RCCrawler Forums

STANG KILLA SS · 10-20-2011, 10:02 AM

ive always wanted to do this but cant figure it out.

its for a boat prop. we hit stumps etc time to time and bend them up. they are CNCed Nibral (nickle brass aluminum alloy)
typically there about $175 to have repaired professionally

ive got 3 good blades that i could easily take a mold of, fiberglass, plaster of paris etc. but i cant think of a material strong enough i could pour into the mold that would be hard enough to take hits from a big hammer to bend the bad blade back to shape (of the mold)
any ideas?

or is there a better way? my old man had the idea to actually shape a block of wood to the shape of the good blade(s) but man that would take forever to get just right. and out of balance vibes are really bad.

anyone know of a material that could work?
definatly open to other suggestions/methods too.

Cory

highlandcrawler · 10-20-2011, 10:16 AM

Go to a different lake and stop hitting stumps with your prop

. We have a couple man made lakes around here that are notorious for the same thing. Would steel be to heavy to use? You can always pour molten metals fairly easy if you have a setup for it. A forged prop sounds pretty tough but I have no clue when it comes to boats bigger than my NQD

tarmo120 · 10-20-2011, 10:17 AM

Probably some kind of metal, that you heat up(difficult to do at home) and then pour it.
When it comes to pouring the material must be in liquid-ish form otherwise you cant pour it.

Just my idea.

C*H*U*D · 10-20-2011, 10:18 AM

What about MIM (Metal Injection Molding)? Not sure how well it would work, but a lot of metal parts are made this way to keep machining costs down.

Metal Injection Molding, MIM | Advanced Forming Technology (AFT), Longmont, CO

edit* Are you talking about something you can do yourself at home?

STANG KILLA SS · 10-20-2011, 10:20 AM

i have no clue what it takes to melt steel. might melt the mold?

chud. yes i want to be able to repair the prop at home, now and in the future.

hmm what about JB weld? looks like they sell a 10oz kit as there largest.
J-B Weld Company - INDUSTRO WELD Product Information

C*H*U*D · 10-20-2011, 10:27 AM

Gotcha...Thought you were looking to go into the business of making them.

rockn · 10-20-2011, 05:06 PM

Gold go down to fort Knox and buy some

Dogbreath · 10-20-2011, 06:17 PM

#1 Go to a lake without stumps

#2 SLOW DOWN

#3 install a Prop Guard

Bart bender · 10-20-2011, 06:37 PM

Looks like you're just bending them. Can you just heat with oxy/acetylene and lightly pound it back into shape? Can you tig with the proper filler if you take chunks out? You'll need it balanced and trued up I'm sure after that.

Gula · 10-20-2011, 09:23 PM

Bang with a rubber hammer back into shape, then take a DuBro prop ballancer to it, easy as that.

Won't the metal that the prop is made of get stress fractures from bending it back to the opposite side? I know $175 may seem a lot, but I'm sure replacing a bearing or multiples of in a boat can't be cheap.

Don't they make a prop protector, something like a shroud on a house fan?

I'm sure that wont slow your boat down too much

viper6171 · 10-21-2011, 11:00 PM

are you trying to make a form to hammer the prop back to the proper shape ? if so then you might try making the form out of jb weld you could make a box out of wood and cover the good blade with saran wrap and build a form around it out of wood . then mix up your jb weld and pour it in and let it cure .

Charlie-III · 10-22-2011, 03:02 PM

Don't care what you use, it won't do a good enough job.
Why???

Because you have to bend the blade BEYOND "correct" to allow it to spring back to correct.
Thus your idea will always leave the prop blade bent a little bit the way it was before.

Using some blocks of hardwood and a hydraulic press (think "shop press" with a bottle jack) may do it. I have no clue if doing that will either work harden the blade or cause stress cracks.

Ask yourself this, "If I do it wrong and throw a blade at full throttle, how much of a PITA will that be (possibly middle of a big lake) and what will I likely damage (and what will it cost in time & money to repair/replace)??"

Gula · 10-22-2011, 04:26 PM

If you do make a mold out of whatever. How you going to get the prop out of the initial mold?

The mold would have to be made from silicone or sand and your prop from wax or styrofoam, so it could melt as you pour the hot metal in.

I have heard a guy made his gears for a powerwheels vehicle from metal. He cut the initial copy of the gears out of styrofoam, put them in sand, then poured in molten aluminum or something like that. then filed them into shape.

Charlie-III · 10-22-2011, 09:47 PM

Quote:

Originally Posted by Gula

If you do make a mold out of whatever. How you going to get the prop out of the initial mold?

