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Yellow P-38 build thread

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Old 08-01-2007, 05:36 AM
  #26  
Doolittleraider
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Default RE: Yellow P-38 build thread

Wow. I am soory to hear that.Thats frustrating I know I would rather crash a plane then lose it like that. We all know that at the rate you build you can replace a loss like that in just a few weeks....tops! I Have had my Yellow p-40 for almost two weeks and I just finished the flaps last night. I am looking it having it done by march.
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Old 08-01-2007, 01:07 PM
  #27  
samparfitt
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Default RE: Yellow P-38 build thread

Counter weights:

pic 1:
I cut the counter weights in half and epoxied in some 4/40 steel rod.

pic 2:
Holes drilled into the elevator and the counter weights dry fitted in the holes.
Will epoxy after all the wet sanding is done.

----------
elevator (cont)

pic 3:
Four large Robart pin hinges epoxied in the elevator.
Note: I made a 1/4" ply (with hole) that will support the outer ends of the control horn rod.

pic 4/5:
Elevator epoxied into the horizontal stab and the control horn rod supports also epoxied in.
The bottoms of the booms were trimmed away to allow access to put the elevator in.
A tight fit and it almost takes three hands to get the elevator attached to the stab.

pic 6:
one inch up elevator (plans call for 3/4" ).
Only about a 1/2" down elevator (there's no way I'm ever going to do outside loops with this plane so 1/2" is plenty!).
I epoxied to the stab in the up position to insure I had sufficient room since the stab has about a 1/4" overlay on the top & bottom to meet the LE of the elevator.

pic 7/8:
Elevator control rods made from 4/40 rod, carbon fiber tubes and 1/4" wood dowels.
I drilled a hole down the middle of the dowel and cone shaped one end and also drilled a hole on the side of the CF tube for the bend of the 4/40 rod to stick 'out of'.
Epoxied slopped on, the bent end of the rod put into the hole in the side of the CF tube and then the dowel pushed into the CF tube.

pic 9:
4/40 rod screwed to the elevator control horn.

pic 10:
the other end will be connected later.




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Old 08-01-2007, 01:21 PM
  #28  
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Default RE: Yellow P-38 build thread

Inner Flaps access panel.
There's not a lot of room in there so I decided to cut an access hatch.

pic 1:
The pencil outline of where I will cut the access hatch to put in the servo for the inner flaps.

pic 2/3:
A dremel cut off disk made quick work of the hole.

-----------------------
Rudders (continued).

pic 4/5:
Rudder parts.

pic 6:
Inside view of upper balsa hinge support epoxied into the rudder.
Not much room in there so I drilled a hole where the bottom of the balsa support is suppose to end so I could look in the hole and just push the balsa support until I saw the balsa support through the hole.

pic 7:
Inside view of bottom balsa hinge support exoxied into the rudder.
Note that this balsa hinge support also gets the rudder control horn so there is a 1/8" ply also CA'ed to the side of the balsa block.
Since the control horns go on the inside of the booms, I made sure the ply is on the inside of each rudder and then scratched in a mark so I can tell later 'which is which'.
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Old 08-01-2007, 06:31 PM
  #29  
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Default RE: Yellow P-38 build thread

Elevator/rudder servos.
All views are with the plane on it's back and from the front.

pic 1:
Installed four HS-645 (133 oz for 6 volts) for the elevator and rudder (two each).
This is the right boom: elevator on the left side and rudder on the right side.

pic 2:
This is the left boom: elevator on the left side and rudder on the right side (mounted horizontally).
With the elevator servos both on the left I get the exact same movement (theoretically!) to each side of the elevator.
At least it is when I move the elevator transmiter stick: no binding.
I did this so no 'reversers' are needed.
I connected up the elevator to the servos because, once I put the vertical stabs on, you can't get to the elevator control rod and horn.
I mounted the left rudder servo horizontally, again, to remove the need for 'reversers'.
I used some 'L' brackets to rotate the servo 90 degrees.
Yellow and Bob Violet sells these.

