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New builder needs help with tail wheel retract

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New builder needs help with tail wheel retract

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Old 09-30-2017, 11:53 AM
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Ipswichfan73
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Smile New builder needs help with tail wheel retract

Good Saturday to you all. I am a new r/c airplane builder currently working on a Top Flite .60 F4U Corsair. I have decided to take my time, ask lots of questions and install all the bells and whistles such as working flaps and retractable wheels. In for a penny, in for a pound. I need help with installing working doors for doors for the retractable tail wheel. I am installing the Robart 121 retractable tail wheel powered through an air cylinder. If anybody can help that would be great. Please remember that I am a first time builder and give simple. concise instructions. Pictures and/or videos would be great. Thank you in advance for your assistance.
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Old 10-01-2017, 08:33 AM
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bentwings
 
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Having built this sized model Corsairs some 40 years ago I'd say leave the gear doors alone. There is not much space to even get your fingers inside the mains and far less on the tail wheel. By all means use the main front door however. Even this will be a bit of a trick to work reliably. I'd study how the full size one works. Early ones had a leather hinge believe it or not.

If if this is your first excursion into scale warbirds I'd stick to basics and learn to fly this model. Fly the day lights out of it, learning the Corsair Blues as the original thread was called years ago. They will wing over on takeoff in a heartbeat and stall quickly on landings. Once you get by this they are fun to fly.

If if you really want to pursue it I'd most surely use a molded fiberglass door system. I pulled a plaster mold off my finished wings on the Ziroli 94" wing. While a bit tedious I made very light weight doors that were very rigid. You only need two hinges but to cut the gaps to a minimum you need either to chamfer the hinge line or use offset hinges. For a long time I used mechanical linkage designed on CAD using motion study. These worked very well and were replaceable in the event of failure to operate....it happens.

The tail wheel shaft needs to be lengthened. If you read some history you should come across this mod on the ful size ones. It applies to the model too. Look carefully at pictures and you will see it. Definitely helps ground handling and realistic look. Tail wheel doors will be very narrow on this size model. Hooking up any linkage will entail long needle nose pliers or forceps. I'd forget them here. Leave them off.

id use a .90 motor as you are going to add a bunch of weight with the retracts. Keep the finish as light as possible. Even on my big models I use one thin coat of primer and one thin coat of paint.

Scale flaps are also more difficult. The kit flaps are functional but not quite scale. Again look at the pictures. The Corsair walk around books are great for detail.

most Corsairs require nose weight so be very carefull of weight on the rear. I'd make provision to move the motor ahead a little to help with balance. Later model Corsairs did this.

Model Corsairs fly much like the full size ones. If you don't use rudder on take off you will most certainly crash sooner or later. The common cause it taking off before flying speed is reached.. Be very wary of cross wind from the left side. I'd surely look at Eagle Tree Guardian to help. I used a heli gyro a long time ago before they were popular on aircraft.

Good luck on your build. Keep it light.

Last edited by bentwings; 10-01-2017 at 08:36 AM.
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Old 10-02-2017, 07:55 AM
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Ipswichfan73
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Thank you for the great information. I have purchased the O,S. 95AX motor for this build.
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Old 10-11-2017, 07:02 AM
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No need for any fancy mechanical system. Two simple spring loaded doors, very lightly sprung in the open position with a band of thin elastic tread going from one to the other.
As the gear closes , the leg pulls down across the elastic and closes the doors.
Least, that how we did it in the old days. Dead simple and works a treat.
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Old 10-11-2017, 08:20 AM
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Yeah, that's what I did with the old pattern planes way back.

The Corsair is a bit different, the wheel well is very shallow and the strut actually contacts the doors and the wheel is pretty wide or large in diameter, usually just slightly smaller than the wheel well width. The wheel almost has to be fully retracted before the doors will clear.

I made a mechanical linkage I designed on CAD using motion simulation. They even had a spring to help with extra motion just as the wheel hit bottom (fully retracted). While complicated it worked very well. It was easy to replace parts as I had a drawing for each part so it was just a matter of making like the print as we used to say.

my son upgraded ( down graded in my mind) later on with a fully air operated system. It took constant fiddling with air controlled timing. And was not very reliable. It seemed like there was always a door hanging open.

Byron
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