Five-blade prop on my Spitfire XIV.  
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All Forums >> RC Airplanes >> RC Warbirds and Warplanes >> Five-blade prop on my Spitfire XIV.
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Five-blade prop on my Spitfire XIV. - 7/10/2006 5:08:20 PM   
tahustvedt



Posts: 426
Joined: 1/28/2004
From: Bardufoss, NORWAY
Status: offline 		I'm gonna get a lot of "You don't fly with that do you?" when I arrive at a field with this.





The prop is a smidgeon under 19" in diameter and I guess ~12.5-13" pitch. I have flown with an 18x12 four-blade on this motor before and that was fantastic, but this prop is going to be hard work for the battery, even though these blades are narrower than the 18x12. I also made a four-blade hub for the same blades which will probably be fine. I will test the five-blade once I get some new blade bolts that I can trust, but the four-blade is ready to fly.

Here're a couple of pictures of the hubs and blades before I painted them. I'm using 17x12 APCE blades.


Unserviceable bolts on this one:



The reason I am able to run these props is that I have rewound an electric motor, and AXI 4130/20 motor, to 24 turns instead of 20 turns. I also used thicker wire than the original wire which increases the torque- and current-handling. The torque is increased greatly while the rpm is reduced so the motor is now suited to running 4500-5000 rpm at 1000-1500 W instead of 6500-7000 like it was originally. I was pushing 1300 W in with the 18x12 four blade prop.
       Post #: 1

RE: Five-blade prop on my Spitfire XIV. - 7/10/2006 5:12:00 PM   
KidEpoxy



Posts: 3655
Joined: 10/14/2004
From: San Antonio, TX, USA
Status: offline 		OUTSTANDING!

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RE: Five-blade prop on my Spitfire XIV. - 7/10/2006 9:33:37 PM   
HUMMERH3



Posts: 286
Joined: 1/4/2004
From: new port richey, FL, USA
Status: offline 		would love to see that fly...any videos?

(in reply to KidEpoxy)
       Post #: 3

RE: Five-blade prop on my Spitfire XIV. - 7/10/2006 9:51:50 PM   
tahustvedt



Posts: 426
Joined: 1/28/2004
From: Bardufoss, NORWAY
Status: offline 		I have a video with the experimental 18x12 prop. The prop was painted in civilian colors because I used it on a civilian model before that flight. Nothing went well that day, we had a crosswind, the sound system was out of calibration which is why there's no sound while taxing, and you'll see what goes wrong in the end of the video. Ttakeoffs and landings are usually much nicer than what you see in the video to say the least. I will try to make a better one the next time I'm visiting that field.

http://www.enrarot.net/videos/spitfire/spitfire10.wmv

(in reply to HUMMERH3)
       Post #: 4

RE: Five-blade prop on my Spitfire XIV. - 7/10/2006 10:51:17 PM   
Jimmbbo



Posts: 1179
Joined: 10/1/2003
From: Fresno, CA, USA
Status: offline 		Now that's cool!!

Looking forward to the result!

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RE: Five-blade prop on my Spitfire XIV. - 7/11/2006 12:38:50 AM   
rustypep


 

Posts: 384
Joined: 9/12/2004
From: Powell, OH, USA
Status: online 		What type of metal did you use in making that hub? I look forward to hearing how the flight tests go. Good luck and great job.

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RE: Five-blade prop on my Spitfire XIV. - 7/11/2006 3:06:45 AM   
saramos



Posts: 2325
Joined: 12/6/2003
From: Northridge, CA, USA
Status: offline 		That's great!!

It's good to see a 4 blade flying. I am installing an RCV 90sp in my TF spit and will be flying with a 15.5 x 12 APC 4 blade. I hope to be airborne this summer.

Scott



(in reply to rustypep)
       Post #: 7

RE: Five-blade prop on my Spitfire XIV. - 7/11/2006 3:43:46 AM   
Baldeagle


 

Posts: 1473
Joined: 2/2/2002
From: Lakeside, AZ, USA
Status: offline 		Nice bird.Whose spinner are you using on your MKxiv ? Thanks Rich

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Rich

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       Post #: 8

RE: Five-blade prop on my Spitfire XIV. - 7/11/2006 9:38:39 AM   
madibav8



Posts: 129
Joined: 3/30/2005
From: NorthamptonNorthamptonshire, UNITED KINGDOM
Status: offline 		Not only looks superb, but sounds lovely too?.

Is there more to this model's sound than just the prop wash?

Mark Morley
Scale Aircrew Supplies

(in reply to tahustvedt)
       Post #: 9

RE: Five-blade prop on my Spitfire XIV. - 7/11/2006 10:33:58 AM   
Multimaniac



Posts: 135
Joined: 8/4/2005
From: Degersheim, SWITZERLAND
Status: offline 		Hi tahustvedt!

Those Props are very interesting!!! You use them on electric planes, but I wonder if props like your construction (three- or fourbladed) also work on Gas/Methanol engines? So I have some questions:

- How do you get the correct size of the props for a spezific engine / Accumulator combination? or for a given Gas/Methanole engine?

