ORIGINAL: pe reivers
ORIGINAL: Umran
Dear Pe,
What i can offer is, since you have large variety of prop brand selection, you feed me the sectional chord lengths. For example,
APC 14 x 10 .... .... .... ...... ......
APC-W 13 x 4 ..... .... .... ...... .................................................. .............. ......
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For each brand, only 1 diameter is enough, for an example APC prop, you have only 14in diameter, this data is enough because plan form design of a brand rarely differ as the diameter grow or shrink. But a different model of does i.e. APC normal and APC-W are different, then say you have APC-W 13 inch, then collect those data as well.
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In the above table example, the base dimension is in inch however for the rest is in meter....
Umran,
APC is a very bad reference platform, because they change the basic propeller design with evry different diameter size. In my spreadsheet I would have to use a dedicated prop constant table for APC alone! Lacking reliable reference data, it is impossible for me to produce it.
No problem Pe... I will get the data slowly....
To all.
Another main use of this estimator is the power required readings. For example, running a 23 x 8 - 2 bladed prop at 7000rpm will require 5.04HP. If somehow our engine can deliver this power so that it can be run at 7000 rpm (typically it can by using most of the 55cc engine in the market today), now for a nice scale look we decided to change our prop to a 3 bladed. What size do we purchase if we want to maintain similar flying speed and performance?
Under this scenario, with the same spreadsheet sheet, we simply change the number of blade to '3' - the result for power required is 6.9HP. Mmmm... given the engine that we have, we know for sure it can't deliver. Therefore we reduce the diameter to 22 inch, recheck... 5.88HP, still higher than 2 bladed prop. We reduce a bit more say 21inch diameter, re-check... the result comes out with 4.97HP which is very close to original 5.04HP with 23 x 8 2 bladed prop.
Now with confident we can obtain similar performance if we change the prop 23 x 8 - 2 bladed to 21 x 8 - 3 bladed prop.... The available thrust reading also similar i.e. 12.89 kg vs 13.03 kg for 3 bladed.
Those scale modellers can now smile!!! don't have to purchase a few sizes to suit their engines....