Mini Contender slimer conversion
 

I spotted this last week when I dropped by the local hobby shop. I intended to set it up electric to add to my electric parkie air force for flying behind our house at the local community center.

But when I started fondling it at home, I started realizing the structure was pretty darn stiff and strong - even the tail surfaces. But very light too. When I held up the wing and the cowl, I immediately pictured an inverted cowled .15 in the nose - the cowl is a good fit and has a generous air scoop already there. Just some exit air is needed. And as an added bonus, look how nicely a Jett 4oz bubble-free tank fits in the fuselage. It's a match made in heaven. I think the tank sits perfectly as-is for a side-mounted engine, but to lower it for the inverted installation I'll cut away some of the central 1/16" ply crutch, and replace the strength with medium hard 1/16" sheet doublers on the inside of the fuse. I'll remove the lekkie motor mount, and laminate 1/16" ply to the existing lite ply firewall then drill for the motor mount. Strip the red covering on the front and a light glass around the firewall and along the fuse sides to behind the LE, then a quick recover job with some scrap red monokote. This will add very little weight but tie the whole front structure together. It won't take much longer to do all that than to type about it. The Conquest .15 admittedly might be overkill, but to me it becomes the equivalent of the hot .61 in the original Contender. This one is an ABC conversion by Ron Young, spins the bejeebers out of a glass-fiber Cox 7x3.5 clone prop.

Seems like a good idea, we'll see!

This would probably be a real treat on a good .10, light gear, 3 oz Hayes tank.

RE: Mini Contender slimer conversion
 

Looks very cool! I really need to get some of my projects goin on too here!

RE: Mini Contender slimer conversion
 

As long as you can get it to balance and the wind loading isn't terminal...

Looks like a fun project!

EG

RE: Mini Contender slimer conversion
 

I can't wait to see this build. I was thinking of doing the same thing. So I'm tuned in for this.

RE: Mini Contender slimer conversion
 

I will run a fairly fine pitch prop to keep top speed down, and use the throttle. In truth this would probably be a really nice sport flier on a good .10 or light non-killer .15 like an FP or equivalent. But I just want to be a jerk and put the Conquest on it.

I posted a bench run of the engine to YT, here the low speed mixture is a bit fat so it hesitates, but you can see what it does to a Bartels 7x3.5 prop. [link=http://www.youtube.com/watch?v=Z3ImgsQJpq0]Conquest bench run[/link]

I realize I'll have to be mindful of flutter. The tail surfaces seem to be framed up of fairly hard balsa, and are quite rigid. If they were more park-lekkie style I would rebuild them from 1/8" sheet.

RE: Mini Contender slimer conversion
 

A .10 might be a better match for that plane, but a .15 should do it if you are careful with the overall weight. The electric ARFs that I have convert so far ended up lighter than the electrical setup indication/recommendation. Most of them have had a rather high wing incidence though, setup to only hang from a larger prop rather than flying off the wing at higher speeds. So check the wing incidence first, it might be set-up as a rather slow flyer and then it will not respond well to more power, unless the wing incidence is altered.

RE: Mini Contender slimer conversion
 

This thing has a big fat symmetrical airfoil like the whole Hots/Pizazz/Twist genre (as Dan Santich was chief designer for TF in the '70's it would be tough to convince me the Contender played no role in inspiring the design of the Hots). I bet I'll find it is set up as a typical aerobatic bird with no slow-flier incidence.

A 2200mAh Lipo weighs about 185g, plus maybe 50g for the motor, and 30g for the ESC = about 265g.

The Conquest .15 is not the lightest .15, at 232g with muffler, plus tank and fuel.

So fueled up maybe 3 extra ounces. This thing has 329 sq in of wing, and projected weight as a lekkie is 28-30oz. The .15 at full tilt generates a bit over 400W of power, so that ought to be enough :D

If this ends up being too much, then I'll either swap the engine or build another one with a .10 or a lighter .15. It looks like too much fun to pass up.

It would be easy to modify the area behind the firewall to accept a Hayes 2oz or 3oz tank, I already checked that out too. But since I already have the Jett 4oz I'll use that. Nobody said it had to be filled all the way anyhow, 3oz would be fine for me with throttle management.

RE: Mini Contender slimer conversion
 

I would save the cox 15 for a bit faster plane and use a regular magnum 15 with a 8x4 prop..........

RE: Mini Contender slimer conversion
 

I thought about that, but this looks fun and I could have it in the air pretty quick. I do have an FP .15 that would be more than enough.

RE: Mini Contender slimer conversion
 

There are many ways to do a conversion, just wanted to give my view of it. Finding the right engine for the job is all part of the fun.
My latest project is a "Mazda" Zlin 50 (arf) with a .15 Norvel in the front. I just love the full scale looks...

RE: Mini Contender slimer conversion
 

I stuffed a .15 Magnum XLS in the front of my HOB P-47 once. Veeeeeerrrrrrry bad elevator flutter on descents over 1/2 throttle. Since you're looking for speed I'd definitely consider some serious reinforcement.

EG

RE: Mini Contender slimer conversion
 

Well, not looking for all out speed and this is definitely not the airframe to do it. But insane vertical is fun. I would be most concerned about the ailerons actually. Many, many years ago, in my teens I think, I built a Sterling Mini Fledgling. The overpowering bug must have already bit me because I figured it needed a .15, and the only one I had was an OS Max .15 with C/L venturi. Flew great! Until flight 5 or 6, when the elevator fluttered off in a shallow dive and it bored itself into a tree.

It is probably true to say the sane approach for the Mini Contender is a plain old sport .15 swinging an 8" prop. But I don't want to get talked out of something that might be all kinds of fun.

