Twin EDF Mig-25 Foxbat - RCCanada - Canada Radio Controlled Hobby Forum
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Old 10-14-2016, 02:25 PM   #1
Dutkoski
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Twin EDF Mig-25 Foxbat


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Well, here we go again. Decided on a 1/9th scale size, 61.33333" wingspan, 87" long from the nose cone to the back of the tail cone. Width of the fuselage where the fans might be mounted is 14.75" and 7.5" in depth. So plenty of room for options, 90 mm, 102 mm or 115 mm fans. There are two Change Sun 90 mm sitting on the plans. This would certainly be the lightess version which is a big plus.

Went to Paragon and got all the views enlarged, only cost $9.90 so was well worth it for the six sheets of paper.

Like the smaller 70 mm version, this will be designed around 1/2" and 1" pink insullation foam. Also, the wings, horizontal stab and vertical fins will be removable for ease of transport. I could see a lot of hangar damage to these items if left on.

Not that I'm cheap, but going to do this model on a tight budget. ie: retracts will be the large inexpensive ones from good old Hobby King. Although I have the fans, in all the sizes and motors too, I might check out some of the modern fan and motor combo's from X-Flight, good guys to deal with. But, the ESC's will be reliable Castle Creation products.

What I really like about it, is it's size, it's pretty big, but not silly huge like some sport scale models.
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Old 10-14-2016, 10:36 PM   #2
Dutkoski
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Re: Twin EDF Mig-25 Foxbat

Found I had enough 2" thick foam to cut one wing. So dialed in the dimensions into the computer, cut the blank and cut the right wing. Hope it turns out. Tomorrow, I'll get another sheet and do the left wing.

I'll be removing 1/4" of the leading edge and 1/2" of the trailing edge so I can replace the foam with balsa.

The entire surface, including the fuse will be covered in 2.3 oz fiberglass and epoxy.
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Old 10-14-2016, 11:00 PM   #3
Dutkoski
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Re: Twin EDF Mig-25 Foxbat

That was better than I had hoped for, the wing panel fitted exactly to the drawing. The dark spot along the root is where the airfoil is the thickest and where it was only the wire thickness below the foam surface, but it's uniform with the rest of the surface. So the wing root thickness is literally just shy of two inches.

For those interested, my airfoil book indicates the scale airfoil to be a TsAGI SR-12S which is Russian. I checked it out and found it was very simular to the TsAGI S-8 that I have on my foam cutting program. Also the 12S is a lot thicker so it would need stacked foam to get it cut. So, if it's good enough for the Mig-29, it's good enough for this model.
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Old 10-15-2016, 01:20 AM   #4
Dutkoski
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Re: Twin EDF Mig-25 Foxbat

Got the vertical fins programed in the computer, but only got one cut successfully. Slight mishap with the hot wire bow. But one came out really nice. There will be a balsa cap on the foam fin to give the proper scale profile. Like the wings, there will be a balsa leading edge and trailing edge.

Also programed the horizontal stabs but for some reason the cutting program doesn't like it, error message about exceeding the stepper motor speed and it'll only cut when the speed is set to .001 mm per second. It's getting late, will figure it out tomorrow.
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Old 10-16-2016, 04:03 PM   #5
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Re: Twin EDF Mig-25 Foxbat

The project is progressing nicely, both wings and vertical fins are cut. The horizontal stabs need to be redone, the heat setting and wire cutting speed need to be tweeted, kinda melted the tip section. Will be done tonight though.

Tackled the huge radome nose section this afternoon. Cut foam circles out of 2" foam, the larger five sections were cut like donuts so it will be mostly hollow. Did all this with the bandsaw.

Here's the disks stacked while the five minute epoxy cures. It's pretty big, the largest disk is rough cut to 5 1/2" but will be sanded down to 5 1/4" to blend with the first one.
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Old 10-16-2016, 04:08 PM   #6
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Re: Twin EDF Mig-25 Foxbat

Used a large razor knife to carve away the excess foam, unfortunately for me, I was a little too aggressive in carving and went beyond what shoukd have been removed in a couple of spots, but, that's what drywall compound is for.
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Old 10-16-2016, 04:15 PM   #7
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Re: Twin EDF Mig-25 Foxbat

After 15 minutes of sanding with 100 grit paper glued to a chunk of foam to act like a sanding block, the radome turned out pretty good. Was curious as to the wieght as it seemed very light, yep, 2 oz. exactly. Not bad at all for that size of foam.

Applied a skim of filler to the whole radome to fill in all the nicks and scratches, and the places where I carved too much away.

I will be cutting away a small portion of the point so I can insert an aluminum or brass tube. The Mig-25 has a sensor rod sticking out the front, I want it removable.
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Old 10-16-2016, 09:15 PM   #8
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Re: Twin EDF Mig-25 Foxbat

All sanded, looks and feels nice and round. Weighed it again, 2.15 oz. Now, if only the rest of the plane can be designed and built as fast. ��

Did some calculations for the construction of the fuselage, figure on using 1.5" foam for the bottom surface and 1" foam for the sides and top. Need thicker foam on the bottom so I can sand and shape the contours of the nacelles and the valley down the center.

But, that's it for now, off to Hamilton for a week.
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Old 10-20-2016, 12:18 PM   #9
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Re: Twin EDF Mig-25 Foxbat

Love it! The Foxbat is a very cool plane. Following with interest
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Old 10-24-2016, 11:31 PM   #10
Dutkoski
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Re: Twin EDF Mig-25 Foxbat

Made the patterns and cut the parts to make up the forward portion of the fuselage today. Even got them glued together with 5 minute and 30 minute epoxy. In it's rough form before carving and sanding, the section tips the scales at 10.1 oz's. the sides are made from 1/2" thick sheet foam and the top and bottom is 1.5" thick foam. There will be a substantial amount carved off the corners as the front is round to match up with the radome. But that's tomorrows project.

Ordered the retracts today, Hobby King was out of stock, but located a USA hobby supplier on E-Bay that sold the same retracts, and with the free shipping, turned out to ve less expensive.
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