Fastening carbon props

I finally found out what ruined my OS .46 LA.
I was using a carbon prop. When checking closer after the fatal runaway. I found that the prop was loose even if the nut was fairly tight. So the engine probably ran twice as fast as the prop.

These carbon props are really difficult to tighten since the material is totally inflexible.
Any advices?

Install a pin in the thrust washer and drill your props to match. You still need to check the tightness of the prop nut often.

Tight lines,

I have been using the carbon fiber props for 2 years on my ST 46 and have never had a problem??

EDIT: I see it helps to have a drive washer that has a good knurl to grip into the prop and prevent slipage.

what you should do is make some washers from 80 grit sandpaper or sandcloth. and insert one between the drive washer and the prop or anytime you need a bit more clearance behind your spinner add more than one. They are mighty handy to carry in your flight box and seem to give a better grip on the prop .It seems that the pressure of the prop nut squeezes the sandpaper hard enough that the grains of sand actually dig into the prop face slightly and seem to work through the paper barrier so they also grip the drive washer better. Quite often someone finds that the spinner backplate is rubbing on the fuse and then you can hand them one of your ''magic solutions''.Its easy to cut the hole out of the material using a leather punch,although it probably dulls the punch.Keith V

Ok i will give this one a try.
Thx.
Norvald Olsvold

Absolutely agree, it works a treat.

>Absolutely agree, it works a treat.
The sand/grit paper I mean.

I especially like the 80 grit that has the blue fabric backing to use between the prop and drive washer. It really gets a bite. Works great when you are using the old slick back veco shaft extensions, too.
I like the paper backed 80 grit better for "spacers" to move the backplate, if necessary.
Bill <><

Quote:

I had a laugh yesterday evening. The other day i received 2 spinners from Tower Hobbies. Great Planes Spinner 2" Nylon Aluminum Red.
When i opened one to put on my new Stalker .51, guess what was inside the spinner.

2 round sandpaper washers (sand on both sides) with holes punched.
All ready to use.

Narvald I too, had a laugh this evening. The sandpaper washers that came with your spinner are worthless!!! They are made apparently by taking two pieces of sticky back sandpaper and sticking them to each other resulting in grit on both sides. Problem is the sticky stuff will just slip, allowing the crankshaft to rotate when you try to tighten the nut. Throw them away, not worth the bother. Don't ask how I found out!!!

Some drive washers have flat peaks on the drive washer pattern. You need a sharp one that bites into the prop. A knullred drive washer is sometimes ok for CF but, the best ones are engraved so the teeth of the patteren come to a sharp peak. Rossi racing engines are a good example.

Not all CF props are created equal. Most proprietary props I've seen are soft enough to be used with boarder line drive washers. A CF prop with the right fiber resin ratio can be very hard.

I've been running a Supercool CF prop on a Tower 40 for more than two years and don't recall the last time I tightened it. Maybe I should check?

A few times I went out in the morning to fly without tighting my propnut. I always wondered what the Law of averages would be for this prop to come loose. It came loose a few times the very last time it came loose it whacked me smack in the beak. Missing my left eye by 1".

One thing not mentioned here is how you tighten the prop. We have a good size wratchet wrench and lean on it a bit to make certain that the prop nut is tight. These little T-wrenches sold in the hobby shops do not give enough leverage to make sure the prop--any prop--is tight.

Of course, some people break their prop every other flight and never have a chance for it to work loose, but if you plan to keep your prop--and if you are using carbon fiber props I hope you do--then you should make sure you have it good and tight.

Remember, good and tight. Tight is good.

I keep box end wrenches in my box for this. Unfortunately I broke a B-Y&O 10-6 doing this, but I still use them, especially on CF props.
I am able to sink the prop washer into the front of a wooden prop with a "cross" wrench, but it is easier to get the correct torque with a good box end wrench.
Bill <><

>I am able to sink the prop washer into the front of a wooden
>prop with a "cross" wrench

Propeller tightening (PE101) starring Bill Little and Fay Ray....Coming to a video store in your home town!

Cheers Big Guy

The trick we used in T/R in the 70's was to insert a nylon washer about 1/16-3/32" thick, between the prop and the prop washer.

>The trick we used in T/R in the 70's was to insert a nylon
>washer about 1/16-3/32" thick, between the prop and the prop
>washer.

I don't get it. Maybe you meant to say "prop driver" instead of prop washer?

As I recall, the F1C guys early in GF & CF prop history, had the same problem. One thing reported to work was a "washer" of 1/32" birch plywood, between prop and prop washer. The idea is to put some "crush" in the stackup. I reckon the nylon washer would work about the same. Steve

Bill Little's hands are so strong that he could tighten that prop nut with his fingers. You think I am kidding,Bill is very strong.Well almost that strong.
Ed

Dan, I'm always a little confused on this English/American terminology. Reading from the back of the engine towards the front, in our terminology we have the prop driver, the prop, the prop washer, and the prop nut. Can you clear up for me once and for all what is the drive washer? Is it the prop driver, i.e. behind the prop, (in which case it's not a washer), or the prop washer, in front of the prop? Or anything else?
The nylon washer I mentioned goes between the prop and the prop washer in the order given above.

