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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Igor Burger on August 28, 2014, 03:21:36 PM
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I just got attached pistures by mail. It is really not good idea to modify modern electric props that way. Some of them are hollowed inside and such modiffication will either damage them or make it danger. Also drilling such large hole for shaft is not good idea, it will certainly break sooner or later.
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What was the attempted modification? Thinning the blades?
AFAIK, people routinely re-pitch CF props, even people who profess to not know what the term "glass transition temperature" means*. So surely some modifications are OK, and some aren't.
I think if I contemplated messing around with something like that I'd start by asking whoever made it whether the violence I contemplated doing unto their work was a good idea or not.
* Howard: one word: Wikipedia.
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I wonder if the owner didn't try balancing the prop by removing resin from the heavy blade.
If that is the end result, it prompts the question, is there a safe way to balance these c/f props? I would think that some removal of surface resin is acceptable, or is it? Surely there are few props that are balanced right from the mold...
r/
Dave
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I wonder if the owner didn't try balancing the prop by removing resin from the heavy blade.
If that is the end result, it prompts the question, is there a safe way to balance these c/f props? I would think that some removal of surface resin is acceptable, or is it? Surely there are few props that are balanced right from the mold...
r/
Dave
That's deeper than surface resin.
You could always paint epoxy onto the light blades.
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Igor may have a particular species of hollow-blade props in mind. Thanks for the warning. Is a 9mm hole too big?
By the way, I owe you money for the prop. I had it at the banquet, but you were not there.
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By looking at the pictures, it looks as if whoever was working on the prop was working on the back of a blade and hit a void in the prop. Small voids are common in hand laid up props. When laying up a prop using CF tow, the voids are easy to see and can usually be minimized. The prop in picture is similar to the Mejzlik props in that the face was first laid up with CF cloth and then tow was used for all the remaining carbon in the prop. This prop also has cloth on the backside meaning that voids cannot be seen and could easily be that large. I've seen one of the props that Igor has been selling and the quality is top notch, but due to their construction, it is possible that voids could be present. In short, I wouldn't be doing a lot of modifying the blades. As they are, the chance of a blade failure are small, if the blade is as it comes from the mould and not modified.
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I wonder if the owner didn't try balancing the prop by removing resin from the heavy blade.
If that is the end result, it prompts the question, is there a safe way to balance these c/f props? I would think that some removal of surface resin is acceptable, or is it? Surely there are few props that are balanced right from the mold...
r/
Dave
Those props come perfectly balanced by adding resin inside the prop, so far I did not need to touch them before flying. Sanding will totally destroy the surface, because it it polished and carbon is covered by thin glass.
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Igor may have a particular species of hollow-blade props in mind. Thanks for the warning. Is a 9mm hole too big?
By the way, I owe you money for the prop. I had it at the banquet, but you were not there.
Those props are made for 6 to 8 mm holes. If you have 6mm shaft, it perfectly fits as delivered, if you have something between, you have to drill it and if you have 8mm (MVVS or axi fron mounting shaft or aeronaut shafts) you have to drill out just to half of the prop, so that existing 8mm diameter will seat to shaft. 9 mm drill will be probably still safe, but I will not go larger diameter, you can open the prop.
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Small voids are common in hand laid up props. When laying up a prop using CF tow, the voids are easy to see and can usually be minimized.
Actually they are not "small" and not "minimized" :- ))) ... the prop is hollow, that is the point. The weight of 12" prop is oly 16g what makes visible advantage in corners.
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Igor,
My new 12 LH prop is about as light as can be done on standard lay up and it comes out at 26.5g. I didn't get to inspect your prop very well but did think it was awfully light. If epoxy were needed to balance, does in get injected near the tip?
Alan
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You are asking wrong man, but I think logic place is middle of blade, where is highest probability of uneven amount of material. (because of widest blade)
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How do you make a hollow prop, 2 halves glued together?
MM
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Guys, you are asking wrong man about technologies, I am not maker, and they are profesionals making life from that so I do not think they will want teach us how to do it ... I simply designed those props for our needs from aerodynamic point of view, nothing else :- ))