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Nov 26, 2017, 09:32 AM
BigTradioman's Avatar
Build Log

DAG120 Build

This is a thread about the completion of a DAG 120 build that was started by Richard Harris some time ago. I think Rich shelved the build due to the usual pressures that arrive unexpectedly to all of us at one time or another and in the interim period, the cost and availability of large servos has so improved.

During the testing and first flights of my DAG60, Rich had mentioned this air frame and later in the year he very generously gifted it to John Keats to finish as he is an experienced large model builder and has plenty of time and a small pile of large engines looking for homes. At first glance it did not look so much bigger than the 60 but it is in fact around 20% bigger. When placed next to a 60 increase in size is more apparent. The power plant will be either a 25cc 2 stroke petrol or a 30cc 4 stroke petrol. To give an idea of the size it is possible to get a JMB can inside the front of the fuz and still clear the mast!

Having seen the issues I have had controlling the blades with the roll only head in anything but a gentle breeze, John intends to make this a Delta head. At the moment he is undecided if it will be load sharing like the RPG or like the Panther style with 2 separate servos, but 2 huge 30kg servos are on the way from BangGood. The plan is to retain the elevator and have some mixes set up so that on a 3 position switch you have, Roll and elevator, Roll and Pitch no elevator except for trimming, and a mix of Roll, Pitch and Elevator.

So, the tail is on, undercarriage and spats sourced, cowl is from Carbon Copy and is off a 1/4 scale Corsair, pilot is sourced but needs painting. Blades will be the same width and profile as mine as John already has the tooling for that, they will be hard balsa and Basswood leading edge and probably 12 inches longer than mine making them 5 foot. The rotor spindle will be from a Gyrone. Target weight will probably be in the region of 15 lbs wet.

Some snaps to be going on with.
Last edited by BigTradioman; Nov 26, 2017 at 09:43 AM.
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Nov 26, 2017, 10:26 AM
The 1st Sofaman
Sofaman NJ's Avatar
Beautifull. Going with the Delta head would be nice. My full cyclic DAG 60 Started with The Delta head. Then I did the pitch towards the nose. Roll on the side. Takes large servos. Although I used 2 servos (slaved together) for roll and pitch and it did work....before the large servos came in.

I used a pot via the radio to control the pitch on the head. I used the elevator as usual. Here is the cool can turn up the pitch and apply elevator and the autogyro almost stops mid-air. So you can see the convenience of using pitch on the head along with the elevator. Flaring out is beautiful doing this way and the best thing is you can point the blades down in the wind.

Nov 26, 2017, 10:49 AM
BigTradioman's Avatar
I suppose he and indeed me could get away with just pitch forward on landing. That would allow the use of a smaller servo for pitch.
Nov 26, 2017, 10:58 AM
The 1st Sofaman
Sofaman NJ's Avatar
For best results if you are sure that you need extreeme down pitch is to separate actual elevator from the actual pitch of the head. My pot I used for pitch had a leaver on the pot so I could pull it back to flare and down in the wind. Elevator operated seperate than pitch of head.
Nov 26, 2017, 01:16 PM
Registered User
106flyer's Avatar
Looking good chaps, lovely to see so much balsa construction

Nov 26, 2017, 04:45 PM
The 1st Sofaman
Sofaman NJ's Avatar
I had a radio similar to this one, I think it was a JR? I cant remember. Assigning the pitch to this pot gives you amazing control. The elevator is still utilized and the pitch is the normal 6 degrees. The great thing about the pitch assigned to the pot in mid-air you can fine tune your pitch. Just some thoughts. Not trying to impose my views onto you. I just want to help.

Nov 27, 2017, 03:58 AM
BigTradioman's Avatar
Food for though Dave, thank you.
Nov 27, 2017, 05:36 AM
The 1st Sofaman
Sofaman NJ's Avatar
You know Horizon Hobbies sells a beautiful 35CC would lool look beautiful on the 60.
You could move the motor back some since it mounts close to the firewall.
Nov 27, 2017, 05:42 AM
BigTradioman's Avatar
This should give an idea of scale. Table is about 6 feet diameter. Dave the radial would look and sound great, but too much money. I think JK would go for a Saito though.
Nov 27, 2017, 05:52 AM
The 1st Sofaman
Sofaman NJ's Avatar
This would look nice on it!!

This is the engine Marty Zellar put on his 60 size PCA-2. I think that engine is made for your 120 Gyro.
Last edited by Sofaman NJ; Nov 27, 2017 at 06:00 AM.
Nov 28, 2017, 04:24 AM
BigTradioman's Avatar
Initial mock up yesterday: undercarriage is too small so a bar of ally has been ordered along with some nice wheels and spats from Carbon Copy. (I think), initial balance proves it is very tail heavy so maybe having to go for a bigger motor. The NGH 4 stroke is about 1.5 kg.
Last edited by BigTradioman; Nov 29, 2017 at 05:12 AM.
Dec 10, 2017, 05:26 AM
BigTradioman's Avatar
Looks like the engine leading the race for the front of the DAG 120 is the NGH38 four stroke gas. Just waiting to see the price when it comes back into HK UK stock.
Jan 08, 2018, 03:48 PM
jodini's Avatar

May 28, 2018, 10:47 PM
The 1st Sofaman
Sofaman NJ's Avatar
Looking HUGE!!!!!
May 30, 2018, 02:38 AM
BigTradioman's Avatar
So getting near the first engine starts. Power box is installed and regulated to 6 volts giving 40kg on the pitch and roll servos. Radio is trusty Futaba 14fg with FASST Rx, at least that will give a reliable failsafe on the throttle, fuel tank is in and plumbed, waiting for a flexi pipe to get the exhaust out of the cowl. If the rain ever stops we might get some taxi trials done and see if these big blades spin up.

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