Hi, All-

I have been selected to do a build thread on RCRCM's most serious design yet, the "TOBA" F3B model.

http://www.soaringusa.com/Toba-F3B-F.html

I'll be building on it a little at a time, and will get to fly it a bit before it leaves my hands, and gets to the members of the US F3B team for more testing and impressions.

More to follow, stay tuned to hear and see more about this reasonably priced F3B model.

Parts weights:
Wing half @ 650g each
Tail half @ 49g each
Fuse @ 230g with cone and pushrods

R,
Target

I learned today that the frames that came with the plane fit the Hitec HS125's perfectly. JR DS368's also fit the frame insides perfectly, as do MKS 6125 mini's, although the holes are perfect for the Hitec's.

Also discovered that The 125's and MKS 6125's would fit below a flat cover, but anything a bit thicker in the aileron would need the bulged cover.

In the flap bays, a 761 or 368 will just fit under a flat cover as well.

I'd bet that a 3421 MIGHT fit under the bulged flap cover IF you took off the lugs.

R,
Target

Tonight I fit the fuse and tail pieces together, and came to the conclusion that the 18mm ballast tube included would only fit the plane if no tow hook were used in the fuse.....

So, I fit the tow hook I had in stock, and looked at the fuse layout.

I have decided to try to save the weight behind the CG by NOT USING the supplied hollow CF rods, they weigh a LOT more than snakes, and most of it is behind the CG....

Worked more on TOBA today...
Finalized the pushrod housings and tail linkages. Happy with the outcome, should save me a couple or more ounces in the nose, I hope.
My wings came with shipping damage from China "pre-crashed" a little, so I worked for a litte on the repairs. I didn't want to get bogged down making a pretty repair, so just did a CA down and dirty fix, with minimal sanding, no filler and a couple squirts of Krylon.
Its far from good, but should look good from far (away)!

Pics attached.

Looks like the flap and aileron bays will both get 761's and the fuse will get either DS11's or Airtronics 94809's if I can get my mits on some.

Tomorrow afternoon I'll start on the wing servo installation. It should go very quickly.

Did some more building on the Toba.

I knew that the geometry on the ailerons was less than ideal, and I should have changed the horns from the beginning, but I wanted to have a RTF plane for the weekend. As soon as I switch from my soft bench test CP1300 x 4 battery to a 2S LiFe, Poof(!) went a 761 on unregulated 2S Life.

After that happened, I resolved to change out the aileron horns, and probably the flap horns as well. The aileron horns were very short, and the hole was @ 2-2.5mm ahead of the hinge line, giving great up aileron, but terrible down aileron.
If I were to only use this plane on the slope, it probably would have been OK, but since its an F3B plane, it will need a decent amount of down aileron for launch camber, and the geometry was really bad for holding that position under load anyway.... So it needed to change, and, I knew I wasn't going to pull the original servo, and leave the horns so short.

I also finalized the fuse install with radio gear and nose weight, etc. Came in at exactly 80oz at 98mm. I am almost certain I will bring the CG back though.

Pics....

I decided to take one more day to change out the flap horns as well.
While the flaps worked reasonably well, they were obviously off a little form one another (you could see it visually), and I had to use the balance feature on my JR 11x to get the flaps to come down evenly on the throttle stick.
PLUS, they had a LOT of throw, for the servos travel, so I figured it would be best to rig them to have just enough travel for full servo throw for better centering and torque.
I am very happy with the results; it did not take much time at all, and the flaps are dead-even on the throttle stick with no adjustments whatsoever.
Centering and resolution is vastly improved as well.
Pics attached.

Toba is pretty much ready to maiden.
Also, I have ordered brass bars for ballast from www.speedymetals.com
My thought is that even though the wing ballast slot doesn't start until after the CG, maybe by adding some slugs to the forward (or aft) cavity of the wing joiner, the CG will be retained (!?) I hope.
I'll report after the brass gets here and I get time to cut it (probably a couple of weeks.

