Official Dynam 1500mm B-26 Marauder Thread

[themudduck]

That's a very interesting mod, we'll anxiously wait to see your report on how it affects the way your model flies (and lands). This will create some drag.... but I agree that it may help with the landings.
Something else you may want to try experimenting with is to slightly "droop" both ailerons. Just an idea...

[xviper]

That's a very interesting mod, we'll anxiously wait to see your report on how it affects the way your model flies (and lands). This will create some drag.... but I agree that it may help with the landings.
Something else you may want to try experimenting with is to slightly "droop" both ailerons. Just an idea...

Or, slightly deploy the flaps.

[Phantom]

Themudduck,

I appreciate the suggestion, however that might actually worsen the problem of tip stall in slow flight, because of the overall increased camber on the trailing edge of the wing with flaps up. On landing with flaps down you are flirting with which part of the wing will stall first, and with the stock wingtip, minus my mod here you'd lose that battle, because the critical AOA will be exceeded on the thin tapered wing tip leading edge before the fuller wing root and midwing portion of the leading edge. I know rc glider pilots create 1 or 2mm uptrim evenly in there ailerons,(any more than that and it becomes a spoileron for most wings), to create aileron "wash out", meaning that in slow flight the aircraft tends to descend due to loss of lift instead of exceeding the AOA, usually around 16° for most wings, and causing a delamination of the attached airflow over the top of the wing, aka a stall. There is a Youtuber by the name of inthetubedeep, who has done this with his FW F-86, aileron wash out, to fly slower than he probably ought to with flaps at 0°. But I might play with your suggestion for downward droop due to my mod on the leading edge preventing the stall starting at the tip, just to see how aggressive of a "high alpha", I can accomplish before the stall, but I'd imagine regardless of what I due to the ailerons as far as drooping, the majority of the lift for the wing is created by the other 2/3rds and is still going to exceed the AOA first thereby dropping the nose and descending the bird. Might be fun we will see. :)

[Phantom]

Xviper,

The mod on the leading edge does have a drag penalty, however not nearly as severe as adding flap. The flap induced drag penalty is what I am hoping to avoid by doing this mod.

[themudduck]

When I made the suggestion about drooping the ailerons a bit, I was thinking that you'd be landing with full flaps. Without any flaps, I agree completely that drooping the ailerons would be a very bad idea!

Flaps do induce drag (they help the model slow down) but they also increase the camber of the inboard section of the wing. In that configuration, generally the inboard section of the wing will stall first, thus avoiding a tip stall (as long as the plane is under reasonable control). I takeoff with half flaps, enter the landing pattern at half flaps, and use full flaps on final approach and it handles like a *****cat, never a hint of a tip-stall. However, flying in a 'clean' configuration, this model will snap-roll in a heartbeat, even with reduced elevator. The "Baltimore *****" has no visible means of support! It snaps faster than my gas-powered stunt plane (a modified SIG Fazer). I snap-rolled the Marauder on my maiden flight (before I did the stab modification, removed the tail weights, reduced the control throws, and adjusted the CG) just doing a mild turn!!

So now I use the flaps all the time whenever I'm slowing down and it seems to work very well. All that being said - we're all very interested in seeing what your LE droop will do! Best of luck!

[Phantom]

The mod is complete. I'll post pics tonight with the wing fences installed. In the landing configuration, drooping the ailerons, like flaperons in conjunction with the flaps is an awesome idea. It would be like an F-14 or F-18 using the whole wing to create extra lift and drag, by adding all that camber on the full length of the wing. I might split my ailerons into two separate channels and program that in. Can't fly it until this weekend anyway. But my real reason for completing this mod was to see if I can cruise around in the clean configuration nice a slow flying patterns without adding flaps or being in the upper 3/4 of the power quadrant to keep from stalling in the turns.

[Phantom]

Mod pics and a vid below enjoy.

[Phantom]

The vid, I couldn't upload.

[xviper]

The vid, I couldn't upload.

Can you load it onto YouTube, then put the link here? I don't believe this site accepts videos in their raw state, only linked from other video sites.

