Originally Posted by WestTexasKing

That will work, I had mine spin so much that it melted the spindle out completely.
I drilled the melted portion out and had just enough to center the prop on the backing plate, which is all you really need.
A washer in front of the hub keeps it true.

Wow, if it's getting that hot from friction, maybe there is quite a bit of slipping. I think I'm going to do what you are talking about, except try and use some sort of a lock washer: (http://en.wikipedia.org/wiki/File:Washers.agr.jpg) to keep the spinner from slipping.

Has the slipping affected things noticeably?

Actually, it was from a ground run.
I always test full throttle right before launch and for some reason it was yawing bad to the left.
I held throttle for a few short seconds to see if there was any change and that's when the left prop just about quit spinning completely and nearly wobbled right off the motor.
Nut was holding when I held the motor and tried spinning the prop so I thought it would hold fine at full throttle...I guess it got loose enough with the added torque.
Friction from the prop shaft is what melted the spindle.
Good thing I didn't decide to hand launch before checking, or else I would have been playing lawn darts with some expensive foam...

I wouldn't rely on the lock washer alone to hold torque, though it probably wouldn't hurt.
This is what I'd use to keep everything solid:
http://en.wikipedia.org/wiki/Nyloc_nut



One problem I see is that most lock washers are irregular in shape so they might distort the back plate under torque from the nut.
In a normal situation, the lock washer is designed to distort from its original shape under pressure between the much stronger nut/bolt and whatever it's fastening.
In this case, the lock washer could distort the lightweight plastic long before washer itself distorts flat causing a wobbly prop.
Best choice would likely be an internal star lock washer (largest, far right in your link) as opposed to an external star (smaller ones to the left) or split washer (right above the star washers).

I'm sure you'll be able to figure something out that works well, surely there's no need for me to over-analyze it like I'm doing right now LOL



----
Completely irrelevant to this thread, but you might get a kick out of it.
My ag-cat continues to have issues with the R1340's updraft carb.
It seems like no matter what I do, the nuts continue to loosen off.
This is a serious safety issue, as without the nuts the carb will literally fall straight down off the engine.
I already had to replace the carb once ($1,400, ouch!) because the nuts became loose and the studs wore the flange completely through.
When I replaced the carb, I used an internal star lock washer, a properly torqued nyloc nut requiring a purpose built torque wrench, and the heaviest duty threadlocker available after replacing all 6 studs with brand new ones and cleaning them with acetone.
Keep in mind that aviation hardware is miles beyond the highest grade stuff you can buy at an average auto parts or hardware store.
It lasted about 2 months, roughly 150hrs of flight time, before 3 studs broke off and the remaining 3 nuts somehow managed to loosen off IN FLIGHT.
Since the carb was hanging down about 1.5", the venturi effect was negated and it wasn't supplying the engine with fuel.
I managed to keep it going for 4 miles to a suitable dirt road by jamming the throttle back and forth using only the accelerator pump to maintain flight.
It sounded like a sopwith camel that didn't have throttle control on landing approach.
Thinking it might be motor mount related, possibly introducing an oscillating force that the existing carb fasteners cannot withstand.
Moral of the story?
Don't trust lock washers, nyloc nuts, or threadlocker with your life
----

V2 bone stock, flew amazingly well - probably the "sweetest" flying airplane I can remember flying. Actually flies better than I remember my trainer flew. There is quite a bit of dihedral, of course, and it is largish for a foamie.
After about 6 batteries, however, things are starting to loosen up: the rudders are ridiculous and are so flimsy, they can't possibly be doing much or they would just break off! The hot glue gun is warming up as I type
The nose gear is getting loose and looks skewed - I swear I was nice to it, but it looks like it needs some kind of bracing. Also, I just took off the nose gear door before the first flight because it interfered with the gear up cycle.
Received delighted comments from everyone with one of the senior members remarking how realistic it looked.
I tried doing high speed ( ) passes, but it wouldn't go very fast.....

Originally Posted by edpare

V2 bone stock, flew amazingly well - probably the "sweetest" flying airplane I can remember flying. Actually flies better than I remember my trainer flew. There is quite a bit of dihedral, of course, and it is largish for a foamie.
After about 6 batteries, however, things are starting to loosen up: the rudders are ridiculous and are so flimsy, they can't possibly be doing much or they would just break off! The hot glue gun is warming up as I type
The nose gear is getting loose and looks skewed - I swear I was nice to it, but it looks like it needs some kind of bracing. Also, I just took off the nose gear door before the first flight because it interfered with the gear up cycle.
Received delighted comments from everyone with one of the senior members remarking how realistic it looked.
I tried doing high speed ( ) passes, but it wouldn't go very fast.....

