Sub 600 Prop Mold

[Motorman]

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[Howard Rush]

Does anyone make a CF 3 blade 10x5.5, 10x6 or 11x5.5, 11x6 that's not hollow?

Chris Cox and Alan Resinger make them.  They're good props.  http://stunthanger.com/smf/gettin-all-amp'ed-up!/coming-soon/

[jfv]

I have several of Alan's 11 inch props and they work great.

[RC Storick]

I think he's looking to make his own. I made a few and quickly found it's not worth the time it takes to make them. But it was more to see if I could do it.

[Steve Helmick]

Attached should be Brian Eather's list of props he molds. He doesn't finish them, but chops off most of the flashing. He takes PayPal, replies quickly to email, and churns out the props in short order.  Hmmmmmmm....Stunt Hangar won't let me load an .odt file type. I'll poke at Sparky and get him to allow it. One of the "benefits" of Win10. I can't open a .wpd file, either. Bastards!   

If I wanted 2-blade CF props in 5"-6" pitches and 10, 11 & 12 inch diameters, I'd copy the RSM props. Don't tell Eric!    Steve

[Tim Wescott]

Attached should be Brian Eather's list of props he molds. He doesn't finish them, but chops off most of the flashing. He takes PayPal, replies quickly to email, and churns out the props in short order.  Hmmmmmmm....Stunt Hangar won't let me load an .odt file type. I'll poke at Sparky and get him to allow it. One of the "benefits" of Win10. I can't open a .wpd file, either. Bastards!   

If I wanted 2-blade CF props in 5"-6" pitches and 10, 11 & 12 inch diameters, I'd copy the RSM props. Don't tell Eric!    Steve

Print your spreadsheet as a PDF, and post that.

[wwwarbird]

 At one time Steve Wilk was making some carbon copies of the Tornado 10x6 three-blade prop. If I recall correctly he used an original Tornado prop to make his mold. He can be found here in the Vendors Corner, under Eliminator Props.

[Steve Helmick]

Print your spreadsheet as a PDF, and post that.

It's an .odt file. If you want to post it, I'll email it to you to post. I don't have the software to build a .pdf. I sent Roberto a PM to allow .odt and whatever new file-types those idjits came up with. Check your email.   Steve


Edit: Actually, Wilk makes a copy of the 10-4 3-blade Tornado and two Bolly 3-bladers, and a bunch of Rev-Up and Stalker copies. 

[RC Storick]

Yep and you good at it!

[RC Storick]

It's an .odt file. If you want to post it, I'll email it to you to post. I don't have the software to build a .pdf. I sent Roberto a PM to allow .odt and whatever new file-types those idjits came up with. Check your email.   Steve 

.odt is now allowed

[wwwarbird]

Well, It's kind of a hobby for me and well worth it imho. Most of these are original designs the rest are modified production props. I've never straight up copied anything.

MM

 Got a mold in there for a 10x6 Super M?

[Steve Helmick]

Here's the Brian Eather prop list. Robert responded quickly and allowed the .odt file type.  Steve

[Tim Wescott]

Here's the Brian Eather prop list. Robert responded quickly and allowed the .odt file type.  Steve

For those without LibreOffice or other compatible software:

[Randy Powell]

Yep, .odt is a LibreOffice file type. Use it all the time.

[Dennis Toth]

If you are looking for a 3 blade prop for a pattern look at the Master Airscrew three blades. They have a nice shape but are a little heavy in the larger diameters, but for a pattern that you can thin out then do up in carbon, its a good place to start.

If you want to look at some information on molding props here is Wayne Trivin's old web site with lots of information. Wayne and I flew together for several years, he showed me how to mold props. I introduced him to Windy and he showed Windy how to mold tanks and other parts.

http://www.nclra.org/TechTopics/WayneTrivin/Actualindex.html

Best,    DennisT

[Dennis Toth]

With the molds you mentioned is the prop hollow? Do you mold the top then the bottom in cloth then fill the hub and bond the two halves together with tow at the LE and TE area? Some pictures of the process would be interesting.

