J-Power Grob 120TP Build Log - RC Groups
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Jan 30, 2017, 11:46 AM
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Build Log

J-Power Grob 120TP Build Log


The J-Power Grob 120TP. It has a 67 inch wingspan, and a very wide fuse. It comes with retracts, flaps and a 5 blade propeller! Very unique.
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Jan 30, 2017, 11:47 AM
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Sep 10, 2015


So this new plane just arrived today! It should be a fun build. I'll post some pictures after the unboxing. This is actually my second of this plane. The first one is still NIB in storage. I never built it but now that I got such a great deal on a second one, I have a backup and I'm going to go ahead and get her in the air. Stay tuned!
Jan 30, 2017, 11:48 AM
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Sep 11, 2015


Ok first day of work, need to hinge the elevator and rudder. Easy process of cutting the control surfaces off and then gluing in the supplied hinges. Sometimes this can get a bit tricky to line things up, but patience is key! I'm using small amounts of gorilla glue to secure the hinges in place. Sometimes I use CA but I find on occasion I wasn't quick enough and I make a big mess trying to rip out a half inserted hinge. I'll make sure my results are good and then tomorrow do the ailerons.
Jan 30, 2017, 11:48 AM
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Sep 13, 2015


Got all the hinging finished today. Now the wait for the final glue to dry. Tested out retracts today and they work great, they seem to be quite heavy duty. I think tomorrow I'll work on power system in spare time, get BEC installed and a wing wiring harness put in place. Also, I'll for sure need to balance this 5 blade prop, might take some time to get it just right.
Jan 30, 2017, 11:51 AM
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Jul 31, 2016


So I finally found some time to work on the Grob. What I did this weekend was get the battery tray area sorted out. I got an AR6210 in there for a receiver. I cut some of the wood tray so I could fit in a larger LX 4S 5200mah battery, I have two of these big flat ones from my LX B-25 and also use them in my J-Power Duke. But even with that larger battery aft of the CG I still had to add some weight to the tail, which I put as far back as I could so I was adding as little weight as possible. I got all the flight surfaces aligned and the plane is bound. I just need to put in the dual rates and set as per the manual for throws and I'll be good to go! Balancing the 5 blade prop was a little tedious, but I had a bunch of spare blades to mix and match to get the best result. It's not perfect, but it is balanced quite good. I did add in the FMS wing connector set to help out with easy disconnect for the wings. Despite the large canopy it still seems a little tight in there with all the wires.

After maiden, I think I plan to do a mod for the nose steering, this pull pull wire setup that comes stock seems to have a bit too much slack, but I'll wait and see how it handles on the runway first. I think I may have a shock absorbing strut laying around in the parts bin I might slap on soon on the nose strut to keep the impact low on it during landings.
Jan 30, 2017, 11:52 AM
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Aug 3, 2016 MAIDEN FLIGHT REPORT


Today was maiden day for this one finally! My rates where left at 100% throw (which kept suggested travel as per manual), but 30% expo, except rudder which was 90% throw with 30% expo. I used my flat LX 4S 5200mah 25C batteries. CG was at 105mm from leading edge. This is one stable flying bird, no problems at all, great cruising around and some aerobatic qualities too, though I'm not much good with aerobatics. Full flaps at 40mm deflection and she glides in nicely on low power for landing, touches down very gently. I didn't have any issues with the stock landing gear at all so I won't swap anything out until I have a reason to. I flew for approximately 5 minutes each flight and the batteries came down at 3.90V per cell both times. This is a great scale looking bird and she flies like a trainer, would be an excellent first larger bird for anyone looking to go bigger than the typical park size foamies. With the 30% expo she's not twitchy at all but still has plenty of maneuverability.

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