I have opted to NOT use the stock bulged covers.... So Vespa, you have won this argument.
I used Merrill's "Servo Bumps" painted red on the inside for the flaps, and he's supposed to hook me up with some flat servo covers that have a tunnel for the aileron linkage. But I don't have them yet.

Here's some pics of the finished (except the aileron covers) plane on my new back yard paving stones.

R,
Target

Well-
I was bushed after a long two days offshore blowing stuff up, and I have to be back at work tonight, so, instead of going to the slope race and wasting time waiting for wind, I decided to be productive and cut up the brass bars I bought for ballast for Toba.

The plane holds 3 large slugs in each wing, and 3 slender slugs in both the joiner cavities.
Total ballast is 40.5 oz, or 1150g....
So, with the empty weight at 79.5oz or 2254g, the full weight moves to 120 oz or @ 3400g full. I think that is good enough for sportsman F3B or F3F.
If one went to molded lead, you could likely add about another 10 oz or a little more.

The CG moves from my empty CG of 100mm to 101mm if I fill up the after cavity in the joiner, while filling up the wings.
The CG moves to 99mm if I fill up the forward cavity of the joiner as I fill up the wing.
The CG moves to 97.5mm if I fill both joiner cavities and the wings.

See attached pics.

One point I don't think I covered, is that I used the "male" MPX Plug (female plastic housing) in the wings, and the "female" (male plastic molding) on the fuse. The plugs stick out of the fuse, but since the fuse was molded with a nice little recess, just opening the hole for the pins means they will NEVER push into the fuse, and that there is plenty of clearance in the fuse for the wires.... Why I have EVER done it differently is unknown to me....

Hi Target,

Thanks for the detailed photos.
Love the paint scheme.
Any guess at the AUW?
I'm in for 2365g.

I will not guess just yet at the RTF weight Chris, but you might be close indeed.
The fuse is nice and light; I wish the tails were a bit lighter, but I will wait and see how the build goes, before casting judgement....
There are several things that I like about this design.

R,
Target

Cool! It'll be nice to have another low-cost alternative to the Strega. And if this can really handle F3B launches it hopefully signifies a major revolution for RCRCM's materials/resins/methods. Even if it can't do B it'd be nice to have a sleek new bargain plane for F. Shame about the bottom-drive ailerons though and very strange considering that every other plane they make is bottom hinged with Hammond's nifty built-in horn bulge. Oh, and please RCRCM, please throw away those crazy bulged servo cover molds! Flat covers will be fine, thanks.

I hear you on the aileron hinging, but I'm not certain that I agree on the bulged covers...At first, I thought the same as you, but after a while, I see the logic.
If your servo choice requires a bulged cover, you are good with these.
Remember, this plane is aimed at the entry-level or budget F3B guys, so just maybe, they will be using 761 or 368's or some other selection that won't fit flush??

That's my thought. If RCRCM wanted to go with two sets of covers included, then a set of flat covers would be a good addition, and cover the option of thinner servos...

Just my thoughts.

R,
Target

Yes, but 761's and 368's are far more expensive than DS095's, which would fit fine and I suspect are the intended subject of the nice included frames. Now, maybe they want folks to be able to throw some old HS-85MG's in there or whatever, but appealing to the lowest common denominator is not a great way to break into the competitive F3B market, even at the low end.

At any rate, a simple flat sheet of carbon with 4 little bubbles near the center would cost them only a dollar to make and would provide the option of perfectly flat covers or flat/bubbled covers depending on how the sheet was cut. But moving on, post some more pics!

The frames are probably for hitec 125mgs.

I have just ordered a full carbon version of Toba. The shop in HK where I got it is offering free shipping worldwide until 12/11/11... Awesome considering I got a quote of $1135 USD to ship a 2nd hand F3B from the US to Perth !!!
This will be my first brand new composite glider,I`m excited
I will be watching Targets build closely
Ian