[Phantom]

I will try that, thanks for the suggestion.

[Phantom]

Xviper, here's the link

https://youtu.be/oXPZMKhwORY

[Phantom]

The TV was on so I suggest you mute the sound, sorry new to this.

[Phantom]

So I was repositioning the B-26 this evening when I heard something rattling in my starboard nacelle. Sure enough there was play with the hub. I bought the bird PNP and thought that the nacelles were glued together, so I didn't check the motors like I normally do. However the front cowling is just attached via magnets, nice surprise. All the reading I'd done on this thread when talking about upgrading the power system, including removing the nacelles from the wing to access the ESC's. After reinstalling the bolt that was rattling around in there. The motor was still loose, so I put lock tight on all 8 bolts, I should have investigated the construction of this bird when I first put together.

[Phantom]

This would have ruined my proof of mod test flight this weekend for sure. I've been lucky, quite a few flights on her...

[Phantom]

Ok update time, unfortunately my Korean friend who flies at the field I go to and is moderately fluent in English, was unable to come today. So I obtained no video of the proof of flight concept mod. I will get video of her flying as soon as I can and post.

Now on to the flight report. Conditions were windy and gusty, 3 to 6ms, winds constantly shifting direction about 70 degrees or so. I powered her up to normal takeoff speed and she rotated and climbed out like normal, I retracted the gear, followed by the flaps. Climbed up to about 3 mistakes high and started to slow her down in the clean configuration. About the speed of the previous snap roll stalls, I noticed a little transitional twitch. I wish I could be more descriptive but it happened all three times I preformed slow flight. Just a momentary twitch, so small I couldn't pinpoint the axis of origination. I really wish I could play it back. After the twitch she continues to slow down and about a walking pace she starts wagging her tail followed by a docile right wing tip stall. No snap to it at all. I wish I had just cut the power and yanked back on the elevator to try to induce an accelerated stall but I didn't think about it. I was hoping for a nose down pitch movement at the stall but, all 3 times the right wing dropped. It could be due to my modification on the wind not being perfectly symmetrical. I completed the elevator incidence mod and the removal of two pieces of lead from the tail at the same time, as the wing mod, so I am not sure if it's a combination of the three or one specifically. Can anybody confirm if they have the same flight characteristics as my flight today? The landing was enjoyable with takeoff flaps deployed, albeit with a cross wind. Touched down at about half my normal touchdown speed on the mains, however the wind got up under my left wing as my nose came down and tipped her over on the right wing tip. Even with zero power applied and prop rotation approaching a crawl the starboard prop threw a blade, hence my one and only flight on her today. I like the appearance of the semi- scale props, but if you look at these damn things sideways they break! I've got one spare set left and when they are gone, I'm putting on quality props! The up side is I was able to cruise around at half throttle while maintaining altitude, I've never been able to do that with less than 75%, and in todays brisk wind at that. I confess that I pushed the power up in the turns, but it was really out of habit. I had planned to forgo that on the 2nd flight to see what would happen. I flew with a Tgy 4000mah 4s, with a 40c rating, and after four and a half minutes landed with 4.0 volts per cell, normally I land with 3.8, so a little better endurance, once again doing the all 3 mods simultaneously I'm not sure which one I have to thank for it though. I am 100% sure that my ability to land slower is due to the wing mod. Thoughts...?

[Phantom]

Upon further contemplation, I remember having to make a second incision on the right wing's leading edge to reduce the downward angle to match the left wing. I held the leading edge at the appropriate angle and filled in the gap with hot glue. Long story short, due to a few more ounces of hot glue on one wing vs the other, I have a lateral imbalance. Not a big deal as it only manifests itself right before the stall, which is now down to a crawl, and requires no trimming for any other flight regime.

[458destroyer]

Hello all, I bought this plane, built it, and came to this thread for tips before I maiden it. I created a spread sheet with everyone's suggestions and flight feedback so I can have a successful bird, but man oh man, there are so many different schools of thought on how to mod her because of how she acts. One common item that is apparent in everyones analysis is she is extreamly sensitive on down elevator, so some added a shim to rear, some gave elevator a few clicks trim to level her out, & some removed the tail weights to tame her elevator sensitivy.

