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Hello, I bought a started kit from a friend (just fuse is in an advanced building state) but find problems with the alignment of pre-drilled holes in ribs and pre-drilled holes in spar web: ribs were not bent correctly (I suppose they came so from factory) and if I make the upper and lower surfaces of ribs matching with spar surface, holes are not matching and should make new ones or enlarge actual ones. What should I do? keep spar holes true and modify ribs holes? make completely new ones (but going this way there should be too much holes in spar webs) Hope to have been clear with problem description...

Thanks for your help.

Roberto Grassi from Italy
(Sonex legacy kit #1433)

Do not make new/additional holes in the spar. How far off are the holes from the rib flanges to the spar holes? Are you sure that you are correctly aligning the top and bottom rib flanges to the spar caps? There is a reference in my set of plans on exactly how to do that. Some photos posted here might help.

Roberto,

This may be irrelevant to your situation but the ribs are identical between the left and right wing. This results in the rib flanges facing the outboard side of one wing and the inboard side of the other. I assume you have this correct but just in case it was not obvious in the plans, I thought I'd mention it.

Best,
Paul

dbdevkc wrote:Do not make new/additional holes in the spar. How far off are the holes from the rib flanges to the spar holes? Are you sure that you are correctly aligning the top and bottom rib flanges to the spar caps? There is a reference in my set of plans on exactly how to do that. Some photos posted here might help.

The holes are far off around 4mm, and it happens when aligning the top and bottom rib flanges to spar caps...one friend that is a certified airframe mechanic suggested to use the spar web holes and make new or elongate ribs holes, and gluing the "wrong drilled" rib with J&B Weld to spar web. The reference you are quoting is also in my set of plans, but I understand it refers to ribs that are scracht made and not pre-drilled...

Thanks for your help, as soon as I return to hangar will try to make photos.

Roberto

thomas wrote:Roberto,

This may be irrelevant to your situation but the ribs are identical between the left and right wing. This results in the rib flanges facing the outboard side of one wing and the inboard side of the other. I assume you have this correct but just in case it was not obvious in the plans, I thought I'd mention it.

Best,
Paul

Thanks Paul, but it is not what are you saying my problem, it is when aligning the upper and lower rib flanges with spar caps that the holes misalignment comes out...not in all ribs, it happens only in some of them...

Thanks for your help,

Roberto.

Roberto,
What I have done for poorly mounted ribs is to cut off the flange that mounts to the spar - and rivet an angle onto the rib to make a new flange. Check with Sonex tech support but I bet they would permit that. I had to do a similar thing on one of my stabilizers as one of the center ribs was too long.

Roberto, could I just clarify something with you? The forward ribs all line up with the forward flange of the spar cap but many of the main ribs don't line up with the rear rear flange of the spar cap. The drawing shown below shows one of the inner ribs. You can see that the ribs don't line up with the rear flange but a continuation of the curve will line up with the forward flange. Hope that makes sense.

I hope I'm not telling you something you already know but I recall when I built my Sonex I was quite surprised by this feature although it does make sense (eventually).

Peter

peter anson wrote:Roberto, could I just clarify something with you? The forward ribs all line up with the forward flange of the spar cap but many of the main ribs don't line up with the rear rear flange of the spar cap. The drawing shown below shows one of the inner ribs. You can see that the ribs don't line up with the rear flange but a continuation of the curve will line up with the forward flange. Hope that makes sense.

I hope I'm not telling you something you already know but I recall when I built my Sonex I was quite surprised by this feature although it does make sense (eventually).

Peter

If I were a betting man, that is what I would think is going on. The rib flanges on the aft ribs do not line up with the surface of the spar cap at the aft edge of the cap - they're not supposed to. cleco those ribs in place, then cut some strips of .025 to lay on the ribs as a test of how the skin would lay. What you should see is that the aft skin will continue the plane of the rib flange - it will be above the spar cap surface at first - but then lay on the spar surface after passing the "peak" or center point. This is most noticeable on the inboard ribs.

robysonex wrote:The holes are far off around 4mm, and it happens when aligning the top and bottom rib flanges to spar caps...one friend that is a certified airframe mechanic suggested to use the spar web holes and make new or elongate ribs holes, and gluing the "wrong drilled" rib with J&B Weld to spar web. The reference you are quoting is also in my set of plans, but I understand it refers to ribs that are scracht made and not pre-drilled...
Roberto

If the ribs are pre-made and pre-drilled from the factory I would be very surprised if they were that far off. But if they really are - and I would like to see photos to be sure and you should probably check with Sonex support - then I would go with Brian's idea. Cut off the flange that mounts the rib to the spar, make a new flange and rivet it to the rib, align the rib to the spar and drill through the spar into the new flange. Be sure that the new flange does not change the original rib dimensions (flange to tip length).

I would not elongate the rib flange holes. I definitely would not use JB Weld - in my opinion that is the wrong way to fix an issue with incorrectly sized holes. Even then I would question the reactive properties of JB Weld with aluminum.

dbdevkc wrote: I definitely would not use JB Weld - in my opinion that is the wrong way to fix an issue with incorrectly sized holes. Even then I would question the reactive properties of JB Weld with aluminum.

Definitely no JB Weld!