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Very Hot Topic (More than 25 Replies) How's about a Pres Bruning Cookup? (Read 1506 times)
Sky9pilot
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Re: How's about a Pres Bruning Cookup?
Reply #39 - May 20th, 2022 at 6:01pm
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This is reminiscent of a Spitfire build on HPA where they talked about washout on the elliptical wing which very much looked like a twisted wing.  I'll try to find the link.
Tom
  

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alfakilo
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Re: How's about a Pres Bruning Cookup?
Reply #38 - May 20th, 2022 at 9:36am
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In looking at the plan again, I noticed something that needed explanation. The ribs are all flat bottomed and seem to be butt-joined to the LE. If so, from the front view, the bottoms of all of the ribs should not be seen (wing chord line parallel with longitudinal axis), but clearly, the bottoms of W1, W2 and W3 are visible. I believe the reason for this is that the wing root has a positive angle of incidence thereby allowing the bottoms of those ribs to be seen.

And then the wing is geometrically twisted resulting in the tip to have a negative angle of incidence (4 degrees?). This permits only the tops of W4, W5, and W6 to be seen.

See pic for wing twist.

Now I just have to figure out how to build this!!
  

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Sky9pilot
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Re: How's about a Pres Bruning Cookup?
Reply #37 - May 19th, 2022 at 2:45pm
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I found this picture of a similar situation in a build of another model. I believe it's called wing reflex. Not sure whether this will help or not. Embarrassed Cry Sad Wink
  

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And ye shall know the truth, and the truth shall set you free. Jn 8:32
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alfakilo
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Re: How's about a Pres Bruning Cookup?
Reply #36 - May 19th, 2022 at 1:54pm
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Sky9pilot wrote on May 19th, 2022 at 11:16am:
That is frustrating. 


Yes it is. As I understand the plan, the TE is flat out to wing rib W3. Then it is raised up to achieve the washout. If this raised TE went up at a constant angle, then W4 would have 1.3 degrees elevation, W5 would be 2.6, and W6 ends up at 4 degrees. But as the plan shows, W4 is 1 degree, W5 is 2.5, and W6 at 4 degrees. This ends up as a TE with a bowed "concave" shape.

This not-to-scale drawing is my confusion. Is the TE bowed down slightly and if so, why? Is the rib degree value measured from the root rib (X), W3 (Y), or something else?
  

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Sky9pilot
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Re: How's about a Pres Bruning Cookup?
Reply #35 - May 19th, 2022 at 11:16am
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That is frustrating.  I'm thinking that the "0" degree is from the building board surface.  The degrees are up from there.  It's a major twist in the wing from rib three to the tip.  I notice that in some flying wing aircraft the ribs are shaped with the washout in the rib and you glue the T.E. to the ribs.  I'd probably wet the trailing edge to get it to conform to the washout.  Similar to what I did with the wings on my U-2 which hasn't been completed yet but the wing is built. I built the wing then propped up the tip and pinned the root down and then used scrap balsa to achieve the curve in upsweep to the tip pinning the whole wing down.  I then spritzed the whole panel very well and let it dry overnight.  Once dry I added the tresses and let them dry overnight before unpinning from the board.  It worked for that wing.
Tom
  

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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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pb_guy
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Re: How's about a Pres Bruning Cookup?
Reply #34 - May 19th, 2022 at 11:00am
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I would pin the wing flat from the wing root to rib W3 (0° washin = 0° washout) and as Tom suggested, make a wedge of 4° under the tip. This would raise the TE of rib W5 about 1/8" from the board, and the TE at the tip about 3/16". Just ignore the elevons at this point.
ian
  
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alfakilo
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Re: How's about a Pres Bruning Cookup?
Reply #33 - May 19th, 2022 at 8:30am
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The ribs spacing is the same but the washout elevation is not. If the washout angle was constant, then I would expect that the TE elevation conformed to that angle...but it doesn't seem to. Instead, it sorta stairsteps from rib3 to the wingtip.

Then, where is the angle measured from? The previous rib or somewhere else on the TE?
  
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Sky9pilot
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Re: How's about a Pres Bruning Cookup?
Reply #32 - May 18th, 2022 at 10:16pm
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I'm assuming he's using a protractor to guage the degrees per rib.  it's like building in washout but specifically those degrees per each rib.

I'd cut my self a wedge from foamboard or cardboard that gives me those degrees at the ribs stations and fix that under the trailing edge as I built the wing.  Hope this is helpful.
Tom
  

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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alfakilo
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Re: How's about a Pres Bruning Cookup?
Reply #31 - May 18th, 2022 at 4:00pm
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Question about Bruning's Boeing 306B plan...

He shows the washout in degrees for 3 wing ribs. What is the degree value based on...meaning where is the washout angle measured from?

What is confusing is that the wing rib spacing seems the same but the washout angle varies a little from rib to rib.

Also, the "0 degree washin" at rib W3 means what?
  

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Sky9pilot
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Re: How's about a Pres Bruning Cookup?
Reply #30 - May 14th, 2022 at 1:45pm
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It was John Regalbuto's Henschel...this was an earlier model of his.  I believe the FACN picture was a later larger model of this model. Click Here  found on Mike Stuart's site in the UK  about 3/4 down the page.

Found the picture I was thinking about, FACN Sept/Oct 2015 pg 12, 54" Giant Scale.
Quick and dirty pic with the phone.
« Last Edit: May 14th, 2022 at 2:47pm by Sky9pilot »  

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If God is your Co-pilot...switch seats...
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And ye shall know the truth, and the truth shall set you free. Jn 8:32
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Re: How's about a Pres Bruning Cookup?
Reply #29 - May 14th, 2022 at 5:06am
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alfakilo wrote on Jan 27th, 2022 at 1:33pm:
I'm looking at another twin for my next build. Another "what if" design from Supermarine prior to WW2. Only three views to reference and they aren't all that helpful. No "V" motor method this time.


Ouch!!! SIX cannons? Shocked
  
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Re: How's about a Pres Bruning Cookup?
Reply #28 - May 3rd, 2022 at 9:10am
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No luck in finding that model. Too rainy to go outside so why not putz around with this one!! I like Bruning plans but they can offer an opportunity at interpretation!!
  

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Sky9pilot
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Re: How's about a Pres Bruning Cookup?
Reply #27 - May 1st, 2022 at 6:24pm
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AK... I read in one of the FACN publications quite a while back where one modeler blew up those plans to Jumbo Scale (Coconut Scale very similar I believe) that's 36".
  

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alfakilo
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Re: How's about a Pres Bruning Cookup?
Reply #26 - May 1st, 2022 at 10:10am
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I should have this ready by the fall!!
  

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Re: How's about a Pres Bruning Cookup?
Reply #25 - Mar 24th, 2022 at 10:57am
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Glad you're feeling better Tom.  Agree with the idea of a fall cookup - the summer flying season is getting into swing, will be more time available in the fall.

Mike
  
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