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Engine sizing feedback

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Old 11-23-2013, 02:39 PM
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goehrle
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Default Engine sizing feedback

I am planning on putting Maxford floats on a new Dragon Lady and am targeting to use a
DLE 20 RA. I would appreciate some feedback from the more knowledgeable/experienced
float plane parties on this combination.

DLE 20 RA weighs 1.8 lbs
Maxford 60 size floats (37") with hardware---3.6 lbs
Dragon Lady kit -- 4 lbs (no landing gear)
Misc for build out--2 to 3 lbs
(covering, fuel tank battery, servos, RX etc)
for a total of 12.5 lbs

The Dragon Lady recommended engines are:
Two cycle .60 to 1.20
Four cycle .90 to 1.60
Gas 16 to 23 cc

The Dragon Lady
66 inch wingspan low wing
54 inch length.

I had considered the Evolution 33GX but is a little to large for the engine bay in my view
and even if mounted downward the air intake is exposed to water spray due to its location.
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Old 11-23-2013, 07:06 PM
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The 20 should work great
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Old 12-18-2013, 12:01 PM
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CARS II
 
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I'm flying a Sig 4 star 60 @ nearly 9 lbs with an OS 65 LA with a set of the Maxford floats without any lack of power. Your set up should work just find.

With those floats I would change the mounting rails for home.made ones because the rails are soft.
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Old 12-20-2013, 11:22 AM
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Sorry I do not know the Maxford floats but based on the length and your projected weights I think at 37inch in a conventional float that you may be a bit short on displacement. I think I would build or be looking for something at or above 40 inchs in length. In my opinion when it comes to float displacement its better to error on the large side.

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Old 12-22-2013, 03:23 PM
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If you multiply the length times max width times depth at the step,to get the "block volume", then multiply by 60%, you will get the approximate volume of each float.
Each cubic inch of float will support 0.6 oz of aeroplane.
So supposing the floats measure 37 x 4 x 3 that's 444 in^3 block volume, or about 266 in^3 float volume good for 160 oz, i.e. 10 lb

You want enough volume in EACH FLOAT to support the aircraft weight, so that each float is only half submerged, so a pair of floats the size of my example is good for a 10 lb model (give or take a pound).
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