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Old Sep 22, 2013, 07:33 PM
Balsa addiction since age 3
ScottSails's Avatar
Upstate NY
Joined May 2005
1,253 Posts
Quote:
Originally Posted by Taurus Flyer View Post
You are kidding
I absolutely am NOT kidding... I have seen a shed prop (~300 watts) destroy the fuse of a plane (imbalance created) and could have blinded my buddy or me - we were lucky blade went other side. Others here have had blades impale themselves into their walls and shop tables - please be careful. Power is the culprit, as you start moving up in RPM, problem becomes more likely.

Manufacturers rate the blades based on RPM - Look at Aeronaut for example...

Best wishes,
Scott
PS - the blades you are using look like they are from an old nylon prop? I would be careful about root stresses where you put your screw through...
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Old Sep 23, 2013, 12:20 AM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
The Netherlands, OV, Almelo
Joined Nov 2010
2,957 Posts
I'm impressed, all that knowledge.
How long do you practicing this modeling hobby?

Edit, two more photographs.
1 the nose, stripes still visible of trimming the airfoil of the propeller
2 Prandtl Rohr of the right side wing tip. these days the more streamlined model is used, 3 (left side wing tip).
The Prandtl Rohr is used for the relative netto variometer.

Airfoil of the wing MH32, silk and dope.
The stab isn't interesting I understand.
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Last edited by Taurus Flyer; Sep 23, 2013 at 01:22 AM.
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Old Sep 24, 2013, 05:25 AM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
The Netherlands, OV, Almelo
Joined Nov 2010
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Quote:
Originally Posted by ScottSails View Post
I absolutely am NOT kidding... I have seen a shed prop (~300 watts) destroy the fuse of a plane (imbalance created) and could have blinded my buddy or me - we were lucky blade went other side. Others here have had blades impale themselves into their walls and shop tables - please be careful. Power is the culprit, as you start moving up in RPM, problem becomes more likely.

Manufacturers rate the blades based on RPM - Look at Aeronaut for example...

Best wishes,
Scott
PS - the blades you are using look like they are from an old nylon prop? I would be careful about root stresses where you put your screw through...
Scott, You could read I wasn't impressed by your advice and of course I didn't expect you back, you are free to do. Point for me was, I was thinking about that budy of you and the "Others here". you all playing with, Russian Roulette.

A few years ago there was no internet, written knowledge was all we had and experience, for each Old School modeler it was the same, and all over the world. Now there is much internet and less "Old School". Result?
Knowledge is evaporated and fairytales came back!

"Screw" you wrote?
Because of the centrifugal forces the pivots of a folding propeller have to be made of high tension and -quality shafts, the diameter of the bore in the blades reamed for the exact diameter to have an optimal fit for a stable AOA and optimal force transfer, prevent local tensions in the root of the blade.
To reduce tension in the adaptor it's better to lock the shaft with one side using a nut and threaded hole. The other hole also has to be reamed to have an exact fit with the shaft. (Taurus Flyer)

Scott, that's the story, and not "I would be careful about root stresses where you put your screw through... "

Of course writing about the stab of the Sagitta and the linking would result in an identic story, but I understand you know enough about mechanics. Knowledge is evaporated and fairytales came back!


Taurus Flyer
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Old Sep 24, 2013, 03:01 PM
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Recommend, when building a stab on a model like this, that you take a scale to the hobby shop and pick very light sheets for the larger balsa parts. Same for the rudder. Only use anything heavier when it's needed for strength.
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Old Sep 26, 2013, 04:51 PM
Balsa addiction since age 3
ScottSails's Avatar
Upstate NY
Joined May 2005
1,253 Posts
Another consideration when making the stab (with electric non winch) is to use a slightly different construction method to really save on tail weight. Consider that if you save 10 grams on tail - it is roughly 30g on the nose (40g all together) which really adds up. And since you are planning on electric, this will be a good benefit.

Pick what airfoil you want - I actually used Dr Drela's HT-14 airfoil for stabs...
Small carbon tube for leading edge and hard balsa top and bottom as the "spar" as well as trailing edge. I saved a significant amount of nose weight by doing this change. This type of stab is NOT bulletproof but it is ok for electric flight. I worry about potential hanger rash when moving up and down from my shop to the car. I have yet to break one (I have 2 sets) this summer but the risk is there. I put in small balsa scraps between the ribs to help prevent finger crushing of the spar while inserting or removing the stabs.

Sorry about pictures, I used fluorescent transparent covering that is hard to take a picture of (and quite heavy to boot - I don't use it anymore but it does help my old eyes to see the plane better).

Scott
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Old Sep 26, 2013, 05:31 PM
AKA - The "Flywheel"
StevenatorLTFO's Avatar
SOAR Chicago!!!
Joined Jan 2005
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huh?

Quote:
Originally Posted by Taurus Flyer View Post
Scott, You could read I wasn't impressed by your advice and of course I didn't expect you back, you are free to do. Point for me was, I was thinking about that budy of you and the "Others here". you all playing with, Russian Roulette.

A few years ago there was no internet, written knowledge was all we had and experience, for each Old School modeler it was the same, and all over the world. Now there is much internet and less "Old School". Result?
Knowledge is evaporated and fairytales came back!

"Screw" you wrote?
Because of the centrifugal forces the pivots of a folding propeller have to be made of high tension and -quality shafts, the diameter of the bore in the blades reamed for the exact diameter to have an optimal fit for a stable AOA and optimal force transfer, prevent local tensions in the root of the blade.
To reduce tension in the adaptor it's better to lock the shaft with one side using a nut and threaded hole. The other hole also has to be reamed to have an exact fit with the shaft. (Taurus Flyer)

Scott, that's the story, and not "I would be careful about root stresses where you put your screw through... "

Of course writing about the stab of the Sagitta and the linking would result in an identic story, but I understand you know enough about mechanics. Knowledge is evaporated and fairytales came back!


Taurus Flyer
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Old Sep 26, 2013, 05:36 PM
I bail out, anywhere, anytime
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The Netherlands, OV, Almelo
Joined Nov 2010
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Stab
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Old Sep 26, 2013, 06:02 PM
I bail out, anywhere, anytime
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The Netherlands, OV, Almelo
Joined Nov 2010
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Quote:
Originally Posted by StevenatorLTFO View Post
huh?
Here: http://www.rcgroups.com/forums/showp...08&postcount=3
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