>Dan, I'm always a little confused on this English/American
>terminology. Reading from the back of the engine towards the
>front, in our terminology we have the prop driver, the prop,
>the prop washer, and the prop nut. Can you clear up for me
>once and for all what is the drive washer? Is it the prop
>driver, i.e. behind the prop, (in which case it's not a
>washer), or the prop washer, in front of the prop? Or
>anything else?
>The nylon washer I mentioned goes between the prop and the
>prop washer in the order given above.

Rustler,

We're on the same page; prop driver, prop, prop washer, prop nut. As to how others describe it, I'm as clueless as you.

I was asking because it would not be my first idea to place a compressible shim of any sort between front face of prop, rear face of prop washer. If it works, it works, and Steve's idea may come into play here. Still seems mechanically incorrect, although shims of sandpaper between prop and prop driver seem to me problematic as well. Again, if it works...

Dan, it was a case of "it works". I think it's something to do with having something which has a little "give" in it, which cushions the firing impulses transmitted to the prop and prop nut.

Check out the latest safety column in SN..precisely about this problem.

>I finally found out what ruined my OS .46 LA.
>I was using a carbon prop. When checking closer after the
>fatal runaway. I found that the prop was loose even if the
>nut was fairly tight. So the engine probably ran twice as
>fast as the prop.

Not to be obtuse- but doesn't this mean that the nut was somehow bottoming out on something, rather than you didn't get it tight enough?

>
>These carbon props are really difficult to tighten since the
>material is totally inflexible.
>Any advices?

I just use a plain old rachet with a deep-well socket to fit over the spinner nut. But lots of people tighten them with the little "cross" wrenches and don't have much problem. It's really never been an issue for me, and I don't use anything like a sandpaper washer or similar.

Brett is right about using a socket and bar to tighten the prop nut...and more than likely correct about the nut "bottoming" onto the crank...it might have run out of threads.
Windy preaches that anyone using carbon props buy one of those jiggling etching devices that Sears sells, and that a good cross hatch pattern be put into all props as the first step in getting the ready to use.
I saw Young Daniel's deal.....very strange and potentially dangerous.

See Ya

Brett, this really was a problem with the carbon T/R props when they came in. The nylon washer cured it.

Brett,

I have had the bottoming out problem on my Ro-Jett when the threaded prop stud unscrews a little and I don't notice it before putting on the prop. It is then too long, and the nut "bottoms out" too soon. Figured it out pretty quick, so now I watch for it. I guess I should lock down the stud, but it is really not a problem any more.

"I saw Young Daniel's deal.....very strange and potentially dangerous.
See Ya Peabody"

Tell us about this incident? Did I miss it, someplace?

I was thinking that if a heat gun or boiling water will work on a CF prop for re-pitching, what about heating up the hub's rear face, slap it on the engine, and snug it down goot und tight. It should take the imprint of the prop driver knurling, and not require anything else. Who'll try it? Report back! Steve

Here's an obliquely related note having to do with CF or epoxy props, tightening thereof.
John mentions props being loose on the first flight of the day.
I am no scientist, but there is a matter of metal expanding and contracting that affects this. A prop that is tight the night before may or may not be tight in the morning, depending on what happened, temperature-wise overnight.
Here's an anecdote: Numerous years ago, the night before a contest, doing pre-contest checks of my racing gear, I snugly tightened the glass prop on a Goodyear plane. Next morning, I came out to the workshop, and found the prop laying on the bench in front of the plane.
In those days, my shop was a detached building. Overnight, the temperature had dropped, the metal contracted, I guess, and the shaft broke.
Since then, I have done my prop tightening in the morning, even though I now have a cozier shop.
--jt

John Thompson

> Here's an anecdote: Numerous years ago, the night before
>a contest, doing pre-contest checks of my racing gear, I
>snugly tightened the glass prop on a Goodyear plane. Next
>morning, I came out to the workshop, and found the prop
>laying on the bench in front of the plane.>--jt
>
>John Thompson

John,

You have the strangest engine failures.

Tells us again how that electric starter knocked the cylinder out of round in your O.S. 40FP.

And what happened to that Fox 35 I spiffed up for ya?

The starter knocked the cylinder out of round the same way it knocked your conrod out of shape! I never liked starters much, and now I don't like 'em even more. I just carry it in my flight box now mainly so that I look like an SSF.
That Fox .35 you spiffed up is still in fine shape, just needs a plane to ride in. You want it back? Glad to ship it to you as thanks for all your help. Maybe you can put it to good use.
--jt

>Tells us again how that electric starter knocked the
>cylinder out of round in your O.S. 40FP.
>
>And what happened to that Fox 35 I spiffed up for ya?
>
>Dan
>

John Thompson

>"I saw Young Daniel's deal.....very strange and potentially
>dangerous.
>See Ya Peabody"
>
>Tell us about this incident? Did I miss it, someplace?
>
Steve
>

Steve,

I can help, but it's a two-step process.

1. Context. Peabody is concerned--and for very good reason, I might add--that I may have a list of questions for him, and he knows his answers will be quite weak. Reference: Questions already hanging out there and which he to date simply ignores, having first made some rather outrageous accusations.

So he kinda roams around taking note of my inputs, but not necessarily with any great care.

2. Translation. Peabody thinks I was the one who proposed the washer between front of prop and prop washer when it was "Rustler" who did so.

I was merely asking for confirmation as to exact placement of extra washer, completely clear to all of us. Less Peabody, of course.

For what it's worth, Ian Russell, a.k.a "Rustler" could tell me to install all CF props backwards and I would at least think about, that's the sort of credibility he has with me.