Prather QM Little Toni build thread - Page 7 - RC Groups
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May 14, 2012, 08:46 PM
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After glassing the wing (top AND bottom ), doing some detail work on the trailing edge, and giving the entire wing a coat of thinned resin, I cut off the ailerons (which I had put in place with hinges, without glue), cleaned up the leading edge and sides of the ailerons, and started sanding.

I dropped all the way down to 80 grit paper on my super-long block to do most of the hard work. Still, I had to put in some extra time around the center section, leading edges, and trailing edges at both root and tip to get them as nice and flat as I liked. Terry calls for that post-glass coat of epoxy, and while it does fill up the cloth nicely and probably strengthen it as well, I ended up sanding almost all of it back off. Sanding primer or spackle would have been a whole lot easier though. I think I'll move straight to primer on the tail surfaces after glassing them.

Then came the fun part... primer. I did a first coat over the entire wing, sanded most of it off, a second entire coat which got me close over most of the wing, and then repeated spot spray and sanding over areas that needed attention. For sanding I primarily used a smaller block with 400 grit and wet sanded. I even found one or two holes I sanded through the glass on the top of the wing once the primer was on... totally invisible prior to that!

Most of the wing went quickly, but there were a handful of spots that required repeated spot applications. For instance, at the corner of one of the aileron cutouts, my Xacto saw had dipped ever so slightly into the trailing edge (the part the hinges go into) that I filled back out with primer. Also near the root at the trailing edge, I needed a few coats to smooth out a small ripple left by my resin coat. And while I was at it, I also filled in around the top center fiberglass reinforcement joint a bit better. It'll all be inside the fuselage once the wing is mounted, but I want a show finish inside and out.

During sanding, I take utmost care to make sure I end up with a level finish... this means always using a block, never putting too much localized spot pressure, and always using long, smooth flowing sanding strokes, both parallel and perpendicular to the span. It was not unlike my initial shaping of the wing leading and trailing edges while sanding the wood. You have to be careful not to sand in depressions or flat spots, especially on the top curve of the airfoil and around the leading edge, where you have the smallest radii (= most risk of sanding through). I like to get the wing wet with a sheet of water and sight down the wing for smoothness.

As an (almost) final step, I put on a sheet of water on the wing and sighted down from one tip to the other, top and bottom. That sheet of water represents your final paint coat and gives you a great indication of how level your paint is going to look at the end of the day. On one of the bottom panels, I was able to detect some subtle low frequency ripples this way ... e.g. ripples that span several inches. They couldn't be more than a thousandth of an inch up and down, but your eye can pick them up in the reflection of other objects off the wing. I got out my medium long block, about a foot long, with 600 grit and used very slow, deliberate, orbital sanding motions with the block parallel to the span over the entire wing top and bottom.

At this point, the entire wing looks like glass... even the primer is shining! The little ripple disappeared. And the triple layers of glass on the center joint, top and bottom, are totally invisible.

I took it out in direct sun the next day to do a final visual check, and wouldn't you know I still found one or two tiny tiny spot depressions... including that same spot near the root near the trailing edge!! I spot-primed them. So now I have to sand those areas, re-inspect, and do another final pass with 600 grit. But it's getting very close.

When this is done, I should have a great surface for painting... which will be the last big challenge on this one. I'll move on to the tail and fuselage next though.
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May 16, 2012, 11:23 AM
Kinetic Sculptor
Originally Posted by rjtw
At this point, the entire wing looks like glass... even the primer is shining!
Once upon a time, somebody told me "never polish your primer". And it makes sense to me that a little bit of tooth on the primer surface would help the paint adhere. Therefore I do try to make the contours smooth (never thought to put water on it; thanks for the tip!) but I always go over the primer with #220 to #320 paper, used dry, before applying the paint. Do you plan to do this?

This has been a great thread so far, please keep it up!


May 16, 2012, 03:14 PM
Registered User
You know, Duane, that's a great question. I've always gone with at least 400, and usually 600, in the past (both on model planes and on a couple of car resprays!!) and have never had an issue. But I think it's best to check with the manufacturer recommendation on the paint in question.