My own engine choice aside, my main reason for posting this is that I think this ARF is a great platform for someone looking for a sporty .10-.15 conversion. Steerable trike gear, all kinds of maneuverability, lots of wing area and light, classic look.

RE: Mini Contender slimer conversion
 

When I hit a snag with the Screamin' Demon project I shoulda put that "on hold" and just built one of these..!

RE: Mini Contender slimer conversion
 

A few years ago, I hung a Conquest on a Mini Ultra Stick (RIP). There was really nothing to the conversion (no cowl to fool with), just re-enforce the firewall. (Pretty close show as to what you're doing; I think). Both planes 'bout the same size, & near the same weight. (But, I think that the MUS was a bit lighter; ... sorry no notes, & memory is now a joke). What a hoot a < 2 lb plane, powered by a stout .15 is.!!!!!! This Thread has lit a fire. Think that I'll have to get another "stick. .......... George K.

RE: Mini Contender slimer conversion
 

Well, if that doesn't convince me to go ahead with this nothing will. If it doesn't work out, big deal, no fortunes lost. I was tweaking the wing last night, it is more than beefy enough for this, and I think the tail surfaces are fine too. I might add 1/64" ply doublers either side of the ailerons where the control horns mount.

RE: Mini Contender slimer conversion
 

RIP? Did you rip the wings off? :)

Any flutter issues?

Now if APC only had a 7.5x3 prop.

RE: Mini Contender slimer conversion
 

Worse than that. I was pretty much a "seasoned" beginner. (Translated, means "slow learner".) I finally had a fair amt of success with a Enya .09 powered Mini Super Sportster & a Saito 30 powered "Lazy Tiger". Now that I was an "expert" (so thought I), I bolted the Conquest to the Mini Ultra Stick. A low inverted, WOT pass over the runway (early morning, no one else there) & I was all smiles. That Conquest must have been doing 20+ K with a 7x5 prop. Near the end of the runway, I yanked "full up". Yeah, dumb ***** rookie mistake. The hole in the Geotech is still there. I had to dig out the Conquest. The engine had NO damage. & the two servos on the wing survived. I think every thing else was destroyed. !!! ................ No flutter, in fact no issues at all.!!! ... I think that MAS has left the 8x3 prop in it's Gen II configuration. Haven't screwed it up to the GF3 type. Just clip a quarter inch off each end, & balance. No need to worry 'bout aspect ratio. .... George K.

RE: Mini Contender slimer conversion
 

Sorry, double post. .... George K.

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.

RE: Mini Contender slimer conversion
 

Finished the front end mods, now it's time for the "how much junk will I have to mount in the tail to get it to balance" stage. I had no intention of shortening the nose, that's not in the spirit of the exercise. The prognosis is not bad at all - it is a little nose heavy fitted like this with no radio gear. But I think if I mount the elevator servo in the rear and locate the battery in the rear of the radio bay it should be pretty close. I added 1/64" ply doublers at the aileron horn mounting points, you can sort of make them out here. 1" wide x 2" long, and I cut the film out underneath leaving about a 1/32" border of film under the ply to lock it in.

Finally found a .19-.25 long mount that fit the engine, I Dremeled away what was in the way or not needed. That RE into a fake SE configuration is a PITA. Cool idea but it just gets in the way.

This thing is light, but it's stiff, I think it will be fine.

RE: Mini Contender slimer conversion
 

Have you tried putting the engine rotated at 90°?
That way you could have a pipe along the fuselage and use the rear exhaust option as an advantage.

RE: Mini Contender slimer conversion
 

I don't have any of that hardware, only the muffler. I guess I could order a fusetop header from MACS, it's only $24.95 and what with the rework I had done on the motor why not spend more? :) And to think I was grumbling about the cost of a Profi F2A motor.

My options here are completely upright or angled about 45 degrees. Either way I'd have to relieve the firewall a bit, but the other thing is that the firewall and cowl shape put the carb really high with the engine upright. At least with the angled mount the carb will be closer to the tank centerline.

The rear exhaust option, however, solves that problem completely. I do have a couple of 2.5cc tuned pipes. It would look cool I guess. Hmm..

I forgot this was a trike gear model when I was fantasizing about inverting the engine and tucking it into the cowl. I could deal with the nose gear mounting, but that rear exhaust kinda gets in the way.

The sane option would be to mount my FP .15 instead, but I am determined to fit the Conquest for all the wrong reasons.

RE: Mini Contender slimer conversion
 

After many attempts to come up with an acceptable mounting config for the Conquest, I've abandoned using it in the Contender [&o]. Just too much hacking and cutting and modifying to make it work with the stock firewall/cowl config. So I rooted around in my .15 department, looking at my old OS FP (nice engine but I want more go), MVVS .15 with tuned silencer (even less able to fit with the RE), OPS "speed" .15 SE (.25 power and weight all in one convenient package.. but a sweet engine), and a assortment of others. No go.

So I ordered a Magnum XLS .15.. this I can mount inverted and still use the nose gear mount etc. Much less exciting I think, but it's a strong engine from all reports and will pull this thing around with authority.

Kind of takes away whatever kewl factor I thought this might have, but in the end it just has to work.

RE: Mini Contender slimer conversion
 

Yep, the XLS .15 is a pretty stout engine right outta the box. Got 3 of 'em. It will really haul a 2 lb (+) Lil' Extra around with gusto!!! .... BUT, abandon the Conquest ??? [:o], [:o], [:o] ....................... George K.

RE: Mini Contender slimer conversion
 

It sound like the only obstacle for the Conquest is the steerable nose wheel, how about making it a tail dragger instead?