Strut attach bars

[Bradrock]

I just had my strut attach bars cut for me by water jet. They haven't quite got the holes exactly right. The hole that sticks out of the spar and the hole directly adjacent are 1/16th short. Is that an acceptable tolerance or should I move the attach bar out of the wing by the equivalent distance to put the attach hole in the right spot? See photo....

[marcusofcotton]

My first concern would be to insure that when you enlarge the holes in the upper and lower capstrips, you are able to fill the holes with the bolts (if that made sense). With that in mind, I'd keep the lower hole as close as you can to the specified position. It probably really doesn't matter too much though if it is slightly shy.

Mark J

[Bradrock]

Hi Mark - I think you mean that I already have holes in the caps trips that I need to match to these bars? I have no holes in the capstrips as yet. I was going to put the holes in according to my strut attach bars.

[geraldmorrissey]

If all the holes have been cut and those two end holes are out by 1/16", that's quite a bit by aircraft industry standards but not as much by homebuilt standards. No tolerance is listed in the title block of that drawing for the Patrol. Unless I'm misreading this, if you use as is and you have to adjust the angle of the strut bars to get the cap strip bolt holes located, you not going to have the 30 degree angle (on the Patrol). If you adjust the angle to 30 degrees, the bolt holes in the cap strips will not be located on the cap strip centerline. If the water jet cutter just screwed it up, I would have them make new ones. In any event, call Bob. He may say "use them as is". I'm curious about the hole diameters cut with water jet. Do you have to drill out the holes? I found that a #11 drill bit gave me the best fit for a -3 bolt. I milked a bunch of -3 bolts and found them to be .1882 to .1886. A #11 is .191. I'll put some of the fat ones in there to minimize the clearance Clarence.
Good Luck
Gerry
Patrol #30 wings

[DesertBearhawk]

Brad, Just put the bars in as per the plans and press on. I looked mine over and I see no issue with the hole being off that much. If it bothers you have the water jet peeps redo them….on them of course!

[marcusofcotton]

Since you don't have the cap strips drilled yet, I see it as a non issue. Don't bother with having them redone, for your sake and theirs - what goes around comes around. Relax, smile, and Enjoy!

[Battson]

Brad - one issue I would mention is the clearance on the wing-skin. The distance from the wing skin to the centre of that hole (once assembled) is only just enough to allow the strut attachment fitting to mate correctly. It basically touches the wing skin. There is not any clearance really. If you left the hole 1/16th closer it might not fit.

Similarly, you would want to make sure, assuming you use those parts are drill the cap-strips sympathetically, that there is adequate clearance to fit the bolts inside the wing when it comes time for assembly.

Also, having the capstrip holes closer to one side of the bottom capstrip would create a weaker point, which will be subject to some increase in stress loading compared to design. It might be a non-event as this increase *might* be insignificant, but you will be testing the design modification for the first time. It might also be significant, you would need to run the numbers or test it to know for sure.