IMAC PAU Extra Build 105" assembly
- Thread starter Rusty 73
- Start date
Rusty 73
100cc
Did a litlle weight and balance this afternoon on my 105" Extra.
Built a vanessa CG machine using a buble that i believe isn't that sensitive . Loaded up the airframe with all the batteries servos wires and CB200 receiver into the fuselage .
Got my son to help tie off the rope when we got it floating , used the buble level and a plum bob to get an initial starting point for the CG .
It was just about at seven inches
which is the Max CG point so I added the Whiterose counter weight of 6.3 oz then the the CG was at six and half inches 
from the leading edge .
The nose wiegth is attached to the spinner
The initial balance right at seven inches
Built a vanessa CG machine using a buble that i believe isn't that sensitive . Loaded up the airframe with all the batteries servos wires and CB200 receiver into the fuselage .
Got my son to help tie off the rope when we got it floating , used the buble level and a plum bob to get an initial starting point for the CG .
It was just about at seven inches
which is the Max CG point so I added the Whiterose counter weight of 6.3 oz then the the CG was at six and half inches from the leading edge . The nose wiegth is attached to the spinner
The initial balance right at seven inches
Dan767
70cc twin V2
With servos in the tail and cans, this isn't unusual. When I put cans in my V1 I had moved everything forward and put the batteries as far forward as possible. The ignition battery was on top of the engine box. You may not like pull-pull, but it does keep from having to add any excess weight.
Rusty 73
100cc
Dan i agree with the servo in the tail added to the heavier CG issue and the tunned pipes added more weight to the rear.
I have all three 2600Life batteries behind the firewall and still will have to run a 6.3 nose weight just to get the balance at 6.5" .
I might take out the rear servo and see how it effect the CG , good idea .
I have all three 2600Life batteries behind the firewall and still will have to run a 6.3 nose weight just to get the balance at 6.5" .
I might take out the rear servo and see how it effect the CG , good idea .
Larry B
70cc twin V2
Your Extra is looking good! I also have a big aversion to putting servos back in the tail. Since I am a scale guy at heart and am completely new to IMAC I just had to make a change to my PAU for the tail servos. With a scale model you have to stuff everything as far forward as you can and then still have to add nose weight sometime.
I flew my Edge all last season at several contest's with the stock hardware and so far have had no problems at all, I did change to just one elevator servo with a carbon pushrod, I thought I could get away with this since my Edge is the smaller 50cc version.
Keep us posted with the flight results, it looks like your getting close!
I flew my Edge all last season at several contest's with the stock hardware and so far have had no problems at all, I did change to just one elevator servo with a carbon pushrod, I thought I could get away with this since my Edge is the smaller 50cc version.
Keep us posted with the flight results, it looks like your getting close!
Rusty 73
100cc
Thanks Larry for the info about your Edge , I do love that color scheme of that Redbull on your aircraft .
I guess if i moved the rudder servo 73g/2.6 oz forward 36" this would help with the balancing .
The PAU hardware with the kit i found to have play in the bushing that seats in the housing of the clevis .
I elected to change mine to get NO play , i have seen planes destroy the servos drivetrain and have watched a couple of planes crash because of flutter in the linkage .
This is the first of two PAU Extra i have so all of this is experimental and the lessons learned on this airframe will be go into the next Extra.
Will keep up dated with flight results , we still have two months worth of winter type weather before flying can occur up here.
I guess if i moved the rudder servo 73g/2.6 oz forward 36" this would help with the balancing .
The PAU hardware with the kit i found to have play in the bushing that seats in the housing of the clevis .
I elected to change mine to get NO play , i have seen planes destroy the servos drivetrain and have watched a couple of planes crash because of flutter in the linkage .
This is the first of two PAU Extra i have so all of this is experimental and the lessons learned on this airframe will be go into the next Extra.
Will keep up dated with flight results , we still have two months worth of winter type weather before flying can occur up here.
Larry B
70cc twin V2
Rusty 73,
It sounds like you have a better linkage set-up than I do, I did end up with a tiny amount of "slop" in my elevator. I am counting on the fact that I made my hinge line an enclosed pocket instead of the big bevel hinge line which gives you a huge angle of control throw. Also I tapered all the trailing edges down to a sharp edge instead of the blunt flat trailing edge that comes stock. By doing these two things so far I have not had any flutter issues and I built the model with the sole intention of only flying IMAC which means I set up very small control throws.
I complain about the weather we have down here but to be honest I have been able to fly almost every weekend since the beginning of this year, I was out just this last Sunday flying my Bf-109, it was 58 degrees and wind was around 6 or 7 MPH. When I see what you guys have to deal with up North I feel real lucky!
It sounds like you have a better linkage set-up than I do, I did end up with a tiny amount of "slop" in my elevator. I am counting on the fact that I made my hinge line an enclosed pocket instead of the big bevel hinge line which gives you a huge angle of control throw. Also I tapered all the trailing edges down to a sharp edge instead of the blunt flat trailing edge that comes stock. By doing these two things so far I have not had any flutter issues and I built the model with the sole intention of only flying IMAC which means I set up very small control throws.
I complain about the weather we have down here but to be honest I have been able to fly almost every weekend since the beginning of this year, I was out just this last Sunday flying my Bf-109, it was 58 degrees and wind was around 6 or 7 MPH. When I see what you guys have to deal with up North I feel real lucky!
Rusty 73
100cc
Beveled ends with the enclosed socket is great to prevent any flutter 
. A fellow racer from years ago who lived in Montana built his F1 racing aircraft with an enclosed pocket for the hinge line , very time consuming with excellent results.
We used to build the tail sections with a thin piece of plywood cut into the balsa and insert about 1/8 " ply around the leading and trailing edges . Very little twist occurred with these elevators and rudder .
Tapered front and trailing edge with the plywood gave us a strong and just about dent proof edges that stood up to 200 mph plus speeds . This was back in the eighties we built like that for our racing aircraft .
You have a lot of patience and really enjoy the finer craftsmanship of our hobby
. A fellow racer from years ago who lived in Montana built his F1 racing aircraft with an enclosed pocket for the hinge line , very time consuming with excellent results. We used to build the tail sections with a thin piece of plywood cut into the balsa and insert about 1/8 " ply around the leading and trailing edges . Very little twist occurred with these elevators and rudder .
Tapered front and trailing edge with the plywood gave us a strong and just about dent proof edges that stood up to 200 mph plus speeds . This was back in the eighties we built like that for our racing aircraft .
You have a lot of patience and really enjoy the finer craftsmanship of our hobby
Larry B
70cc twin V2
You have a lot of patience and really enjoy the finer craftsmanship of our hobby
Thank you Rusty, I have always enjoyed building but as I get older the building part of this hobby seems to be even more enjoyable.