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Author Topic: 46LA Prop Extension  (Read 2920 times)

Offline Tim Wescott

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46LA Prop Extension
« on: August 28, 2015, 10:52:52 AM »
Short story: I need t extend the prop on an OS 46LA by about 1/4".  With all the stack-up, that means that I can't just bung on a regular prop nut (unless I want to go fly with only two threads engaged).

I've never played with prop extenders -- what's good to do, and what should I watch out for?  I assume I'll need some sort of long prop nut that reaches down inside the prop, and that I'll need to ream the prop washer and prop to clear it.  Does anyone sell these, and if so, what brands are good?

Long story:

Paul Walker was giving away planes this past weekend.  I was lucky enough to be in the right spot at the right time, and I got his Atlantis.

It originally had an OS 40 SFR in it, which Paul disrecommends (and which isn't available on eBay anyway -- I looked when the fit issues came to light).  He recommended I try a 46LA instead.  Judging by the location of the holes in the plane, the thing is about 1/4" longer than a 46LA, and 3.5mm wider.  I can deal with the width issue by making oval holes in an LA crankcase, but I need to deal with the length issue by either relocating the holes or a prop extender.

A Magnum 51 drops right in, but it causes Paul to make pained comments about humongous engines and how the CG was perfect with the original engine.  Since the Magnum is about 3 ounces heavier than the 40 FSR, the all up plane weight would be something like 5 ounces greater after I finished putting lead in the tail.

Relocating the holes is complicated.  I don't see how to do it without at least some weakening of the engine bearers.  Given what's in there and an urge to only modify the wood once I'd be tempted to go with thick aluminum pads bolted to the bearers, with the motor bolted to that -- but making the pads and reworking the bearers in the plane, just so that I can bung an engine in there and get in the air seems to present a complication to results ratio that's a bit high, even for me.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Mark Scarborough

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Re: 46LA Prop Extension
« Reply #1 on: August 28, 2015, 12:56:25 PM »
Tim,, call scott Riese,, he made one for my Avenger,, he can set you up with exactly the length you need to make it work
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Offline Steve Helmick

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Re: 46LA Prop Extension
« Reply #2 on: August 28, 2015, 01:56:49 PM »
Quote from: Mark Scarborough on August 28, 2015, 12:56:25 PM
Tim,, call scott Riese,, he made one for my Avenger,, he can set you up with exactly the length you need to make it work

Mike H. had to do this when he put a .46LA into his late & lamented JD Falcon. I think that spinner backplate is on my Skylark, in fact. Basically, you need the prop nut/sleeve thing from a 1/4-28 Fox shaft extension and make a disc to JB Weld to the spinner backplate. The disc can be sawed from 1/4" aluminum plate, or turned in a lathe. Since Tim has a lathe, he's probably going to find it there, amid some chips...early in the AM.   y1 Steve
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In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline tom brightbill

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Re: 46LA Prop Extension
« Reply #3 on: August 28, 2015, 02:13:36 PM »
How about shortening the nose 1/4"?  I don't think Paul would mind.
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Offline Tim Wescott

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Re: 46LA Prop Extension
« Reply #4 on: August 28, 2015, 04:24:34 PM »
Quote from: tom brightbill on August 28, 2015, 02:13:36 PM
How about shortening the nose 1/4"?  I don't think Paul would mind.

I'd rather make adapter pads for the engine bearers to take Any Engine, Ever.

I was just in town, so I got what I needed to build something up.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Tim Wescott

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Re: 46LA Prop Extension
« Reply #5 on: August 28, 2015, 07:07:29 PM »
Long nut made.  I just got a 3/8" bolt from the hardware store, parted it off, drilled it & tapped it.  I just need to make the spacer and the washer, properly ream a prop, and go.

Or, maybe I could redneck the thing and just stop here -- a pile of washers ought to work pretty well, yes?
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Steve Helmick

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Re: 46LA Prop Extension
« Reply #6 on: August 28, 2015, 07:46:24 PM »
Well, the pile of washers will give you a thickness to aim for with an aluminum spacer, but they'll be heavier and I'd expect them to slip at some point, probably on an official flight at a contest a long way from home. But Mike will tell you that I worry too much about stuff that could happen. I started in the fishingboat shipyard and Boeing, where stuff that broke was dangerous or really inconvenient. With models, everybody can do what they want, tho, even if it's wrong in the view of others. Pretty much, anyway.  y1 Steve
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"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline Tim Wescott

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Re: 46LA Prop Extension
« Reply #7 on: August 28, 2015, 10:52:24 PM »
Done.  If I'd thought of making the long nut out of a bolt I probably wouldn't have started the thread at all -- the rest is pretty obvious.