Pic 3:
Elevator in the full up position.

pic 4:
Elevator in the full down position.
(both of these throws will be dramatically reduced for flying).

pic 5:
I used Debro's 4-40 swivel ball links (#861)
I used 3/4" servo arm distance (center screw to ball link) on the elevator and 7/8" servo arm distance on the rudder.

pic 6:
No time like the present to start routing the wires to where they will actually be located.
The receiver will be in the front of the center fuse.

pic 7:
It's a mess already and I've only done elevator and rudder!
The elevator used one 'Y', two 12" and one 18" extensions (as did the set of rudders).
I used HD twisted extensions from air wild: they have some very good prices on HD twisted wires.
(www.airwildpilotshop.com)

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Old 08-01-2007, 07:33 PM
  #30  
orvel
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Default RE: Yellow P-38 build thread

Samparfitt, first of all, great job, man you work fast! Second, your Yellow P-38 has a polyester based fiberglass fuse, what are you using as an adhesive to glue the wood parts to the fuse? When I built my Yellow jug, I used polyester based Bondo mix.
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Old 08-01-2007, 08:09 PM
  #31  
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Default RE: Yellow P-38 build thread

Orvel,
Are you saying that the epoxy may not stick to the FG?
I just got some Zapa dap a goo II that the instructions also recomments!
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Old 08-01-2007, 09:02 PM
  #32  
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Default RE: Yellow P-38 build thread

Sam, as is the usual, I enjoy watching your build threads. I know from building
myself, it takes alot of work, to work out all the details. then add in all the pics
you do, the steps taken to post it all, and being organized with it makes it even
more work![X(]. nice work, look forward to seeing it all come together
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Old 08-01-2007, 10:31 PM
  #33  
orvel
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Default RE: Yellow P-38 build thread

Sam, that's precisely what I'm saying! Yellow fuses are made of polyester fiberglass, regular epoxy although it will appear to hold initially, will not hold over time. That's why in their instructions (at least on my P-47 which I bought 5 years ago) they recommend a product called "Stabilit" (which they sell) for gluing wood to their FG. I personally used Bondo "Ultimate Lightweight Body Filler" which is polyester based and it works very well. You might want to check this out, you don't want to have what I'm sure is going to be a beautiful P-38 fall apart on you in flight!
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Old 08-01-2007, 10:37 PM
  #34  
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Default RE: Yellow P-38 build thread

Todd,
Taking pictures, downloading them and writing this thread probably eats up 1-2 hrs a day...but it's worth it.
It helps me stay focused, be more organised and think things through for the best options.
It also helps me learn new approaches from other builder's input.
An example is the polyester (green) FG that the P-38 is made from.
Pic 1 shows the glue that I think that Yellow recommends for FG to FG.
I was going to use this on the vertical fins to fuse.
A reference was made that regular epoxy may not be the best for this type of FG.
I'd appreciate any input on this.

--------------
Tank trays (cont)

pic 2:
I used 4/40 blind nuts on the tank tray.

pic 3:
Tank tray screwed in using 4/40 hex head bolts into the blind nuts.

--------------
pic 4.
Some #6 blind nuts added to the stearing servo tray.

pic 5:
The stearing servo tray mounted using hex head bolts.
Since yellow recommends a heavy duty servo (I used HS-645), I used 4/40 rod and those same ball sockets as on the elevator/rudders.
Without that access door on the nose, mounting this servo would be very difficult.


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Old 08-01-2007, 11:03 PM
  #35  
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Default RE: Yellow P-38 build thread

Orvel,
My instructions have stablit also at the beginning but in the building process, they say use Zap-a-dap-a goo which appears to be what I have purchased. The instructions seem to be inconsistent: Use Zap-a-dap-a for hinge dowels glued to the elevator but suggest using 30 minute epoxy to glue the vertical stabs to the rudder post. I'm assuming yellow thinks the elevator will get more stress than the vertical stabs.
My main concern is high stress points like the servo mounts on the inside of the fuse wall.
Yellow recommends to also glass them to the fuse.
I can used the Zap-a-dap-a to additionally secure those.
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Old 08-01-2007, 11:22 PM
  #36  
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Default RE: Yellow P-38 build thread

Sam! You shame us all with your speed and sophistication!

Just watching one of your building threads makes me want to build another one.

Six years ago, I too struggled with the choice of epoxies. I bought some of their Stabilit, but found it difficult to work with and not that strong when cured. Eventually I settled on the slow epoxy Nelson Hobbies sells (System Three?), but of course made sure I sanded the finish off all FG parts I glued. It looks like Yellow glues their ply formers to the polyester glass with some kind of hot glue, but those glue joints aren't the greatest...they seem to rely more on fit and internal pressure to hold together.

