatar
Damned good info!

Great photographs!

Pre-painted canopy saves a lot...a lot...of work
Mar 29, 2009, 08:06 PM
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Ok. I got a chance to get back to working on my P40. What I like to do is to start to assemble things than determine what I will need to do to modify it for the better, Then I disassemble it and then epoxy it all up. I am using a older Saito 65 for this bird so I had to make the mount holes in the ply firewall a little wider than the max the stock holes allow. I also had to grind down the sides of two of the T-nuts because they end up close to the edge of the motor box. To get the proper 115mm distance for the prop washer the carb ends up directly against the firewall. This makes it real close for the fuel tank lines to get past the carb but I got it to fit. Once the motor was mounted I started cutting up triangle stock to epoxy to the side, top, and bottom of the motor box. I cut reliefs in the piece that goes at the back of the top of the engine firewall to clear the T-nuts. Put vaseline on the bolts and nuts to keep them from getting glued.
Last edited by chistech; Mar 29, 2009 at 08:16 PM.
Mar 29, 2009, 08:25 PM
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Started working all the ply surfaces and joints for the addition of plywood, triangle stock, and epoxy. I found a rough round open sanding sponge in my Dremel box. This is exactly what is needed to sand down the ply and joints. For the corners and edges you can't get into, a very sharp 1/4" carpenter's chisel works great. I was able to just peel the rubbery hot glue right out of the joints. It too doesn't stick to the wood very good. It is unbelievable how much glue you end up getting out of the joints. Epoxy would just not come out this way. When we scratch or kit build we all use an assortment of different glues for the different areas we assemble. Why do the ARF manufacturers think you can use the same glue throughout the whole airframe?
Last edited by chistech; Mar 29, 2009 at 08:39 PM.
Mar 29, 2009, 08:56 PM
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I cut two side frame doublers out of 1/8 ply to go inside the back of the motor box. One is slightly longer than the other because of the right thrust of the firewall. To be able to get the doublers thru the hole in the second bulkhead you must put them thru diagonally. The doubler can't be wider than 2 5/8" wide or you can't get it thru the hole for the tank. You can see on the doubler a little tab on the end where it goes in between the triangle stock mounted on the back of the firewall. I mark the two pieces so I don't try to put the wrong one on the wrong side once I've applied the epoxy. Once all was cut and fitting well, I sanded all the inside with the course wheel which really good for the inside of the box. The side frames of the P40 are much stouter than the Hien and might not need the additional ply but with me using the 65 I thought it would be cheap insurance.
Last edited by chistech; Mar 29, 2009 at 09:07 PM.
Mar 29, 2009, 09:03 PM
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mike early's Avatar
How difficult might it be to fit a larger fuel tank, do you think?

Would you measure the distance between the leading edge of the wing and center of the wheel well?

Have you used the mechanical retracts on all of your Kyosho P-40's?

Did the old P-40s lack enough glue as well?
Mar 29, 2009, 09:17 PM
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Hi Mike,
I don't think it would be hard to mount a larger tank. A longer tank that is the same size around would be a no-brainer. There is quite a lot of room for additional length. I will measure the wing tomorrow for you as my shop is out in my garage which is detached from my house. I'm in for the night. All the P40's I've built have used the stock mechanicals. With the weight of the plane, how well they have functioned, and how well they have held up on grass, gives me no reason not to use them. The older P40's did not seem to have glue lacking in any joints like this one does. It was the same hot glue though and I would epoxy the inside of the firewall like one would do to a H9 bird. The older versions did not have motor boxes but a full firewall the size of the fuse. The tail was what was at question and it appears the construction is the same on the old one. Check the firmness of the balsa in the leading edge of the stab.
Last edited by chistech; Mar 29, 2009 at 09:28 PM.
Mar 29, 2009, 09:34 PM
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Decided to start cleaning glue out of the other areas that needed it. The servo tray is barely glued in, as is the reciever tray in front of it and the wing mount plate. The servo tray is glued in in a way that if the glue fails it can just fall out and float. This will get the epoxy and triangle stock treatment too as will the wing mount plate. When I'm waiting for epoxy to dry I usually start doing other things. While I was waiting for the front of the plane, I drilled and installed the servos, then removed them again. I also cut out all the plastic pieces and cowl. You'll be amazed how fast you can get a plane built if you move on to something else while waiting for another.
Last edited by chistech; Mar 29, 2009 at 09:44 PM.
Mar 29, 2009, 09:52 PM
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Removed glue from the wing mount and the rear of the second bulkhead. The rear of the second bulkhead will also get the triangle stock treatment. With the design of the motor box, a lot of the engine's load is transferred to second bulkhead and it needs to be reinforced. The glue at the wing mount was very soft and peeled right out will just a little effort of the chisel. There is no wonder that these planes with age will fail. The design and flyability of the Kyosho warbirds is excellent and it is a shame they just don't use the proper glues in the proper areas. Of course, it is not just Kyosho that practices the policy of just one glue throughout the airframe. Most ARF manufactures seem to do it.
Last edited by chistech; Mar 29, 2009 at 10:02 PM.
Mar 29, 2009, 10:15 PM
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mike early's Avatar
It is the best looking P-40 cowl for an ARF that I've come across.

Do you have room to mount the engine a few degress from 180 to give you room for the 90 fitting? Looks like a pretty tight fit...
It would be wonderful if it is possible to avoid cutting the side of the cowling out...

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