Final Up-Drilling of Wing Attach Assemblies

[sonex1678]

Like a few others, I am at the spar mating stage for Sonex 1678. I am clear on the mating procedures (have up-drilled the alignment holes and am in the process of up-drilling the blocks, all using the drill press method), but was wondering what the latest thoughts are on the final block up-drilling of the blocks from 1/4" to 3/8"? I have the 1/4" to 3/8" Fastenal bit recommended on the forum, and intend to use it unless there is a reason not to (such as if the experience of others indicates that the resulting hole is too big, and a smaller drill/reamer is really necessary. Also, what are the thoughts on when to up-drill? Should I up-drill now (while initially mating the spars) and then use the "alternate" method described in the forum using drill guides to drill the airframe angles once the wings are installed in the fuselage; or, up-drill the blocks and the airframe angles at the same time once everything is assembled?

I appreciate any and all comments/suggestions, as like quite a few others before me, I am pretty apprehensive about this step.

[sonex892]

Its your decision alone which way you go here. If you look at and visualise the processes of both methods you will see they are both exactly the same, just using different tools. The actual centre of the attach block hole will be in exactly the same place whether updrilled now, or updrilled later while rigging.

As for the problems many have with this, I believe its not the piloted bit at fault. It is that drilling a 3" deep hole with a 3/8" bit, with a hand held drill, in an awkward position is bloody hard to do. A drill press on the other hand is made to drill holes like this.

I updrilled the bolted together spars using a drill press to 3/8", where you are at now. I just used a 3/8" drill, didn't ream, the bolts are tight, I have to tap and turn them to insert or remove. My friend and fellow Sonex builder who assisted me with the rigging of my wings had only recently prior to this rigged his own wings using the piloted bit method. He couldn't believe how much simpler and quicker the bushing method was.

[sonex1678]

Thanks for the input and info on your experience. After up-drilling the blocks to 1/4, I flipped over the mated spars and found that what I thought was a nice job in fact had elongated holes on the other side. I believe this may have been due to the alignment of the pilot hole in the blocks being slightly off, and the up-drilling not able to compensate/correct. I do not want to take the chance of the final up-drilling not being able to correct, so I am going to remake whatever blocks are necessary again until I get it right. At that time, I think I will do what you did, and final up-drill while the spars are mated as I do not want to discover or create another problem when everything is together and the wings are being mated to the fuselage--I think any fixes would be easier at this stage.

Can't believe the blocks drilled as they did after all the prep I did. In the military we use to say "there are no problems, just opportunities to excel" so I guess I just have another "opportunity" at hand....

[dtwolcott]

After two tries I decided to up drill to 3/8 before rigging the wings to the airframe. The drilling of the 3/8 holes went very well using the method of bolting the wings together and up drilling while the wings were not in the fuselage. When rigging I did used the stainless steel bushing in the 3/8 hole to drill the 1/4 hole in the fuselage and then up drilled using the 1/4 guide 3/8 drill. Everything went as planned and I too have to use a hammer to tap the pins in. It is very hard to make a good clean 3/8 hole thru the wing attach blocks and the fuselage with a hand drill in the cramped space inside the cockpit.
Don

[Bryan Cotton]

Don,
Where did you get your bushings?

[Sonex1517]

Bryan

I have bushings or you can get them from McMaster-Carr

[sonex1678]

One last question--after using the bushing to drill the 1/4" hole in the fuselage, did you use the 1/4" guide 3/8" bit through the predrilled spar to up-drill the fuselage, or did you remove the wing and just up-drill the fuselage (don't want the bit turning in the spar any longer than necessary...).

[sonex892]

One last question--after using the bushing to drill the 1/4" hole in the fuselage, did you use the 1/4" guide 3/8" bit through the predrilled spar to up-drill the fuselage, or did you remove the wing and just up-drill the fuselage (don't want the bit turning in the spar any longer than necessary...).

Hi Doug. If you are asking me? After I ran the 1/4" bit through the 3/8"OD drill guide I just went straight to a standard long 3/8" bit through the predrilled attach blocks. A piloted bit at this point would also work. I wouldn't remove the wings until the rigging operation was totally finished.
To avoid chewing away the hole with the 3/8" bit. Only rotate it counter-clockwise when inserting and removing, so the cutting edges don't do any unwanted cutting. When drilling its only 1/8" of metal so it doesn't take too many turns to get through.

Steve
Sonex 892

[sonex1678]

Thanks Steve--just what I needed to know, especially the tip about turning the bit counterclockwise....

[dtwolcott]

Bryan
They weren't bushings per se. My company my son owns provides part and service to the natural gas industry and there is stainless tubing that has a 1/4 in id and 3/8 id. I got the tubing from my son. I would thing any tubing supply company would have this. If you don't find any I will give you the ones I used. Since tolerances are not the perfect you may need to put the tubing in a drill press and use emery cloth to reduce to outside diameter slightly to fit your hole in the blocks. I found that I had to do that.
Donald Wolcott