Official Dynam 1500mm B-26 Marauder Thread

[Mad Baron]

I just checked the covers on my plane and they appear to be secure. I am hoping to remaiden it next week I have repaired the damage. I hope the next flight will be successful! Here's a pic of it before the unsuccessful maiden.

[rifleman_btx]

Sounds good, hope this one goes much better

[quitcherbitchen]

Since the Bi Fold doors are way too complicated I decided to redo my fiberglass Bomb Bay Doors. This time I wanted to make a little overlap so the doors wouldn't cave into the bomb bay if I gripped it from underneath or had to make a belly landing. I learned from my earlier attempt to make the doors that 2 layers of 3oz and .07 oz layer was just too flimsy. This time I did three layers of 3 oz.

[borntoolate]

Nice work, Adam!

[themudduck]

I just checked the covers on my plane and they appear to be secure. I am hoping to remaiden it next week I have repaired the damage. I hope the next flight will be successful! Here's a pic of it before the unsuccessful maiden.

Its a real nice-looking model MB, I hope you get it fixed back up. From the pics I just can't tell if you have done the shim for the stabilizer. Without the shim, you do have to have up-trim set on the elevators, at least 3mm up. Its sitting there with level elevators and without any shim, its not going to want to take off like that.

[Mad Baron]

I did install a 3mm shim it doesn't look like it though. I was inspecting the elevator throw today and noticed one side of the elevator had more throw that the other one and I put some CA on the pushrod tube as it was moving with the push rod now both sides of the elevators have the same deflection. I am thinking this might have caused the crash on takeoff. I am glad that it didn't get air born it might have been worse in the air. Its all back together again except for a couple of battle scars when the prop broke it cut a small gash in the wing.

[DavidCalder]

I've been told on one of my facebook groups to shim the horizontal stabs, unless I don't mind lots of elevator trim, what's the required amount of shim? Mine is in the mail on its way.

[borntoolate]

It looks like 3mm is what is needed for the shim.

[themudduck]

MadBaron, Brontoolate, David Calder,
I took some more pics and a short video at the field today.

The pics show my shim - installing the shim corrects the incidence of the stab and makes the model fly a lot better. Without the shim, you need a bunch of up trim and flying like that causes some aerodynamic problems (in effect your stab is undercambered). I used a 2mm shim plus I lowered the LE of the stab by sanding down the front of the saddle by 1mm. Same difference as the recommended 3mm. In the pics the shim is unpainted white Depron foam.
Its important MadBaron to check that the two elevators are set exactly the same deflection, like you said.

By the way I have also mixed a little rudder in with the ailerons, that helps a lot in the turns.

You can also see that I've used the middle hole in the elevator control horn (less slop) and I still have a few mm of up trim set.
I also took a picture of the 3600 4S battery to show the position - its almost all the way forward in its tray. I stuck a piece of foam behind it to stop it from going further back. (I also removed the tail weights)
Last pic shows the new wheels (the nose wheel is slightly bigger than the stock wheel - which raises the nose slightly and helps with takeoffs)
Main wheels are 2 3/4" (DuBro) and the nose wheel is 2 3/8" (Dave Brown).

Link to the video: https://youtu.be/Ds3McW7c-QA
The video just shows a quick demo with a pair of takeoffs and landings, using the flaps, and shows a closeup of the stab showing the small amount of elevator throw I'm using. I've made better landings, but it is what it is!
First landing was faster than usual... second landing features a bounce then a nice flare.
I just wanted to show that the model will take off from grass without any problem.
I flew this model three more times this afternoon (full flights) and made some beautiful landings! Of course no one taped them!!

[Bearcat]

Guys the wing hatch fix I used was simple, I figured that one of the magnets was flipped and the polarity was repelling the other magnet- so the hatch was not sitting correctly. So I removed the mount and flipped over the magnet and reglued it-- worked like a charm!! So the front was not seating well either and it appeared that the lower magnet was set too high in the fuselage so I removed it , small amount of cutting and lowered the magnet mount by 2-3 mm and glued it back in - hatch now fits well.

[Mad Baron]

themudduck

Thanks for the advice on B-26 I am going to sand the front of the saddle on the vertical stab and see if that helps with getting my plane air born. Where do you have your CG set? Mine is at 60mm.

