IMAC Double Build, Carden Pro 124" Extra 300 40%
- Thread starter orthobird
- Start date
-
- Tags
- 40% airplane build thread imac
, my guess is 0.3 oz for the Air Wild armsSomething very interesting. Regarding the airplane's CG and balance.
According to the manual, it is supposed to be at 3.5" to 3.75" aft of the leading edge at the tip.
What did I do?
I elevated the tail of the airplane until the fuselage was level with the ground, then
I used my laser light, and transferred the 3.5" mark to the top of the fuselage.
Now I know where the CG point should be on the fuselage.
Then, I measured the distance from the CG point on the fuselage to the center of the main wheel axles. this is 165 mm for 3.5", or about 160 mm for the 3.75" point.
I then used the Xicoy balance and CG, and it states my balance point is at 210 mm aft of the main wheel axles. Which is going to be 45 mm more back than what it should be, which would be equivalent to a balance point of 5.25", which would be consistent with being tail heavy (by about 2 pounds).
SO now, I have to remove the pilot, and use a very light pilot, and place the batteries forward to the wing tube, and then maybe it will work out. very interesting. I may even have to use a three blade prop.
According to the manual, it is supposed to be at 3.5" to 3.75" aft of the leading edge at the tip.
What did I do?
I elevated the tail of the airplane until the fuselage was level with the ground, then
I used my laser light, and transferred the 3.5" mark to the top of the fuselage.
Now I know where the CG point should be on the fuselage.
Then, I measured the distance from the CG point on the fuselage to the center of the main wheel axles. this is 165 mm for 3.5", or about 160 mm for the 3.75" point.
I then used the Xicoy balance and CG, and it states my balance point is at 210 mm aft of the main wheel axles. Which is going to be 45 mm more back than what it should be, which would be equivalent to a balance point of 5.25", which would be consistent with being tail heavy (by about 2 pounds).
SO now, I have to remove the pilot, and use a very light pilot, and place the batteries forward to the wing tube, and then maybe it will work out. very interesting. I may even have to use a three blade prop.
I had to order some foam pilots from AI, that weigh 1.1 ounce. And I will move the batteries forward. I might have to core the bottom belly pan some, closer to the tail, to help decrease tail weight. Even 4 ounces removed from tail will help big time. i will do some tests to see how much that weighs.
These pictures are courtesy of Dean N. @Fixed Wing
I need to ask him, how much weight was removed by doing this.
I need to ask him, how much weight was removed by doing this.
Actually, it will be easy. I knew about this way before the build. I intentionally did not cut out any, thinking the airplane would be nose heavy. But to cut this out will be very easy. It is thin balsa and then using a hot wire, going into the cut made with an cacti knife, it will be a done deal!
But first, I will make a special CG mount to test my position of the balance point and compare to the CG point. I just do not trust computers and scales 100%
Again, I am going thru all this trouble not to fine tune the Balance. This is only for me to assure the maiden is a smooth one.
After the maiden, I will then adjust the balance point (& trim) following the criteria and recommendations of Goldsmith. (Or Goldman, I forgot exactly his last name. Think Peter is first name).
Bunky.F.Knuckle
150cc
Pete Goldsmith.
Been out of town for past few days. Went to the National Judging School in Fort Worth. Here Russell, I met some Canadians while I was there, including Gordon, whom has helped me in the past with the build threads. It was nice to finally put a face on the names.
When I arrived yesterday afternoon, I saw a box by the front door. Not a huge box, but was too tired to open it. This morning, I was able to do so, and was excited to install them.
These are the lightest pilots. 1.1 ounces. I have installed both into each Carden. Both of the airplanes, right now, are tail heavy, so time to go to work, and see what happens.
When I arrived yesterday afternoon, I saw a box by the front door. Not a huge box, but was too tired to open it. This morning, I was able to do so, and was excited to install them.
These are the lightest pilots. 1.1 ounces. I have installed both into each Carden. Both of the airplanes, right now, are tail heavy, so time to go to work, and see what happens.
Here is what I will be doing when I get home from work today.
Getting some preliminary things done 1st.
Done already:
1. I cut the plywood in half:
2. I then drilled a 2" hole and a 1/2" hole on the CG frame, and made sure it fits on the fuselage side:
one will be on each side.
then
3. I mark the 3.5" balance point.
from here, I removed it, and also made a square line to the top of the fuselage.
4. I began to mark out the different balance points that are possible, my goal being 3.5"
SO, once I get home, I will drill out these holes on top, for the pulley hanging system, and then put everything together, wings and canopy, batteries, no fuel, and see where she balances.
then, I will begin to cut out from the rear underbelly, til we get some balance point moving forward to the CG point.
Getting some preliminary things done 1st.
Done already:
1. I cut the plywood in half:
2. I then drilled a 2" hole and a 1/2" hole on the CG frame, and made sure it fits on the fuselage side:
one will be on each side.
then
3. I mark the 3.5" balance point.
from here, I removed it, and also made a square line to the top of the fuselage.
4. I began to mark out the different balance points that are possible, my goal being 3.5"
SO, once I get home, I will drill out these holes on top, for the pulley hanging system, and then put everything together, wings and canopy, batteries, no fuel, and see where she balances.
then, I will begin to cut out from the rear underbelly, til we get some balance point moving forward to the CG point.