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Author Topic: "Chieftain" by Berkeley Models  (Read 2112 times)
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Dan Snow
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« on: February 08, 2019, 09:46:33 AM »

Since I'm still waiting out the weather so I can get out and fly the Doodlebug and the Hemiptere, I have finally picked out my next build.

The "Chieftain", a 26" 1941 design by Berkeley Models.  I found the plans here http://smallflyingarts.net/free-plans_4.html

For a while it was a toss-up between it and the Senior Dart by Comet, but after some cogitating on the subject I decided that the I liked the lines of the Chieftain over the Senior Dart.

Step one will be getting the plans into a usable format. The download is tiled into 6 sheets so I'll be trimming and taping and then making several copies. Step 2 will be going through them to  compare my balsa stocks to what the plans call for so if needed I'll only have to make one trip to my not so local hobby store.

Once I have that done and I'm ready to start cutting I reach my first decision point. Do I want to make the built up wingtip and tail feather outlines or try to simplify them? Since simplifying them likely means laminating them, I probably won't.  Stay tuned.

Now, all that said, Flydean1, how far forward do I move the rear peg?  Grin Huh Grin Huh Grin  Huh Grin
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Dan Snow
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« Reply #1 on: February 09, 2019, 05:57:34 PM »

Got the plans all taped up and off to Staples I went.  3 full size prints $5.27!  Now I can cut them apart when I get ready to build.

Made a run to the not so local hobby store and stocked up on some balsa for the build. Since 3/32" is the thinnest material called out on the plans I got some 2/32" x 3" sheets. I splurged on the 3/32" square stock for the main longerons because it called for hard stock and my stripper kinda struggles with the denser grades. I also picked up the wire and tube to make a 20in/oz torque meter from Herb Kothe plans.

I think my first task will be to make up some templates for the ribs. It is interesting that they list the ribs as R1, R2, R3 and yet all ribs are exactly same size, shape and thickness.

If I understand the plans correctly the wing is built as one piece and slid through the fuselage. I'm thinking of cutting the fuselage bottom under the wing and making it part of the wing.

Think I should consider modifying it for a dethermalizer?
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FFScott
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« Reply #2 on: February 09, 2019, 06:21:40 PM »

Neat looking airplane.  Is it eligible for any FAC events?
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Dan Snow
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« Reply #3 on: February 09, 2019, 08:16:18 PM »

If I read the rules correctly, it should qualify for either Old Time Rubber Fuselage or 2 Bit +1 Old Time Rubber Fuselage.  Of course that likely makes my contemplated mods ineligible, but since there is zero scale and very little old Timer in this area it's not an issue for me.
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« Reply #4 on: February 10, 2019, 09:31:14 AM »

moving the rear peg is ok for FAC Old Timers.  Laminating tips that were built up is not.

P.S. FF - OLD TIME RUBBER would be the appropriate category.

--george
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« Reply #5 on: February 10, 2019, 04:38:33 PM »

Hi Dan, the  Chieftain is the subject of an upcoming group build instigated by SAM-27, with Oakland Cloud Dusters participating. The build will end with a couple, potentially 3 one-design contests in the SF Bay Area. I'll keep you posted or keep an eye on OCDs web site.

Charming model. I'm looking forward to get started on mine.

Best,
--atesus
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Dan Snow
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« Reply #6 on: February 10, 2019, 05:53:11 PM »

Hi atesus, sounds like fun, but I avoid the bay area by any means necessary.  I  had to deliver from the C&H Sugar plant to San Jose many times while driving an 18-wheeler and learned a strong distaste for it! Sorry. I might tell you a not so funny at the time story about a rookie driver, an 18-wheeler, and the intersection of Geary an Market Streets.

I didn't realize there was an Old Time Rubber forum when I asked Ratz to move it, maybe this belongs there? I asked Ratz what he thought.

