Cardinal WIng Construction Question

According to my Brodak Cardinal kit plans, when I lay my four foot Exact scale on the wing plan along the location of the leveling bar, the leveling bar has a few degrees of rear sweep. Is this correct? I know the LE is swept for sure...and the TE has a tad of sweep in it as well.... For you guys that are familiar with this kit, is that correct?

Joe,
I have found that some copies of prints have problems with keeping lines straight. If you are confident of the straightness of your level, I would go with that and then use the plan for spacing. Generally the trailing edges of most airplanes I have seen around are straight. Good luck and happy building.
John

LAST EDITED ON Feb-18-03 AT 00:12 AM (CDT)
 
>Joe,
> I have found that some copies of prints have problems with
>keeping lines straight. If you are confident of the
>straightness of your level, I would go with that and then
>use the plan for spacing. Generally the trailing edges of
>most airplanes I have seen around are straight. Good luck
>and happy building.
>John

While it is true that most stunt wings have straight trailing edges, the location of the levelling bar, as used in most Brodak kits, is not always related to the trailing edge. But, in this case, the levelling bar should be straight from wingtip to wing tip.

The bar can be angled, and often is because it relates to the amount of taper in the wing ribs, top to bottom. It all depends upon the percentage of thickness between the root and tip ribs. Once agai though, in this case, the bar should be straight.

Best wishes, John Miller

I'm wondering why everything is spinning around?

And the distance from the TE to the TE side of the levelling bar is 2 1/4".

>>Joe,
>> I have found that some copies of prints have problems with
>>keeping lines straight. If you are confident of the
>>straightness of your level, I would go with that and then
>>use the plan for spacing. Generally the trailing edges of
>>most airplanes I have seen around are straight. Good luck
>>and happy building.
>>John
>
>While it is true that most stunt wings have straight
>trailing edges, the location of the levelling bar, as used
>in most Brodak kits, is not always related to the trailing
>edge. But, in this case, the levelling bar should be
>straight from wingtip to wing tip.
>
>The bar can be angled, and often is because it relates to
>the amount of taper in the wing ribs, top to bottom. It all
>depends upon the percentage of thickness between the root
>and tip ribs. Once agai though, in this case, the bar should
>be straight.
>
>Best wishes, John Miller

Is that you, John???

Yep Ion, That's me.

I posted it there so I could use it as my Avatar.

No more anominity I guess.

Best wishes, John Miller

I'm wondering why everything is spinning around?

The TE of lthe Cardinal is straight. During printing or copying a print, the lines can and do get a slight "sweep" to them. I found this on one of my sets of plans. I just use a 48" long straight edge to aline the TE and the support bar ahead of it where it should be. The end result is a straight wing. But do follow the instructions. This wing is very fragile in the initial stages of construction. As it progresses you can feel it get stronger. Several people including me add vertical webs or angled webs between the two main spars to make the wing very stiff and the weight added is less than an ounce.

OK...so we have confirmed that the Cardinal TE should be straight, not swept, as should be the leveling bar. Even if I set the leveling bar staright I cannot go off the plans for the spar location because the spars will have too much sweep (since the TE and leveling bar lines on the plans are swept). I guess I will have to set the bottom spar loose on the plans and place the root and tip ribs on the spar so the TE of the ribs is on a staright line...and parallel to the leveling bar. I can then mark a new line on the plans for the the spars location.

Thanks

Joe

The spars are not straight. Set your spars 5.812" forward of the TE at the tip--that's the back of the TE that you see on the finished wing, not the edge inside the wing--and 6.09" at the root but with the TE and the levelling bar in place, the ribs should locate the spars. Also, there is about .264" taper in the wing so you might want to shim the lower spars to allow for the taper when you finalise their positions.

Good luck, Geoff

>Joe
>
>The spars are not straight. Set your spars 5.812" forward
>of the TE at the tip--that's the back of the TE that you see
>on the finished wing, not the edge inside the wing--and
>6.09" at the root but with the TE and the levelling bar in
>place, the ribs should locate the spars. Also, there is
>about .264" taper in the wing so you might want to shim the
>lower spars to allow for the taper when you finalise their
>positions.
>
>Good luck, Geoff

Geoff, Thanks for the specs. I know the spars are not straight, but the procedure you describe will determine the correct location and sweep of the spar. The kit instructions are good and they do specify the spar shimming procedure...

Joe

>According to my Brodak Cardinal kit plans, when I lay my
>four foot Exact scale on the wing plan along the location of
>the leveling bar, the leveling bar has a few degrees of rear
>sweep. Is this correct? I know the LE is swept for
>sure...and the TE has a tad of sweep in it as well.... For
>you guys that are familiar with this kit, is that correct?

I got this from John Miller, the guy that made the CAD plans for the Cardinal:

"On the wing center line, between the two ribs R-1
Leading edge to trailing edge = 9.510"
Leading edge to front of spar = 3.170"

Rear of spar to extrem leading edge. (Where the flaps aill attach) = 6.340" (84.836mm)

At the tip, at the line where the tips and tip block will attach.
Leading edge to trailing edge = 8.207
Leading edge to front of spar = 2.145"
Rear of spar to extreme trailing edge. = 5.812"

Centerline to centerline of the rib = 2.969" (2, 31/32")

Centerline dimension between the R-1 ribs at the center of the wing is .438", or 7/16".

Dimension between the opposing faces of the ribs. This dimension is 2.906" or, 2, 29/32".

Building tip. I make a spacing jig out of two pieces of 3/32" balsa. The two pieces are cut and sanded to act as a spacer between the ribs as I set them into place. I connect them together with two pieces of scrap balsa so that they are far enough apart that they will correctly align the rib with one biece near the trailing edge, and the other near the leading edge. Use the tip rib to figure this distance, and make them tall enough to clear the top spar.
Distance between the to R-1 ribs, at the center is .375", or 3/8".

I would set the wing up as explained i the plans and booklet. Place a few pieces of 3/8" scrap balsa between the two R-1, or root ribs. Align them so they are staright, and perpendicular to the trailing edge, and tack glue them first. Now, using the spacing jig, set it so that one side is tight to R-1, and palce R-2 tightly to the other side of the jig. Continue in a like manner until all the ribs are in place. (I'm assuming that you'll be using your rod jig to build the wing here) Only slight modification of the method will result if you build the wing as outlined inthe manual, using the "levelling bar system. "

I am just starting to fill and finish a modern stunter built from Cardinal ribs from Brodak and yeah, it's a chore to build it straight on a flat surface. I wound up wetting, jigging and adding 1/16 shear webs over maybe 2/3 of the span which gives it a lot more stabiltiy and seems to have helped in holding out the warp. In building, I most definitely noticed something out of whack with the wing plan's spar sweep and TE. This, of course compounded the wing construction problem.
This airplane is basically a homebrew using Cardinal/Evolution moments and areas but non cowled, inverted engine, different top deck and lines. Power will be SSW 35FP and it should be in the air in a week or two. The wing now looks straight and I have 3" stationary flap tabs both inboard and outboard which with some judicious 'kote twisting should get it flying properly in the event the warp is still there.