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Old Jul 10, 2006, 05:08 PM
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East Anglia, UK
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Making a WWI wooden prop.

Well, as promised, after a swift e-mail or 4, in the post today came 4 bits of laser cut bass from Charlie (portablevcb) ...well..

After admitring the excellent work..I stacked em up on 3 hack GWS motor shafts..checked they were tight, and drizzled thin CA between the laminations. It came out the other side so I reckoned it had got all through all right.

Then off they came and a lot of work (about 2 hours) with files, rasps, and various blades and bits of sandpaper, I had a pretty reasonable looking 8x6 prop that looked like it came off a WWI plane..Bass is a perfect wood for this sort of hand carving.

Needed a LOT of CAREFFUL sanding and scraping, and it wasn't perfect, but I hurried on anyway as this was very much a prototype..its really thin, and light, and feels somwhat fragile..but I was absolutely amazed at both how even the spiral came out, how easy it was to get it smooth by simply running fingertips over it to identify high spots, and how MUCH sandpaper it took to get the slight undercamber into it.

It was pretty far out of balance at first, but the fingertip test identified that the heavy blade was really just thicker, and wasn't quite sanded down..

Then a quick rub with the only bit of woodstain I could find, and a coat of sanding sealer, rubbed down and then a wipe with some thinners..all in the name of speed really.

Checks against a GWS 8x6 showed it had a similar thickness, less blade area outboard, more inboard, was MUCH stiffer and looked INFINITELY better..and weighed less..

Time to test it a bit..so a quick spin up of the B geared GWS IPS on the Eindekker, with the APC 8x6 SF..E-tech 3s 450... pack was a bit flat so I didn't get what I had before, which was that the APC SF drew 10% more current than the GWS SF..and dropped a couple of hundred RPM (2.0A/4150 RPM 11.2v versus 1.8A/4380 RPM 11.4v..) and I reckoned it probably wouldn't load the motor up as much as the GWS...but I was wrong.

Of the three, it loads up the best..is my pitch too great? Dunno. Mathsd says not, and teh tip angle looks similar to the others..Sounded great and I got 5% more draw than the APC SF (from 1.9A/10.7V/3930 RPM to 2.0A, 10.6v, 3840 RPM)..and it looks fantastic (well I think so) so flying tests will be done in due course when the wind drops way back (like next year?)

Now as far as I am concerned, the drawing was the hard work, and I have given that to Charlie to do what he wants with, so if anyone else wants to go this route, its up to you to cut a deal with Charlie directly.

I WILL, if time, energy, motivation, my wife, and all the other bits of Life that get in the way, also attempt to draw up more props on an occasional-if-you-ask-me-nicely basis, so that all our Rakeian (and other) models can sport nice wooden props - 4 bladers and the like..if this one turns out to actually fly the model..but I think it will. Needs Pat to get in there with some micro brass shim and make leading edges...

I also issue a word of caution. I have NO IDEA what RPM a few bits of laser cut bass can withstand..my gut feeling is probably more than a APC or GWS slofly. 8K RPM is the limit on the APC slofly of this size, more or less. So if anyone wants to load this sort of prop on a 200W brushless, fer gawds sake keep out of the plane of the prop disk.

Enjoy..
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Old Jul 10, 2006, 05:40 PM
frenzyscot
Dundee, Scotland
Joined Oct 2004
652 Posts
That is magic! This is the first time I got across this approach and it seems very neat.
excellent job vintage
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Old Jul 10, 2006, 05:40 PM
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Charleston, SC, USA
Joined Jan 2001
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Hi Vintage1,
I love the prop! It looks like the real deal on the nose of the Eindecker. Keep up the creativity ;-)

Mark
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Old Jul 10, 2006, 07:54 PM
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Albuquerque, NM USA
Joined Sep 2003
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Vinto! Great job. Must be why your EIII pilot is smiling.

Given the dimensions can I simply scale up for 9, 10, or 11" props? I would assume (a bad word ) that they would all still come out at a 6" pitch?

If that is indeed the case I'll send you one of each to try out. Still gotta find some 1/8" mahogony that's cheap.

