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Old 10-21-2012, 05:00 PM
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MJD
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Default RE: Mini Contender slimer conversion

So after a lot of poking and prodding and thinkin', I decided on a few modifications to toughen this thing up for a shuddering glow engine up front and the potential for some decent airspeeds:

(1) strengthening the nose

- sawed off electric motor mount and sanded flush to firewall
- stripped off red covering except for last 1/2" over wing high point
- traced a firewall doubler to 1/16 aircraft ply, marked and drilled the holes for nose wheel bracket, nosewheel pushrod, and top hatch pins, and laminated it to the existing firewall with thick CA
- traced sides from firewall to halfway point on remaining red covering onto 1/64" ply, laminated to fuselage sides with thick CA (and thin from the internal cutouts), then blended in with a sanding block
- traced firewall and 1-1/2" overlap down each side of fuse, 1/4" on fuse bottom, onto 3.2 oz glass cloth. Misted with 3M 77, smoothed in place, and soaked in thin CA (I felt like being lazy and skipping mixing epoxy).

You can see the changes this far in the bare side photo. The other side has just been recovered in scrap red Monocote. It took about as long to type it as it did to do it (ok, not really but it was quick work). The result is a few extra grams weight (very few) and a very stiff and strong front end. It now feels plenty solid enough to hold the engine.

(2) doubling the ailerons at control horn mount. The aileron chord is over 2" at the root, there could be some fair aero loads.

- I cut four strips of 1/64" ply 1" wide x 2" long. These have been primed and painted in white Lustrekote, ready to glue on. I will strip the covering over the control horn mount and on the TE, leaving a small lip of covering, and bond the doublers to the aileron top and bottom each side. This will tie the control horn, LE and TE into a stiff box structure.

(3) mounting the tail surface servos in the rear of the fuse.

- this will put a little weight in the rear to counteract the engine, and of course shorten the pushrods at the same time.

(4) layer of glass int he cowl.

- it is a typical wafer-thin molded plastic part for electric cowling duties. Not suited as is for cutting out engine openings. Need a glass cowl but will make do.


Apart from feeling it needs a bit extra in these areas for this conversion, I am surprised how strong, stiff and light this aircraft is. I am really impressed with the construction. I couldn't build a nicer .15 sport model wing if I tried. I know it will be a fantastic electric sport flier, and I think a sport .15 would be ideal for it as a conversion.

Mounting the Conquest is actually a PITA, it has all the annoying features of rear and side exhaust all wrapped into one package. But I am determined. I have abandoned the idea of inverted cowled mounting - I forgot about the rear exhaust manifold completely interfering with the nose wheel mount. Instead it will be upright or angle mount, still weighing the options and I need to go buy a mount that fits. At that I still have to relieve the firewall for the muffler.

I did a little mock assembly today with the engine rubber banded to the firewall, wing bolted on, tail surfaces fitted, some junk under the hatch just to get a feel for the overall size and heft of it - gut impression in other words. I was happy to find that it looked and felt "right", and you know what they say about that.

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