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AMR 33% J-3 Cub

Old 03-12-2011, 04:00 PM
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Default AMR 33% J-3 Cub

Hi Guys,
I thought I would post some pics and discuss the build of my AMR 33% J-3 Cub. I built the plane last fall for a product review in Fly R/C magazine. It is in the March issue. I did not do a build thread due to obligations to the magazine so now that the review is out and the issue is off the shelves I thought I would post about the Cub. If you have read the review this may be a little redundant.

The kit comes with a very complete hardware package consisting of all the fasteners required and Robart hinges. The landing gear is pre-formed and welded. All the formed parts ie: ribs, formers etc: are laser cut as well as the windows and windshield. The cowling is fiberglass with the engne detail molded in, the cowl halves must be joined and glassed together. The fit between the two halves was good.

Unfortunately just as I was starting the covering of the Cub I lost the hard drive on my PC and lost the majority of the pictures of the Cub being framed up as I had not backed the images up on CD(live and learn). I do have a few pics which I will post.

The build started with the tail surfaces, the perimeter is made from laser cut 3/8" balsa parts. The part fit was very good. The hinge line is made up from spruce stick stock. I taped the leading and trailing edges together in pairs and drilled the holes for the Robart hinges befoe assembleing the parts, this assures perfect alignment of the hinges. The parts are assembled directly over the plans.

The fuse is a mix of stick construction and laser cut parts for the cabin. I framed up the basic fuse structure in one weekend. The supplied laser cut gussets make for strong joints on the truss structure in the aft end of the fuse. The wing center section is built over the plans then it locks into the top of the fuse. The design is very strong and was easy to align and install. The door on the Cub is functional and all the hardware to construct a functional scale door latch is included in the kit.

Thats all for tonight. I will post a few pics, if there is interest I will continue with the post and pics.
Anthony
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Old 03-12-2011, 04:16 PM
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Default RE: AMR 33% J-3 Cub

Anthony, Don't stop now. Keep the build going to completion. Dan.
Old 03-12-2011, 04:24 PM
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Default RE: AMR 33% J-3 Cub

I second what DAN REISS said. Thanks for taking the time!

Joe
Old 03-12-2011, 04:50 PM
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Default RE: AMR 33% J-3 Cub

OK Guys,
I will give ya some more tomorrow, I have to work in the morning.
Later!!
Anthony
Old 03-12-2011, 05:57 PM
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Default RE: AMR 33% J-3 Cub

Thanks for the thread so far. I have a 1/4 scalle Bud Nosen kit that I built 30 yrs ago, finished it last season and crashed it royally... I will rebuild it soon and have been loking closely at your detailed pics. Waiting tosee how your main wing issecured in place..

Keep it coming

Thanks

Rafeek
Old 03-13-2011, 10:06 AM
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Default RE: AMR 33% J-3 Cub

The wings are built in the supplied jig, AMR supplies wing jigs for all their kits and it assures a straight wing everytime. The ribs are set into the notches in the jig then the top spars are installed. The wing panel is then turned upside down on the jig and the bottom spars installed. There are laser cut ply shear webs supplied for the critical stress areas of the wing such as the root and the strut attachment points and the remaining webs are cut from balsa sheet stock. The aileron's are built into the wing and then seperated after sheeting. The L/E of the aileron and the aileron bay is then capped with balsa. The wing ribs are capped with 1/8" balsa and everythng sanded smooth. If I remember right it took me about 2 evening to construct each wing panel.

The wing panels have 2 anti-rotation dowels in the root rib and there is only one bolt holding each panel to the fuse. The struts are functional. The struts are made from pre-shaped spruce. It required a bit of sanding to smooth them out to prepare them for covering.

I turned the fuse upside down and installed the wing panels, the fuse was blocked up 1" off the floor and the struts were cut to fit and assembled. There are servo pockets supplied with the kit, these are assembled from laser cut parts. I installed Hitec HS645MG servo's for all the control surfaces.

The pre-welded landing gear require a scap piece of spruce stick stock to be epoxied across the top of the gear legs to atatch the fabric. I found the gear to be very strong and they do a nice job of cushioning the landings. No problem with bouncing.

The windows are laser cut and the fit was excellent. Very little sanding was required to get a good fit on the windows. I chose to paint the interior of the Cub before covering. The Cub was then covered with Cub Yellow Solartex. The covering was too transparent for my taste. I had a quart of latex color matched to the Solartex and gave the cub 3 coats of paint. The lightning bolt was masked and painted.
I installed a YDA-56cc engine and I am running a 6 volt pack on the ignition and the radio. The Cub balanced at 28% MAC with no added weight. The batteries are installed in the nose under the fuel tank. The rudder servo is installed just behind the rear seat and the elevator servo's are in the aft end of the fuse. The all up weight is 26lbs. Not bad at all for such a large plane.
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Old 03-13-2011, 11:29 AM
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Default RE: AMR 33% J-3 Cub

The assembly time at the field is about 10 minutes. There is only one nylon bolt in each wing panel that attaches from inside the cabin and the wing struts require 2 bolts each side at the fuse. I leave the struts attached to the wings. It is possible to mount the wings by yourself as I have done this a couple of times but it does help to have an extra set of hands.

Flying: The Cub takes off at 1/2 throttle and will putt along at 1/4 throttle. The light wing loading alows the Cub to just float along at a very scale speed. I was only able to get 4 flights on the Cub before the weather turned sour for the winter. Of those 4 flights I was able to stick the landing on 3 of them without the slightest bounce on landing. The you must really slow the Cub down on the landing or it will just keep flying when it gets in the ground effect. I fly at a sod farm and have the luxuxry of long landing approaches from any direction. Very nice for putting the 1st flights on any model.
I did perform basic aerobatics with the Cub, loops are big and slow and the roll rate is really slow. Make sure you have plenty of altitute before attempting a roll until you are used to the roll rate. Stall turns look very nice and are easy to perform.

I am very happy with the Cub, it was a joy to build and it is a great flying plane. I cannot wait for the weather to warm back up and get some more flying time in. If anyone has any questions about the Cub I am more than happy to answer your questions.

Here are a few completed pics.
Anthony
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Old 03-13-2011, 11:32 AM
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Default RE: AMR 33% J-3 Cub

Some more pics,
Anthony
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Old 03-13-2011, 11:38 AM
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Default RE: AMR 33% J-3 Cub

That is a lovely airplane. Thx for the efforts.
Old 03-13-2011, 12:15 PM
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Default RE: AMR 33% J-3 Cub

Thanks Pat,
This will likely be my last model for a long time as I am now building a full scale Hatz Classic bi-plane. I really enjoy building and decided to go a bit bigger
Anthony

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