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Design => Stunt design => Topic started by: Dennis Toth on July 01, 2014, 07:49:10 PM
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Guys,
Now that the building board clear (again) I wanted to do an update on my electric profile a kit bashed Tutor II. This was my first venture into electric stunt. I liked this ship because it had a deep over wing fuse section that allowed me to include a cutout to mount the battery through the fuse and back over the wing to correct the CG without adding weight. This worked fine but does put the vertical CG a little high. All in all it has been a fine ship and over the past several years I have learned a lot about electric power with it.
The ship has a few short falls that I think can be corrected to make it a more competitive profile machine. To me the big weakness is the thin aft fuse section that allows considerable twist to the tail section. This causes the ship to kinda go all over in the wind. To strengthen this I added a new aft fuse outer skin from 1/64" plywood. I added formers over the existing skin and increase the aft section to 1/2" all the way back (it is tapered to 3/8" now). I used a little curvature to add stiffness and reduce the flat fuse drag a bit, also added some 1/2" fillets and reduced the height about 1/2".
The other annoyance I have had with this ship is in the wind. It has a very long tail moment (19" hinge to hinge) it seems to want to turn around a point pretty far back of the CG. Normally, I will try to move the CG back a bit then reduce the flap movement relative to the elevator. The current ship has a stab/elev that is 17% of the wing area. I added a new stab/elev that is 23% of the wing and to get the corner a little sharper shorten the tail moment to 17" (H to H).
The ship is now in final re-assembly. The tail is now very stiff and the weight increase was about 1/2 oz. I intend to work on the motor/battery package to reduce weight an oz or so.
Best, DennisT
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Photos?
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Guys,
Well I finally got myself motivated to get this finished so I can resume some other build projects. Attached are a couple of photo's. One shows the original tail next to the new (new one is about 15% bigger), the second shows the ship ready to go. The two main changes were to stiffen the rear of the fuse and second was to shorten the tail moment to 17" (was 18 1/2"), last was to increase the tail by about 15% to get it to about 23% of the wing area. Stiffening fuse is probably the biggest change. The original fuse is very thin at the rear and twists a lot in the wind causing the ship to kinda wander. The shorter tail moment was to get it a little crisper in the corner coupled with the increase in tail size which also allows a little more rearward CG location, again to smooth/crisp the turns. Hope to do some test hops this weekend.
I did do a motor test to make sure all was hooked up correct. Seems just like it was when I took it apart for the rebuild. 11x5.5 APCE-P, 9500rpm, 35amps, battery is a TT Pro Lite 4S;3300mah. Ship all up is 62oz with battery. I am looking into going to a 5S pack around 2500mah which should save a couple oz (this ship can use all the weight reduction tricks I can pull). I also want to try the 12x5, because of the weight it will likely need more prop.
Best, Dennis
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Flew the ship yesterday, it felt really good. Seemed smoother then the original set up had a solid corner. Turned and stopped on the marks. This ship is gonna be a great weapon this summer. Worth doing the mods.
Best, DennisT
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Dennis,
I just saw this.
You didn't mention changing the stab & elevator.
What iron-on is that?
Perfect color match.
Field tomorrow!