stunthanger.com
Engine basics => Engine set up tips => Topic started by: frank mccune on August 28, 2013, 07:38:22 PM
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Hi:
I have a Zero and Hellcat that would look much better if they sported three bladed props. What are the pros and cons of running a three bladed prop?
Would a TF plastic 10-6 three blade work well on a .35-.40 engine? If not, what size of a three blade would work well with these engines
Tia,
Frank
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You could run a MasterAirscrew 3-blade, but they are really heavy!
Floyd
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Hi Frank,
Traditionally, using a prop with 1" less diameter is used for 3 blade props. If you are talking engines like the Fox .35 then a 9-6 would be right for the 3 blade. Some modern engines might go with a bit more prop in the 3 blade. I like the 3 blade props and use them a lot on piped engines.
BIG Bear
RNMM/AMM
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Other than the MA 3-bladers, what is out there that's readily available? I'd like a decent 3-blade prop to use with a T&L ST46, but Brian Eather and Bolly aren't making them any more, and Randy doesn't have any suitable Majic ones in stock. I've found the MA 10x7 3-blade works quite ok with an Enya 45-I, so would probably do the job with the ST46 as well, but I really wouldn't mind looking into other alternatives if they were available.
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I had a Brodak Zero for a few years with a tower 40. Ran lots of props on it and surprisingly the M/A 10/5 3 blade gave excellent performance. Most of these props are under pitched and mine was around 3.75 pitch which turned out to be a winning combination for the model. They are reasonably priced and really not excessively heavy for sport models. It gave me some of the most satisfying flying I had with a profile model
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I'd like more opinions about the MA 3-blade props, since they're easy to find here.
I'm aware they don't perform like Bolly's and others, but are they OK to use for sport models?
Who else has been running them??
Thanks a lot in advance...
Marcus
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Don't worry about the weight of the prop. A 1/4 oz in the tail weight box will fix that. If the prop doesn't work, it doesn't matter how cute it looks, or how much less $ it cost for a MA than a CF prop.
One of our Dutch members reported that he used the Graupner 10-7 3-blade on a ST .46...which should also work on an Enya .45 #6001, since they are essentially copies (parts interchange?!). He did admit that the prop was reworked, which is not hard to do, by both scraping and sanding. I have one of these Graupner props, but no longer have a ST .46. The airfoil is sorta semi-symetrical. I'd expect it would be better flat bottom and thinner, but I have had good results with Graupner's props. y1 Steve
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A local flier uses a 12x6 master airscrew 3 blade cut down to 11x6 in an LA-46. Gets incredible runs. There are no concrete answers here, you just have to experiment and see what works. 8)
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Pulling 10 ton on the old OS 35 Max's , the 9x6 didnt work but 10 x 4 Tornado 3 blades 9 the silver ones ) do fine , vertical and all around etc .
Youre on dangerous territory , as covetiusness & Tornado 10 x 6 3 blades are on the same page in my notebook .
I ve recovered brittle yellow Tornados by doseing them with Armour All . works good .
the 10 x 6 was a favoured prop for the ST 21 / 46 , so you could save the worry , & send the PROPs to ME ;D
On a strong schneurle , hard out , theyed be getting along fairly quickly .
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You could run a MasterAirscrew 3-blade, but they are really heavy!
Floyd
This might not be such a big issue. As was mentioned above, 3-blade equivalent of a 2-bladed prop is 1" smaller in diameter. Spinning prop is like a motorcycle wheel: once spinning, it does not like to change direction. This means that part of up/down force generated by a deflected elevator is used to make the spinning prop turn. The larger the prop diameter, the more force is required to make it change direction. The opposite is also true: the smaller the prop, the less effort is needed to make the model turn. By going to smaller diameter prop of the same weight, the model will behave as if it has more rearward CG.
This effect will therefore offset some of the extra weight in the nose.