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General control line discussion => Open Forum => Topic started by: Robert Zambelli on March 30, 2009, 08:57:50 PM
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Although this is for a scale plane, I've used the same technique for stunt plane spinners.
Quick and easy, the spinner is 2 1/2 inches in diameter and around 3 1/4 long.
Weighs 1.5 ounces with the backplate.
Bob Z.
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Well I think you need to be careful when you purchase those "sheathes". At least you had better already have your story for the wife.
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Hobby Poxy had a kit years ago for making fiber glass bits. For spinners, the form was covered with Saran Wrap and the glass and epoxy applied. Then a partially inflated balloon was worked down over it and deflated using the pressure of the rubber to equallize the pressure on the part. It made very nice parts, but you had to over run the form quite a bit because the pressure at the edge would make that area thinner. I made a number of very light weight spinners for rubber scale models.
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Yes TY, please more details on how you formed the nose cone of the spinner!! #^ That is one cool lookin' spinner!!
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Well, as usual, you fellows ask all the right questions - here are the answers.
First off, I did a complete article on cowl molding in the January, 2007 (Volume 1, Number 1) issue of Control Line World. It gives step-by-step instructions. Pay particular attention to the last paragraph.
Molding a spinner is the exact same procedure but you have one additional step - the backplate.
My procedure is basically the same as the one from Hobbypoxy.
Ty - I machine all my backplates - either in plastic as you see here or from aluminum. If I need a bit of extra noseweight, I can make them from steel or brass. You are right - hardwood would definitely be a better choice but I did not have any handy at the time. I ran the lathe at 1,250 RPM.
To compensate for material thickness, the male plug (ironic? LL~ LL~ LL~) must be accordingly a bit smaller than the desired end product. I normally apply enought layers to yield a .040 to .060 thickness. Also, a bit of draft is needed to remove the part from the plug. Coating the plug liberally with talcum powder before applying the release membrane really helps.
If you make the spinner and it's a bit too thin, just apply another condom to the plug, put the part back on and apply a few more layers of cloth.
Super simple.
If you have more questions please ask and I will try and give more info but the article really says it all.
Bob Z.
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Well, as usual, you fellows ask all the right questions - here are the answers.
First off, I did a complete article on cowl molding in the January, 2007 (Volume 1, Number 1) issue of Control Line World. It gives step-by-step instructions. Pay particular attention to the last paragraph.
Molding a spinner is the exact same procedure but you have one additional step - the backplate.
My procedure is basically the same as the one from Hobbypoxy.
Ty - I machine all my backplates - either in plastic as you see here or from aluminum. If I need a bit of extra noseweight, I can make them from steel or brass. You are right - hardwood would definitely be a better choice but I did not have any handy at the time. I ran the lathe at 1,250 RPM.
To compensate for material thickness, the male plug (ironic? LL~ LL~ LL~) must be accordingly a bit smaller than the desired end product. I normally apply enought layers to yield a .040 to .060 thickness. Also, a bit of draft is needed to remove the part from the plug. Coating the plug liberally with talcum powder before applying the release membrane really helps.
If you make the spinner and it's a bit too thin, just apply another condom to the plug, put the part back on and apply a few more layers of cloth.
Super simple.
If you have more questions please ask and I will try and give more info but the article really says it all.
Bob Z.
Cool method....easy to understand. Can I borrow your lathe? I'm not sure I can accomplish that on my drill press LL~ H^^ ;D
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John,
I did all my forms on a drill press before I had a lathe. If you carve it roughly to shape before you mount it, all you have to do is sand it to finish shape in the drill press.
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Hobby Poxy had a kit years ago for making fiber glass bits. For spinners, the form was covered with Saran Wrap and the glass and epoxy applied. Then a partially inflated balloon was worked down over it and deflated using the pressure of the rubber to equallize the pressure on the part. It made very nice parts, but you had to over run the form quite a bit because the pressure at the edge would make that area thinner. I made a number of very light weight spinners for rubber scale models.
I think they called it the E-Z Does It method. It was good for forming cowls, etc. too.
George
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John,
I did all my forms on a drill press before I had a lathe. If you carve it roughly to shape before you mount it, all you have to do is sand it to finish shape in the drill press.
Okay then.....I'll givver a try! H^^
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Although this is for a scale plane, I've used the same technique for stunt plane spinners.
Quick and easy, the spinner is 2 1/2 inches in diameter and around 3 1/4 long.
Weighs 1.5 ounces with the backplate.
Bob Z.
HI Bob
Good job, and what is the plane this will go on?
I am think about making a Martin Baker spinner using this technique
Regards
Randy
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Hi, Randy - it's for a quarter scale Shoestring.
Bob Z.