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70cc Mamba build thread

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Old 01-23-2019, 08:12 AM
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daveopam
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Default 70cc Mamba build thread

I thought it might be interesting to do a little build thread on this Mamba. A few things about me. I am a budget flyer so a plane like this is a rare treat. Along those same lines I have to use parts I have on hand. I am picky about things being right so I wont use any junk but this may make some of you question my choices. Also this is going to be a few month project. Time is hard to find.

For starters this thing is bigger than I thought. The 50cc extra I am replacing is a touch longer but the diameter of the fuse and cowl as apples and oranges different. After checking all the parts and sorting hardware I got started on one of the 4 wing panels. A words of cation. Each aile has 5 hinges. One of the hinges on each aile is turned 90 degrees so the surface will stay straighter during bagging (at least thats my assumption). So if you are like my and start deflecting the surface as soon as you pull it out of the bag you will ruin one hinge. It's an easy fix with a 1/4 Dubro I had on hand. The fit on this first wing half was excellent and required no extra work in the hinge area. I thought while I was making epoxy I would prep the control horns also and do it all at once. Another word of cation.The horns for the aile are slightly different than the horns for the elev. So count them. the ones you have 4 of are elev. The ones you have 8 of are aile. There are also several choices for the rudder as this can be set up for pull/pull or push/pull.
The install of the hinges and control horns was straight forward with no issues. I did have to clean the holes for the horns a little but that's to be expected. The holes were already opened which was nice. It looks like a soldering iron was used so a little covering residue is going to be in the way.
One of the pics I'm posting today is the cabane mount and it will be installed when I put the servo in.

Thanks guys, question, comments and hints are welcome.

david


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Old 01-31-2019, 07:35 AM
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A little more progress. Both lower wing halves are done. Servo screw is missing because I don't have it centered as yet. One thing I like. The treaded rod has reverse threads on one end and a small wrench that fits in the center of it. This allows for fine tuning of the length without removing either end to rotate the ball link. The book gives the length of the rod on center as a good starting point. So it should be close. One mistake I did find. There is no way to get the 3+ inches of down throw on the ailerons. The supplied control horns hit the wing at 2-5/8" of throw. Now this is probable plenty for me as I am no QuiQue, but it may be an issue for some.
I really like the setup on attaching the cabanes to the wings. The blocks took a little trimming to get seated right but it was minimal. The fit is so good thin CA probable would have held them in place but epoxy takes an worry out of the mix. The rod that pushes through the cabanes and through the blocks is in the 4/40 range and is a very sturdy piece. Field setup is supposed to be a 3 minute job. I firmly believe it will be.

Thanks, David



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Old 02-03-2019, 08:02 PM
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Old 02-04-2019, 07:31 AM
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Much progress as can be seen above. Upper wings hinged and ready for servos. (waiting on parts) Elevator servos in. I decided to go with two instead of one. QQ says use one 400oz servo with joiner wire to save weight. I fail to see much weight savings. The joiner wire weighs half of what the 2nd servo weighs. Add the epoxy I don't think there is much savings. I also prefer to use 2 servos on the the elev. I think it's a tighter more reliable set up. Just my opinion of course but it's my plane. The stab is in but not glued. I measured from the wing tube to get it straight but wanted to do the same using the wing tips. I got the wing bolted in but ran out of time. I am going to need to power up the Aile servos to get a good stable place to measure from.
These steps went pretty smooth. Small issue with the 2nd elev servo opening. The covering is cut for the location if you are going to use one servo. On the opposite side of the fuse there are 2 ply trays made for the 2nd elev servo and the rudder servo if you are going to use a push/pull on the rudder. Cutting the covering is no big deal but these servo openings are not the right size. There is no way two servos would fit here. I had to cut away 1/2 of the ply that divides these two opening to be able to fit one servo. The size is right fore/aft but not up/down. Not a big deal but I am picky. Only other thing on the top wing halves. Just like the lower wing throw is going to be limited to when the horns hit the wings. There is no way to get 3+ inches QQ calls for on high rate.

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Old 02-11-2019, 07:16 AM
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More progress. Stab is glued in. Elev halves are epoxied on with control horns in. Fin and tail wheel are on. Control horns epoxied in rudder. Everything went pretty smooth here. I did vary from the plans slightly. Since I am using two elev servos I thought it would be a good idea to fill in the holes made in each half with dowel rod. There is no hinge in that area but it is close to the control horn. I was afraid leaving a void there might weaken the structure.
David


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