Official Dynam 1500mm B-26 Marauder Thread

[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.

I hear you. The CG, as I understand it is where the wing chord is the thickest, so, by feel, you can get it pretty good, for a straight wing.

http://www.rcflightschool.com/SetupPDFs/CG.pdf

Dave has more information on swept wing CG as well, I can recommend his books as I have several and they have a lot of great information in them.
I'll drop him a message and see if he would be interested in explaining it for us.

Grossman56

[UK Arthur]

Cold-fail retracts

Further to my post #1300:-
This mornings retest (0630 GMT) simply confirmed post #1292 by CFIT Rob, that at less than 50°f there is a problem.
My spare room temperature had only fallen 2degrees to 47°f since last night's test, this morning all three legs deployed at first, and retracted ok, but at the next try only the mains came down, then next only the port leg deployed.

[Mark 2]

Yeah, IMO Dynam retracts are not fit for purpose. The only solution is to replace them I’m afraid. Hobbyking do, or did, a set of very reasonably priced retracts that just drop straight in and are very reliable. I can recommend them.

[quitcherbitchen]

After adding a magnet to the door and readjusting the pushrods geometry I got the bomb bay doors to work..

[themudduck]

Hey quitcherbithen, that looks good. I'll bet its awesome to see all those bombs coming out of the belly, eh? Its looks like you have a relatively simple setup (although tight) and those magnets look like a good idea.
Can you take a video as a demo?

[themudduck]

Grossman - I guess that having a full-on discussion about CG is probably "off-topic" for this thread and most of us would rather talk about the B26 here. Maybe a new thread could be started elsewhere on the squawk to really get into it, and how to set the CG on various wing types using the MAC, how to do flight testing and so on.

With the B26 I think that some of the variance I've seen with the balance point people are going with (55 to 75mm) comes from "Where to measure from" - because the front of the wing has a fillet where it joins the fuse so it's hard to know where to put your ruler. In otherwords it can easily vary 5mm or more depending on exactly where your starting point is.

[rifleman_btx]

After adding a magnet to the door and readjusting the pushrods geometry I got the bomb bay doors to work..

I like it! Awesome job! On to the cg note, with the cg being a larger issue with this plane. I feel it's pretty relevant. As well as everyone been finding the sweet spot to be in a 5mm range from 65-70. So all in all I guess we shall go back to the b26 and make sure everyone gets the proper fixes if needed. As it looks like maybe dynam made some adjustments on their own in regards to the horizontal stab, seeing some not needing the shims. If that's the case, thanks for listening dynam!

[capecoral]

With all the painting mods can any one suggest a good tape or method that will not peal off the silver???? I have a yellow painters tape for "gentle surface masking" but do not dare try it????

[fhhuber]

EPO is the next best thing to teflon, so anything that sticks is likely to peel paint.

Damp paper towel or weighted paper works for masking. If using the weighted paper you have to use care about angle of spray to prevent lifting the paper edge.

[UK Arthur]

The CG position

Mudduck raises a valid point about the wing-to-body fillet; it blends in to the body on a tangent, so is open to error.

60mms back from the straight portion of the wing leading edge is a joint line running between fuselage and engine nacelle(s). I used that as my reference for easy consistency.

This model is tolerant of CG position because of its "shoulder wing" - more tolerant than a mid wing or low wing set up.

[RRHandy]

I have used this, low tac and can be reused. R.

https://www.amazon.com/gp/product/B001OO3JQ8/ref=ox_sc_sfl_title_8?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

[Hardway]

Large and small Post-It notes work pretty well. They won't peel the paint. But sometimes adhesion is an issue.... Just another option...

[Mad Baron]

I used the green frog tape I got at Lowes it has a low tack. I used it when I painted O.D. stripes on the fuse and wings it didn't pull any of the silver paint off.

[TiredIronGRB]

Waterever tape you use stick it to your pants leg before putting it on the plane.

[capecoral]

all great suggestions thanks for the help. Just thinking of a simple red tail and wing tip trim..

[UK Arthur]

Paint masking

Children's modelling clay? Plus newspaper.

[Bearcat]

After taking out the rear weight I rechecked my CG to see how far it moved and I was totally surprised that I had to move my 3600 5-6mm backwards and my 4000 back 15mm back from where it was..
Plane does balance out at 60mm so I am happy but surprised with how far things changed.. sad part is I flew it horribly nose heavy last time out but it flew ok..so now with the battery back farther back and the CG is closer to balance now it should fly well. Will find out Sunday as the weather should be very nice here in the Cincinnati area.

[rifleman_btx]

Yes! I'm flying mine tomorrow as well!

[NoDirt!]

While I did get a chance to set how straight it will taxi and do a range check, it was too windy for a maiden. And it's supposed to rain tomorrow :Crying2:

I'll get to fly this thing yet!

[rifleman_btx]

I feel your pain, I was hoping to get my carbon z t28 from my buddy this weekend, and was hoping I could fly it tomorrow as well. Even bought the receiver for it. But I'll have to wait til Tuesday when my va check comes in