The bad news on this is that each set of prop blanks is going to cost about $5 before shipping. If folks are still interested I can keep going on this. Or, any votes for making the props an option on the WWI kits?

Since Pete has tested the wire wheels they will be going on the site soon. Will put the props there as well if the interest is there.

Thanks again Vint!

charlie
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Old Jul 10, 2006, 07:57 PM
Formerly of mcba fame
Matthew Allen's Avatar
Luxembourg
Joined Apr 2001
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Lovely work vintage! It looks fantastic. So do you think balsa simply isn't up to it?

I once carved a small balsa prop for rubber power as an experiment, just to see if I could do it. It's was immensely satisfying. I wonder... I don't think I have any models worthy of such a device though.

Matthew
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Old Jul 10, 2006, 08:05 PM
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East Anglia, UK
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Quote:
Originally Posted by portablevcb
Vinto! Great job. Must be why your EIII pilot is smiling.

Given the dimensions can I simply scale up for 9, 10, or 11" props? I would assume (a bad word ) that they would all still come out at a 6" pitch?
..Umm. I am not sure..I THINK so..but I have a horrid feeling that unless you scale the wood thickness, the blades will end up 'corrugated'.

I thinks it's probably better to actually design each one seperately, for a given model.

Quote:
If that is indeed the case I'll send you one of each to try out. Still gotta find some 1/8" mahogony that's cheap.
Now I see that Pete's pilots is pulling in canadian laminated props made of birch...no reason to go mad on mahogany..let me fly this one, and if its not a total dog, I'll try and produce some other sizes and shapes. The bass takes stain well.

A 4 - blader for the FE8 would be high on my list I think.

Plus stuff for the SPAD and so on.

Quote:

The bad news on this is that each set of prop blanks is going to cost about $5 before shipping. If folks are still interested I can keep going on this. Or, any votes for making the props an option on the WWI kits?
Why so pricey? Wood? Or cutting time?

I can cut down on wood by changing the ears..I dont like them much anyway..can't get a decent looking hub easily. Also you may find a better source of sheet hardwood. If you end up doing a lot.

If it helps, its easy enough to send them out pre-glued as well Slips the blanks ovcer a jig, add thin CA and remove..the work is all in the final carving and sanding.

Quote:

Since Pete has tested the wire wheels they will be going on the site soon. Will put the props there as well if the interest is there.

Thanks again Vint!

charlie
I need a Spandau...
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Last edited by vintage1; Jul 10, 2006 at 08:11 PM.
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Old Jul 10, 2006, 08:09 PM
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East Anglia, UK
Joined Sep 2002
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Quote:
Originally Posted by mcba
Lovely work vintage! It looks fantastic. So do you think balsa simply isn't up to it?
I think the quality is too variable, and I wanted somethimng that would not flex at reasonable RPM, also balsa grain is and it whiskers up like mad when you stain and varnish it.
Quote:
I once carved a small balsa prop for rubber power as an experiment, just to see if I could do it. It's was immensely satisfying. I wonder... I don't think I have any models worthy of such a device though.

Matthew
Yes, I never had the courage - till now. I think we used to be supposed to dope 'n' tissue cover the balsa props didn't we?
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Old Jul 10, 2006, 08:40 PM
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NJ - Exit 6
Joined May 2005
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Quote:
If that is indeed the case I'll send you one of each to try out. Still gotta find some 1/8" mahogony that's cheap.
Charlie, I have some 3/4" mahogany laying around the shop. I should have enough for some prototypes that I can resaw to 1/8". What size would you need, 2 x 12 or so, and how many pieces?
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Old Jul 10, 2006, 08:42 PM
Formerly of mcba fame
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Quote:
Originally Posted by vintage1
I think the quality is too variable, and I wanted somethimng that would not flex at reasonable RPM, also balsa grain is and it whiskers up like mad when you stain and varnish it.


Yes, I never had the courage - till now. I think we used to be supposed to dope 'n' tissue cover the balsa props didn't we?
I just doped it and then put it aside to be fondled and admired for years to come. I imagine tissue and dope would result in a pretty strong prop.