The mold would have to be made from silicone or sand and your prop from wax or styrofoam, so it could melt as you pour the hot metal in.

I have heard a guy made his gears for a powerwheels vehicle from metal. He cut the initial copy of the gears out of styrofoam, put them in sand, then poured in molten aluminum or something like that. then filed them into shape.

Pulling molds off an existing part is easy, I do plaster molds of wheels so I can pour led wheel weights. Earlier it was stated to wrap the prop in plastic wrap so you can pull it out.

SlickRockSpider · 10-23-2011, 10:14 AM

The prop spins at way to many rpms to f*ck with. I would have a pro fix it. What about a jet.

Evan

STANG KILLA SS · 10-24-2011, 09:47 AM

well i gave up on trying to make a mold i could hammer the prop back to shape in.

decided to go back with a simple beat it back to shape method. 2lb sledge and a block of rounded wood. but i wanted to something to check to know if it was exactly back to factory shape (or damn close) so i still made a mold.

used an old speakerbox making technique for making complex curves and organic structures. fleece and fiberglass resin. worked awesome as i expected.
wrapped one of the good blades in fleece and added fiberglass resin. now i have a perfect replica of a good blade and can slowely work the bent on back to this shape and be able to check progress and get it bent back just perfect.

thats the plan anyway

STANG KILLA SS · 10-24-2011, 12:46 PM

made great progress at lunch. got it to within 1/8" of the mold(started 1" out). and its nice and straight and smooth too. we ran out of time and shapes of blocks of wood. another round of beating tonight or at lunch tommorrow and plan to test tuesday at the lake. the mold was a huge help. after about 20-30 minutes it was impossible to tell which blade was bent lol. had to mark the bad blade.

10-20-2011, 10:02 AM	#1
STANG KILLA SS ~THE SCALE SHOP~ Join Date: Apr 2006 Location: KILLEEN TX Posts: 10,056	material that can be poured into a mold that can be hammered? ive always wanted to do this but cant figure it out. its for a boat prop. we hit stumps etc time to time and bend them up. they are CNCed Nibral (nickle brass aluminum alloy) typically there about $175 to have repaired professionally ive got 3 good blades that i could easily take a mold of, fiberglass, plaster of paris etc. but i cant think of a material strong enough i could pour into the mold that would be hard enough to take hits from a big hammer to bend the bad blade back to shape (of the mold) any ideas? or is there a better way? my old man had the idea to actually shape a block of wood to the shape of the good blade(s) but man that would take forever to get just right. and out of balance vibes are really bad. anyone know of a material that could work? definatly open to other suggestions/methods too. Cory

10-20-2011, 10:16 AM	#2
highlandcrawler Rock Crawler Join Date: Oct 2007 Location: Grants Pass Posts: 806	Go to a different lake and stop hitting stumps with your prop. We have a couple man made lakes around here that are notorious for the same thing. Would steel be to heavy to use? You can always pour molten metals fairly easy if you have a setup for it. A forged prop sounds pretty tough but I have no clue when it comes to boats bigger than my NQD

10-20-2011, 10:17 AM	#3
tarmo120 Quarry Creeper Join Date: Jan 2009 Location: Estonia Posts: 317	Probably some kind of metal, that you heat up(difficult to do at home) and then pour it. When it comes to pouring the material must be in liquid-ish form otherwise you cant pour it. Just my idea.

10-20-2011, 10:18 AM	#4
CHU*D No idea what I'm doing Join Date: Oct 2008 Location: Underground, CO Posts: 4,529	What about MIM (Metal Injection Molding)? Not sure how well it would work, but a lot of metal parts are made this way to keep machining costs down. Metal Injection Molding, MIM \| Advanced Forming Technology (AFT), Longmont, CO edit* Are you talking about something you can do yourself at home?

10-20-2011, 10:20 AM	#5
STANG KILLA SS ~THE SCALE SHOP~ Join Date: Apr 2006 Location: KILLEEN TX Posts: 10,056	i have no clue what it takes to melt steel. might melt the mold? chud. yes i want to be able to repair the prop at home, now and in the future. hmm what about JB weld? looks like they sell a 10oz kit as there largest. J-B Weld Company - INDUSTRO WELD Product Information

10-20-2011, 10:27 AM	#6
CHU*D No idea what I'm doing Join Date: Oct 2008 Location: Underground, CO Posts: 4,529	Gotcha...Thought you were looking to go into the business of making them.

