main spar detail ?

[fairchild]

I have my sacred and working master rib forms made (yeah) complete with steel drill bushings. About to cut out the cutting templates for cutting the nose rib blanks.
Remembering that there are 2 or 3 different lengths of them (depending on how many 1/8 layers are on the spar at the rib's position) So I have to know the lengths to
know how to size the cutting template. So i go the the spar page (5b) and look at the spar drawing. As I start at the root and go out to the tip (on the drawing) ----
when I get out to the tip area--- where the last 2 or 3 ribs would go---- the 1/8 reinforcements are not shown--- only the .032 sheet core. It shows the last 2 lightening
holes in the core .032 sheet and no other stuff attached there---- and then there seems to be an "end cross section" which looks like only the core. If there REALLY
is nothing else out there--- what do the last 2 ribs attach to ???? (this is a Bearhawk B )

I have Eric's CD coming ..... but prob wont be here till next week.
I looked for a pic of the spar on the web but most of the good pics showed it from the root end. -or it was the las version.....

Tim

[sjt]

IMG_5167.v01.jpgIMG_5169.v01.jpgIMG_5168.v01.jpg
I am scratch building a patrol. However, Bob would recommend you make all nose ribs , center ribs the same size and trim them only at assembly time. Remember to make a left and right version of each rib. Also, the ribs are attached with 032 angles at rib-spar connection. The need for ultra precision is not there. I

I made my master out of the mylar glued to a 032 sheet. On the mylar there are markings for the main and rear spar. Lay the rib blank down such as that there is a flat edge. Then lay the template - with spar markings down over top the square edge. You can use the outside of the line as an accurate 032 reference. Then with a transfer punch - pin punch holes in your rib blank using the bushings in master template. Also take a magic marker and draw the outside edge using a 9/16 washer. Drill the tooling holes thru your rib blank. In the case of the nose rib there is one in the front , and most people put another one up toward the cap strip area. The tooling holes should be placed in your master so that all ribs are routed the same.

Below is my full size rib template used for wing tips.
​ fetch?photoid=12506.jpg

[fairchild]

OK- you are just bringing the rear of the nose spars back to the front spar centerline-- knowing that will be a little long-- and trim the back when you attach them.
I thought of that-- but seeing how the bent top and bottom flanges extend right to the end - I didnt see an easy way to cut them nice and clean across those bends.
Can't cut them on the jump shear because of the bent flanges. snips would be a little messy...... I should think youd want to be pretty close so as not to run out of
riveting surface between the rear tail and the attach angle.

i thought i'd drill my pinch bolt holes in the cutting template- which I should be able to use for both sides (L and R nose ribs). (same with bending blocks)
One hole will be the front hole from the master template. The other somewhere in the rear out in an open area.
Since my master working template is 1/2 mdf with steel bushings..... I thought Id make a little transfer punch which will just fit into the bushings (3/16) and put a small
sharp end on it to make a tiny v shaped punch mark on the form blocks or cuttings jugs as needed. I plan on NOT cannibalizing any of my MDF forms just in case
later on I have a bad slip with the rivet gun and need a replacement rib somewhere along the way.

How exactly do you plan to cut them ? I plan on having them all done and chromated when they are ready to put on.....

Tim

PS neat idea using elevator bolts.....

[Chris In Milwaukee]

I cut all my ribs the same length: the shortest length after spar caps. I’ve cut the rib attach angles longer on the rib side so I have room to adjust.

As for what to attach to, if there’s no spacer bar down there to go through, attach directly to the spar web.

[sjt]

I think Chris means that they are the longest length.

A line on a drawing does indeed imply the center of the spar. But, the line has a thickness, and it is not that far off to assume that the visual edge of the line is the correct length. All I really care about is a clean edge that can be used for a reference.

What Chris said is the key point. Suppose the ribs were accidentally -or on purpose- a shade smaller. The 032 rib attach angle flange are arbitrarily long. So long as you do not violate the rivet to edge distance of the rib blank. The ribs are 025, the attach brackets are 032. The brackets are stronger the the rib. A rib does not have to be perfectly flush with the spar or a cap strip - SO LONG AS THE ATTACH ANGLE FLANGE MAKES UP THE DIFFERENCE. I have recommended keeping them full length until assembly time (BOB'S suggestion) All that you need to do is cut a notch out for the cap strips if you wanted. The extra length does not feel anything. The rivet is way back relative to the bracket.

As to cutting I cheat. I have a table saw with a 10 inch 100 tooth aluminum cutting blade (TENYRU). It makes cutting spars to length trivial.
IMG_5171.v01.jpgIMG_5170.v01.jpg

The saw can not reach the edge, but a few snips and it is done.
For what it is worth, I do not use the 10 inch alumicut table saw blade that much. I did use the 12 inch tenyru alumicut chop saw blade for cutting thicker stuff. John (n3uw) has youtube videos showing how he used it. I copy a lot of his work. If he does not start posting more videos I probably will be stuck.

[marcusofcotton]

Later, while assembling, I like to make sure that the ribs do not butt up against the spar or cap strips. A strip of masking tape is enough clearance, just like to make sure that there is not an edge possibly causing a defect in the spars after years of use. better to have the ribs trimmed slightly short and make up via the angle mount.

[fairchild]

SJT------ All Right ! There is some nuggets of wisdom ! I guess anywhere one can prevent painting ones self into a corner--- thats a good general strategy !
Ok-- that makes it easy---- Ill just cut them to the face of the spar. Maybe later when its time to trim them I can make an MDF form block somehow that will
surround the center and flanges so the saw blade wont bend them. or maybe a FINE band saw blade.
I am trying to model John Snapp's method..... it looks like how I would do it if I had done this before ! :-)

Marcus: Yes-- you wouldnt want any long term chafeing or even just rubbing through the primer even- would be a great place to get corrosion started. Condensed
moisture here in Florida is REALLY bad inside wings. Durring day- 100Degrees and 100% humidity---- then overnight maybe 65 or 70 and dripping wet. You can look into a wing
with the tip off and see where the big water droplets just hang there on the upper surface every night. a corrosion spot at every drop location. I will have to watch for all of those little
detail things.

I will try to cut out a rib blank Like J. Snapp did and see If I can get a good result. Might try that tomorrow !
Thanks so much for the guidance ! This seems much like other things Ive had to learn---- its not what they say thats confusing -- its what is never mentioned ---
I usually figure they thought it was so obvious that they didnt need to point out the obvious. but as my dog used to laugh at me and say "Daddy Stupid!"--- Chauauahas say stuff like that......

Tim

[sjt]

I like what marcusofcotton said. You do not want the rib actually touching the spar. Yet another reason to be less concerned with absolute precision.

[fairchild]

YESSS .... I see noww !