[themudduck]

themudduck

Thanks for the advice on B-26 I am going to sand the front of the saddle on the vertical stab and see if that helps with getting my plane air born. Where do you have your CG set? Mine is at 60mm.

I noticed the stab part was not sitting flush with the fuselage at the top edge....so I ended up lowering it about a mm at the front and then I also installed the 2mm shim at the back. It was necessary to trim just a little foam to keep the rudder from hitting the stab. (Once the back of the stab is raised, it can hit the rudder) You can see this in the third picture in post #989

I did specific flight testing to test the balance point. The CG is very important, especially for this model.
Others in this thread say 60mm works for them, but I found that my model was still displaying tail-heavy flight characteristics.

Here are two specific tests you can do with any plane... assuming that your plane is trimmed for level flight. (a) in flight, run the plane upwards at a 45-degree angle and let go of the sticks. A tail-heavy plane will pitch further up all by itself... a neutral plane will maintain the heading, a nose-heavy plane will tend to pitch downwards. (b) Second test: invert the plane and fly it level. A balanced plane will need just a little down elevator, where a tail-heavy plane will need hardly any down elevator at all to maintain level inverted flight... a nose-heavy plane will need a lot of down elevator. (its not the easiest thing to judge, so I prefer the first test.)

My model at 60mm still tended to "pitch up" all by itself in the first test, and in the second test it would fly upside down without hardly a touch of down elevator. So I am flying now at 55-57mm. It will still snap-roll if I force it, but not during normal flight. I am using 38% expo on the elevator - so I don't get full elevator as quickly, which helps. I also use takeoff flaps for takeoff and full flaps for landing, every time.

I posted this video in late August, and during the flight I demonstrated how this model will violently snap when you apply full elevator, aileron, and rudder at the same time. See at 1:34 and at 3:40. And this was done with the reduced elevator throw, no tail weight, balance at 55mm, and the stabilizer adjusted!! It snaps like nobody's business but it is very well behaved during normal maneuvers. Some people on this thread have had decent results at 60mm. I found that the model flares better with the CG at 60mm, so I'm not saying 60mm is wrong. Because of these mods, our planes are not all exactly the same. But for me, I like 55 better.

[Bearcat]

MIB66 , if you havent already, make sure your cg is 65mm or less. Some are flying at 55mm ,60 mm,65mm. It seems that no one flying beyond 65mm(i'm 60mm and love the way it flys). The plane is a widowmaker if tail heavy. Also give it 2-3 mm up elevator(i gave mine 1mm and had to give it most of my available trim. I ended up at 3mm. Really sucks to have to madly click trim on a maiden. Go easy on the elevator on take off to keep it from leaping into the air. Full flaps and bring it under a little power and its very easy to land. If I come in to fast it has a tendency to bounce. Hope this helps.

So do you recommend using the 60-65 mm range and not the 70-75mm? I noticed mine balanced around 60mm with a slight lean to nose heavy which is fine with me.
I will go with 60mm for CG and elevator w/ 55% throw on high and 30/35% low.. dial in 20-25% expo. I will fly with the lower setting and see how she is as I am a scale flyer and don't get into flying a bomber like a fighter.. so I believe i will be fine there.

[Bearcat]

Some defect I found while assembling this bird, the wing is the one I am not sure what to do outside contact Motion RC

[themudduck]

So do you recommend using the 60-65 mm range and not the 70-75mm? I noticed mine balanced around 60mm with a slight lean to nose heavy which is fine with me.
I will go with 60mm for CG and elevator w/ 55% throw on high and 30/35% low.. dial in 20-25% expo. I will fly with the lower setting and see how she is as I am a scale flyer and don't get into flying a bomber like a fighter.. so I believe I will be fine there.

Regarding CFITrob's post, you'll eliminate all or most of the up-trim he talks about by installing the stab shim as discussed earlier, and the model will fly better as well. Take out the weights in the tail and balance the model no further back than 60mm (I am at 55 to 57mm). A 3600 battery saves a little weight... lighter is always better and the 3600 provides plenty of flying time.

When I get home I'll post my radio settings for the B26. Everyone of us is a bit different but we're all pointing out the same thing.

[themudduck]

Some defect I found while assembling this bird, the wing is the one I am not sure what to do outside contact Motion RC

So what it looks like is that the bottom of the right wing panel is fitting properly, but the top has a gap. I'm thinking that this probably won't affect the flying and maybe you can just install a shim to close the gap.