- How do you cut the props apart for a smooth fitting in the new prop? Or do you use single prop blades (e.g. from APC) for it?

- Can you tell us about the construction of the center section of your 4- or 5-blade props? How do you fit the spinner?

Greetings

Chris

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(in reply to tahustvedt)
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RE: Five-blade prop on my Spitfire XIV. - 7/11/2006 2:26:58 PM   
SCALECRAFT



Posts: 1557
Joined: 1/7/2002
From: MONTEBELLO, CA, USA
Status: offline 		Hi

I have something like that going with my 109. The blades are variable pitch scale shape carbon blades. The prop arc is 19.5 pitch range is around 8-12.

I am about run this set up on a Moki 210.

A RCV 120 did well but could'nt get more that 3500 rpm.

I did turn the set up on a 3.5 hp router. It turned at 5000rpm and had around 18lbs of thrust.

(in reply to Multimaniac)
       Post #: 11

RE: Five-blade prop on my Spitfire XIV. - 7/11/2006 4:14:34 PM   
tahustvedt



Posts: 426
Joined: 1/28/2004
From: Bardufoss, NORWAY
Status: offline 		I'm sure it could work on a gas/glow engine too but it would have to be geared down to run a scale (or close to scale) diameter in the power band of the engine. I have made a plywood belt drive system for my other warbird, a 1:6 scale P-40, which spins a 20" three-bladed Soloprop.

Figuring out what prop combo works was a long process. I spent a lot of time winding and rewinding the motor until I got the performance I needed with a 2-blade 20x13 prop. I ended up at 24 turns LRK. Later I decided to try to make a four-blade prop. Using a power system calculator I concluded that 18x12" would need about the same power as a 20x13" at 5000 rpm. To get enough airspeed with the low rpm (<5000 rpm) I needed a pitch of 12", so I used two 18x12" APCE props and chopped them up and glued them together at the hub using a homemade jig. The first plane I flew with this prop was a The World Models Velox Rev II using the same motor I'm now running in the Spitfire. The 18" prop was the scale size for that plane.

The hub plates of my new props are 3 mm aluminium. I'n not sure precisely what kind of aluminium but it's not pure soft alu and they are strong. I'm a helicopter technician and have access to a sheet metal workshop and got the material for these in the cut-off bin. They're easy to make but it's important to be as accurate as possible. Som inaccuracy is inevitable with hand-made things though but that doesn't mean it won't work. I started by sawing out the circle on a bandsaw and drilling the 8 mm hole in the middle. Then I made a 6 mm plywood jig for drilling the blade holes, one for the four-blade prop and one for the five-blade. I also made a jig for drilling the blade hub. I still haven't made the center piece that goes between the plates so that they don't distort when I tighten the nut but that's a quick job. When the blades are being assembled to the hub the tips need to be spaced out equally while the botls are being tightened.

Four-bladed props are much quieter than two-bladed props. Especially if they are the same size and run at lower RPM. They make some sound at high rpm static running of course but at low to mid rpm they just make a wooshing sound. In the air they are very quiet compared to two-bladed props.

The spinners are homemade fibreglass ones with 6 mm plywood for the backplate backplate. Not difficult to make but a lot of work. I don't have time to make them on order.

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< Message edited by tahustvedt -- 7/11/2006 4:23:19 PM >

(in reply to SCALECRAFT)
       Post #: 12

RE: Five-blade prop on my Spitfire XIV. - 7/11/2006 4:25:48 PM   
madibav8



Posts: 129
Joined: 3/30/2005
From: NorthamptonNorthamptonshire, UNITED KINGDOM
Status: offline 		Oh, so it's as easy as that!!

Great thread, and your use of English is enough to put us 'limeys' to shame!

I thought I heard an ic engine sound coming from the up-turned model, as though you had a pre-recorded engine sound on a chip or something; was I hearing things?

Mark
Scale Aircrew Supplies

(in reply to tahustvedt)
       Post #: 13

RE: Five-blade prop on my Spitfire XIV. - 7/11/2006 4:32:06 PM   
tahustvedt



Posts: 426
Joined: 1/28/2004
From: Bardufoss, NORWAY
Status: offline 		Yes that right, I'm using a sound processor and amplifier with two lightweight 4" speakers in the wing. It's playing sound samples of the RR Griffon engine and the sound character and frequency changes with the throttle position. It works pretty well, but it's not really possible to achieve a completely realistic in-flight sound. I'm happy with it now though.

The electronic sound system was made by www.benedini.de

(in reply to madibav8)
       Post #: 14

RE: Five-blade prop on my Spitfire XIV. - 7/11/2006 7:04:42 PM   
SCALECRAFT



Posts: 1557
Joined: 1/7/2002
From: MONTEBELLO, CA, USA
Status: offline 		Heres a pic of one method to attach blades.

Steve

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(in reply to tahustvedt)