CMP BF109F BUILDING THREAD
05-24-2015, 01:20 PM
#2152
I installed gyro stabilizer from Nitro Planes. They were on sale for $19 so I bought three. Only hooked up the rudder and the gain at about 1/3. It helped on take off and the landing roll. First flight good, maneuvers good with plenty of power and a good landing, three point with 1/2 flaps. Next flight take off was better and maneuvers good, but got windier with quartering cross wind. Landed on mains and bounced, bounced again, but didn't nose over or ground loop and was able to taxi in ok. No damage. I think I'm getting this beast some what tamed. The NGH 35cc with a 17-8 three blade tached at 7,550 rpm. We are having an informal meet at the club tomorrow, and somebody has to be the "bad guys" so I'll take the 109 (and maybe the Zero) and see if I can get a video.
06-05-2015, 03:02 PM
#2156
The wind calmed down around here and I finally got in four or five flights. However the other day, after I had landed with the plane idling, I gave it a little throttle to taxi, and nothing. All the other controls worked. Then throttle started working ok. Did trouble shooting, couldn't find a problem. Then yesterday while flying the 109 at about half throttle, it went to full power by it self. I was able to move the throttle control all the way forward and then back to get it to throttle down. Decided I had better land. On short final it went to full throttle on its own again. I went around. At full throttle it was steady and at idle, steady, but part throttle erratic. So I flew a high pattern, throttle to idle turning final, using a steep decent but landed on the mains and bounced, was afraid to try to go around what with the throttle acting up, and hit hard on then mains again. Bent one strut and broke the prop.
Post accident investigation lead me to believe that the throttle servo was getting too hot and caused it to malfunction. The servo is in the rear of the engine compartment, and the rear muffler of the HGH is near the servo. Also I found that the muffler was slightly loose allowing hot exhaust gas to escape no doubt adding to the heat. So I'm going to have to replace the strut as it broke as I was trying to straighten. Its made of aluminum. Since I'm not sure of the make of the retracts, maybe I can get some 160mm struts from Hobby King and use them. I'm going to replace and move the throttle servo to behind the firewall and use a long cable, probably Golden Rod.
The servo is in the stock location and the DLE 20 never caused a problem because its exhaust was up near the from on the side. I'll post pictures later.
Post accident investigation lead me to believe that the throttle servo was getting too hot and caused it to malfunction. The servo is in the rear of the engine compartment, and the rear muffler of the HGH is near the servo. Also I found that the muffler was slightly loose allowing hot exhaust gas to escape no doubt adding to the heat. So I'm going to have to replace the strut as it broke as I was trying to straighten. Its made of aluminum. Since I'm not sure of the make of the retracts, maybe I can get some 160mm struts from Hobby King and use them. I'm going to replace and move the throttle servo to behind the firewall and use a long cable, probably Golden Rod.
The servo is in the stock location and the DLE 20 never caused a problem because its exhaust was up near the from on the side. I'll post pictures later.
06-05-2015, 05:01 PM
#2157
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Sorry to hear about your mishap. Your diagnosis is spot on. I had the exact same thing happen to the throttle servo on my P-40. I wrapped it in heat reflective tape and it still wasn't enough. I moved it inside the fuse and all was well. Good luck.
06-05-2015, 06:48 PM
#2158
irocbsa, thanks for your thoughts, that makes me feel more certain about my diagnoses. The retracts are Sierras so I have sent an e-mail to them to see if I can purchase a new strut. The prop was an expensive Zoar three blade, which says something for the use of much cheaper two blade props, but then I would need a new spinner. So its just a matter of replacing two parts and moving the servo back behind the firewall. Could have been worse. 
06-05-2015, 07:03 PM
#2159
Still getting it sorted out. The last time I tacked the NGH it was turning 7,600 rpm with the 17-8 Zoar three blade. Plenty of power, it does all the maneuvers effortlessly. I thought about just belly landing but didn't want to break the prop, so I tried a gear down emergency landing and still broke the prop and bent the strut. Oh well, thats how it goes sometimes.
06-05-2015, 08:25 PM
#2160
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I've also lost a plastic gear throttle servo, most likely due to heat and vibration
I have replaced it with a sturdier metal gear servo (still in engine bay), it's been OK so far
I have replaced it with a sturdier metal gear servo (still in engine bay), it's been OK so far
06-11-2015, 10:49 AM
#2161
I have a 3 bladed prop spinner drawn for 3D printing , but I have not been able to print it out yet. Its designed for Ramoser 3 blader 16D hub. PM if interested in printing one.
06-18-2015, 06:59 PM
#2163
I got back in town and started on repair of the 109. It turns out the muffler was not loose, but broken. Looks like a design defect to me. Out to a welder who does aluminum, we will see. Darrell at Sierra Giant Scale got my strut repaired an back to me in two weeks. The gear is now reinstalled and operational. I relocated the throttle servo to behind the firewall to prevent this from happening again. I have 10 flights on the NGH 35 with no problems until the last one. So I suppose the broken muffler leaked too much hot gas into the rear cowl heating up servo causing it to malfunction. Another Xoar 17-8 three blade is on order but every website of those that carry it say "on back order" so no telling when if ever one will show up. I've got a Master Airscrew 16-10 three blade so I'll try that.
