didiwatt

My Feedback: (38)

OK, I need some help.............

I am just finishing up on a Modaire Aero Commader with twin 50cc's.

Here is my problem, the all up weight is 57lbs. With a wing area of approx 2000 inches, the wing loading calculates to be 65.66oz per square foot.

For all you guys with lots of experience with big multe-engine planes, is this doable or did I just create a giate wall flower?

Thanks
Paul

boingram

Paul,

Their web site says 44# +-. Where did all the extra weight come from, and will you have to get an AMA waiver for the over 50# provision?

How was the kit?

Thanks,

Bo

aerowoof

should be okay,larger plans can handle higher wingloadings,but watch the airspeed taking offand landing.

TLH101

My Feedback: (90)

Should not be a problem at all. As the models get larger, the actual wing volume helps with the loading.

Prairie Mike

Paul, I've got one of those also. Take some pictures and let us know how your maiden flight goes

didiwatt

My Feedback: (38)

Mike:
Here is a couple pictures for now...... Will have some better ones shortly. I did have to add 4lbs to the nose for the suggested balance point with the gear up. I do have a few goodies like nose brake and smart fly system but I was very suprised. I used an old UPS scale and weighted the components seperately so it could be off a little. Center section weighted 25lbs, fuselage also weighted 25lbs and each wing panel weighted 3.5lbs for a total of 57lbs...........

TLH101

My Feedback: (90)

Nice finish, what is painted with?

didiwatt

My Feedback: (38)

Yellow and black on the leading edges is base coat clear coat. The pictures were taken at the vinyl shop where all the stripes and lettering were applied. Full rivits top and bottom.

boingram

Those look like Intairco wheels. Are they, and why not brakes on the mains instead of the nose only?

Bo

didiwatt

My Feedback: (38)

Bo:
I got the plane from a friend who had it professionaly buildt but it was crashed on the maiden. Nose had to be rebuildt, tail snapped off and damage to the wing tubes, etc. I think it was more work rebuiding it than starting over. This may explain the extra weight but I was very careful and actually thought the plane would weight less because I scrapped off and enormous amount of paint and replaced 5 lbs of nicads with li-ion. Original weight was unknown. I think the cause of the first crash was low airspeed combined with a rearward cg. I got ahold of the current manufacturer for the correct cg, thus the 4lbs in the nose. The cg is recommended less than 2" behind the firewall with the wheels up which is several inches forward of the traditional 1/3 of the cord which is where it was balanced before. The plane was completely stripped so I can say that it is a well put together kit.

I can't remember the manufacturer of the main wheels. The nose wheel is a BVM with brake and I use the BVM smooth brake system. I put it on the nose only for simplicity and the fact that I just wanted to keep the plane from rolling on pavement at idle and controlling at slow speeds.

Can you explain the 50lb AMA waiver process? Not familiar with it...........
Paul

boingram

Paul,

Thanks for your information. The reason I ask about the nose wheel brake is the concern that there will be eough tire patch area to stop a 55# airframe! I have the Intairco brakes on a TF Cessna 310. Way cool to taxi to the main runway, run the engines up, and have the plane sttting on the tarmac ready to go...goose bumps!

I believe I have this right re: AMA's weight waiver. Any airframe over 55# has to have the waiver to fly under AMA's auspices..insurance, etc. An AMA rep will check the airframe for airworthiness, then check out the pilot on a set of typical (for that airframe) flying manuvers. I am sure the AMA can give you more info on the phone or on their website.

I've got the hots for this plane..always wanted a Bridi Aero Commander and just waiting for one on e-bay...

Bo

Prairie Mike

Paul,
Thanks for the pictures. I LOVE the way it's trimmed. I understand that the Aero Commander has a nasty habit of tip stalling when slowed down too much. I've got two of them. One is the 79" version and then The Modaire one. Haven't finished either yet, but both are ongoing projects. I think the Aero Commander is one of the most beautiful airpanes ever designed.
Good luck with your 1st flight.

didiwatt

My Feedback: (38)

Mike, thanks.

Bo:
Yes, just checked out the AMA site and it is 55lbs for the waiver. I need to trim off 2lbs and am working on it now. Dropping dual 5600mah li-ions for dual 2600, maybe c/f nose cones instead of Tru-turn, etc. I am confindent I can drop the 2lbs therby elimating the hassle of a waiver. Noted I have an ispector right here in town and did not know it.

One thing I did notice on the regulations is that to even qualify, the wing loading cannot exceed 60ozs..... That has me worried a little... I will calculate the wing area I have rather than using the manufacturer statistics and try getting a more accurate weight and go from there.

Thank you guys for all your input.
Paul

boingram

Paul,

That's interesting about the AMA wing loading requirement.

What are you using for engines and why the large batteries?