So I cheated a little on some critical areas to get more structural integrity, like on those servo platforms for the rudders and elevator........I carved out a plywood plate that ran all the way across the boom and held both servos....giving it a lot more solid feel pressing against both sides of the boom rather than clinging precariously to each side like a cliffside swallow's nest! This required carefully cutting out enough of the plywood for the wheels to retract, but worth it for two such critical control surfaces. I'll try to dig my Yellow out of mothballs and post a picture, if you like.

You're gonna love this plane and I'm sure yours will be a lot prettier than mine, which served as kinda my "Workhorse 38" for four seasons.

mt
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Old 08-01-2007, 11:36 PM
  #37  
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Default RE: Yellow P-38 build thread

Sam:

There is a right and a left rudder, identify by the little molded tail light on the outside of each. Yellow actually sent me two lefts, but I never corrected it....wasn't that scale-detailed a plane for me.

There is also a subtle difference between right and left cowls (other than the R and the L markings!). I just can't remember what it is.

There will be A LOT more stress to the glue joints in the rudders and the vertical stabs than those hinge dowels for the elevator. As my Yellow got older, I actually re-did the wood in the rudders and vertical stabs and reinforced them with tiny little button head screws.


mt
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Old 08-01-2007, 11:49 PM
  #38  
samparfitt
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Default RE: Yellow P-38 build thread

MT,
Thanks for the info.
My servo trays have an extra support which is epoxied to one of the formers.
I'm going to glass around them too.
I also used 1/4" thick ply which doubles the surface contact area.
I like the button head pin idea: not much will break away from steel!
(looks like rivets but functional)
Thanks for the heads up on the R/L vertical fin: I bought some LED's at Radio Shack and will be attempting to set up a light system.
I'll need to run the wires before gluing any of those fins on.
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Old 08-02-2007, 09:16 AM
  #39  
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Default RE: Yellow P-38 build thread

Sam have you considered using two recievers? I used two on my Bronco and C130. it saved a lot of Y connectors. Just a thought . Rich
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Old 08-02-2007, 05:41 PM
  #40  
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Default RE: Yellow P-38 build thread

Rich,
that is a good idea that I hadn't considered.
I know I pulled out a ton of wires when I changed my old F-82 from 1 to 2 receivers.
I'll probably now stick with one reciever since another PCM is 160 bucks and I already bought all the extensions.

---------------------
Tail feathers (cont)

pic 1:
Thanks to Orvel, I Zap-a-dap'ed my rudders and filler pieces.
This stuff is really good: it's clear and works like weldwood's contact cement.
After a minute, the two pieces to be glued hold together so no clamps are needed.
I went over my plane and put the zap-a-dap on all the door hinges, four already installed servo trays and tank tray support.
I put Robart's 1" control horns on the rudders before putting in the balsa fillers so I could make sure all screws were going into the ply.
Also, this way, I know I don't put them in backwards, later on!

-------------------
flaps (cont)

pic 2/3:
The inner flaps control horns.
I removed those black plastic on the CH's, will epoxy the CH's to the flaps and then use the dubro's landing gear straps to support the CH's.
Note that there is about a 5/8" elongated hole in the inside of the flap well.
This allows me to put the hinges into the flap and wing while the CH is attached to the flap.
Note air tank sticking out the back access hatch.

pic 4:
Here's the front of the tank: the nose wheel clears the tank by about a 1/2" when in the up position.
The separate brake tank will go next to the gear tank on the upper level.
The servo and air valve will be on one side of the nose wheel and the brake servo and air valve will be on the opposite side.

pic 5:
Two 3000 MA packs: that should be enough power!
Won't hurt since nose weight will probably be needed anyway.

pic 6:
Dry fit inner flaps in wing flap wells to insure all fits OK and the CH's meet in the middle.

pic 7:
Dry fit inner flaps servo and tray.
Without that access hatch, I think this would be impossible to do(at least for ME)!

------------------
gear doors (cont)

pic 8:
Most of the doors needed sanding to keep the doors from 'catching' the fuse.
The hinge side of the door edge needed sanding and the outer lip of the door opening on the fuse also needed sanding.

------------
Tail feathers (cont)

pic 9:
I zap-a-dap'ed some balsa fillers around the stab so I can later epoxy the cut out FG back onto the fuse.

