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How To Measure Construction Angles (Read 932 times)
Reply #8 - Jul 2nd, 2018 at 2:39pm

alfakilo   Offline
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Good stuff, Tom. I made similar jigs that set the parasol wing height and the angles of the cabane struts between the fuselage and the wing. Not too sure about the incidence angle, I was just trying to square things up visually.

Your method of attaching struts to the fuselage is much better than mine. I made little boxes in the fuselage and in the wing out of scrap for the cabane struts to go into. It worked but lacks the finesse I see in your way.
 
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Reply #7 - Jul 2nd, 2018 at 10:23am

Sky9pilot   Offline
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Alfa...
check out the jig I made for the New Standard I made a while back.  One of my favorite models. Click Here  reply#36
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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Reply #6 - Jul 2nd, 2018 at 9:55am

pb_guy   Offline
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What I have done in similar situations is to make a jig to fit between the wing and the fuselage to hold the correct angle while the struts are fitted and glued. It helps to not have a canopy in the way at this point. Once the wing is in place, you can check the position of the stab in relation to the wing before final gluing.
ian
 
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Reply #5 - Jul 2nd, 2018 at 8:23am

alfakilo   Offline
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I didn't find your post misleading, Tom, I wasn't very good at phrasing my question. I was trying to ask about how to determine the angle and then how to install the wing with that angle.

The YO-43 Comet plan shows the angle is being 1/16" up from the TE. While that is pretty easy to visualize, actually building it is a different matter, it seems to me. Your description of level table, etc helps a lot. Getting things level seems a little iffy since tiny errors will result in fairly large deviations.

One of the P-56 references that I used called for a 5 degree angle on the wing and my questions came from that. Rhetorical question...how exactly did the plan designer intend that we achieve this? I then answered my own question by suggesting that math could be used to solve for the LE elevation in inches. Or are there better ways?
 
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Reply #4 - Jul 1st, 2018 at 8:44pm

pb_guy   Offline
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The incidence from the designer is built into the plan. But 'the plans of mice and men gang aft aglay', so you want to check actual incidence in situ. Make a pattern (from foamboard?) according to the plan that will go from stabilizer to just past the wing being careful to mark the LE and TE of wing and Stab. Then put it at the fuselage/wing joint. align the pattern to the wing and check to see how the stabilizer matches the indicated incidence. Usually it is much easier to adjust the angle of the stabilizer to match the wing incidence than it is to adjust the angle of the wing to match the stabilizer. This is basically what Tom just said.
ian
 
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Reply #3 - Jul 1st, 2018 at 8:14pm

Sky9pilot   Offline
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Sorry for the miss leading measures...that was just to illustrate.  non of the figures are accurate...just a quick CAD drawing to illustrate the process. 

Another way would be to cut a cardboard or foamboard template with the desired incidence in the top edge.  a rectangle with an angled top the desired 2 or 3 degrees of incidence.  Level the aircraft on a level table and use the template to set the wing incidence.  Some will cut the template (side profile of fuselage and wing empennage setup) from a copy of the plan and glue this to cardboard or foamboard to use as a jig to make sure the incidence is correct on the fuselage after construction.  I didn't mean for the measurements to represent any actual degrees in measurement.
Sorry for the confusion. 
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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Reply #2 - Jul 1st, 2018 at 7:14pm

alfakilo   Offline
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The horizontal stab example is clear. But the wing incidence is not. I understand your picture, but the question I have is why the 3/64 difference in the LE and TE? Once the desired angle is determined, it seems that your technique is then to translate that angle into different LE and TE heights (as if it was calculated that a line extending from the TE to 3/64" above the LE equals the desired angle.).

Am I understanding this correctly? If so, then this becomes a relatively simple trig problem by using the chord value and the desired angle as the knowns and then solving for the elevation value.
 
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Reply #1 - Jul 1st, 2018 at 5:17pm

Sky9pilot   Offline
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Having been a pilot I'm sure you completely understand wing incidence and it's relation to horizontal stab incidence  For those not sure here's a picture below to show this.

Now how do we measure this on our models.  First we have to level the fuselage as well as we can.  I just use the bionic eyeball, some use a bubble level based on some level spot of the fuselage. 

The key factor from here is the incidence angles of the wing and horizontal stab at this point.  Most model designers like to have +2 to +3 degrees incidence on the wing.  With the horizontal stab at 0 degrees incidence in relationship to the wing.  To measure this after fuselage is leveled is to measure the L.E. of the wing compared to the T.E. of the wing. On a nice level flat table!!! Then measure the L.E. and T.E. of the horizontal stab.  Then plot the differences of the measurements on a piece of paper.  Then check the angles with a protractor to get the degrees of incidences.
Hope this makes sense.
 

incidence.JPG (38 KB | 51 )
incidence.JPG

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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Jul 1st, 2018 at 8:51am

alfakilo   Offline
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Retired USAF and TWA.
St Louis, MO

Posts: 1132
****
 
How do we set angles of incidence, etc when building our models? Can simple protractors be used, if so, how?
 
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