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Dry weight vs auw

#1
What id dry weight? Is it the plane without any electronics or the plane with everything but the battery? I built a simple cub and painted it but could not get it to fly. I think it wouldn't fly because it was twice as heavy all up as the recommended spec. I know part of the problem was that I use Elmer's foam board and mounted the servos too far back so it was severely tail heavy. To get the CG right I had to add a huge lead weight to the nose and I think it was too much. Now I am building a second simple cub and was thinking that if I needed to I could drill some holes in the tail to lighten it up (like the video where Peter and Josh drilled the crap out of a plane until it wouldn't fly). Before I drill I would like to have an idea about how much the plane should weigh without electronics.
 
#2
Mine weighs 380g with four servos. As for it being tail heavy, was it not possible to just shift the battery all the way to the front? I'm not familiar with using that foam board, but my guess is that might be your problem.
 
#4
Are you putting on the landing gear? That's another part that isn't really necessary, especially if you are trying to save weight. I'm pretty sure the AUW includes all electronics, because that's similer to mine with all electronics.
 

Merv

Well-known member
#5
Make a trial CG test before installing the components. Build the plane, use a bit of tape to tack everything down, test the CG, them move thing around until can get the plane to balance. Instead of adding nose weight, try adding to length of the nose to achieve the proper CG.
 

leaded50

Well-known member
#6
"The aircraft gross weight (also known as the all-up weight and abbreviated AUW) is the total aircraft weight at any moment during the flight or ground operation."
That should then be with battery/electronics, everything to get it airborne.
 

"Corpse"

Well-known member
#7
The term "Dry weight" comes from full scale aviation and fuel tanks. When the fuel is drained, the tanks are "dry" Same with batteries, they are your fuel tanks.
 

Hai-Lee

Old and Bold RC PILOT
#8
What id dry weight? Is it the plane without any electronics or the plane with everything but the battery? I built a simple cub and painted it but could not get it to fly. I think it wouldn't fly because it was twice as heavy all up as the recommended spec. I know part of the problem was that I use Elmer's foam board and mounted the servos too far back so it was severely tail heavy. To get the CG right I had to add a huge lead weight to the nose and I think it was too much. Now I am building a second simple cub and was thinking that if I needed to I could drill some holes in the tail to lighten it up (like the video where Peter and Josh drilled the crap out of a plane until it wouldn't fly). Before I drill I would like to have an idea about how much the plane should weigh without electronics.
I use a heavier FB for all of my builds and you can even make the original heavy version fly well with a simple addition.
As you are building a new version there are a few things you can do to actually reduce the tail heavy issue.
1. Remove all of the internal paper on the fuselage tail boom.
2. Use lighter servos for the tail control surfaces, (I have used 3.7 gram servos successfully in the past).
3. Fit a slightly larger and heavier motor than specified.
4. Add a propeller spinner, (metal spinner can add significant weight to the nose).
5. Fit "Tundra" type tyres. They are normally heavier and really improve the landings.

Now if you do all of the required work and it still needs nose weight OR it is still too heavy to fly or fly well the aforementioned addition is to add a paddlepop stick under the wing Leading edge, (on top of the fusleage), to increase the wing incidence angle.

My first version was a real hand full and really terrible to fly when maidened even though I managed ot get it to balance perfectly. I increased the wing incidence angle and the bird calmed down and became docile and flew very well. It now even tends to float on landing. It is still grossly overweight but it flies beautifully.

Just what worked for me!

Have fun!