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Author Topic: Need Help with Walt Mooney's The Old Howard Bostonian  (Read 496 times)
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vtdiy
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« on: December 11, 2018, 07:39:21 PM »

I started building the Old Howard a couple years ago and had the fuselage sides framed up, and then had put most of the cross members in. At that point I started looking at the nose area, and for the life of me I just can't figure out how the rectangular fuselage section becomes a round cowl section. Construction stopped at that point, and it's still sitting on the shelf.

Can anybody explain, (maybe with a picture or two?) how to build that part of it?

The plans and article are in the Builder's Gallery here:

http://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=1043

Thanks!
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Need Help with Walt Mooney's The Old Howard Bostonian
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« Last Edit: December 11, 2018, 08:06:55 PM by vtdiy » Logged
mescal1
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« Reply #1 on: December 11, 2018, 09:36:18 PM »

I'll try.  here's a modified plan.  you want to first build the side views in yellow. then when you get to the stage you are at now you would crack the the fuselage right above the landing gear to match the yellow in the top view.  you would then add formers to create the rounded front end.  I marked the former on the bottom right with colors matching where you would cut the formers to create the shape.  I'll look around and see if I can find a picture that shows something similar.
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vtdiy
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« Reply #2 on: December 11, 2018, 10:14:09 PM »

Ahhhhh.....click!  

I think I get it! The cracking part is the key. Well, so is the rest of what you pointed out!

I was wondering how anybody could possibly build something from a profile view that angles in (like the sides). I was thinking the fuselage would have to suspend up in the air to do that, and how would you get the right lengths of the angled longerons then?

Now I see, you build it flat on the profile (like I did), but then you break part of it and move it in. Okay!

So cracking -- there must be a right way to do that, and probably a wrong way. Do I just score on the outside of the joint, and then crack it in.

Then....I'm just guessing here.....put a drop of glue on the crack?
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VictorY
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« Reply #3 on: December 11, 2018, 11:12:18 PM »

I'd think you could bend the wood that much without having to break/cut any fibers. My Chambermaid has some bends around the nose section that require what appears to be at least as much deflection. I used water to soften it up a little.
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Indoorflyer
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« Reply #4 on: December 11, 2018, 11:37:15 PM »

Nice explanation, mescal1.

Plans with a major taper in the nose section (like this model) usually don't account for the foreshortening of the nose, when the ends are brought inboard to the narrow front station.  I usually swing a compass arc in the top view, then drop the adjusted front end of the fuse side frame down to the side frame pattern below it. The "true length" of that section is thus generated.  You don't want to "cheat" the length of the cowling on an already stubby front end...

The taper back to the tailpost is generally not as big a concern, since it typically is a smaller angle, due to the longer distance back to the end of the fuse. (slight foreshortening on this end, which tends to be the "heavy" end may be advantageous when balancing the plane)

Some model designers account for this in the fuselage side framework layout.  (Greg Thomas did this in his updated kit version of the Walt Mooney Bostonian Beaver)

We've gotten so used to seeing inaccurately drawn plans ( where the side frames are not built over a true-length layout) that we tend to ignore these interesting  discrepancies.  It's most obvious when you have a wide cross section, "Stubby nose" design like a radial engine airplane, built with this type of box fuselage. 

I've attached a hastily drawn sketch, not to scale, slightly exaggerated to illustrate this point
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vtdiy
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« Reply #5 on: December 12, 2018, 07:48:08 AM »

Thanks VictorY, I think, however that those curves are fair, while those shown on the Old Howard plan are sharp corners with straight sections.

Indoorflyer, I understand that discrepency in projection well, and that was one of the things that confused me about this plan. I did know I could get the true length of diagonals with some work, but I didn't know whether that was intended on these stick and tissue plans or not. That plus not knowing you could break a longeron like that.

Anyway, I'm very grateful to you all for your help and explanations!
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USch
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« Reply #6 on: December 12, 2018, 08:30:28 AM »

Question about how to crack the longerons.
If a sharp change of direction is asked for as in this case, I prefer to score/cut slightly on the inside, leaving the outer fibres intact. Even cutting with a very sharp razor blade you squeeze the wood just a little bit, enough to accomodate the change of direction.
My 2-pence worth

Urs
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Crabby
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« Reply #7 on: December 12, 2018, 09:39:35 AM »

Urs, thanks for that tip! I have been doing it the other way for a long time now! Maybe even soften it some with a spit ball too!   
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Indoorflyer
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« Reply #8 on: December 12, 2018, 09:44:00 AM »

Paul Bradley has an elegant solution. His excellent CAD version of the Comet Models Stinson SR-7 plan shows how to build the tapered section as a separate assembly, using a removable jig that keys to the main fuselage box. Have a look at page 10 of this plan . He also replaced the paper wrap on the cowling with thin sheet balsa.

https://0201.nccdn.net/1_2/000/000/0f9/bdb/Comet-25-inch-Stinson-SR-7.pdf


His main website is here   http://parmodels.com/

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USch
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« Reply #9 on: December 12, 2018, 10:15:05 AM »

Crabby, the spit ball is always an excellent mean to cure difficult points  Grin
If it works ok, if not, no damage done. Works really well on these last, small wrinkles on the covering tissue.

Urs
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vtdiy
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« Reply #10 on: December 12, 2018, 10:36:09 AM »

Urs, thank you kindly! I was wondering about that, too. Although I imagined a razor saw in my mind to give a little kerf width. But if a razor blade is better I'll use that.

Crabby spit, too!

Indoorflyer, that's a neat way to do it -- I was stuck on trying to do it "per plans" and hadn't been able to figure out any alternatives. Also I was afraid that any change would add weight. But now I realize that on a radial model, extra balsa weight forward is often not such a big problem, because ballast is often needed anyway to balance.

I hadn't looked at that Stinson plan before. That's a very nice illustration. I do know the wonderful Parmodels site, and have built the Termite motorglider, and the Bradley's No-cal SE5a

Also just because we're talking about tight bends and Parmodels, I have done pretty tight radius curves (as opposed to hard corners) with the Bradley's method of (yes, Crabby) wet balsa and soldering iron. Here's the tail of the Piper Cub Bostonian I have been building the last couple days -- not laminated, but using the spit 'n soldering iron method. The perimeter is just one piece of 1/16" square balsa:

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vtdiy
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« Reply #11 on: December 12, 2018, 10:46:09 AM »

Link to spit-n-solder page......I mean damp balsa and soldering iron method:

http://parmodels.com/wet-forming-balsa-outlines.html
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