And, frankly, one of the big drivers on 600 grit was the Dupli-Color high build primer (which I saw on your build log -- I love this primer -- thanks!) I just found that I was moving way too much material with 400 grit for a final sanding... the Dupli-Color is really easy to sand off, and I found it too easy to make an accidental low spot. 400 is perfect for the first pass right after you spray it on, though. So, for the finishing touch, I just moved up to 600 and found that the level of control I had there was much more comfortable.

By the way, although I probably should have checked this first, here's a guide I just found for PPG Deltron, an OEM-style car paint which I'm looking at for the Toni as well. It calls for preparation with 400- to 600-grit paper:
Last edited by rjtw; May 16, 2012 at 03:23 PM.
May 29, 2012, 08:18 PM
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I've gone back and filled in a few details.

- I've created a small fillet on the bottom leading edge of the wing, to fair it into the fuselage. I probably should have done this before I primed the wing, but my thought was to leave it until later to both allow for completely unrestricted sanding of the leading edge (otherwise the fillet would interfere with block sanding in that area) and also to only build up the fillet after finalizing the wing saddle area, which effects fit of the wing and thus size of the required fillet. I'm happy with the result, though.

I first taped off the fuselage and surrounding areas of the wing, removed the primer under the fillet, and built up a first pass with 45-minute epoxy with a large dose of micro-balloons to make a sticky putty. I used a scraper coated in denatured alcohol to form the initial shape of the fillet by simply bridging the gap between the bottom forward lip of the wing saddle (which projected below the wing leading edge by about 1/8" at the deepest point, right at the centerline) to the area at the aft edge of the landing gear box. I made sure that, if anything, I slightly underfilled at this point because I didn't want to spend a lot of time sanding... this stuff gets pretty hard when it's fully cured even with all the micro balloons!

At the same time, I filled up the bottom horizontal leg of the landing gear with the epoxy mixture, to fair it out all the way to the wing surface. I Scotch taped around and into the forward and back edges of the little landing gear box I made so that it wouldn't stick. This made a nice fit fore and aft on the landing gear fillet, and the gear popped out nicely when the epoxy cured. This fillet does nothing more than fill up the landing gear box... it does not protrude aft beyond that onto the wing proper as it doesn't need to, to make a smooth contour from the fuselage saddle lip.

After another spot application or two of epoxy/micro balloons, and a final layer of Bondo putty which was mostly sanded off to fill any remaining irregularities, I topped it off with a layer of 3/4 ounce cloth faired right into the finish. I also put 3/4 ounce cloth on top of the fillet on the landing gear. With a spot coat or two of primer, the wing can now wait for final prep prior to painting.

- I then drilled back out the 1/4" holes in the landing gear (going through the epoxy fillet in the gear itself) and countersunk to accept the 1/4-20 nylon bolts supplied in the kit. I had also previously drilled and tapped the receiving blocks in the fuselage, and also countersunk the location for the rear bolt (which is a 10-24). As the fillet on top of the landing gear is very thin around these bolts, about 1/16th or so, and the bolt heads are 1/2" wide, the countersink goes right through to the very base of the aluminum gear. Best done with a drill press on slow RPM.... which I really need to purchase one of these days... Seriously though with a regular power drill (no press) it's very hard in general to stop chattering. In this case, I did just use a power drill and the aluminum gear itself provided a solid enough material to prevent chattering and gave a clean countersink. For the aft holddown, though, where there is only a dowel, I found the best way was to literally twist the countersink bit completely by hand to get a good result.

This is all pretty similar to Terry's instructions, except that Terry never tells us if the gear itself is left removable or if it is permanently glued into the wing. I've made mine removable, but that's only because I didn't feel I could get the finish I wanted around the base of the gear if I built the gear into place. However, I've left the fillet over the aluminum landing gear bonded to the landing gear itself because it's so thin... 1/16" max at front and about 1/8" max at rear (I was originally pondering whether this, too, should be removable).

- Finally, I've glassed the stab, elevators, fin and rudders both sides with 3/4 ounce glass cloth. I'm beginning to love this stuff again, when it's done right it really comes out nicely. I also laid in a strip of tow top and bottom on the stab under the glass just for fun, though hardly necessary (it did make the stab virtually unbendable though!) The trick with this fiberglass cloth, as always, is how to handle the leading and trailing edges. More to come later!
Jun 02, 2012, 10:17 AM
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Looking good! If the finished product is as nice as the work that's going into it, I'm sure it's going to be a great looking airplane.. can't wait to see it!
Jun 22, 2012, 04:59 PM
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Yeah, me too Fizz! Thanks for all the nice comments you've made along the way.

