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How Heavy is Too Heavy

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How Heavy is Too Heavy

Old 04-12-2015, 02:53 PM
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vindee
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Default How Heavy is Too Heavy

I have just completed my 30cc Dehavilland Beaver and with the addition of the floats and struts it is weighing in at around 14lbs.
This is supposed to be a 10-11lb plane. It has an 87" wing span (935 sq in). Recommended engines are 1.10 to 1.40 4 stroke and I'm running an OS 1.20 4 stroke with a 15x8 break in prop and a 16x8 for the maiden flight. I'm not really sure what is an acceptable weight.
I did modify the wing for flaps to assist in getting off the water.
Ant thoughts?
Thanks.
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Old 04-12-2015, 07:09 PM
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Roger Gray
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I'm curious how much weight did you have to add to balance. What % of the cord did you balance on. I'm asking because I have just finished a 96" wing span Otter that I scratch built using pink and foam and glass for the fuse construction and a wood built up wing and Sig coverall. I had a BME 44 on the shelf and knew I would have to add lots of weight to the front to balance. I still had to add 1.6 pounds to balance. Still need to final weigh.
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Old 04-12-2015, 07:11 PM
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Roger Gray
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I used a 1.20 saito in my 6 ft. beaver.
Old 04-13-2015, 07:44 AM
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vindee
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Originally Posted by Roger Gray View Post
I'm curious how much weight did you have to add to balance. What % of the cord did you balance on. I'm asking because I have just finished a 96" wing span Otter that I scratch built using pink and foam and glass for the fuse construction and a wood built up wing and Sig coverall. I had a BME 44 on the shelf and knew I would have to add lots of weight to the front to balance. I still had to add 1.6 pounds to balance. Still need to final weigh.
So far I have not added any weight. I balanced off the main spar which is only a few inches back from the leading edge. I'm using a weighted spinner nut which probably helped balance.
I'm curious what your beaver weight was and how well it flew with the 1.20 in it.
Old 04-15-2015, 09:05 AM
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MJD
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34.5 oz/sq ft wing loading - on the heavy side but flyable in a model that size. Stall speed will likely be somewhere in the 25-28 mph range less flaps.. don't horse it off the water.
Old 04-15-2015, 11:03 AM
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Originally Posted by MJD View Post
34.5 oz/sq ft wing loading - on the heavy side but flyable in a model that size. Stall speed will likely be somewhere in the 25-28 mph range less flaps.. don't horse it off the water.
Thanks for the input MJD. I think your right on the stall speed based on modeling this plane in RealFlight. I have been landing at around 30 mph to keep the plane level when touching down. I have tried adding more weight on the sim to get the feel for a heavier plane, but I don't think stalling on the sim is not as accurate as the real thing.
Thanks again.
Old 04-17-2015, 05:48 AM
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Agree with all above. I have added smoke to some gassers and that is an extra battery, pump and 16 oz tank and tubing/fittings for a couple extra pounds. And then put 44" fiberglass floats underneath. The Mentor-G in the image below is just under 18 lbs gassed up - with an 82" WS and 26cc Zenoah magneto engine. The manual claims 11.1 pounds with fuel! Very heavy as flown (but I think the manual is wrong - I was around 13 dry once assembled with wheels). Flies great. Drops like a rock in knife-edge so I have to keep the wing flying.



If the model has bad traits when light they will be amplified as you add weight. But the Beaver (full size) is designed to be heavily loaded. Relatively high aspect ratio wing. Keep some speed up in landing, or use the flaps, and know it takes a little more altitude to recover from aerobatics.
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Old 05-06-2015, 06:16 PM
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Thanks Charlie.
I don't plan on doing much aerobatics with this plan. Call me boring, but, the plan is scale and I like flying scale like. So as it seems, might weight should be within reason.
Thanks for the input. That's just the kind information I'm looking for.
Steve
Old 05-24-2015, 07:11 PM
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Carlos G
 
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Hi vindee,

Have you put the plane in water to see if the floats will support the total ready to fly weight including fuel? Just curious is all.

Carlos G
Old 05-26-2015, 07:32 PM
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vindee
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Originally Posted by Carlos G View Post
Hi vindee,

Have you put the plane in water to see if the floats will support the total ready to fly weight including fuel? Just curious is all.

Carlos G
I have a Koi pond in the back yard. I have been meaning to set the plane in there to see how it sets. I'll let you know.
They are Sea Commander Floats designed for a slightly heavier plane so I don't anticipate a problem there.
Thanks
Old 05-27-2015, 11:46 AM
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As said above DON'T horse it off, just let it do it's thing until you get used to it . Also KEEP power on on landing, DON'T float it in, when it touches down it will slow down quick so keep some speed on . As far as the weight goes it may be a bit soggy ( you like that word ? ) flying but if you take your time you should be able to feel it out and Enjoy it . ENJOY !!! RED
Old 05-28-2015, 12:54 PM
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I'm not a seasoned float flier but I get by - the first thing I think I learned was the difference between water and ground landings.. fly it in.

Oh yeah, and that leaky floats suck, and no matter how hard you try you're going to eventually lose it if you scoop up about two cups of water in the left float of a .46 size Stik.. but I almost got it down.
Old 05-28-2015, 03:05 PM
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I landed a Saratoga 40 with 10 oz water (measured) in one leaky float. I thought I had lost one aileron and got her back in. It flew amazingly well for what was happening. I added a drain plug (that's when I had the opportunity to pour out the trapped water inside).

Worse was my G-44 Widgeon. Already a very heavy model (twin engine fiberglass fuselage. I was showing of the differentle throttle fr water steering and, when I eventually took off it went nose up and then fell out of the air.

I'd left the drain plug out. Water came in and all went to the tail when I lifted off. Ugly.

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