But I agree this problem is a defect - my guess is that the two halves of the wingtip were glued together incorrectly. (If it was the wing center section that was off, the other wingtip would have the same problem but reversed and the nacelles would be screwed up as well.) So its possible a replacement right wingtip panel will fix this.

[xviper]

Flew my B-26 again this morning. Got one flight in as the retracts were acting up. One didn't come down after several attempts at cycling. I had to land it on one main and the nose gear. No damage. Upon bench testing the nose retract was delayed. It had to "think" about it before coming down. This happened once before but when I got home, they all worked. Flew it the next day with no incident.
Anyone else notice something weird about their retracts? Does this plane use some kind of retract controller? It seems after powering it up, it takes several second before the retracts "wake up". Does it need the controller or can the retracts be hooked up directly to the RX via a triple "Y"?
BTW, my old Dynam Grand Cruiser exhibited a similar oddity with its retracts. I gave up on it and gave the plane away.

[OV10]

Flew my B-26 again this morning. Got one flight in as the retracts were acting up. One didn't come down after several attempts at cycling. I had to land it on one main and the nose gear. No damage. Upon bench testing the nose retract was delayed. It had to "think" about it before coming down. This happened once before but when I got home, they all worked. Flew it the next day with no incident.
Anyone else notice something weird about their retracts? Does this plane use some kind of retract controller? It seems after powering it up, it takes several second before the retracts "wake up". Does it need the controller or can the retracts be hooked up directly to the RX via a triple "Y"?
BTW, my old Dynam Grand Cruiser exhibited a similar oddity with its retracts. I gave up on it and gave the plane away.

Every Dynam etract I've had does this(FW-190 and ME-262). Energize the system and then like 5 seconds later you hear the etract "wake up".
The controller you refer to XV must be something new from Dynam versus using the internal card, either way the delay is obviously there.
I don't personally have this bird but when I look at the parts page for this bird the etracts are the standard Dynam type that doesn't require an external controller :Confused:
A etract that uses an external controller will only have two wires with no signal just + and - voltage leads.
I'm thinking that what your calling a controller is nothing more than a "junction/distribution" card for the rats nest of wiring if it has one at all. ;)

[CFIT rob]

Bearcat...Cg of 55mm to 60mm are the magic numbers for me. Flew mine sunday (only 4 flights but 8min per flt. CHL 4000 ) I test my aircraft Cg in a similar manner mudduck posted and i get a "neutral" cg test response at 57ish also. XVIPER...i had one of the wheel collars catch the wheel cover during pre build servo testing and on my second flight it failed half retracted. From this i learned dynam gear is easily damaged from a jam situation. It retracted everytime when i had her upside down but would fail in flight. The retracts have no common board or controller. They do have some sort of "arming" procedure that is internal to the gear. Short video about it on motions site. I learned with my gear failure to pause at least 5 seconds between up/down switch changes to give them time to "reset". A bad connection on that gears part of the threeway will give you that failure. I believe any interruption in power supply and they need to re-arm.

[xviper]

Every Dynam etract I've had does this(FW-190 and ME-262). Energize the system and then like 5 seconds later you hear the etract "wake up".
The controller you refer to XV must be something new from Dynam versus using the internal card, either way the delay is obviously there.
I don't personally have this bird but when I look at the parts page for this bird the etracts are the standard Dynam type that doesn't require an external controller :Confused:
A etract that uses an external controller will only have two wires with no signal just + and - voltage leads.
I'm thinking that what your calling a controller is nothing more than a "junction/distribution" card for the rats nest of wiring if it has one at all. ;)

I yanked out that rat's nest of wires and separated each retract plug and tested each one via a servo tester. It does the same thing in that it takes a few seconds to wake up. That's weird that Dynam does this. There is no "controller", just a triple "Y". All retracts worked individually after "waking up" so failing to find anything wrong, I replaced the triple with another one and tested all the retracts together via the servo tester. All worked. Then plugged it back into the RX and they all worked multiple times. But this was the way the last time. One retract failed to deploy during the flight. I'll give it another go tomorrow. I'm getting good at landing with only 2 retracts deployed.
If this continues, I'll look into getting non-Dynam retracts later on. This plane is too nice to give away.