Best,    DennisT

[Air Ministry .]

Very Nice .

Ive Gotta SILVER ( Nylon ) 9x6 three blade Grish / Tornado , & 10 x 4s  .

got unused Nylon ( White ) 10 x 6 two blades , If you used one blade Thrice youd have a THREE ! .

Could Also do a 11 x 5 three blade Grish , ( Coustom ) if you tryed this trip .

Send a p.m. if you like .

THIS prop never had a pitch guage near it , or calc .


Set Center and worked all dimensions of that equally & symetrically .Used A Verneer but thickness came in even with cuts to marks & Equal File
cuts , though took abit of walking And deviceing as Changed ends every six file cuts .

[Dennis Toth]

MM,
Just a little confused, you indicated you preferred the male/female mold approach as apposed to the two piece mold that is described in Wayne's site. Then you said you don't know how they do it? Have you ever molded a prop? Who are "they" that you referred to? Many of the prop sellers use the two half approach, some have machined aluminum molds others use the leveling epoxy that Wayne describes (some have used Bondo - works for a half dozen or so).

As far as the "narrow" blade Rev-Up 10x6 I think the answer is no. They had a standard blade, a wide blade and a very wide blade designs.

Best,    DennisT

[Avaiojet]

Motorman,

I'm really impressed with your accomplishments in the designing and making of your own props. 

Outstanding to say the least.

Charles

[Air Ministry .]

 /DVTheres a bog called ' Newtech ' thats GF impregnated , so akin to devcon or JB Weld , perhaps - for durability .
Likely better for this purpose as its a late arival , tecnologically .

Supercool did a HOLLOW copy of that wood prop there , back in 2002 for me , dunno how.
I assume foam ' inners ' at say 2 mm less than the outer would work in effect .

I faired of the pitch going out ( less at tip ) so it wouldnt ' tip stall ' , as in the outer disc'd keep going if the plane bogged down in a gust .
Very effec tive prop that had other wonderous characteristics and accoustics . You could hear it shifting gear .

[Howard Rush]

I don't know how they do it, I don't see where it's necessary at all on an E prop and I'd have to see it to believe it.

I'll believe it when people start winning stunt contests with hollow props. 

[Howard Rush]

That's in line with my thinking. if there's more pitch at the tips then they will stall going up hill...

Does your thinking account for the reduced change in angle of attack with airspeed at the tips?

[Dennis Toth]

MM,
I'm interested in the mold system you are using. I looked back at the pic you posted of the props you made and they look the same as the ones I've done with Wayne's top/bottom approach. How do you make your molds to get a male/female set?

A few years ago I saw a post on here that talked about re-pitching woods with heat like we were doing the APC and carbon props. Until then I had assumed the only way to re-pitch wood was to sand in the pitch. For grins I took an old Zinger 11x5 (I checked the pitch on with pitch gauge to start). I got out the heat gun and proceed to warm the blade root as I would an APC (I am lazy and only set one station about the 60% out from the hub). I warmed both top and bottom sides and let it soak a bit them gave it a pretty hard twist. Let it cool the rechecked the pitch. I was surprised it increased a whole inch. I let it sit overnight and checked it again fully expecting it to relax back. It didn't change, put it in my car and parked it in the sun for a day at work came home and checked again thinking the heat would relax it, no change. Checked it several weeks later and still held the same new pitch. At this point I did a flight prop and flew it several times, rechecked the new prop after flying, re-pitch held. So now I get RMS props and set them were I need the pitch and go. The wood props are lighter then the carbon or APC and the RMS are very stiff and pull very well. Try it you may like it.

Best,   DennisT

[Tim Wescott]

Wood bends when you heat it.  It bends when it's wet, too, but mostly, if someone is taking dried lumber and bending it, they're using heat.

"Steam bent" wood just uses steam to get the wood up above the point where the wood gets flexible.