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Old 08-02-2007, 08:50 PM
  #41  
JeffH
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Default RE: Yellow P-38 build thread

BVM Aeropoxy sticks very well to polyester, as does his new V-poxy. Of course to save a little money, you can use Hysol epoxy, which is what BVM relabels as his. Aero-Tech also sells some Methacrylate epoxy which really sticks to polyester. Slow set epoxy will stick, you just have to REALLY rough the surface up, and then clean it with some sort of solvent. ie Acetone, Laquer Thinner, etc....

Back in the day, Byron's told you to use White Vinegar to clean the surface before and after scuffing it with 80 grit paper.

Jeff
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Old 08-02-2007, 09:46 PM
  #42  
samparfitt
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Default RE: Yellow P-38 build thread

Inner flaps (cont).

pic 1:
The profile of the inner flap servo tray.
Also, I put the four access door mounts around the hole.

pic 2:
Inner flaps access hatch dry fitted.

pic 3:
One inner flap servo tray zap-a-dap'ed in.

------------
engine choke/thottle servos.

pic 4:
Relative position of the G-38 on the fire wall (plane upside down).

pic 5:
Left boom view:
Since the tank is in the middle and the carb is on the left (plane upside down), the choke/throttle servos must be to the left(right in this picture).
Plenty of room there to mount a new servo tray.

pic 6:
Right boom view:
Not too much room in this boom.
All that space to the left in this picture is useless for direct access to the engine carb being on the opposite side.

pic 7:
Left boom:
Two supports clamped to the retract mount while the epoxy dries.
Servo tray cut out and will be screwed to the two supports for easy maintenance.
All ply is 1/4" thick.

pic 8:
Right boom:
Maybe I can cut out some servo holes in that retract mount!
The blue line is the edge of the retract mount.
Have to sleep on that!
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Old 08-03-2007, 09:13 AM
  #43  
samparfitt
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Default RE: Yellow P-38 build thread

Rich,
I'm out there putting all those wires in and I think your twin receivers is looking better all the time.
It's not like I won't need extension wires 'down the road'!
I'm thinking one in each boom on the outside wall just behind the wing.
Run all batteries and switches to the nose.
I run double batteries so with each 6 v 3000 MA, I'll add a second 6v 1400 ma battery (that should be enough nose weight!).
One receiver will get a rudder, throttle, choke, center flaps, aileron and half (one servo) the elevator for one side .
The other receiver will get a rudder, throttle, choke, outside flaps, aileron and other half of the elevator for the other side.
I just tried moving one elevator servo and it has no problem moving the other, should it go bad (assuming not locked up).
The two outer flaps to one receiver so I always have flaps in 'even numbers' (even if only half).
Gear and brakes can be divided between the two receivers.
Let me know if I've got any flaws in my logic.
thanks
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Old 08-03-2007, 04:53 PM
  #44  
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Default RE: Yellow P-38 build thread

Sam That is what I had except I put both the throtals on one rec . If I got a glitch or had a problem both throtals should be the same. I can see pors and cons both ways but it worked for me till the stab broke loose. Then it didn't matter.
I had the batteries in the center pod and the switches and rec in the booms. The flaps ,elev ail and rudders were as you have it. Hope this helps Rich
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Old 08-03-2007, 05:02 PM
  #45  
samparfitt
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Default RE: Yellow P-38 build thread

Throttle/choke servo tray (cont)

pic 1:
#6 blind nuts and bolts hold the servo tray to the retract mount.

pic 2:
1/4" thick ply added to one servo (choke) to raise it so the control rod will pass over the throttle servo.

pic 3:
Tray with servos mounted.
-------------
stuff:

pic 4:
Picked up a few things at Home depot.
1/4" dowel for ends of carbon fiber rods.
Aluminum solid rod to drill and tap to make standoffs for the engines.
Some electrical boxes to make servo brackets to rotate the servo from horizontal by 90 degrees (as the rudder servo).
I figure if these boxes can withstand fires, they should be strong enough to hold servos (good price too!).
Run them through the band saw should yield quite a few!