Well here is my theory as to why acts like an acrobat when given down elevator. No one throughout these 82 pages has mentioned that both Motors are mounted slightly pointing down giving the bird a downward thrust angle, that would make this bird automatically pull up. I put a level on each motor and they both have the exact downward thrust angle hence leading me to believe this is why she tends to be over sensitive to elevator movement and pilots are modding other areas to compensate for this behavior.

I have done zero mods on this plane because Ryan and a few other pilots were successful in flying her without any mods except giving warnings to all about trimming elevator with a few clicks to help level her out.

So, before I put a washer behind the lower motor mount screws to give the motors a zero/neutral thrust angle I would like to hear feedback from you guys. Do you think giving the motors a neutral thrust angle is good or bad idea? I'd like to hear from pilots that did NOT remove the tail weights since I don't plan on removing them.

PS.
I am using a 3300mah battery which balances perfectly at 65mm.

I look forward to all of your feedback.

Cheers,
Rudy - Houston, TX

[xviper]

Hello all, I bought this plane, built it, and came to this thread for tips before I maiden it. I created a spread sheet with everyone's suggestions and flight feedback so I can have a successful bird, but man oh man, there are so many different schools of thought on how to mod her because of how she acts. One common item that is apparent in everyones analysis is she is extreamly sensitive on down elevator, so some added a shim to rear, some gave elevator a few clicks trim to level her out, & some removed the tail weights to tame her elevator sensitivy.

Well here is my theory as to why acts like an acrobat when given down elevator. No one throughout these 82 pages has mentioned that both Motors are mounted slightly pointing down giving the bird a downward thrust angle, that would make this bird automatically pull up. I put a level on each motor and they both have the exact downward thrust angle hence leading me to believe this is why she tends to be over sensitive to elevator movement and pilots are modding other areas to compensate for this behavior.

I have done zero mods on this plane because Ryan and a few other pilots were successful in flying her without any mods except giving warnings to all about trimming elevator with a few clicks to help level her out.

So, before I put a washer behind the lower motor mount screws to give the motors a zero/neutral thrust angle I would like to hear feedback from you guys. Do you think giving the motors a neutral thrust angle is good or bad idea? I'd like to hear from pilots that did NOT remove the tail weights since I don't plan on removing them.

PS.
I am using a 3300mah battery which balances perfectly at 65mm.

I look forward to all of your feedback.

Cheers,
Rudy - Houston, TX

I would dissuade you from doing this. Virtually ALL electric model airplanes have down thrust (and a bit of left except for reverse rotation motors) built into their motors. This is NOT what makes this plane act the way it does. I've left horizontal tail surface as is and both my weights are still in the tail and mine flies fairly normal. I find that I have to fly it at higher throttle as it tends to stall a wing easily. Pitch sensitivity is easily controlled by lower rates and higher expo. I don't consider my B-26 to be pitch sensitive at all. I use a 4000mah, 4s battery all the way back and it flies fine. It just needs to be flown a bit faster than many people want to fly it.
There are certain planes that just need a bit of "reflex" on the elevator to fly level. This is one of them. The LX A-10 is another. And there are others that don't come to mind at the moment. It's just normal. Sure, you can dial some of this out by changing the angle of attack on the tail surface but I've never bothered.

[Hardway]

I have built in down thrust and right/left thrust on the B-17's (big ones) and it works great. Same with the other single engine warbirds.... zero zero zero works for aerobatic birds, but the warbirds need it... ;)

[fhhuber]

On multiengine, the angle of each engine is often different.

Find a good picture from directly above a full scale B-17 and you can see each engine is pointed a little different.

Even Pattern Aerobatics models typically have some offset of thrust line. The goal may be 0-0-0 (0 wing incidence, 0 stab incidence, 0 thrust offset but the swirling air coming off the prop usually makes an offset necessary.)