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-   -   Good Ground Run, No Takeoff (http://www.rcuniverse.com/forum/s-p-d-aircraft-coroplast-design-178/11642370-good-ground-run-no-takeoff.html)

ETpilot 10-18-2017 03:02 PM

Good Ground Run, No Takeoff
2 Attachment(s)
Today was a beautiful day. Not a cloud in the sky. Temp 80*, humidity 37%, light breeze. So I cut my runway and got my airplane ready to fly. Preflight OK, engine started running good. Pointed airplane down the runway, held up elevator, tail dragger, added power all good. Ground run straight reduced the up elevator. Airplane did not seem to be gaining airspeed. Kept on the ground to end of runway. Added up elevator for takeoff and plane just stayed on ground, kicked up some dirt and came to a stop still on its gear. I was not sure what happened until I saw the engine and engine mount. The engine was pointing down.

ETpilot 10-18-2017 03:07 PM

2 Attachment(s)
Upon removing the engine with engine mount and firewall, I discovered I had not epoxied the engine mount to the firewall. Only thing holding it together was 2 drywall screws. Amazing as this engine mount and firewall has had a few flights logged. The engine was powerful enough to bend the screws.

Easy fix. Drill out the screw holes and glue in hardwood dowels. Dado the firewall for the engine mount. GLUE THE MOUNT and drill and add the screws. It should work.

aspeed 10-18-2017 04:56 PM

Some guys use something like 3/8" or 1/2" birch ply and screw it into the bottom of the downspout. The tank may not squeeze in, and you have a hole behind the motor. I use plastic mounts, or aluminum T bar that I machine up. It takes forever to do. Your new improved way sounds ok too. I am not a fan of wood any more. It needs paint, and there is not much good paint around any more.

ETpilot 10-18-2017 06:33 PM

Thanks aspeed. This wooden mount really works good. I just have to make sure I fabricate it right, like add glue. Lol.
Wood is easy to work with and good for a SPAD airplane. I have used plywood for my balsa models.

aspeed 10-18-2017 07:13 PM

Yes, the standard maple crutch on a balsa fuselage is long forgotten too. Glass filled nylon is pretty standard.

ETpilot 10-19-2017 03:56 AM

What really baffles me is that there was no indication of the engine mount problem. Prior to the flight I checked the engine installation. I ran the engine idle to full power several times on the starting stand. Before takeoff one last full power run on the ground. No clue of any kind of problem. Just goes to show things can just happen. But better on the ground than in the air.

rgburrill 10-19-2017 05:33 AM

They way those screws are bent suggests you hit a hole in your runway during the takeoff roll. That would account for the mount looking good during run-up but failing on takeoff.

ETpilot 10-19-2017 02:32 PM

Originally Posted by rgburrill (Post 12376500)
They way those screws are bent suggests you hit a hole in your runway during the takeoff roll. That would account for the mount looking good during run-up but failing on takeoff.

Good point. That may be what happened. It took some force to bend those screws. I'll make the engine mount a bit stronger this time. I'll see if I can fine the resting spot for the airplane. Then check the runway area. Thanks

ETpilot 10-20-2017 02:55 PM

2 Attachment(s)
I had some time to work on my engine mount. I dadoed the firewall for the engine mount. I got a nice tight fit. I checked for straight and square, all good. Then I drilled the screw holes on the engine mount and glued in the dowel. Tomorrow I will epoxy the engine mount to the firewall and add the screws. Should be stronger than before. It will be flying soon.

ETpilot 10-21-2017 03:10 PM

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Well, it is all back together again. I just have to set the idle and give her another try.

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