Bo

didiwatt

My Feedback: (38)

Bo:
Each engine has a Froemco 2600mah Li-ion and regulator located in the nacelles. I have a single 40oz B&B fuel tank in the fuselage and the engines pull the fuel that far with no problems. I have about an hour on the ground thus far. The radio batteries are located in the front under the dashboard. I am using two batteries with a Smart-Fly regulator and panel. At first, I used two Foemco 2600 mah which is plenty expecially since all servo's are non-digital. All flying surfaces have Futaba 9206's at 6 volts which far exceeds AMA's requrements of 100oz. per surface. Another AMA requirement is engine kill switches (not just throttle trim kill), which I do not have.

I switched to the 5200mah Froemco li-ions when I discovered I had to add several pounds to the nose for the cg. I figued I might as well add some usable weight instead of all lead........... Hopefully, if it flys, I can start removing lead nose weight. It seems to me that this plane should have a fairly wide cg range since the full size was designed for several passengers who sit behind the cg. With the gear down, it is very nose heavy at the suggested cg of 4 5/8" behind the firewall. Will probably require flaps at all times when the gear is down.

Sure would be nice to find someone who has one of these flying so that I could pick their brain, but alas, none to be found.
Paul

nine o nine

My Feedback: (1)

If you drop below the 55 lb weight limit, the wing loading rerquirement will be a moot point. My Yellow P-38 calculated to 80 oz and it flew fine....landings had to be flown on...no float even with full flaps and the takeoffs were easy....just let it run until it's ready to fly without trying to horse it off.
When you calculate the wing loading you must include the area covered by the nacelles and fuselage too. I'm assuming you did that but just in case. Also AMA requires that the flying weight is calculated with full fuel...not empty as the FAA does in it's certification process. The AMA position on that requirement is completely wrong as far as I'm concerned. Mitch

didiwatt

My Feedback: (38)

Mitch:
Man you just made my day............................ I already figured I would have to fly it to the ground.......

Plane is still at the vinyl shop so I will not have time to make wing measurements for a few days........... anyway, what do you mean by "measure the fuselage area"? Do you mean just the portion that is under the wing saddle?

Because if that is the case, measuring all the area on the midsection when it is removed (including the nacelle area with cowl's) would include that area, correct? cause you would be calculating the area of the midsection that is covered by the wing saddle area of the fuselage.......... Am I making sense?

I also agree with the fuel issue. I also have a 40oz smoke tank....... Hope they don't want that full also!!!!!!!!!!!
Paul

nine o nine

My Feedback: (1)

Yep...you measure the total planform of the wing as if the fuse and nacelles don't exist. I believe it's done that way because the fuse and nacelles have enough aerodynamic efficiency to "lift themselves". Mitch

didiwatt

My Feedback: (38)

Mitch:
Thank you............ just one more question then I will leave you alone.... on your Yellow with the heavy wing loading, did you use any flaps at all during take-off...........
Paul

Leo

Assuming the firewalls on your Commander is roughly in line with the leading edge of the wing, I think the CG is too much forward. I am comparing with my 1/5-scale Commander where the CG is located 3,5 inches back from the leading edge. That is about 25% MAC. The plane is very stable in the air. Even at slow speed. The huge amount of wash out in the wing helps I guess. ( +3 deg. at wing root, -3,5 deg at wing tip! )

Your Commander is gorgeous! Good luck

nine o nine

My Feedback: (1)

I never did use he flaps for takeoffs since the plane tracked as if on rails and I just waited until there was flying speed. I imagine I could have shortened the run by a few per cent with 10 degrees or so of flap but I never had to do that. Mitch

TLH101

My Feedback: (90)

If you are concerned about the C/G, try this calculator: http://www.palosrc.com/instructors/cg.htm
Start with a conservitive number like 25-28% for the MAC.

didiwatt

My Feedback: (38)

Leo:
I was wrong on that. It is recommended at 4 5/8" behind the firewall. The firewalls are just a little ahead of the leading edge.
I will determine the percentage of MAC when I get the plane back but my guess is about 20%. Will let ya know....
Paul

didiwatt

My Feedback: (38)

Terry,
That's cg calculator is cool. I have saved it to my favorites for latter use.

Since the Shrike has a wide center section and both the cord and span of the root section is considerable larger than the wing panels, it is a little confusing what figures to imput. Would you consider the "root" measurement where the center section touches the fuselage?

Or, would you just imput the measurements of a wing panel and disregard the center section?

Of course it has a forward sweep so I assume you would enter that amount the same as a rearward taper, correct.
Thanks
Paul

TLH101

My Feedback: (90)

Your root cord is the measurement at the center line of the model. Carry the imaginary L/E and T/E lines in to the center and measure. The calculator will figure the rear taper, since it asks for root cord, tip cord, and sweep. T/E taper will automatically be figured.