This is turning into one of those hot rod & motorcycle hurry-up build shows.  I started in mid-March and want to be flying by June 1st.  I don't want compromise quality too much, but I don't want to fly in 2017 either.  As you can see, I prefer the modular build, painting as I go.

I carbon-veiled the nacelles, body and outer wings.  I used silk on the stress area of the wing.

Block-sanding the ten attachments to the wing is the next chore.  Counting wingtips, ailerons, outer & inner flaps, and nacelle fairings there are ten blocks that need to be blended into the trailing edge, top & bottom of the wing, and each other.  And also make right & left match.  Not impossible, just a lot of hand work.

I will have to edit the pitcher to spell Mitchell correctly.

Thanks.  I went with the 2.4.  I was never entirely happy with the Roberts 3-line system, although I used it for 50 years on single engine models.  My confidence was really shaken when a new 3-line bellcrank failed on the first day of flying.

The 2.4 system with a Y-cord and two servos sure beats a mechanical twin or multi.  

This is my scheme for aligning the main gear.  I left on leg loose and clamped the wing to my bench, then solidified the loose leg.

I went with outdoor leadouts to get them on the vertical CL of the model.  They are now MORE adjustable than any inside leadouts and the ribs are not slotted.

Thanks for the advice.  I'm sure this will take a bit of fiddling around, but not as much as doing the same thing with mechanical.  I have two years experience with getting 2.4 to work OK on several single engine planes.  

I like the ability to rev the engine while I'm walking out to the handle.  Also the ability to dial down the idle speed with the throttle trim BEFORE I call for takeoff.  That way, if it quits, I'm still off the book.

Here's the Harbor belt sander I bought to deal with the many parts that need to be sanded.

Here are the engine nacelles being hollowed-out and sheeted-over.  The back ends are sheeted to eliminate the step at end of the doublers.  Also the blocks I made to align the nacelles, wing, and fuselage.  

I went to 3 MM bolts and t-nuts.  The MUCH bigger diameter of the t-nuts is intended to prevent the chronic problem of t-nuts spinning loose.

I used to use the 2/56 Dubro stuff with mechanical systems.

Now, with small servos I go with the RC type screw connectors and small diameter wire.  I find that even 2/56 stuff is too heavy for the servo arms.  I use thin wire with a z-bend to relieve any stress caused by overtravel.

I noticed quite a few off-scale issues with the Brodak kit design.  I corrected some of them.  
The Brodak B-25 kit is one heck of a good deal for the price.  The laser-cutting of the wing parts was a huge piece of work that I didn't need to do.

This is only my second twin, after a successful 1/2A.  I saw several successful examples of this kit design, so I accepted Pete's engineering, up to a point.

The kit design was "scale enough" to win Profile Scale at The Brodak Fly In and the AMA Nats.  I'm making this for Fun scale.  If I build one for
 Profile I will correct the other issues.

I would like to build a B-25 or B-57 for Sport Scale, but I will not waste my time building a model that will be penalized under the "NO retract" rule.  You cannot expect to win contests if you build planes that are penalized, even if the penalty is small.  Contests are won by less than a full point.

The Autocad drawing you posted is for somebody else's STUNT B-25.  I am building Brodak SCALE kit designed by Pete Klepsik.

The B-25C posted is 3/4" = 1' scale for Profile Scale competition. The C/L kit is my design.

Pat

The Brodak kit appears to have a scale factor of 6.8% or 14.7-to-1.  So it's a little bigger than 1/16 scale.

Wing area is a fuzzy thing in profile scale. You gain some effective wing area due to the road-killing of the fuselage and nacelles.  Funny things happen, like the landing gear comes out of the wing instead of the nacelle, or else if you make it come out of the nacelle, but then it's too wide-track.  

Yesterday was a day of tool-making, as in jig-and-fixture.  Things don't align themselves.  Once I get the tool mastered with just the nacelles it will be time to add the fuselage.  

Radio check? Lima Charlie.  Five by & tree top high.

The servo boxes allow the servos to be swapped out with a pair of 4/40's, not those pesky little servo screws.

