Official Dynam 1500mm B-26 Marauder Thread

[Mad Baron]

Are you sure about your CG(60-55mm)? Did you do your mods before first flight? Calibrate your escs? My blackwidow escs were way off before calibration. My b26 flies great. Half flaps takeoff,full on landing. Mine first batch,bone stock,no mods,weights in the tail. I did reglue several things....,wingmounts,nacells,wing panels, weights. I am rarely below 3/4 throttle in level flight. 8min flights with china hobbyline 4s 4000 40c with another minute + in reserve. Very curious as to what is wrong with yours.

I check the CG before every flight so I can get the battery in the right location for proper CG. I have a Dynam Gavin radio and the receiver has a gyro with 3 settings such as 3D, stabilization, & normal. I didn't check the receiver mode before I took off it was in 3 D mode got it back down reset the receiver to normal (gyro off) and it still was almost impossible to fly. I don't know what went wrong because about a week before the last weekend it flew great. I have a new wing center section and engine nacelles that I am using on the rebuild so hopefully it will do ok. I'm wondering if it is the radio system causing the problem.

[rifleman_btx]

Interesting... man I cant figure what's going on there... just weird it went from great to crap in a weekend. Hopefully the new wing set will lead to some results.

[themudduck]

Hey there MB - it does sound very suspicious. Something must be wrong that's not obvious. I would check things like the wing and stab mounts (is anything loose) and the servos (make sure they aren't loose in the pockets) and the control horns (Dynam is notorious for not gluing them on well, so they might be loose) or the hinges. A broken-loose servo or loose control horn can be deadly.

Check all the controls on the ground when the motors are running (are all the servos operating correctly - maybe one of them is intermittent or "twitchy". Maybe a servo has a broken gear tooth.). One of the servo connectors may be partially unplugged (like in the wing connector) which could result in an intermittent aileron. Are all the flaps going down the same amount. My thought is that something has come loose or a servo is going bad.

[rifleman_btx]

I concur with the Duck!:Cool:

[Pauly]

Great advice Mudduck!

[Pauly]

My experience with Dynam is not so bad! Yes, you do have to do and pay a little more attention to some of there products, but for the money they aren't so bad on most planes. Just pay attention to pretty much everything. That is a part of building a plane and the fun of the hobby. (Mostly)

[rifleman_btx]

Much agreed

[Mad Baron]

The rebuild is underway after I get the plane back together I am going to check all the servo operation with and without the motors running. I really like flying this plane I just hope it will fly like it's supposed to.

[rifleman_btx]

It does look awesome in the air

[Saltydawg]

I flew me "26" yesterday with multiple 4S batteries, 4500 (twice), a 5400 and lastly a 6000mAh. I think the plane actually flew better with the heavier batteries. I had them as far back as they could go and rollout and V1 and V2 were all the same really. I did notice that with full flaps doing touch and goes she actually had a natural nose up/flare when landing. With the 4500mAh when turning the tail seemed to want to drag or slip in when turning tight not using the rudder much. THIS WAS ALL DISCOVERY AND EXPERIMENTLY FLIGHTS. When turning just using ailerons and elevator you can bleed off A/S really quick and get yourself into a pickle. Personally with this plane I find making coordinated turn with the rudder and counter ailerons mixed in with some elevator gives ya the best turns.

I just like many of you all hate the landing gear though. As I'm taxiing to the end of the runway to start my run, you can see the landing gear struts shake along with the while engine nacelles.

I did try running some 11x7×3 blades on mine from Master Air Screw. I don't know if it was just a bad day of flying with the crosswinds but it seemed to lack thrust. YES, I KNOW THE RULE OF THUMB ABOUT PROP SIZE, PITCH ANGLE....BLA BLA AND THE PROPS ON THE 4 BLADE PROPS ARE 8. THIS WAS ALL FOR EXPERIMENTATION AND DISCOVERY.

On real planes with variable pitch props, unless the manufacturer says otherwise, you're settings for the prop are low pitch/ high RPM.

Other than that, I like flying her. It's always a head Turner for whomever is at the field when i fly it. Still thinking about putting nav lights on it. With the thin wing tips I may use LEDs like on the Flightline P38.

Happy flying and remember altitude is your friend....

And for even the most seasoned pilots, practise "Dead-Stick" landings it could save your plane and your wallet.

[Saltydawg]

Interesting read. I'm a career Aircraft Mechanic so I tend to read manuals on planes I own...

I'm going to incorporate some of the settings on flight controls (to scale) on my plane. Like the up/down/deflection on the ailerons.

http://www.avialogs.com/index.php/en/aircraft/usa/martin/b-26marauder/pilot-training-manual-for-the-b-26.html

[rifleman_btx]

Very cool, I like my 4000 packs, I may have to push it forward alittle as well as I feel like it drags the tail a bit as well

[themudduck]

It needs to be said that aerodynamic flight characteristics on full-size planes don't necessarily transfer to models. The Reynolds numbers are different... the wing loading is different... and the power-to weight ratios are different. Without getting really deep into the weeds regarding aerodynamics, the main thing to realize is that when you scale down a real plane, the weight doesn't scale down proportionally and the air molecules remain the same size.

A loaded B-26 weighed about 37,000 lbs (Wikipedia) and our 1/14 scale model obviously doesn't weigh 2,600 lbs - because weight doesn't scale directly (mass is cubic). I don't have the formula handy but basically, our models are super light and grossly overpowered when compared to the real thing, and yet, they are flying in full-scale air. So its not wise to expect them to behave just like the real ones, in terms of control throws, stall speed, propeller pitch, and so on. But as Saltydawg said, he was experimenting and I totally get that. Its a lot of fun. I find it completely fascinating that even with the realization that things aren't the same aerodynamically, our models do show many of the same flying characteristics of their full-size counterparts.

[fhhuber]

Some aspects scale up and down quite well.

I've had 10 different versions of Tiger Moth from appx 18 inch to 54 inch spans, glow and electric, RTF/PNF/ARF/Kit/ and built from plans.... all flew basically the same. All needed the same aileron differential and control deflection angles.
Power to weight differences were noticeable in how much throttle was needed.

Following the basic flap positions for takeoff and landing used on full scale P-51s has worked well for me on assorted P-51 models from 24 inch span to 80 inch span. (and other heavy models that were prone to dropping a wing in a stall without flaps)

[themudduck]

It was interesting to see in Saltydawg's B26 manual (link posted a few posts back) that the full-size B-26 required a negative-5% incidence on the horizontal stab. Just like what we've done with this model!

[rifleman_btx]

Oh yes indeed, I noticed that as well

[Mad Baron]

Time for some more Foam Tac! This B26 rebuild is using up my supply LOL

[Mad Baron]

Here is the progress so far. When I installed the motors one blind nut on each side was stripped out (no access to the blind nuts to replace them) so I hope that 3 screws on each motor will be enough to hold these motors in place. Now I have to tame the rats nest of wires!

[fhhuber]

Can't knock the bad blind nuts out then install new ones using a long piece of all-thread going back into the retract bay?

[Mad Baron]

There's not much room to get at the blind nuts.