--------------
Rewiring for two receivers.
OK folks, I'm not sure if any wiring was saved when you see the rats nets in each boom.
The good thing is that only two 'Y' were needed (rudder/steering & outer flaps).

pic 5/6:
Left boom.
All but the gear outlet was used (in other receiver)
We used the usual stuff for left boom only: throttle, aileron, elevator, rudder(steering) but no gear.
Aux 1 is inner flaps
aux 2 is brakes (will mix into the down elevator)
aux 3 is left engine choke
aux 4 and batt are two sets of batteries (in center fuse nose, with switches).

pic 7/8:
Right boom.
All but the aux 2 (brakes)
Again, but for right boom only: throttle, aileron, elevator, rudder and gear.
Aux 1 is two outer flaps
aux 2: not used
aux 3 is right engine choke.
aux 4 and batt are two more sets of batteries (in center fuse nose, with switches).

everything seems to work...amazing.
I've got to 'tiddy' this mess up, yet!
Since both chokes are on one channel (none left), I'll have to choke both engines before trying to start them.
One nice thing about double receivers is it should reduce the amount of current going through one receiver (especially since there are 15 servos!).

pic 9:
mini gear and brake servos.

pic 10:
Five wires to the nose: four for batteries/switches and one for nose steering servo.

pic 11:
Wires going from one side to center or other side (flap only) routed along the back spar.

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Old 08-03-2007, 05:07 PM
  #46  
samparfitt
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Default RE: Yellow P-38 build thread

Rich,
That a good point on throttles: rather have both dead than just one!
I'll change that.
I'm figuring nose weight will be needed so batteries went way up front: should I actually have the luxury of too much weight up front, I'll transfer them to the booms (but only if a two sets can be moved for lateral balance).
thanks.
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Old 08-03-2007, 08:45 PM
  #47  
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Default RE: Yellow P-38 build thread

Engines (cont).

pic 1:
mmmmm, there isn't much room for servos in the right boom when the retract is added!
Not sure how to remedy this one with G-38's...have to sleep on it.
The last plane I had, the G-38 in was the TF P-51 with the throttle servo mounted above the engine (magneto).
Never had any glitches but Dick Bennett says they should be 12" away.
I talked to either DA or 3W (can't remember which) and they said no problem with the servos next to the engine (electronic).
I may have to mount the servos to the outside (like the left boom) and then put in control horns to route to the left side of the engine after entering the engine compartment: going to have to make sure that linkage is tight!

Well, nothing will be done until Monday: another pilot and myself just packed up my trailer with his Neuport, FW-190 and my SBD dauntless and Spitfire and we're heading out tomorrow at 6 AM to Louisville, KY for a warbird flyin.

Oh yes, Ralph as RC ignitions called and said he can only convert the G-38 to clockwise rotation with electronic ignition (about $125).
bummer!
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Old 08-03-2007, 09:30 PM
  #48  
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Default RE: Yellow P-38 build thread

Hey Sam, I take it you want to use magnetos on your engines. I assume Ralf can't reposition the flywheel.

I don't know if this would work on the Zenoah, but we used to run limited modified gocarts with out a key on the flywheel because you can't get enough timing with an offset key.

We used lapping compound to mate to fly wheel to the crank. when they match each other perfectly they would not slip when tightened together. we had to get them off with a puller.

I suppose you could move the fly wheel for it to run in reverse. (where, I have no idea)

This might solve your problem. if it will work.

Of course I could be totally wrong (and probubly am) But I was just thinking, and sometimes thats dangerous.

BTW, Looking good on the build, I was hoping to build one this winter if everthing goes well with my other projects.
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Old 08-03-2007, 10:05 PM
  #49  
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Default RE: Yellow P-38 build thread

Tbolt,
My expertise is not in small engine updates: I'm going to have to rely on Ralph as the expert.
Ralph said the G-38 is one of the few engines taken from a chain saw (versus most of today's engines are 'plane' engineered) and chain saws were never meant to run backwards.

pic 1:
mmmm, looks like others are putting servos by the engines!!!

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Old 08-05-2007, 10:51 PM
  #50  
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Default RE: Yellow P-38 build thread

engine mounting

pic 1:
Fire wall to front of cowl: 6 1/2", G-38 back of prop to back of engine mount: 5 7/16" gives standoffs of 1 1/16" long.
I cut aluminum solid rod from home depot 1 1/16" long with a hacksaw.

pic 2:
Used the belt sander to square away the cut.

pic 3:
Four per side.

pic 4:
center punched both ends of the rod.

pic 5:
Drill a pilot hole from both ends meeting in the middle to insure holes were centered at both ends and using cutting oil for all drilling/tapping.

pic 6:
Drilled a 17/64" hole.

pic 7:
Used a 5/16" X 18 threads to tap the rod holes.

pic 8:
Used 5/16" X 3/4" long bolts from home depot to secure one end of the rod to the engine and another bolt to secure the rod to the fire wall.

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