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Guillow's de Havilland Chipmunk (Read 4810 times)
Reply #61 - Sep 18th, 2019 at 6:51pm

Dan   Offline
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Sky9pilot wrote on Sep 18th, 2019 at 11:21am:
Dan...you can just add gussets to the center leading edges and central 1/16" sq root rib, like you did at the trailing edge.

That's the route I took. After I made some usable gussets, I took some photos to show how I did it using S-1 as a template. I traced the better edge and the notch, then turned S-1 over and traced the other line. I traced the leading edges of the stabilizer and made the cuts.

Gluing on the horizontal stabilizer is now done! Once the glue has dried overnight, the stabilizer should need nothing more than sanding (both to shape the corners properly and get a super-smooth finish) before it is ready to cover.

Edit: now that the horizontal stabilizer is nearing completion, I must give consideration to the rest of the airframe. I will have to pick up a sheet of 1/20" balsa so I can make a new wing rib. However, I must seek help with the fuselage and vertical stabilizer. If the notches in the fuselage sides are cut for 1/16," am I better off making formers from 1/16" sheet or using the "Dutchman" method mentioned in the Meyers article? For the vertical stabilizer, am I better off making replacements for the die-crunched pieces out of 1/16" or sanding the sticks flush?
 

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Building stick-and-tissue models is a hobby, not work.
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Reply #60 - Sep 18th, 2019 at 11:21am

Sky9pilot   Offline
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Dan...you can just add gussets to the center leading edges and central 1/16" sq root rib, like you did at the trailing edge.  You're not tied to place the original part there.
 

If God is your Co-pilot...switch seats...
Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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Reply #59 - Sep 17th, 2019 at 8:08pm

Dan   Offline
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KF: your NoCal models look pretty good. I'll order one in the not-too-distant future.

Today was a day of brainstorming. I was scarcely able to maintain focus at work, as I was thinking about how to finish off the Chipmunk's horizontal stabilizer. After dinner, I took measurements and did some further brainstorming, then did a quick chore and got going. I eventually decided to trace along the better of S-1's trailing edges, outline the notch, trace the other side, and finally trace the leading edges. When cutting the notch, the new part broke, so I extended the stringer all the way to the leading edge. After test-fitting, I did some sanding...and broke the new gusset. The new stringer was already in place, so I'll make new gussets tomorrow. New gussets and some sanding should have the horizontal stabilizer ready to cover!

I also made a replacement R-2 piece. It is head and shoulders above my previous effort. A set of jeweler's files will need to be purchased before I'm ready to put the vertical stabilizer together. The sheet balsa I bought at my local hobby shop seems to be quite fragile!
 

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Building stick-and-tissue models is a hobby, not work.
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Reply #58 - Sep 16th, 2019 at 11:14pm

Kittyfritters   Offline
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Dan wrote on Sep 16th, 2019 at 4:37am:
KF: you make kits? If so, I'd be interested in getting my hands on one...



No problem,  http://hjlmodels.com/


KF
(Howard Littman)
 

Qua sublata omnia praecepta legis
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Reply #57 - Sep 16th, 2019 at 4:37am

Dan   Offline
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KF: you make kits? If so, I'd be interested in getting my hands on one.

Mike: I have a copy of the Meyers article saved on my tablet, but not my phone. I'll need to save it on my phone as well. Not every modification suggested will make it into my build, but the braces will.

As regards perfection, I'm more concerned with achieving "pretty good" right now. Were I to adapt the Sir Henry Royce method, I'd crash-land on the funny farm! Another member's signature (I don't recall who) contains a quote from Salavador Dali that relates to perfection.
 

Building stick-and-tissue models is a hobby, not work.
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Reply #56 - Sep 15th, 2019 at 9:35pm

MKelly   Offline
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Dan,

The marked-up picture AK provided matches Stew Meyers suggestion in his article almost exactly - braces top and bottom across the formers.  Highly recommend this - I've suffered several former crushes on my Typhoon (which didn't have the bracing).

The revised stab looks much better, but don't sweat getting every joint perfect on your first model.  You'll learn and your skills will improve with every one you build, and you'll learn a lot about what works and what doesn't work as you cover and fly your early builds.

Cheers,

Mike
 
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Reply #55 - Sep 15th, 2019 at 8:10pm

Kittyfritters   Offline
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That's why the formers in my Simplified Model kits are made of cross laminated balsa.  That way I can lay them out on the sheet for minimum waste when laser cutting without needing to consider the direction of the grain and they don't need additional bracing.

KF
 

Qua sublata omnia praecepta legis
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Reply #54 - Sep 15th, 2019 at 2:47pm

Dan   Offline
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The grain on the Chipmunk's formers does run vertically. Makes sense that the braces are put on them! When it comes time to get the fuselage together, I will definitely make them as long and as close to the openings as possible. Having a former break on me would be frustrating, especially since I already have to make a replacement former C.

And thank you, alfakilo, for your kind words. I'm happy to hear that, for a first-time build, my results are st least decent!
 

