Official Dynam 1500mm B-26 Marauder Thread

[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.)

[Phantom]

458destroyer,

Like others have already said, I wouldn't shim the angle of the motors. The downward angle is to compensate for the under slung position of the motors, to give you a more neutral attitude when you have to throttle up quickly. If not for this, the aircraft might pitch up suddenly on a go around making an already slow airspeed scenario worst by aggressively increasing the AOA, inducing a possible wingtip stall that this bird is already infamous for. Not good at any altitude much less a few feet off the deck.

As for the mods, xviper is correct you can fly this bird with no mods whatsoever, some up elevator trim programmed in, along with a lot of expo and a reduced elevator deflection. However any time your are at flaps zero,... fly it like an edf that has high wing loading. With a take off flap setting it flies much more like any other twin motored warbird, albeit a we bit underpowered. I removed the weights, (I hate dead weight), along with a few other mods like cutting a rectangle hole in the back of the battery compartment right down to the belly of the bombbay which allowed me to move my battery back another 1 1/2 inches. I fly her on a 4000mah 4s pack, with a CG of 72mm. Some of us can't get a bird without modding it. But I had about 7 or 8 "exciting" flights on her before modding her to a much more docile flyer that she it now. I'd encourage you to use a light pack and fly her before doing any mods.

[F4ucorsair]

this bad boys parkd at present but here is the story its flack bait in presentation looks awsome,,,,,,ok maiden off longish grass great take off no roll
as with single engine planes warbirds .... mine r all dynam but all with 650kv motors .. gear up cool but then plane down,, i replaced fuse ,, clevor dick like all of us i took out weights in fusealage ,,,,, and battery back 4 cg correction ,,,, after all my local dynam man agreed next try with cg correct but no weights in rear ,,up in air no control ,,crash 30meters from launch , since then i crashedv evry frigin plane oh boy,,, ijust got good ,,now i cant ,, na that wont do,,, range check good plan me..... range was about 80 metrs ,,,, airial wire off back of transmitter fixt now all flying well except 4flak bait ,,ihave replaced weight att rear and corected cg will fly soon ,,,,2 stories here',,,range and dont take the weights outa the back ,pendulam effect???????????rocket scientest help req

[themudduck]

this bad boys parkd at present but here is the story its flack bait in presentation looks awsome,,,,,,ok maiden off longish grass great take off no roll
as with single engine planes warbirds .... mine r all dynam but all with 650kv motors .. gear up cool but then plane down,, i replaced fuse ,, clevor dick like all of us i took out weights in fusealage ,,,,, and battery back 4 cg correction ,,,, after all my local dynam man agreed next try with cg correct but no weights in rear ,,up in air no control ,,crash 30meters from launch , since then i crashedv evry frigin plane oh boy,,, ijust got good ,,now i cant ,, na that wont do,,, range check good plan me..... range was about 80 metrs ,,,, airial wire off back of transmitter fixt now all flying well except 4flak bait ,,ihave replaced weight att rear and corected cg will fly soon ,,,,2 stories here',,,range and dont take the weights outa the back ,pendulam effect???????????rocket scientest help req

Man, your story gave me brain damage just reading it. I have absolutely no idea what you're doing. Sounds like the aerial on your transmitter was bad? Range should be 800-1000 meters, well beyond your ability to see it.

The B26 doesn't need tail weights unless you enjoy flying heavy planes that fly like bricks. Take the weights out, use as smaller battery, and balance it. Set the elevators so you have a little "up" trim and than use no more than 5mm throw each way. Use half-flaps on takeoff and whenever you are slowing the plane down for landing. Use full flaps on final. You shouldn't have any problems with this one, its a great model.

[xviper]

Man, your story gave me brain damage just reading it.

Just curious if your observation is the same as mine. When you say it gave you brain damage, do you mean how difficult his posts are to read or the actual story? I really want to help and comment when he asks for help but I can't get past the first line. The spelling, punctuation (or lack of it), sentence structure, grammar and lack of capitals is very hard to decipher. It may be just the way he learned to type with texting and such, but on a public forum, it's so hard to read. I find I have to read through it 3 or 4 times and by then, I'm just to mentally whacked to think of a reply.

[F4ucorsair]

i do talk in circles ..but u did get it..yes on maiden it crashed .at the time i was not aware ,the arial was off internally... the transmitter that is,,so new fuselage and left out weights ,moved battery back 4cg crashed again, still at this point unaware of arial problem , but your info was everything i was looking 4..thanks.. i cannot wait fly it..do u fly off grass??? the props r very low ... lastly why r the weight there in first place.. hope that was better thanks again....

[xviper]

i do talk in circles ..but u did get it..yes on maiden it crashed .at the time i was not aware ,the arial was off internally... the transmitter that is,,so new fuselage and left out weights ,moved battery back 4cg crashed again, still at this point unaware of arial problem , but your info was everything i was looking 4..thanks.. i cannot wait fly it..do u fly off grass??? the props r very low ... lastly why r the weight there in first place.. hope that was better thanks again....

Yes, much easier to read. Thanks. I believe the weights were put there (and sometimes, one or both are loose and just rattle around back there), to aid in balancing with the recommended battery and also to reduce the amount of UP elevator for it to fly level. Some have observed that the angle of incidence of the horizontal tail surface is incorrect and needs to be shimmed or re-positioned, thereby needing some UP. If not for those weights, it would need lots of UP, which many find disconcerting. The plane flies fine once trimmed out properly even with some UP elevator dialed in. I fly with a 4000mah battery pushed as far back as it will go and I still need a bit of UP and my weights are still in there. When it's back there, it's hard to do up the strap. If you fly with a lighter battery, it might be better for balance but then, your flight time will decrease. You'd have to experiment with it to find what works for you.
PS, You should do a range test (or two or three) with the plane in different orientations before taking it up.

[Flyingtigerbazz]

My B-26 Marauder....

[themudduck]

i do talk in circles ..but u did get it..yes on maiden it crashed .at the time i was not aware ,the arial was off internally... the transmitter that is,,so new fuselage and left out weights ,moved battery back 4cg crashed again, still at this point unaware of arial problem , but your info was everything i was looking 4..thanks.. i cannot wait fly it..do u fly off grass??? the props r very low ... lastly why r the weight there in first place.. hope that was better thanks again....

I fly off of grass mostly... and I replaced the original "race car slick" tires with wheels that are more scale-looking (they are not as wide) - narrow tires have less drag in the grass. However, you are correct that the props are close to the ground. Many people here have commented that it is very easy to break a prop. My advice: just before touchdown on landings, cut the power completely right before you touch down. No power to the props = less chance of breakage. However, on the B26 model the nacelles do flex and the props can hit the ground if you are not so smooth! So be careful. I have broken a few props.

Here's a video of my model flying. Two flights - I was trying to demonstrate how easy it is to snap-roll this model (on purpose). This is the reason why the elevator throw needs to be very small.
You'll see that I didn't slow it down very well for landing... but the plane can handle the grass easily.

[themudduck]

My B-26 Marauder....

I like the paint job and the attention to detail! Nice job! it looks great.