It's neat to read the old articles like these:

http://theplanpage.com/esp/skua.htm

Readers would be instructed in every aspect of the build, including carving the prop. I also love the gentlemanly tone of the whole thing. Sometimes I think I was born 40 years too late.

Matthew
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Old Jul 11, 2006, 01:05 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,750 Posts
Looks great Vintage - I got inspired by your efforts and sawed up some cedar and baltic pine to 1/16" thick. Now I've got to do something with it

Pat
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Old Jul 11, 2006, 08:31 AM
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Thanks all.

Vint, I'll try a scale up to 10" and see what happens, but, like you I'm afraid the dimensions (chord) will get too big.

Cost is divided equally between wood and cutting. Decreasing those ears would be great. Then I could fit two or three sets on one sheet (4x24). If so I could offer one sheet of props for hopefully $5-7.

Grr, hold off on the mahogany for now. Once we noodle out the sizes and such then I can look seriously at the rest.

charlie
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Old Jul 11, 2006, 12:08 PM
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Joined Jun 2005
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Old props

That really looks nice, Vintage! (I thought you lot called that stuff "Lyme wood"). Just kidding. I don't know how to do it with CA, but most of the old props used pretty dark glue between laminations. Might be something to try, in future.
Attached is how I did the brass sheaths on the big, 26.75" scale props for the once-in-a-lifetime, 8 years in the making, 18.5 foot span, museum model of the Loughead F-1 flying boat we just finished & flew last year. I doubt I'll ever get involved in a scale electric plane that big again, (I hope!), but anyway, I used .003" brass shim for those, but for our normal sized planes, .001", or even thinner material, should do fine. Trick is to properly anneal the brass, so it will stretch & form easily. I just held it with forceps over the kitchen burner, (best done in subdued light, so you can see the color), then burnish the brass into the epoxy-putty molds I had taken off the prop tips.
In no way intended to be boastful, just hoping to help.
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Old Jul 11, 2006, 12:23 PM
Light and floaty does it
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Cambridge, Great Britain (UK)
Joined Sep 2004
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8x6 slow-fly is a size I use quite a lot, and I expect to break a few, being a pretty ropey RC pilot, so I've ordered five sets from Charlie and will report back. It looks like a fun project to while away the odd hour, and it's something I can do while I'm travelling around since the parts and equipment required are all compact... and a nice finishing touch to an oldtimer or pre-war scale type model.
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Old Jul 11, 2006, 01:25 PM
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East Anglia, UK
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..that full size prop..I saw you post those pictures elsewhere earlier,and it helped push me over the edge.


..glue types..I WAS going to use glassing epoxy, but since this was a prototype and I expected it to be utterly useless, thin CA seemed to be a way to go.

As to being utterly useless, all I can say is that apart from massive glitching and a crap landing, it flies my EIII as well as, if not better than, the APC 8x6SF.

I am fairly sure that I have a tad more pitch..seemed easier to fly at lower throttle settings anyway.

To say I am quietly pleased in a Frank Whittle sort of way* is an understatement..

I suspect that I have been able to use the wood properties to craft a thinner section and better finish than a moulded glass/nylon type prop. the model turned over on landing..but the prop did NOT break.

Charlie: I will redraw the prop to economise on wood, as that seems to be a serious issue. Hold back tell I send updates on the ears..

The rest of you: If you can come up with photos and 3 views of props that you need, first come is first served. These things take several uninterrupted hours to draw up, but I think this time I can do the next one much faster..as I know HOW to do it. I took this prop from a photo of a CAMEL prop. No idea if it suits an Eindekker..


*After about 15 years of trying to get the ministry to take a jet engine seriously, getting messed around, working all the hours that god gave..someone remarked on the maiden flight of the Gloster Whittle, "Frank, it flies!"..he is alleged to have responded in a fit of utter exhaustion "Well that's what it's well supposed to do, isn't it?".
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Old Jul 11, 2006, 01:31 PM
The "pro" in procrastination
Steve85's Avatar
Canada, ON, Kingston
Joined Mar 2004
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Vinto,

The world is a better place for unrepentant tinkerers like you.

Steve
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