Official Dynam 1500mm B-26 Marauder Thread

[themudduck]

Good comments - Xviper thanks for the flight report. I have some other models that have tendencies that mirror some of the characteristics of the full-scale plane... for example the F104 with its small wings requires some careful handling, you have to keep the speed up in turns or it will just fall out. Apparently the model Marauder needs to be flown "fast" just like its big brother and flaps are needed at slower speeds - well that seems appropriate. In some ways, I think this is part of the fun of having a scale model and helps builds better flying skills. I am happy that the Marauder is very close to the correct shape - the designers could have lengthened the fuselage or enlarged the tail to make it fly more gently, but I do like that it's scale.

I'm just not completely convinced (yet) that its nose-heavy. The elevator trim may be off due to a slight stab incidence error. (I'm experimenting with that and will report my results after this weekend's adventures).
A nose-heavy plane will have other characteristics which can be observed, such as not wanting to flare during landing (which it does very nicely with flaps) and heading downhill fast when it's inverted. (I don't remember). So far I've had 4 flights, with the 4000mah battery not pushed all the way back. Its sitting where the front strap can grab the front of the battery. That's about a full inch forward of where XViper described his.

I had very similar results as what XViper described. But at high speed, I could induce an instant snap-roll by giving it full elevator. Since it doesn't seem to be really tail-heavy, that snap might be due to high wing-loading - the plane may simply be heavy. Anyway that's what I'm leaning towards. Just my opinion. So I took out my tail weight and I want to try flying it with a smaller battery to see how it does.... With a smaller battery it will less nose heavy, and lighter overall. The balance point will be further back and I'm guessing it will fly better, at least that's what I'm hoping.

[TiredIronGRB]

I think a 3000 battery would be better suited for the B-26, the 4000 seems pretty heavy for it and a 5000 is just asking for trouble.

[themudduck]

I think a 3000 battery would be better suited for the B-26, the 4000 seems pretty heavy for it and a 5000 is just asking for trouble.

Agreed. After a 6 minute flight my 4000 battery was only down to 3.92 volts so a smaller battery should still provide decent flight times.

[ryramZ]

Snap roll sounds like three things.
Tail heavy...
Too much throw....
Uneven throw...

There is a lot of mass forward of cg as compared to our other twins which means the tail has a lot of work or holding up to do.

[rifleman_btx]

Just for grins anyone else weigh your planes, mine came in at 4.5 lbs with the 4000 installed so I appear to be 1/2lb under the manual weight with the 5000 directly on 5lbs. I really wouldn't think those weights equal to a half pound. no way

[rifleman_btx]

They weigh in at 4oz for both together

[OV10]

Just for grins anyone else weigh your planes, mine came in at 4.5 lbs with the 4000 installed so I appear to be 1/2lb under the manual weight with the 5000 directly on 5lbs. I really wouldn't think those weights equal to a half pound. no way

I always weigh the birds to ensure that the weight to electric thrust ratio(watts per lb) is satisfactory. My sweetie always laughs at me when she sees me standing on the bath scale while holding a new bird.

[rifleman_btx]

Heck yeah me too

[ryramZ]

[rifleman_btx]

The MOS for window licking wasn't available in WW2 hence the clouded windows

[CFIT rob]

Outstanding work ryan. Your pilots must be cheech and chong flying the" labrador" run to have it that smokie. Thanks for the left over p38 nomenclature idea,wil make use of mine. Anyone have wingnuts cockpit 3D printed yet? Curious as to fit and cost.

[xviper]

Flew the B-26 back at my home field (very lumpy, bumpy but short grass). In this video, I used a 3300mah, 4s, Eflite battery, which is 86 grams less than the 4000mah one I was using in the last video. I found the amount of ELE trim only changed by 2 clicks less UP for it to fly level. Inverted flight felt no different. I conclude that the UP incident on the elevator is likely a function of the angle of attack of the horizontal tail surface. That little Uvula looking antenna on the underside fell out on one of the lumps after landing. I'll use a magnet to help hold it in. I have to remove it so I can transport it with the retracts up.
You will also notice that it took off in considerably less distance on the short grass field. In fact, it's as good as all my other prop driven warbirds. Did a big loop at full throttle, after a shallow dive and it looked effortless and tracked straight. Landings on full flaps were once again, a non-issue and the gear seems to be able to take a mild bounce or two without worry. As I get more used to it, I don't stress anymore over the tip stall characteristics. Keep the throttle in upper 2/3rds and just enjoy the flight.
There were more people at this field and the B-26 drew a lot of attention.

[rifleman_btx]

Very cool, what may I ask is your all up weight?

[TiredIronGRB]

I must say I'm really loving this plane, I'm getting 12 minutes on the new Admiral 4S 4000s. She is very well behaved and landings are very predictable...and she just looks awesome!

[rifleman_btx]

Well my parts made it in time. Ready to fly tomorrow just a 1/4 lb under the manual weight with the 5000 and 1/2 lb under with the 4000.

[xviper]

Very cool, what may I ask is your all up weight?

I've never weighed any of my planes so can't say.

[xviper]

OK, just put mine on a luggage scale. With the weights in the tail present, no battery, it weighs in at 4.85 lb. Add another 0.94 lb. for my 4000mah, 4s battery and you've got the total weight of 5.79 lb.

[rifleman_btx]

Oh goodness, now I see why the planes fly like lead bricks and need so much power to keep flying!

[handyman220]

I did the same mod as borntolate to get my top hatch fitting correctly. All it takes is a few minutes and a sharp razor. I'll relocate the magnets to pull the front of the hatch to fit better.

[themudduck]

I had a few more nice flights today on mine - I tried out a few things (as I mentioned in a previous post):
a) I removed the tail weights
b) I adjusted the incidence of the stab, lowering the LE about 1/16 inch.
c) I tried using a 3600mah battery instead of the 4000.

Total weight with the 3600 battery: 5 lbs 10oz (5.625lbs)

I played with the balance a bit, moving the battery forward bit by bit. My original balance point was 60mm back from the LE. After three flights now I have it set at 55mm and it seems to be very close to where it should be.
The front edge of the battery is about 1.25 inches in front of the edge of the strap.

Testing the CG - With the balance point at 60mm, I flew the plane into a 45-degree up-line and released the stick, and the model continued to rotate towards vertical (indicating tail heavy)
At 55mm, did the same thing and the model held the line (indicating its close to correct)

I can still force a snap-roll if I try very hard, but it is much better than before. I've reduced the elevator throw to just a little under 1/2 inch. It flies wonderfully.
I've had no problems at all at low speed with tip-stalling but I use flaps.
After a 5.5 minute flight the battery read 3.92 volts per cell (same as the 4000).