You can bend small-section balsa (1/16") very nicely by getting it wet then bending it around the shank of a soldering iron or (I've seen in videos) a 100 watt light bulb.  The water is mostly there to turn into steam that'll conduct the heat through the section.

I've tried heat-bending thicker pieces of balsa this way, but the heat doesn't penetrate -- one day I may make a steam bender and see what I can do with 1/4" square or bigger pieces.

[Steve Helmick]

For what it's worth, I have been told and also read in SN that increased pitch toward the tips will improve line tension overhead. Late this last season I had a prop that worked fairly well, but I really needed some more tension overhead. So I went off the deep end and figured out a method to get some decent results with repitching my one good prop.

The prop was a 12 x 3.75 "red" undercambered 3-blade Brian Eather prop. I measured it at 4.25" pitch for all the blades, over all the stations I measured. Can't recall exactly which stations they were, of course. But I pitched it up
to 4.75" at 8, 10, and 12 on my Prather gauge. This gave excellent results, partly by letting me launch richer, I think. I then reworked the squared tips by sanding a rake into them (used a template) and put a sharp edge on them. This seemed to let the engine spin it up easier, definitely letting me launch richer at the same launch rpm. It really worked nicely...until I buzzed the tips off it on my second official at the Stevenson Memorial Raider's Roundup. So I made a duplicate, and first flight, buzzed the tips off of it the next weekend. Lesson learned: extra ground clearance is good!

What Howard didn't divulge is that Igor used hollow carbon props on his latest WC winner. I know Mike Haverly has one from Igor. I held it in my hand, and it's hollow, at least in the hub. Mike "proved" that! Alan and Chris are working on foam cored CF props, but I'm not sure how far they've got their program on that. While their standard props are ok for IC, I don't think the hollow ones are IC suitable. I don't want to fly with electrons.  Steve 

[Howard Rush]

What Howard didn't divulge is that Igor used hollow carbon props on his latest WC winner.

The current European champion, the current US National champ, the top two guys at the most recent US F2B team trials, and the 2015 Golden State Stunt Champs Jr. Varsity winner all used hollow props.  I'm kinda double counting, although alas not in the last example. 

[Avaiojet]

MM,

WOW! A work of art. 

Do you think it would be a good idea to put a couple of hard wood pins in each blade?

Or not necessary?

Three props get you two 3-blade props.

Not bad at all.

Charles

[john e. holliday]

Is this going to be a pattern for a mold?

[Air Ministry .]

Three props get you two 3-blade props.

or three broken two bladers get you a new three blade prop . 

[Dennis Toth]

MM,
Glade the heat pitch worked for you. You may want to look at the RMS props they are very stiff and thin. The prop you built looks great. Bob Hunt and his father built 3 blade props that he used on the Genesis. His used a center section similar to yours but they used I believe an aluminum top and bottom plate that bolted through each blade.

Best,    DennisT

[pipemakermike]

excellent work, I am really enjoying the pictures

[Glenn (Gravitywell) Reach]

I certainly do NOT have the skill to do what your doing, but I am thoroughly enjoying this thread.  Lots of interesting stuff here.

[Randy Cuberly]

For what it's worth, I have been told and also read in SN that increased pitch toward the tips will improve line tension overhead. Late this last season I had a prop that worked fairly well, but I really needed some more tension overhead. So I went off the deep end and figured out a method to get some decent results with repitching my one good prop.

The prop was a 12 x 3.75 "red" undercambered 3-blade Brian Eather prop. I measured it at 4.25" pitch for all the blades, over all the stations I measured. Can't recall exactly which stations they were, of course. But I pitched it up
to 4.75" at 8, 10, and 12 on my Prather gauge. This gave excellent results, partly by letting me launch richer, I think. I then reworked the squared tips by sanding a rake into them (used a template) and put a sharp edge on them. This seemed to let the engine spin it up easier, definitely letting me launch richer at the same launch rpm. It really worked nicely...until I buzzed the tips off it on my second official at the Stevenson Memorial Raider's Roundup. So I made a duplicate, and first flight, buzzed the tips off of it the next weekend. Lesson learned: extra ground clearance is good!

