Official Dynam 1500mm B-26 Marauder Thread

[Wag727]

I just finished putting mine together and was wondering if the CG that they tell you in the instructions was correct or if it needs to be more or less?
Does anyone have any info?

[Wag727]

[Bearcat]

I just finished putting mine together and was wondering if the CG that they tell you in the instructions was correct or if it needs to be more or less?
Does anyone have any info?

Funny you asked that question and that depends on your setup

• Did you remove the weight in the back? - check balance but normally farther forward than stock
• what battery are you using also changes the CG location - mark it inside!!!

Mine flights at 55-60mm range but I might move it back to 65mm to see however it flies there.

[Wag727]

I' using the admiral 4000mah battery they recommend but would like to put my 5200mah battery in it for a little more peace of mind. It balances with the 4000mah battery just a little nose down at about 72 mm. The 5200mah battery would let me put it at about the 60 - 65mm range so I might try that.
Thanks for your reply.

[Grossman56]

https://www.rc-airplane-world.com/balancing-rc-airplanes.html

Some good information on balancing .

Grossman56

[rifleman_btx]

I fly mine with 4000 and 5000mah. The cg is set at 65mm

[Mad Baron]

This is how my B-26 balanced out I set my balance point at 70mm and with the gear up its slightly nose heavy and with the gear down its near level and it flies great. I fly mine with a 3600 4s lipo I haven't used a 4000 in it yet as I am getting 5-6 minute flights from the 3600 and the battery is at 3.8 a cell after a flight. My plane didn't have the weights in the back.

[rifleman_btx]

Here are my battery positions for both 4k and 5k mah batteries

[nollzman240z]

really love my b26 great flying bomber i'm flying it with a 2200mah 4s pack getting 5 min flights with 45% left in the packs also flew it with 4200mah pack. no shim mod i did remove one weight flying at recommended cg and control throws. replaced retracts with flightline p38 retracts so i can fly in the cold and added robart wheels overall i love the plane even with the problems people talk about most are simple fixes for the average builder. also on a side note it does great belly landings but typically ends with at least one broken prop lol also if you do the retract mod check all retracts before installing them i had one that binded up and motion quickly sent out a replacement great service from motion .

[rifleman_btx]

Great to hear, and looks good!

[Wag727]

I finally got to maiden my B-26 today with a 5200mah battery with the CG set at 65mm. Flew terrible at first, had a natural roll to the right. After a new friend at the field came over and gave me 80 clicks left trim on the ailerons and 8 clicks left rudder and 8 clicks up elevator it flew great! When I made my flyby to lower the retracts, only the front came down. I cycled them about 5 or 6 times and then none would come down. Had to apply flaps and belly land her and all that happened was a broken prop, destroyed belly football, and some belly scrapes. She set down perfectly just wish the retracts would have worked. After looking at everything, we determined that the wing is warped since there was about an 1/8 inch down ailerons on the right side. I have shimmer the wingtips to compensate for this and hopefully it fixes the issue.
If it wasn't for Rick, my girl would have been a complete loss.
Does anyone know if e-flite retracts will fit without too many mods?

[CFIT rob]

My post #1218 may help. Eflight mains appear to drop in. No one has reported trying the nose gear yet. What was the air temp when you were flying? Under 50f seems to be a problem. Hoping that dynam will improve the gear this summer. Add that to your list alpha. Bet its already on it...

[Wag727]

I just ordered the tricycle set for it. It was 47f when I flew. I measured the mounting screws and they seem to be able to drop in. I appreciate your reply! I will post later about the nose gear weather it' a drop in or not. Thanks again.

[themudduck]

https://www.rc-airplane-world.com/ba...airplanes.html
Some good information on balancing .

Grossman56

I like seeing articles like this, they are helpful, but this one is lacking in a few ways. It does a good job of explaining how to physically balance a plane using the position recommended by the manufacturer. I would have liked seeing a discussion on how to determine where the CG should be.

The article does advise the general "rule of thumb", the typical range of 25-30% back from the LE - but this rule of thumb only applies to straight wings.

Wings with more complicated shapes (for example like swept-back wings or other shapes) require a different method to determine where the balance point is located. (You need to determine where the Mean Aerodynamic Chord is and measure at that point). I guess that's a bit nerdy.... Here's another article that explains how to determine the 25% CG using the MAC.

And it would be useful, I think, to also talk about how to carefully evaluate what your plane is doing in the air and how it relates to the balance point, so you can understand what the affects are when a plane is nose-heavy or tail-heavy- because there seems to be a lot of confusion about that.

The other thing I noticed is that it said to measure your plane "flight ready" - i.e., with the fuel tank full. This is really important!
Now, I've always measured my CG with the batteries fully charged. If the fuel tank is empty that could drastically change things. Batteries are much heavier when they are full of electrons. LOLLOLLOLLOL

:(OK, sorry, I'm done, back to my coffee...

[Hardway]

[QUOTE=themudduck;n114365]

Batteries are much heavier when they are full of electrons. LOLLOLLOLLOL

I hate that when the electrons get cold. They get even heavier!!! :Cool:

[farmflyer]

What if the tires aren’t full of air one must account for that and if it is summer or winter because the winter air in the tires will be much heavier because it is denser:Silly:

[themudduck]

Yeah maybe that's why the retracts don't work in the winter, its because the tires are too heavy. ;)

[farmflyer]

Good point !

[CFIT rob]

Wag727...you are very welcome. Let us know of your progress with the swap. I will be buying the p61(and the gloster meteor) when its available so if there is no improved dynam retracts by end of summer, i will change them all out.(expensive but worth it...like divorce) As for the cold and density i believe the previous posts are correct. My ex-wife was cold and quite dense. Really...really dense.

[UK Arthur]

Cold-fail retracts.

A few weeks ago after leaving my Marauder in my front hall at 40°f for an hour, two of the retracts would not deploy (of course). In the hope of being able to fly soon (weather's been crap for weeks, and me similar), tonight I've repeated the test after leaving the plane for an hour in my unheated hangar (err, spare bedroom) at 49°f. The retracts all worked fine. With luck, the test can be done at in-between temperatures tomorrow morning (assuming I remember!). Then I can choose a safe minimum flying temperature for my Marauder.
The tests were done with a battery at 3.8volts per cell, and the battery was also left in the plane for the 1 hour soak before the test.
This could save me bothering to swap the Dynamic retracts out for ones that can stand the cold.
One alternative for flying in the cold is to deploy the gear and then remove the retract plug from the receiver before take-off, to avoid unintended retract.