I'll be starting construction in a day or as the forecast for rain or wind for almost the next whole week.
« Last Edit: February 10, 2019, 06:03:52 PM by Dan Snow » Logged

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« Reply #7 on: February 10, 2019, 07:19:29 PM »

Did some preliminary sketching on the plans this afternoon.

Pic #1 is where I'm thinking of moving the rear peg to. It's about equidistant from CG as the front hook.  That's an estimate as there is no indication of CG on the plans. And the instructions only say that as built the model should "balance perfectly"Huh  I also raised it vertically to get the rubber off the top of the wing.

Pic #2 is my estimate for the CG range from 25% to 35%
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« Reply #8 on: February 10, 2019, 07:51:36 PM »

For anyone else who might be interested in this design, you can find a one piece plan on Outerzone.
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Dan Snow
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« Reply #9 on: February 11, 2019, 07:28:27 PM »

I Hate Cutting Print Wood!!  Grin Grin  And that goes Triple for Stringer Notches!!  Grin  I would so loved to have found a laser cut short kit of this model, but alas   Angry

Okay, it's not THAT bad, but not a favorite activity. Usually have one or two parts I need to cut more than once to get right.

Now, about the part sheets supplied with the plans for the Chieftain.  This is what I have found so far.  There are two S1, one for each half of the stab.  They are NOT drawn the same. One is noticeably wider than the other but the shape pretty well matches the plan.  Will just need to sand out the inside of the fat ones curve.

It was the fuselage formers where things got interesting. The plans show 10 top formers. The print sheets have 10 top formers.  Only thing is formers T7 and T8 are labeled as T1.   I looked at the tail former T10 and just shook my head. It is tiny, miniscule, almost not there. I did cut it out, but I can see myself making more than one before I get all the stringers installed.  I've got 3 more fuselage parts to cut and then it's just the ribs.  I'll make a pair of templates from 1/32" ply and stack cut/sand them all at once.

More tomorrow.

Pic #1 Some bits o' balsa
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« Reply #10 on: February 12, 2019, 01:56:38 AM »

Quote from: Dan Snow
Usually have one or two parts I need to cut more than once to get right.
Only one or two?  Blimey! You are good. Smiley
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Dan Snow
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« Reply #11 on: February 12, 2019, 06:42:32 AM »

Well, that doesn't count the ones that I look at and say " once it's covered no one will know!"  Grin
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Dan Snow
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« Reply #12 on: February 12, 2019, 06:04:12 PM »

Actually started construction on it this afternoon.

Pic #1  Building the stab. Trying a new to me method, using push pins to clamp the pieces to the board.  Feels awkward.
Pic #2 Building the Rudder
Pic#3 See, a little judicious application of sandpaper and those ugly hand cut parts don't look all That bad!  Grin
Pic #4 Top and bottom longerons for the first side bent to shape.

The down side of using push pins to clamp is that I intend to stack build the second side over the first, and the pin isn't quite long enough for me to feel comfortable that it won;t shift.

And for those eagled eyed among you, the picture #2 is actually a recreation for the photo and I didn't do a good job of lining up the assembly with the print. The rudder really does match the exterior curve of the plan!  Wink
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« Reply #13 on: February 12, 2019, 07:02:29 PM »

Dan this is a nice looking model. I may be too late but did you consider putting that top fuselage in hot water and forming it close to shape before starting the fuse construction. It has a fairly strong curve and could distort the fuselage.

I had a similar problem with a curved bottom longeron pulling the fuse out of alignment as I had not formed the the curve. I had to spray the complete side of the fuse, while pinned to the board, with "windex" window cleaner(watered down ammonia) and left them pinned down for a couple of weeks.

John
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« Reply #14 on: February 12, 2019, 08:44:08 PM »

Dan:

I found a set of little collars that are used with regular dress pins to hold the balsa in position.  I don't recall where to get them, but probably someone reading this does?
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Dan Snow
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« Reply #15 on: February 12, 2019, 09:38:16 PM »

OZPAF the longerons are just pinned to shape, nothing is glued to them yet.