What Howard didn't divulge is that Igor used hollow carbon props on his latest WC winner. I know Mike Haverly has one from Igor. I held it in my hand, and it's hollow, at least in the hub. Mike "proved" that! Alan and Chris are working on foam cored CF props, but I'm not sure how far they've got their program on that. While their standard props are ok for IC, I don't think the hollow ones are IC suitable. I don't want to fly with electrons.   Steve  

Serguei (SP) Belko of Ukraine has been making foam core three blade stunt props for many years I have several of them.  They are very light and stiff.  However they also cannot be repitched.   I'd post a picture but I haven't pulled the files from my old computer yet.  Too lazy and having too much trouble getting the new one set up.  Wish I had paid attention a little more in programming classes...constantly having to relearn everything.

The workmanship in your props looks excellent!

Randy Cuberly

[BillLee]

Yep, .odt is a LibreOffice file type. Use it all the time.

And LibreOffice has a built-in "Export to PDF" capability on the "File" menu

[Randy Cuberly]

Is that the one with the carbon/kevlar cloth on the outside? It looks really cool in a basket weave kinda way. I wonder how much is foam. Please cut one open and post pics.

My prop will be helium core and need to be weighted down when not in use.

MM

I do have a broken one that I will cut for photos when time permits.  what I have seen of the props inner constructions is that the carbon/Kevlar (I think) is fairly thin.  These props are fairly thick air foiled.  They are very light.  I'll weigh one and cut the broken one tomorrow if I can break free for a bit!  The props I have were specifically designed and constructed for Belko's long shaft engines (.56 and .61, and .75).  They are relatively low RPM engines that run on No nitro fuel only but develop good torque characteristics and a very good 2-4 stunt run.  The props have a Scimitar profile shape.

Randy Cuberly

[Keith Renecle]

Hi All,

I also love Sergey Belko's big model and prop. The model growls through the pattern with total authority. I took some pics at a few world champs and here are a few from the Bulgarian world champs.

Randy, it would nice to see what's inside the props!

Keith R

[Randy Cuberly]

Hi All,

I also love Sergey Belko's big model and prop. The model growls through the pattern with total authority. I took some pics at a few world champs and here are a few from the Bulgarian world champs.

Randy, it would nice to see what's inside the props!

Keith R

Keith,
I found two of the good props today but haven't been able to locate the broken one yet.  I hate to cut up a good one because I still have two of the Belko engines that definitely run and fly best with these props.  I still have a couple of places to look in some boxes from my move a couple of years ago.  Seems a lot of stuff is missing after that move...or buried in junk somewhere! 

I did weigh the two props I have and they weigh 1 oz each.  They are both three blade and look very much like the one in the picture above except only one is the multi colored material and the other is just carbon and all black.   The multi colored one (like the one in the picture is a 12-5.5 (on my prather pitch gage).  The other is a 11.7-6 yet they both weigh exactly the same. 

They are both extremely stiff all the way out to the tip!  The one I broke was on a Long shaft .56 (Belko) in a GeoXL and worked very well.  It was like the all black one.

Randy Cuberly

[Randy Cuberly]

Don't cut up your good props! I was just joking about that. The prop I'm making will be a thin blade 10-5.5 too small for any kind of foam core. I would love to know the pitch distribution on Sergeys prop.

I've got an APC 11-4.5 MRP on order. They say it's something between an electric prop and a slow flier prop in thickness. I think I can modify the blade width, re-pitch the tips and make it a 3 blade.   

MM

I'll check the pitch distribution in the morning.  I've had meetings at the University all this week and haven't had time to spend in the shop!

Randy Cuberly

[Randy Cuberly]

This is the Pitch distribution for the two Belko props.  No surprises.