Building stick-and-tissue models is a hobby, not work.
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Reply #53 - Sep 15th, 2019 at 1:17pm

alfakilo   Offline
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Dan, your redo of the stab looks good.

About those braces, perhaps these are the 1/16" small strips that the plan shows being glued to the formers (dashed lines). Typically, the grain runs up and down in formers making them easy to break when squeezing the fuselage from the sides. Usually, a simple piece of stringer glued 90 degrees to the grain is all that is needed to provide enough stiffness to minimize this problem and at very little increase in weight. If the formers are cut from 1/32" sheet, then the problem is greater, especially if the wood is soft.

In your pic, the braces for formers E and F seem to indicate that the braces do not extend across the whole former. OK, that's because the rubber motor goes thru there. However, I am dubious about the effectiveness of those small braces. For me, I would omit these and, instead, glue a brace across the top and bottom as close to the opening as possible. Having formers break when working on the fuselage is a common problem and anything that I can do to minimize this is good for me. Here's what I mean:
 

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Reply #52 - Sep 15th, 2019 at 12:05pm

Dan   Offline
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Sky9pilot wrote on Sep 14th, 2019 at 11:08pm:
Quote:

One aspect of the fuselage former braces puzzles me a tad. The plans call for braces on the front only. Would bracing them at the rear be an okay idea, or just unnecessary weight and effort?

Uncertain just what braces you are referring to...didn't see them called for on the plans side view of the fuselage.

Trotting out an old cliché, a picture (in this case, of a copy of the plans) is worth a thousand words.

Rework on the horizontal stabilizer continues. I made two efforts at cutting a new S-3 piece after excessively sanding one of the die-crunched ones. Another try at it might be necessary, as the side touching the trailing edge seems a little short. But there's much less daylight passing between the S-3 pieces and the square strips, so I'm happy enough...for now. I'll brainstorm a good plan for replacing S-1 later. Later today, I might make another attempt at cutting a new R-2 piece.
 

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Reply #51 - Sep 14th, 2019 at 11:08pm

Sky9pilot   Offline
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Quote:

One aspect of the fuselage former braces puzzles me a tad. The plans call for braces on the front only. Would bracing them at the rear be an okay idea, or just unnecessary weight and effort?

Uncertain just what braces you are referring to...didn't see them called for on the plans side view of the fuselage.  Usually adding more than what the plan calls for (unless it's a redesign of that part of the plan) just adds weight.
 

If God is your Co-pilot...switch seats...
Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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Reply #50 - Sep 14th, 2019 at 5:08pm

Dan   Offline
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Sky9pilot wrote on Sep 14th, 2019 at 5:00pm:
If you have a fireplace...the small scraps that you'd toss are great for kindling to get a fire started.

I do have a fireplace, as I'd suspect most homes built in the 1920s did. We don't use it, as it was previously converted to gas and I'm unsure if any work will be needed to safely burn wood again.

One aspect of the fuselage former braces puzzles me a tad. The plans call for braces on the front only. Would bracing them at the rear be an okay idea, or just unnecessary weight and effort?

Edit: I just noticed that I managed to damage fuselage former C. Added it to the list of parts to make. I'm really glad I bought that sheet of balsa, and I will definitely be more careful with my next build!
« Last Edit: Sep 14th, 2019 at 6:13pm by Dan »  

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Reply #49 - Sep 14th, 2019 at 5:00pm

Sky9pilot   Offline
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If you have a fireplace...the small scraps that you'd toss are great for kindling to get a fire started... Grin Wink Cool  Most modelers throw away very little Shocked Cheesy Wink
 

If God is your Co-pilot...switch seats...
Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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Reply #48 - Sep 14th, 2019 at 4:55pm

Dan   Offline
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I see it now...remove the leading edge pieces entirely and cut two new ones that will butt up against one another, much like the trailing edge. I'll fix that tomorrow.

At the rate I'm going, I'll have a shoebox full of little bits of balsa in no time flat! Those little bits will come in handy when it comes time to fabricate the braces for the fuselage formers.
 

Building stick-and-tissue models is a hobby, not work.
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Reply #47 - Sep 14th, 2019 at 4:34pm

Sky9pilot   Offline
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Dan...you might want to reread AK's suggestion...on the leading edges of the horizontal stab.
alfakilo wrote on Sep 10th, 2019 at 9:38pm:
Looks good! Now is the time to start thinking about how you are going to attach the wing. Is it to be built as one piece or two sides?
IMO, the S-1 joint is a poor design, a weak area that could have been easily done differently. I would have extended the two leading edges to butt up to each other and then trimmed S-1 so that it backed that butt joint. No difference in weight and much stronger.


I have several boxes of scrap balsa.  You never know when a piece in the boxes will be just the fit for a repair or part for a new build or replace a damaged kit part.  Stringers in one box, circles in another (spinners laminations/or wheels) , other scrap pieces in another box.  Old shoe boxes make great storage boxes... Grin Wink
 

If God is your Co-pilot...switch seats...
Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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