Been totally swamped at work so not much happening on the airplane -- but getting close to finishing up the primer on the tail surfaces. I decided to prime them before mounting, because I wanted to be able to use my long flat sanding blocks on all surfaces. From past experience, once those tails are mounted on the fuselage, I just don't get the results I like because I can't block sand across the entire span. So the plan is to get them essentially ready to paint, cut the slots on the fuselage to accept everything, scrub away primer to get a good glue joint, glue on and then touch up the joint area. I will say I'm happy with going straight to primer after putting on the glass; the weave is super easy to fill. I'm sure I'm saving weight over using an extra coat of resin to fill the glass, and I know after doing that on the wing that I'm saving a whole lot of extra sanding time.

Now for the fun stuff. I was really inspired by this log. Just discovered it yesterday:

It's a 200MPH+ electric custom Reno-like racer. Beautiful airplane and astonishing speed. Looks like it was running the Neu BAM on 9S and a custom 8.8x10 prop. So why not aim a little higher for the Toni?

That sent me back to Motocalc. With a 1115/1Y or similar motor (1900kV) on 4S turning a 7x8, I'm at about the same speed as the 1.5Y I discussed earlier on a 6x5 (mid-160s pitch speed, but I'm more comfortable that it'll get there with the bigger prop). A 7x10, 196MPH. A 6.5x10 shows 207 MPH. And using less amps then the 1Y too. Or for over the top, go 5s with a 6.25x9... 231MPH. I like the additional variety of configurations the lower kV gives -- mild to wild!
Oct 08, 2012, 01:12 PM
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Time to bring this thread back from the deep freeze! It was a long and busy summer, almost none of which spent on airplanes

I ordered my Neu 1115/1Y in June and received it in September. This is a 2800kV motor and I'll be using a 6x5 or 6x6. After some back-and-forth with the friendly folks at Castle on whether to add a rear support or not, I went with a front-only mount setup. I happened to have some sample carbon fiber 'sheet' material that ACP Composites had given to me earlier in the year when I visited them in Livermore. It's preformed, about .050" thick and incredibly tough. I cut out five round disks -- just big enough to fit inside the nose of the Tony, which is made for a 1.75" spinner -- and laminated them together with my handy ACP resin and squeezed together between thick aluminum sheets in a vice for 24 hours. This left me with a nice 1/4" thick, virtually indestructable yet very lightweight nose motor mount.

I also purchased a Tru-Turn Turbo Cool 1.75" spinner and decided that I will try a setup that relies only on air through the spinner for cooling. (If anybody has tried this and it isn't enough, let me know!) By the way, when you order this spinner, it comes be default with cutouts for a very large propeller, so be sure to order it with custom cutouts for whatever prop you'll be using. I'm going to start with a Cam Speed so sent them a damaged 6x6 I had lying around.

After drilling through the carbon plate and countersinking for the four motor mount screws, I used a 3/8" Dremel grinding wheel to bore four big holes surrounding the four motor mount screws. I'll post pics later, but my initial impression is that this setup has at least decent cross-sectional airflow area and I'm cautiously optimistic that it should provide adequate cooling. Still have to decide where and how to place exit vents though.

I should back up a moment and also say that I really wasn't sure whether I'd have to cut into the side of the fuselage or not (for instance, cutting into the area originally intended for the glow engine). As it is, the fuselage is nice and solid, with only some tiny molded-in lines to indicate where to cut for the glow engine to drop in. (The original design calls for the glow engine to then be covered by a removable right cheek cowl). My plan has always been to not make that cutout if at all possible to preserve strength -- especially with a front-mount -- and that would allow me to permanently attach the special right hand cheek cowl I made. The downside is that motor access would then only be through the nose ring and through the wing saddle area. But the Toni's nose is so long and narrow, I can barely even get my hand in through the wing saddle, and there's no way to reach inside through to the nose at all. So I wasn't sure if this plan would work or not. Now that it's done, though, I think I'll be fine with access only through the saddle.