Done on my Prather Pitch gage.
Multi-Colored (60 size Prop):               Black  (56 size Prop)
Station                                              Station
4 - 5.2                                               4 - 5.0                                              
5 - 5.5                                               5 - 5.5
6 - 5.5          .22 Thick                        6 - 5.5        .20 Thick
7 - 5.5                                               7 - 5.1
8 - 5.5                                               8 - 5.0
9 - 5.3                                               9 - 5.0
10 - 5.0         .18 Thick                      10 - 5.0        .162  Thick
11 - 4.8                                            11 - 5.0
12 - 4.7         .12 Thick                      12 - 4.8        .100  Thick
13 - 4.5                                            13 - 4.6

The pictures were taken about a year ago and don't include the bigger 60 Size prop but it looks essentially like the one in the picture from Keith Renecle.

I would add that these props are very efficient on the Belko engines.  I have never run them on anything else.

The .56 engine is on the left in the picture and the .60 on the right.

The .60 weighs 10 oz with the Muffler and spinner.  The .56 is 9.8 with the muffler and spinner

Airplane is my GeoXL with the Belko .56

[Howard Rush]

How would you balance a Belko prop?  You wouldn't sand the yellow stuff, and you probably couldn't drill a wee hole and squirt epoxy in as we do with the hollow props (Motorman will think I'm kidding). 

[Randy Cuberly]

How would you balance a Belko prop?  You wouldn't sand the yellow stuff, and you probably couldn't drill a wee hole and squirt epoxy in as we do with the hollow props (Motorman will think I'm kidding).  

They come from surgey very well balanced.  If for any reason they need balancing you coat the light blades with thinned epoxy.  I did it once and because they are so light it worked pretty well.  The epoxy obviously doesn't change much from wet to hardened.  It doesn't take very much to make a significant change in the weight of a blade.

Motorman:
Glad to do it.  The Belko engines are relatively low RPM runners with high torque in low to mid range and a pretty flat torque curve.  I would think that is the reason for the thick blades and lower pitch angles at the tips.  They do just "Growl" through a pattern as Keith mentioned before with little change in RPM anywhere.  For what it's worth they are very quiet also!   They are set up to run on No Nitro only and the .56 uses a bit less than 4 oz to fly the pattern.  The tank for the 60 is just 4.25 oz.

Randy Cuberly

[john e. holliday]

Epoxy does not lose weight as it cures.  Dope loses weight because of the evaporation of the solvents used.  Don't believe me, take a 1/4 ounce of each and leave in open air after epoxy is mixed.   

[Randy Cuberly]

Epoxy does not lose weight as it cures.  Dope loses weight because of the evaporation of the solvents used.  Don't believe me, take a 1/4 ounce of each and leave in open air after epoxy is mixed.   

Yeah, I know Doc, but in this case the epoxy is thinned with a tiny bit of thinner and that does evaporate so it's possible it does change a tiny bit.  Probably not enough to make any difference though.

Randy Cuberly

[Crist Rigotti]

Cool!

[MikeyPratt]

Good for them. Anyway, here is my gamesters of triskelion prop building board that I just invented. It has lines for marking cut lines and aligning blades and a 1/4" dowel in the middle. Took a while to get those joints to fit real nice. I glued it with epoxy.

MM,
I built about 12 of these in the early eighties for running on the OS .40 FSR-S.  They were close to what you built only with aluminum washers on the hub.  They worked pretty good at that time for wheat they were.  But better engines came along and C/F props were introduced shortly after that so I spent more time flying than messing around building special props.

Later,
Mikey

[Crist Rigotti]

Still watching!

[Randy Powell]

Cool.

[Avaiojet]

Motorman is talented! 

Keep up the good work.

Charles

[Steve Helmick]

Very good! I had good feelers about this, since you're using a Graupner prop for the master. An excellent choice. An APC would also be an excellent base for a master. 

Only problem, it appears like these are LH props. None of our local 'lectric experts use LH props except Alan Resinger, and that's only because he flies clockwise. The LH prop works good except the 3rd corner of the hourglass, they say. They're that fussy.  Steve

[Crist Rigotti]

Pretty neat.  Glad they are working out.