The knurling hardly rates the term, so the thing may still slip -- I'll probably glue it to the spinner backplate, and make sure to tighten it down good when I use it.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Mark Scarborough

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Re: 46LA Prop Extension
« Reply #8 on: August 29, 2015, 12:18:49 AM »
Tim,, I put a "disk" of 120 grit sandpaper between the spinner backplate and the spacer disk,, The Avenger has flown that way without slipping the prop since 2006,, well excepting the regionals when a line clip flipped over and I bounced the prop,, wood special carved one,, which lead to a test flight over the grass complete with handlaunch from Pat, GULP,,,

anyway,, back to the point,, The sandpaper disk , PSA backing, seemed to give it just the grip needed,,

glad to see you with a better airframe,,
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Offline Tim Wescott

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Re: 46LA Prop Extension
« Reply #9 on: August 29, 2015, 02:49:48 AM »
Thank you Mark.  That's obvious in hindsight, but I'm not sure I would have ever twigged to it on my own.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Steve Fitton

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Re: 46LA Prop Extension
« Reply #10 on: August 30, 2015, 09:39:10 AM »
Is that an HP 32 SII calculator there?  Those were my favorites...
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Offline Tim Wescott

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Re: 46LA Prop Extension
« Reply #11 on: August 30, 2015, 09:55:06 AM »
Yes it is.  I still use it all the time.  I'd lament the demise of RPN calculators, except that there's at least one really good smart-phone app that does a great job emulating one.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Steve Fitton

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Re: 46LA Prop Extension
« Reply #12 on: August 30, 2015, 12:19:19 PM »
I thought HP brought them back after Carly Fiorina got ousted (I heard from our HP rep that she had them dropped because she couldn't figure out to work one). 

I have an HP 33S that is RPN, just not as sturdy as the 32SII
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Offline Tim Wescott

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Re: 46LA Prop Extension
« Reply #13 on: August 30, 2015, 12:50:30 PM »
Quote from: Steve Fitton on August 30, 2015, 12:19:19 PM
I thought HP brought them back after Carly Fiorina got ousted (I heard from our HP rep that she had them dropped because she couldn't figure out to work one). 

I have an HP 33S that is RPN, just not as sturdy as the 32SII

Hmm.  It seems they're back.  I'll keep mine for the moment, though.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Air Ministry .

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Re: 46LA Prop Extension
« Reply #14 on: August 30, 2015, 11:10:06 PM »
Er , if your redrilling it , can you go the whole hog & redrill 1/4 aft , too . No spacer Reqd. then .  :-\
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Offline Steve Helmick

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Re: 46LA Prop Extension
« Reply #15 on: August 31, 2015, 11:33:43 AM »
I just wanna see how a .46LA does in a 680-ish square inch Impact predecessor. At "Roundup", I hope.  y1 Steve
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"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline Tim Wescott

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Re: 46LA Prop Extension
« Reply #16 on: August 31, 2015, 01:36:09 PM »
Quote from: Steve Helmick on August 31, 2015, 11:33:43 AM
I just wanna see how a .46LA does in a 680-ish square inch Impact predecessor. At "Roundup", I hope.  y1 Steve

Paul said "try it".  So I'm tryin' it.  If it doesn't work there's always that Magnum in the nose and a hunk of lead in the tail.  Or an OS 46AX, which I really think that someone needs to try for stunt.

I might make it up -- the plane fits in my car, so that's one barrier dealt with already.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Mark Scarborough

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Re: 46LA Prop Extension
« Reply #17 on: August 31, 2015, 04:30:53 PM »
there are other options too Tim,, aside from an unproven quantity,,
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Offline Tim Wescott

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Re: 46LA Prop Extension
« Reply #18 on: August 31, 2015, 04:35:32 PM »
Quote from: Mark Scarborough on August 31, 2015, 04:30:53 PM
there are other options too Tim,, aside from an unproven quantity,,

Well, yes, and some known-good stunta-motas that'll fit those bolt holes.  Which is what I'll use if the 46LA doesn't work out.

Except for the 40 SFR, which is what Paul told me was in there, most available options weigh around 11-13 ounces.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

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