ProfLooney

OK guys My kit shipped today for my 1/3.5 scale hurricane with a 138" ws. I been working out all construction in my head etc while drawing the vectors for my kit and tracing the plans while waiting for kit.

Background info: The plans are Vailley Hurricane blown up 150% to 1/3 and a half scale. the wingspan is 138"

The plans (before I enlarged them) call for a 2 deg washout. Now all the planes I have ever built either had the foot tabs or a jig on the plans which set this. My question is how to build the washout in on this where the ribs dont have feet or anything to auto set it up. Don SMiths B-17 has the same washout and wingspan and he has a jig for his. the problem iswhere the washout begins on his is like close to the center rib and runs the length of the wing. My Hurricane has a center panel that is flat with wings that go from there up at a dihedral. is there a way I can use his jig for the shorter wing panel or would I have to do it another way.

Thanks
Joe

monocoupe

My Feedback: (40)

Joe,
What I do is take a drawing of the tip rib, and draw a line under it to represent the building board surface with the rib at 2 degrees washout. Then I measure the distance between the bottom of the rear spar and the building board suface. Let's say it's 3/4".
Then I find the same measurment for the center section rib but at 0 degrees to the board surface. Let's say it's 1/2". Next measure the length of the rear spar from the center section to the tip rib. Let's say 65". Now make a tapered strip of 1/4" thick wood that is 65" long x 1/2" wide at one end and 3/4" wide at the other end. Simply stick the tapered strip over the rear spar on the plans, with the 1/2" tall end at the root, and the 3/4" tall end at the tip rib, and start building.
I hope that is what you were looking for

Cheers, Nigel

ProfLooney

I followed ya Nigel but how many inches is 2 degrees lol. Also since the Don Smith B-17 has a 2 deg washout couldnt I get by just shortening his jig? and set the inboard section of the jig in place and just use that and cut off the extra of the jig that O dopnt need because my panel will be shorter or use the highest part of the jig for the end rib? I may be over complicating this more than it needs to be but when people say degrees I say ok how many inches is 1 degree

Joe

monocoupe

My Feedback: (40)

Just use a drafting protractor on the tip rib! Done!

Cheers, Nigel

ProfLooney

Duh never thought of that hehehe I just trying to get it figured out asnd my jig made while waiting on kit I am so ancy to get started

thanks

Joe

PS but still like to hear more ideas if anyone has any different always nice to increase knowledge with different methods

monocoupe

My Feedback: (40)

O.K, Joe...if you want to do the math, we can:
It's the same formula as for figuring out a circumference.
Treat the cord length of say 10" as a radius.
so 10" x 2 = 20" dia.
20"dia x 3.1416(pie)=31.416" circumference
31.1416" divided by 360 deg. = 0.0872666" per deg
0.0872666" X 2 deg. = .17453" washout

Use the same formula, but with the actual cord length that you have there, instead of 10". Did you get that?

Cheers, Nigel

ProfLooney

Now that I can understand. then I just run the other end down to zero and that will set the washout of the entire panel correct?

I guess I got too spoiled by designers doing all the math and stuff for me. I work in feet and inches instead of degrees lol also helps if I would get some sleep at nights instead of doing cad work til 5 am then getting up at 9 am and starting right back in thats why i need to be building

thanks

Joe

ProfLooney

do I want the chord of the ip or the root

Joe

ProfLooney

OK I did the math and looks right to me

root 27.485 x 2 = 54.97 x 3.1416= 172.693 / 360=.47970486 x 2 = .959 or basically 1" washout

tip 13.829 x 2 = 27.658 x 3.1416= 86.8903728 / 360 = .241362146 x 2 =.482 or basically 1/2" washout


Joe

patternwannabee

My Feedback: (1)

In your CAD program, Draw the tip rib, Horizontal line below that, measure TE to Line, Rotate the Tip rib 2 deg (centered at the LE I assume), take a new measurement, take the difference.

To get each rib foot, draw a line representing the TE (angled accordingly), mark positions of all ribs on this line, Draw a horizontal line starting at the Root at TE. Dimension the distances from each Rib station to horizontal line.

ProfLooney

thanks pattern wannabe will do that next set of plans I trace without feet. This one I am stuck building a jig as kits in the mail :0)

Joe

monocoupe

My Feedback: (40)

Joe,
As long as one is at 0 and the other is at 2, relative to the cord line, it's going to work. Just make sure that you have washout , and not washin! You can, and should check your calculations with a protractor on paper, to make sure that you got the math right, and actually have 2 deg.
I always draw a line that represents the building board under the root and tip rib profiles on the plans, at 0 deg and -2 deg respectively to make sure, and so I can measure the actual distances between the rear spar and the board in both cases, so I can make my tapered strip. That way you don't have to throw away the first wing, and start again!...I hate it when that happens!!

Cheers, Nigel

P. S. you didn't need to figure out the root at 2 deg in your last calculation. The root is zero, remember that the math only gives you the difference in angle relative to the cord line, not the building board. you still need to draw it out and measure under the rear spar at the root and tip, to get your jig dimensions.
Just using a protractor and a pencil on the plans is still the most foolproof and easiest way to figure out your jig, which is the object of the exercise after all!!

ProfLooney

OK I will wait til I get my plans from printers tomorrow and mess around.

I just was looking at my plans and notice the rear spar runs at an angle which my rear spar is basically the trailing edge where the ailerons run. will this angle throw everything off? I figure to be correct I should run it parralell to the main wing spar.

Joe

PS am I trying to hard to figure this out and making it tougher or am I just having a blonde moment lol

ProfLooney

I had to reboot so went and got me a cup of java and then it hit me everything you were saying (except the angled part i asked about).

Lets see if I get this correct.

When we did all the mathematical stuff what we did was to come up with the dimension for the centerline of the rib at the rear of the rib. I then draw a table top line and set the rib on this raising the tail end of the rib to that measurement. then I have to goto the part of the rib where the rear spar is and measure that and use THAT measurement for the jig and do the same with the root rib but set that at zero.

by georgy i think i got it. sometimes it just takes a moment of two to let your brain rest.

Joe

monocoupe

My Feedback: (40)

By Jove, I think he's got it!

Very good, my wife is calling and so I have to sign off now.
Good luck with it, and I hope it all works out well for you, Joe!

Cheers, Nigel

ProfLooney

Thanks again and gnight