Official Dynam 1500mm B-26 Marauder Thread

[quitcherbitchen]

No one has modded the outer third of the wings as far as I know. Just the tail incidence, which is way off. I don't think the tip/accelerated stall is much of an issue as long as you don't use too much elevator throw. My biggest problem with flying this model is lack of power and wind issues causing it to get really tossed around in crosswinds. I plan on putting a Gyro in mine. Power wise stock is just sufficient. In wind it is barely sufficient. Flying around at full power in a 8 knot breeze is not comfortable.

[Phantom]

I have just completed the removal of the two lead weights in the tail and the 3mm tail incidence mod. Before reading this thread, I was ready to borrow deeper aft into the foam to shift the battery further back, in order to get the aircraft to stop flying "nose heavy", however I am hopeful that the incidence mod on the tail will improve that undesireable characteristic. The only thing worse than flying around in a underpowered model in a stiff breeze, is flying one where your are in the upper 3/4 of your power quadrant and having to keep the speed up and the elevator stick pulled back because you've run out of up elevator trim adjustment on your radio. :( I have experienced the wing tip stall on my second flight right after take off. The first flight was uneventful aside from the rodeo that the elevators sensitivity took me on haha. The second flight she flipped right over on her back before I could think. My take off/ rotation technique is simple and in my personal opinion a tried a true method. I set take off flaps somewhere between 10 and 25 degrees depending on the model, accelerate to full throttle at a moderate pace, and when tracking true I apply a little back pressure on the elevator stick and let the plane decide when to become airborne. I never yank her off the runway. On that second flight she decided to become airborne, and then about 10 feer AGL, at a very modest AOA in the climb, snap rolled inverted. So I am going ahead with the aforementioned mods, and I'll post some pics after there completed with a flight report. :Cool:

[quitcherbitchen]

3mm isn't enough. Try 4 to 5mm

[Phantom]

Really!? Well I basically raised it to meet my programmed up trim after turning on the radio. I have three successful flights on it since programming that up trim, of course as soon as I start to slow down and configure for landing, I have to start pulling back on the stick to maintain level flight so.... I'll try it with the current 3mm. I can always increase it. Thanks for the tip.

[themudduck]

Really!? Well I basically raised it to meet my programmed up trim after turning on the radio. I have three successful flights on it since programming that up trim, of course as soon as I start to slow down and configure for landing, I have to start pulling back on the stick to maintain level flight so.... I'll try it with the current 3mm. I can always increase it. Thanks for the tip.

Hey Phantom, I did what you did (increased the stab incidence about 3mm to match the up trim) - but I am also using a smaller 3600 battery (and no tail weights). Lighter weight means the motors aren't working quite as hard, plus it won't be as nose heavy. You don't need a 4000mah batt in this one.

[Phantom]

Thanks for the info Marc, my last 3 flights were with a 4000mah 4s pack. I've tried 2200 4s all the way to a pair of 2650mah packs in parallel. So I am hoping that I can still use the 4000 4s pack because of having to fly this bird at such a high power setting I'm not getting the flight time I want with a lower mah capacity pack. Hopefully matching the previous up trim on the elevators with the incidence mod will give me level flight, and further more the mods I am making to the leading edge of the outer 1/3 of the wings will allow me to fly at a lower power setting without wingtip stalling. The only other option is repowering her if this mod doesn't yield the desired results.

[Phantom]

Step 1 of mod

[Phantom]

Removed about 6mm tapered down to 3mm at the wingtip, leaving about 2mm of foam depth on the top of the wing to allow bending.

[Phantom]

Creates a "V" incision inti bottom edge of the wing's underside

[Phantom]

The end result is increasing the camber on top of the outer 1/3 of the wing so that in landing attitudes the lift is evenly generated the full length of the wing. More importantly the outer 1/3 of the wing doesn't benefit from the induced lamenent flow of air, what we call "apparent wind" from the props. That portion of the wing's ability to create lift lies solely with your head wind and the aircrafts forward speed.

[Phantom]

At higher AOA it ensures that the 1st 2/3 of the wing stalls before the wing tip, thereby ensuring the preferred nose down stall instead of the wingtip stall. Sorry forgot to add, just add some hot glue and bend and hold the leading edge down for a minute to complete the mod. Wing fences will go on tomorrow.

[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.