Dynam 1200, P-51 V2..Specific Gravity

[newoldguy]

Hi everyone, I'm a 55 old kid whose been wanting to fly RC planes ever since the day my dad used to to take to a local club to watch back in the early 70's. I've trained up to my first adult foamy, the Dynam P-51 1200 mm. I've spent the better part of the entire winter learning everything I could to get the beast in the air. This last weekend, I pulled together the confidence and failed miserably. After several nice taxi's at full throttle, she starts to lift, but them takes a left turn into the grass. I checked and rechecked the control surfaces and they look 100%. No damage, except to my pride!!
I noticed that when I tried to establish the CG, I had to use a ton of weight. Something to the effect of 4-5 oz. So much, as a matter of fact, that I replaced the battery with a 3S, 4000 mah batt in order to switch the dead weight in lead, to battery weight. It fit in the nose with minimal modification. I know that Dynam recommends the 2100 to 2600 but I figure what the heck, its all lead anyway. Is it just too heavy now to fly? I saw on Motion RC, they used a 2600 and only added about an 1 - 1.25 oz of lead? How they got the CG with that little is beyond me!! So depressed, I thought I finally graduated from the toys..........lol......

Sorry in advance if this has been covered, I did a search and didn't see any posts like this. Please help with any wisdom you can.

[fhhuber]

I have the previous version, modified with the larger motor from the Dynam Me109 (heavier than the original), Castle ESC, DuBro Spinner (MUCH heavier than the OEM spinner), 4 blade prop and use 4S 3000 to 4000 mah (it does best on 4S 3300 mah) The airplane likes the added weight and power.
I also made the flaps operational.
Currently I am working on adding lights for night flight.

I used to fly it on OEM motor and ESC, with the OEM prop + spinner, on 4S 3000 to 4000 mah. I did get 4S 5000 mah in once. I don't recommend it.

For CG, at some point in the mods, I carved some foam from the canopy so the battery could be further back rather than pushed all the way forward. I think that was needed a little with the 4S 3300 and more with the higher capacity packs.

This is my second Dynam 1200 mm P-51. The first had a mid-air doing RC combat vs .25 glow powered models. (both airplanes destroyed)
This one is now a bit over 2 years old. Lots of high G and the nature of EPO, has had me need to re-glue and toothpick-pin the pieces holding the wing spar back in place. (all glue joints in EPO are guaranteed to fail eventually) Most of the hinges have been redone using CA hinges also. Again, this is something guaranteed to be needed eventually with any EPO model.

The updated version uses the same foam parts, motor and ESC as the older version.

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To avoid the left turn, you use up elevator to keep the tail down, giving the tailwheel some "bite" on the runway until you have about half of takeoff speed, then let the elevator go to neutral. You still need to be GOOD with operating rudder to keep it straight. This issue is more pronounced with the higher power I am using, but you CAN learn to keep it on a straight line.

Double check that the left main turns slightly more freely than the right, as this will help. My left spins for about 3 seconds when I give it a good spin The right spins for just about 1 second (that is very little drag difference) Adjust with thin plastic shim washers to fill space between wheel and wheel collar. (essentially cut washers from blister pack plastic, slight curve is good as you can use the spring effect for very light drag)

[newoldguy]

This is great fhhuber!! Thank you!

So many things to learn and know...............I love it! I'll look into all of this, thanks again!

[Hippie 64]

I notice no one has said anything about the prop thrust . Sounds like that's what it may have been …..


Bryan

[farmflyer]

I have had one for several years and fly it regularly on a 2600 Admiral 3 cell with only 1/2 oz in the nose behind the spinner. I also changed out the prop and spinner so I could use a APC 12x6 two blade prop it has much better performance with it. The left turn on take off is due to the torque from the prop and motor as advised earlier keep some up elevator and feed in slight right rudder to keep it going straight until after lift off.

[fhhuber]

Stock prop, 2200 mah 3S and correct CG is adequate to get the airplane flying.

At this weight its pretty light for dealing with the prevailing winds around here. (its a challenge to make forward progress against the wind with the Parkzone micros most of the time) But the P-51 can take off at appx 60% throttle when set up as specified in the manual if you are gentle on the elevator.

Lack of thrust is unlikely to be the issue.

[newoldguy]

Thanks to everyone again for all the tips, hopefully back with some success