Good Idea, will do that lest I forget.  Okay, just soaked them for a coupe minutes in hot water and repinned the top longerons to dry overnight.
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« Reply #16 on: February 13, 2019, 11:34:12 AM »

Some more construction while the rain pours down outside!

Pic #1  The fuselage sides almost completed but not joined.  Just have to add the plate for the rear peg to each and a bit of sanding before tackling the stress of joining the sides without creating a banana!
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« Reply #17 on: February 14, 2019, 09:58:58 AM »

Here's another question for the smarter than me crowd.

As seen in Pic #1 There is a root rib, R1, on each side of the fuselage/center section of the wing. Looking at the plans they call for a butt joining of the leading.trailing edge and spars and a 3" dihedral at each tip. Would a gusset, say 1/2" on each side of each R1 at leading and trailing edge be sufficient you think?  Other alternatives might be to make R1 two thicknesses and sanding the dihedral angle into one of them ( or half the angle into both)

What say the experts?  Grin
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« Reply #18 on: February 14, 2019, 10:18:10 AM »

You are butt joining the R1's together, and not the wing to the fuselage.... Gussett away my friend. I assume this is to be a pass through wing. That's always a pain, make sure that wing center section is good and sturdy, and the pass through is dead on or you may induce a twist or warp! I would prefer butt joining the wing to the fuse, but that's in my kitchen!
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Dan Snow
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« Reply #19 on: February 14, 2019, 02:29:23 PM »

I hear what you're saying Crabby, I need to do some more cogitating on the wing fuselage marriage thingy.  I just might laminate some 1/32 ply behind the fuselage filler piece chop out the bottom of the fuselage and glue it back in after the wing it mounted.

Decisions, decisions!

In the meantime:
Pic #1 The start of my roll your own magnetic building board.  14" x 22" 14ga steel @ $4.43 and 17 magnets at $10.00  I'll put a light clear coat on the steel and paint a centerline on it, Then mount it to some 3/8" ply to make it easier to grab and move around.
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Dan Snow
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« Reply #20 on: February 17, 2019, 08:22:44 AM »

Took a couple days off from building the Chieftain to work on a mag building board and start a woodworking project for a friend.  The woodworking project will give me a reason to dig out my biscuit joiner tool.  Grin

Pic #1 The finished mag board ready to go.
Pic #2 It quickly becomes apparent to me that there is a trick to using one of these successfully.
Pic #3 As you can see I will need to learn through experimentation (Or knowledgeable advice from those with experience!) on the best way to use one of these new fangled things! Smiley
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« Reply #21 on: February 17, 2019, 06:54:32 PM »

Dan, clever use of those brackets with the magnets. Kudos!

I too started a magnetic board project, collected all the pieces but haven't finished it. This gives me inspiration.

--Ates
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« Reply #22 on: February 20, 2019, 01:16:45 AM »

Neat - it's coming on well Dan. Your use of those brackets looks effective Dan. You could also knock up some custom right angles in wood perhaps with magnets permanently attached to the bases.
This would enable you to have a spacer equal to the longeron thickness, on the front vertical leg of the square, with a similar thickness strip behind aligning the top and bottom longerons similar to the arrangement aligning the formers and the sides on the attached pic.
It helped me to align these sections and also acted as a clamp to hold them in place. Masking tape worked well to hold the spacer and stick in place.
Happy building.

John

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Dan Snow
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« Reply #23 on: February 22, 2019, 03:33:33 PM »

My first fuselage using a magnetic building board!!  I'm very happy with the results, No Banana!!! It was a little awkward at times so I did something a little unusual for me, I stepped back and took my time, measuring as I went, and lo and behold it stayed pretty darn straight!

Thanks everyone for the suggestions and encouragement to try building this way.

Pic #1  The fuselage sides joined, ready for top and bottom formers.
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« Reply #24 on: February 22, 2019, 06:12:43 PM »

Very neat effort, Dan.

John
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