10-20-2011, 05:06 PM	#7
rockn Rock Crawler Join Date: Sep 2009 Location: Temecula Ca Posts: 566	Gold go down to fort Knox and buy some

10-20-2011, 06:17 PM	#8
Dogbreath Rock Crawler Join Date: Aug 2009 Location: Sandy Oregon Posts: 517	#1 Go to a lake without stumps #2 SLOW DOWN #3 install a Prop Guard

10-20-2011, 06:37 PM	#9
Bart bender I wanna be Dave Join Date: Jan 2006 Location: Iowa, the antirecreation state! Posts: 2,227	Looks like you're just bending them. Can you just heat with oxy/acetylene and lightly pound it back into shape? Can you tig with the proper filler if you take chunks out? You'll need it balanced and trued up I'm sure after that.

10-20-2011, 09:23 PM	#10
Gula I wanna be Dave Join Date: Jun 2006 Location: Here Posts: 2,320	Bang with a rubber hammer back into shape, then take a DuBro prop ballancer to it, easy as that. Won't the metal that the prop is made of get stress fractures from bending it back to the opposite side? I know $175 may seem a lot, but I'm sure replacing a bearing or multiples of in a boat can't be cheap. Don't they make a prop protector, something like a shroud on a house fan? I'm sure that wont slow your boat down too much

Sponsored Links

10-21-2011, 11:00 PM	#11
viper6171 RCC Addict Join Date: Dec 2008 Location: pullin somebody else out of a mud hole Posts: 1,759	are you trying to make a form to hammer the prop back to the proper shape ? if so then you might try making the form out of jb weld you could make a box out of wood and cover the good blade with saran wrap and build a form around it out of wood . then mix up your jb weld and pour it in and let it cure .

10-22-2011, 03:02 PM	#12
Charlie-III I wanna be Dave Join Date: Nov 2010 Location: 07456 N. NJ USofA Posts: 8,314	Don't care what you use, it won't do a good enough job. Why??? Because you have to bend the blade BEYOND "correct" to allow it to spring back to correct. Thus your idea will always leave the prop blade bent a little bit the way it was before. Using some blocks of hardwood and a hydraulic press (think "shop press" with a bottle jack) may do it. I have no clue if doing that will either work harden the blade or cause stress cracks. Ask yourself this, "If I do it wrong and throw a blade at full throttle, how much of a PITA will that be (possibly middle of a big lake) and what will I likely damage (and what will it cost in time & money to repair/replace)??"

10-22-2011, 04:26 PM	#13
Gula I wanna be Dave Join Date: Jun 2006 Location: Here Posts: 2,320	If you do make a mold out of whatever. How you going to get the prop out of the initial mold? The mold would have to be made from silicone or sand and your prop from wax or styrofoam, so it could melt as you pour the hot metal in. I have heard a guy made his gears for a powerwheels vehicle from metal. He cut the initial copy of the gears out of styrofoam, put them in sand, then poured in molten aluminum or something like that. then filed them into shape.

10-23-2011, 10:14 AM	#15
SlickRockSpider Rock Crawler Join Date: Apr 2008 Location: Albany Posts: 640	The prop spins at way to many rpms to f*ck with. I would have a pro fix it. What about a jet. Evan

10-24-2011, 09:47 AM	#16
STANG KILLA SS ~THE SCALE SHOP~ Join Date: Apr 2006 Location: KILLEEN TX Posts: 10,056	well i gave up on trying to make a mold i could hammer the prop back to shape in. decided to go back with a simple beat it back to shape method. 2lb sledge and a block of rounded wood. but i wanted to something to check to know if it was exactly back to factory shape (or damn close) so i still made a mold. used an old speakerbox making technique for making complex curves and organic structures. fleece and fiberglass resin. worked awesome as i expected. wrapped one of the good blades in fleece and added fiberglass resin. now i have a perfect replica of a good blade and can slowely work the bent on back to this shape and be able to check progress and get it bent back just perfect. thats the plan anyway

10-24-2011, 12:46 PM	#17
STANG KILLA SS ~THE SCALE SHOP~ Join Date: Apr 2006 Location: KILLEEN TX Posts: 10,056	made great progress at lunch. got it to within 1/8" of the mold(started 1" out). and its nice and straight and smooth too. we ran out of time and shapes of blocks of wood. another round of beating tonight or at lunch tommorrow and plan to test tuesday at the lake. the mold was a huge help. after about 20-30 minutes it was impossible to tell which blade was bent lol. had to mark the bad blade.

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