I mounted the carbon disk by cutting an approximate 1" hole in the front of the nose area (behind the spinner), then applying just a small amount of 45-minute epoxy around the area where the disk contacts the front inside of the fuselage. I mounted the motor to the disk, fed it through the wing opening to the nose, attached the prop and spinner, and placed some 1/64" ply spacers between the spinner and the nose ring., then set the position carefully and finally taped everything firmly in place until the epoxy set. (If I need a little more space between the spinner and fuselage, the spinner can be set on the motor shaft at any location). Later, I came in behind the carbon disk with a strip of 3 ounce fiberglass, about 3/4" wide. I fed in more ACP resin (by sucking some into a straw, then sticking the straw through one of the cooling holes in the front mount and letting the resin flow out) and positioned the glass to overlap the back of the mount with some angled tweezers. I then hung the fuselage nose-down to dry, so the resin flowed to form a really nice ring (filling the gaps left by my initial epoxy 'tack' of the mount) all the way round.

Pics to follow!
Oct 29, 2012, 04:59 PM
Kinetic Sculptor
Beautiful, beautiful work! And with that motor, she will certainly hum right along.
Oct 29, 2012, 06:26 PM
Registered User
Can't wait to see the finished product, and hear flight reports!
Oct 30, 2012, 10:02 AM
Carbon fiber is our friend
Steve C's Avatar
Looking good.

If you're going to have any problems, it's going to be with that spinner causing vibration. The small motor shaft, long spinner and high rpm make for trouble. If there's even the slightest wobble or un balance, it gets amplified by the long nose. Having the motor mounted securely helps though.
Oct 30, 2012, 03:36 PM
Registered User
Thanks for the encouragement! I'll take all I can get I'm re-creating my own little monument to 70's pylon racing and have really enjoyed being able to share the kit and my own take on the "traditional" techniques as I learned them at that time.

For anyone interested, here's another website that gives more background on what these racers were like back in the day. It's by Dave Shadel, one of the top F1 pilots of the time. This is a fantastic read:

On another topic... Steve, I've been concerned about vibration as well. The prop shaft is only 1/8", and with prop and spinner mounted, it's a little unnverving to be able to put a little pressure on one prop blade or the other and be able to flex the prop shaft slightly. What would you recommend for balancing -- any specific balancer or technique? I used to have a simple cone balancer but it's long gone and I'll have to pick up some kind of balancer anyway. I saw an article online somewhere about even using an iPhone for final balancing which sounded interesting -- the idea is to first static balance, then use the iPhone to measure how vibration changes as you put on the prop or spinner at slightly different circumferential locations on the prop shaft to determine a minimum point. At 34K estimate RPM I'm going to have to be right on the money, or else
Oct 30, 2012, 05:24 PM
Carbon fiber is our friend
Steve C's Avatar
I've had trouble with this stuff too, even if the spinner and prop are balanced. It's probably a good idea to set up a dial indicator to make sure the adapter is true. If that's off, it makes it just about impossible. After static balancing, I usually run things at low power and feel for vibration. Then I stick a small bit of tape on a blade and see if it gets better or worse. Worse and you swap to the other side and try again.

Tru Turn has always been pretty good with balanced spinners, but it wouldn't hurt to check it too. If you have a long 1/8 shaft handy, you can put the adapter, prop and spinner all on that and stick it on your 4 wheel balancer.

I hate to say I think 1/8 is too small, but don't let me stop you from at least trying it.
Nov 02, 2012, 11:59 AM
Registered User
I contacted Castle Creations and Neu Motors with my concerns about the 1/8"/3.2mm shaft. Part of the issue here is the Tru-Turn spinner, which clamps on to the prop shaft fairly far out and even when fully bottomed out it leaves the first 1/4" of the motor shaft exposed. I imagine the spinner also somewhat larger/beefier than what typically might be used on this size motor. In the event, after explaining all this to the nice folks at Neu Motors, they have graciously agreed to build me up a new motor with a 5mm shaft free of charge. They really stand behind their products, and beyond that in my case, they obviously really care to see their customers succeed. THANKS NEU MOTORS!!

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