06-20-2015, 03:05 PM
#2165
I tried the Master Airscrew 16-10 three blade on the NGH 35. Turned up 8,450 rpm static. That means it will be turning up about 9,500 rpm in he air with the clear airframe. That will be over reaving the engine as it should be limited to not more that 9,000 rpm. Probably because so much if the prop is inside the big spinner.
06-21-2015, 10:12 AM
#2166
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Do you think it will gain 1,000 RPM in the air? That seems a bit high. I have used those props on my DLE 30s for a long time and haven't had any problems with over speeding the engine.
06-27-2015, 11:30 AM
#2167
The 109 saga continues. Darrell at Sierra was very helpful. $24 and less than two weeks later I had the new strut. A week later a new Xoar 17-8 three blade prop. Tested the repairs. The take off was fairly straight with the help of the gyro. Maneuvers good, flying great. Then the engine pitch suddenly changed louder. The throttle response was still ok. Put gear and flaps down and landed ok. The muffler was loose, again. Because the muffler is two piece and you have to mount the first part to the engine and then install the rear part, you can't runs the engine to heat up the engine and further tighten the mounting bolts. So this time I cleaned the bolts with naphtha and used permatex high temp high strength thread locker. I heated up the mufferl with a heat gun and maybe got another 1/16 of a turn on the bolts. Did a lengthy test run on the ground. Checked out ok. Also tacked the NGH 35. It is now turning 7,750 rpm with this three blade prop.
06-27-2015, 07:35 PM
#2168
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RBean
Not sure which 2-part muffler you're talking about, I had the same problem with a wraparound Pitts on the 109, kept coming loose no matter how much tightening / threadlock / teflon tqape.
I figured out that the root cause is the overall "softness" of the engine bay on this plane causing vibration harmonics that loosen the bolts.
Solution: I made a bracket that supports the far end of the muffler barrel, problem gone!
It is on this pic - you have to look closely as it is painted flat black
Not sure which 2-part muffler you're talking about, I had the same problem with a wraparound Pitts on the 109, kept coming loose no matter how much tightening / threadlock / teflon tqape.
I figured out that the root cause is the overall "softness" of the engine bay on this plane causing vibration harmonics that loosen the bolts.
Solution: I made a bracket that supports the far end of the muffler barrel, problem gone!
It is on this pic - you have to look closely as it is painted flat black
06-28-2015, 03:27 PM
#2170
LDM I got the props at justmodelprops.com They took my money and I goy the props. They seem to have them when every one else is out of stock. w1ndbura, maybe I'll try a rear bracket if I can figure out how.
07-04-2015, 06:19 AM
#2171
The 109 (or maybe NGH35) saga continues. I got one flight in chasing a Hanger 9 Mustang, or was it chasing the 109? Any way, the throttle was at mid range and went to full power by itself. Moved the throttle stick all the way up and back and had throttle control. Put gear and flaps down and landed ok. Once stopped no on the grass runway, I nudged the throttle to taxi off and went to full power. I hit full left rudder and it went into a tight circle while I hit the kill switch. Inspection showed the muffler was broken again. A club member said he had seen that before, and the broken muffler sets up a vibration the effects the throttle servo, even though it is attached by a plastic Golden Rod and not metal. I have acquired an after market muffler. It is smaller with no baffles so I'm sure it will be louder. Had to alter the cowl some, but not too bad. Have not run yet and no pictures.
07-06-2015, 01:36 PM
#2173
The 109 came to an end yesterday. I flew it for the first time with the after market muffler. Tacked at 7,600 rpm, so it lost a little power with the smaller muffler and more back pressure. However while getting ready to land at a high idle, I nudged the throttle forward and it just quit. I was able to land ok. I think it was just too lean on the bottom end. Changing the muffler effected to mixture. So I richened up the mixture, more on the low but a little richer on the high needle. Then fueled up and took off again. This take off was not as straight, but got off ok, but the engine was too rich, not putting out much power. Come around to get ready to land. On the turn from down wind the tail started osculating. Looked like the rudder gyro was malfunction. I was going to leave the flaps and gear up and belly her in. However, just come over the end of the runway, started going up and down and wing waggling the just rolled left and straight down. This was not a stall and snap, but an uncomanded roll. Hit just off the runway, engine at idle but straight down in soft mud. The plane is totaled, but engine appears to be ok.
I think the gyro malfunctioned and interferred with the receiver. This plane has been "snake bit" from the beginning. I'll put up a nice set of Sierra retracts up for sale. They survived the crash without damage.
I think the gyro malfunctioned and interferred with the receiver. This plane has been "snake bit" from the beginning. I'll put up a nice set of Sierra retracts up for sale. They survived the crash without damage.