The Brodak kit appears to have a scale factor of 6.8% or 14.7-to-1.  So it's a little bigger than 1/16 scale.

Wing area is a fuzzy thing in profile scale. You gain some effective wing area due to the road-killing of the fuselage and nacelles.  Funny things happen, like the landing gear comes out of the wing instead of the nacelle, or else if you make it come out of the nacelle, but then it's too wide-track.  

I believe that the engine centerlines on a profile twin should be in the scale locations. that puts the outboard side of the nacelles at the positions of the scale engine centerlines, and the nacelle centerlines different distances from the centerline of the airplane. If the gear are mounted on the outside of the nacelles they are basically on the centerlines of the engines. This puts the gear in the proper locations.  The effective wing area of a profile airplane is larger than the effective wing area of a full fuselage airplane because almost no wing area is blanked by the fuselage or nacelles.
470 square inches of wing area is not much for a pair of .25 engines. 235 square inch stunters are normally powered by .061 engines.
It looks like you are doing a great job with your build.


Pat

I believe that the engine centerlines on a profile twin should be in the scale locations. that puts the outboard side of the nacelles at the positions of the scale engine centerlines, and the nacelle centerlines different distances from the centerline of the airplane.

Pat

 FWIW I agree, that's exactly how I did my PBY stunter, the engine centerlines are equidistant from the fuselage centerline.

Paul,
I know that the wing shape of my kit matches the wing shape on the government 3 view for the B 25C. At 1/16 scale that gives 340 square inches of wing area the way we measure models. My calculations say we would have 400 square inches if the wingspan is 55 inches. Having never seen the Brodak airplane and not having a plan view picture I can't be sure, but it appears that the wing is wide at the tips. That may account for the advertised 470 square inches.

Pat

With the engines safely in hand I was able to proceed with final assembly using my hardwood fixture.  
Precision paint stirrers center the fuse visa vis the nacelles.

Mini me.  A toy grade B-25 model provides a perspective, if not reliable evidence.  Can you pick out all the flaws in this "Doolittle raider".  In addition to the flayed-out guns and the single pilot?

OK, forward turret, cheek guns and side windows, all of these were long after the B-25B.

Righto.

The plastic toy is basically a J model with B model decals to make it into a Doolittle raider.  83 of the 100 surviving B-25 are J models.  Many, including the fake Doolittle raider in the Nimitz Museum, are J's retrofitted into the more heroic B, C, and D models.

It's ready to fly now.  June 6th, 2016.  I got the wing jig on Mach 13th.  Ready to fly in under three months.

100 ounces, 6 pounds 4 ounces.  I could get away with two .018" lines but I made up a brand new set of .021's.  The pull will be 31.25 pounds (child's play).

The pictures I posted seem to have been lost in the SH computer glitch.

About 83 of the remaining 100 or so B-25's are the J model, which was the final and most numerous mass-produced rev of the B-25.   But the majority have been modified to look like the more heroic B, C, D, G, and H models, which had more glorious war records, but were lost in the process.

The prime example is my prototype, which trained countless pilots for nine years (at great risk to it's airframe), but now sits in a museum disguised as a B model that only flew ONE combat mission.

The ARMY Air Force used this design for seven years.  The US Air Force used it for 13 years, thus the modern markings on mine.

No need to risk a model of this size with bare-minimum lines.

I've flown 1.5 pound combat planes on .018" for decades.  I can't get my head around flying six pounds on the same size.

In scale there are no speed and stunt points, so I'll be better safe than sorry and use .021's. 

I put together some .014" and .016" solids for Perky & Fox 35 Speed.  I don't mess with solids unless they make me.  While solids have more steel for the frontal area, the chance of failure due to a minor handling accident is too much for me.

.027" was way over the top.   If a model really needed (3) .027's with a total strength of 375 pounds, nobody should have been trying to fly it.

The theory that all 3-line systems share the load equally was always a shaky theory to put your trust into.  Realistically, they often bottom out and carry the load on two.  Even then, two .027's would have 250 pounds of strength. 

The 2.4 system gets rid of the weakest link of all - the three-line bellcrank.