# Thread: -Penn Foster? HVAC transition piece

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Hi,

I think I followed the text correctly to find the true lengths. It's what to do next that I am stuck at. I think I have what you said correct now.

Thank you so much for helping me and everyone on these forums out especially on a Saturday.

2. Oops, I just noticed that the circle is offset from center so B-10' is not equal to A-10'

Don't type in the radius - use snap points.

Your next step will be to determine the length of arc from 10-9.
Not the cord length (many books miss this) you need the arc length.
Once you find this it is the same for all (9-8 is the same as 10-9).
Tip- you can find the arc length by
copy and paste pie shape away from the drawing.
trim the pie
list the arc

Draw circle of R 10-9 arc length at point 10' in your flat development..
Draw circle of R A-9' at point A

Where these two circle intersect is point 9' you now have line A-9

3. No, its not centered. Do I have this first stage correct?

4. Ok, I have done that step, hopefully correct

5. I'm not at my CAD computer thus the reason for my question. Are you working on the Penn-Foster HVAC project?

6. Yes I am. I have seen the pictures of Plate 3 posted. It shows that the end result is supposed to be but not how to get there. I attached a picture of where I have reached. I assume I do the same thing on the left side but not sure what to do next on the right.

7. This is what I have come up with following instructions that I found online, though they were for a symmetrical piece. I know something is wrong as my arc on the inside isn't correctly meeting the lines for each point. However, I do not know what. Please help when able.

8. It should be a spline curve - not an arc.

But you have point D in the wrong location.
Draw circle R A-D at A.
Draw circle R A-7 with center at 7 (A-7 and 7-D are same length).

Where these two circles intersect is the actual location of point D.

Point D.jpg

9. HI,

Think I have it all correct now...hopefully

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hello,