When I maidened mine, I actually lost the top half of the right rear rudder. It went into a spin and I had to put it down in the stubble field next to the runway

Originally Posted by gwidgery

When I maidened mine, I actually lost the top half of the right rear rudder. It went into a spin and I had to put it down in the stubble field next to the runway

Ouch! Bummer.
I actually did break the right rudder, too - but it stayed on. I didn't even find the break until I "landed" .

Originally Posted by edpare

Ouch! Bummer.
I actually did break the right rudder, too - but it stayed on. I didn't even find the break until I "landed" .

I went on ahead and made the tail section permanent with some carbon fiber rod, toothpicks, and CA. I got it on video to, i was in the middle of a loop when it came off. I'll post the video when I get home from work.

Originally Posted by WestTexasKing

I wouldn't rely on the lock washer alone to hold torque, though it probably wouldn't hurt.
This is what I'd use to keep everything solid:
http://en.wikipedia.org/wiki/Nyloc_nut



One problem I see is that most lock washers are irregular in shape so they might distort the back plate under torque from the nut.
In a normal situation, the lock washer is designed to distort from its original shape under pressure between the much stronger nut/bolt and whatever it's fastening.
In this case, the lock washer could distort the lightweight plastic long before washer itself distorts flat causing a wobbly prop.
Best choice would likely be an internal star lock washer (largest, far right in your link) as opposed to an external star (smaller ones to the left) or split washer (right above the star washers).

I'm sure you'll be able to figure something out that works well, surely there's no need for me to over-analyze it like I'm doing right now LOL

Yeah, on second thought, the lock washer idea is probably only going to tear up the backplate even more in the event of a prop strike, etc.

Up until know, I was just using el-cheapy GWS 3-blade 9x7 orange propellers without the spinner or backplate of the original airplane. That worked well, but it really looked dorky.

But I think I've figured out a combination of washers, etc, that should allow me to go back to using the old spinner and backplate and the master airscrew 3-blade props that I was using before my spinner broke. The whole assembly is based on your ideas.

Here's a little video to show yo what I finally ended up with:

Propeller assembly.... (1 min 50 sec)

Once the propeller is on, I should be able to bolt on the spinner to the backplate and it will look pretty stock once again.



At some point, I really just need to get some decent motors with some better shafts and the right sized prop adapter with a nice solid grub screw to hold the prop on correctly.

I'm using my first P38 as a platform for experimenting. When I get ready to build my other one (airframe only), it will incorporate all of the improvements that have been listed in this thread, along with some nice retracts, etc, etc.

Looks like you got it all figured out!
I noticed the front washer is a bit larger than the shaft diameter, do you think that'll mess with the prop balancing any?

On examination of the nosegear mount, I found the ply mount plate was only large enough for 3 wood screws, one of which had missed the hole: and was only screwed into foam! The screws are also about 3mm too short and do not entirely engage the plywood. So, we still have some quality control issues.

I'm of the opinion this plane is too complex and too large for foam. I do not feel it will have the longevity of a standard balsa-ply-film model.
On the other hand, my "go-to" plane is a DC-3 twin foamie I got from Nitroplanes and have been flying almost daily for 7 months. Ive torn the port motor off four times on that thing and one can't really tell from 100 feet.....

Does this thing have enough rudder authority (when they stay on) to fly a knife edge pattern??

Originally Posted by cbr998

Does this thing have enough rudder authority (when they stay on) to fly a knife edge pattern??

Affirmative. I can confirm this because I've done it! :-)

Originally Posted by WestTexasKing

Looks like you got it all figured out!
I noticed the front washer is a bit larger than the shaft diameter, do you think that'll mess with the prop balancing any?

Probably, but my plane is such a disaster at this point, I don't think it will make that much difference. I'm up to "Phoenix VII" at this point, (1 midair, 3 catastrophic engine failures, one prop blade flying off, one crash where I "lost" the plane flying formation, and the last crash where I "dumb-thumbed" it into the ground while knife edging it!!@!_)

So it's been trashed so many times, it's mostly an epoxy composite plane....but it's still going, and going, and going.

Thanks to Dangaras for the free battery lid! I will pay it forward whenever and however I can. Marge hit a tree branch on final last weekend sending it unceremoniously to the pavement nose first. So I repaired it best I could. Hope to have her in the skies this weekend.

Originally Posted by Aros

Thanks to Dangaras for the free battery lid! I will pay it forward whenever and however I can. Marge hit a tree branch on final last weekend sending it unceremoniously to the pavement nose first. So I repaired it best I could. Hope to have her in the skies this weekend.

Good you sourced one as that is the easiest way. Mine flew off in flight & there was no finding it. I fabbed one out of a block of foam and it is as good looking as the original but far more functional with very strong magnets and a lift tab. Little elbow grease, spackle WBPU and paint and good as new.

Alan