[bartman]

Hello all,
I have an older cub (han1500) arf. The kit states with a saito 50 4s very little if any balance weight should be required. With a lighter 2 stroke expect to add some weight. I am useing a thunder tiger pro 46 with pitts muffler. To obtain 3 1/4" from leading edge ballance I have had to add 400 grams weight (aprox 14 oz or 56 stick on weights). This seems very excessive to me for this size air frame. All other components are mounted as far forward as possible. (battery is at firewall under tank). Anyone have a similar set up?

Here is a quote from the manual,

Section 16: Balancing the J-3 Piper Cub

An important part of preparing any aircraft for flight is properly
balancing the model. Don’t inadvertently forget this crucial step.
The recommended C.G. (Center of Gravity) location for the first
flights with the J-3 Cub is 3-1/4" from the leading edge. With
the Saito .50 installed, very little, if any, additional weight will be
needed to balance the model. If you’re using a lighter 2-cycle
engine, expect to add weight. Stick-on weights are available at
your local hobby shop and work well for this purpose.

I had the c of g too far back with no added weight on the maiden but it was touchy. I ran 1/4 throttle and four oz of fuel for 10 min. With the added weight it ran at 3/4 to full throttle and 8oz of fuel at 6 min aprox. Seems very underpowered with engine at upper recomended displacement and proper ballance.

Thanks in advance Brian

[supercub1974]

I know this is no help but my great planes 81" cub is 4" from the leading edge.

[ss40a]

I have a Hangar 9 80" Cub, about 6 years old?? anyway I had a ASP .61 FS installed with wheels and no weight required. I added floats and needed some weight.
Now I have an ASP 80FS and regret adding the weight .

Another one locally has been flying off wheels with a .91 four stroke so I think the .46 is light but for scale flying the power is probably about right. With the .91FS it is definitely uncub-like!

[hifly2104]

Originally Posted by ss40a

I have a Hangar 9 80" Cub, about 6 years old?? anyway I had a ASP .61 FS installed with wheels and no weight required. I added floats and needed some weight.
Now I have an ASP 80FS and regret adding the weight .

Another one locally has been flying off wheels with a .91 four stroke so I think the .46 is light but for scale flying the power is probably about right. With the .91FS it is definitely uncub-like!

I also think with a 46 it is underpowered.Overpowered is still restricted to throttle control.I would think a 60 size motor more appropriate. The other way to add some weight if you still wish to use the 40 size is a Higley prop nut made of brass adds 2oz but its right up front so it is better than flywall weigh. It is also usefull weight

[bartman]

Thanx Everyone,
I do have a brassprop nut on already plus the 400 gram steel plate mounted on the motor mount.. I am going to put it back together and weigh it. The manual said it shold be around 6.5 pounds. Something just is not adding up in my brain.

[alexrock23]

I have the 80" with hangar 9 floats, very nice plane. I run a YS .63 in mine, inverted with a 13x6 APC prop. The floats were ultracote covered, which I didn't like. So i stripped em, filled em, glassed and painted them. I found the rigging to be right on. The cub sits idle in the water perfectly, tracks and taxis great and requires no trim between water and land flying setups.

[bartman]

Quik update,

I rebuilt the fire wall on the weekend. I upgraded to an OS 70 surpass. Added some du bro 5 inch inflatable rubber. With the heavier motor (but still lighter than old engine and weight) the plane balances at 3.5 inches. I suspect the center of mass on the four stroke is farther forward helping the center of grav. The manual expects wight to be 6.5 to 7 lbs.
Mine is around 9.5 lbs. I have to expect a little extra weight from 70 size four stroke instead of 60 size 4s and the bigger wheels but 2.5 lbs?? witout the optional scale parts(dummy engine, wing struts ect.). With the larger fuel tank I expect to land with a fuel reserve. I will try to fly her this week with c of g at 3.5 instead of 3.25. Also as supercub stated the great planes 80inch cub ballances at 4 inches. Im pretty sure the wing cord would be almost the same?? So anyway I now have a lighter plane with a bigger engine. Win Win I hope.

Brian

[bartman]

bump for a nice guy lol couldn't help it.