MarkGrabowski

Question.... what is a good way to cut the hole in a set of cores for the wing tube..
I know how to set up the jigs and such to hold the boring tool in alignment...
I'm not sure what's the best way to do the actual cutting? I mean, what kind of "cutting head" goes on the end? I can see installing an exacto knife blade on the end of the tube with an O.D. just a bit larger than the O.D. of the wing tube sleeve but then how would the waste material be drawn out of the hole? I'm not sure I can procure a piece of tubing (aluminum or otherwise) that will have the correct O.D. so I'll need to use the next smallest size and then tack on a blade....
Any suggestions?

TedMo

Sharpen the inside edge of the tube then just cut by twisting and pushing it thru.It will require removing to clear out cut foam from time to time.

nonstoprc

My Feedback: (90)

I file the edge of the alum wing tube to shapes like the teeth of a saw blade. Then just rotate/push the tube from the other side. The tube has to be supported by the jig. The hard part is build the jig and align it right. I use two pieces of 1X2 hard wood and precisely drill the hole (of same OD as the wing tube) through both. The distance from the edge of the wood to the edge of the holes should be such that it will cut through the location on foam core. Then secure both pieces on a flat work bench with screws. Align the jig at the same time.

The cutting takes less than 5 minutes.

ArchNemesis

Just to provide confirmation to you, I agree 100% with everything QC described.  When we were kitting the Arch Nemesis and others that was precisely how we made the jig and drilled the holes. Quick and easy.  Be sure you have someone holding down the cores so they don't move while you 're doing it.

speedracerntrixie

My Feedback: (29)

I measured in how far in I wanted the wing socket to go and cut the core into two parts. Then made a couple templates that were square in sape with a hole the size of the wing socket but with a slot at top. I attached the templates onto the root and at the end that was just cut. I was able to drop the hotwire trough the slots in the templates and cut the holes. The far end of the socket gets supported with a peice of 1/8 lite ply that is full depth vertically so it will tie to the wing skins. The outter part of the core is glued back on and sheeted normal fashon.

burtona

My Feedback: (50)

I built a jig to hold the foam and a fixture to hold a Forstner bit with a drill extension and drilled with a 7/8' ot 1' bit and an electric drill. I always drilled the hole in the block of foam before the wing core was cut

MarkGrabowski

I should have been a bit more clear...
I have a carbon fiber wing tube so sharpening the end and using it as the cutting tool isn't an option...

MarkGrabowski

I would have thought the Forstner bit's teeth were too coarse and would "tear" the hole more that drill it cleanly...
Does it cut clean?

JeffH

My Feedback: (43)

I had older kit, can't remember what now, that had a 2x2"ish square hole through the core where the wing tube stopped. A template was fitted with the tube hole and wire slot inside of the 2x2 hole, and then the root template with the hole and slot was used to to cut the tube hole without cutting the core in half.

Magne

I don't use the wing tube as a cutting tool, but rather the sleeve. After all, it is the sleeve that will be glued into the core, so the hole has to be cut for the sleeve, not the inner tube.
The (fiberglass) sleeves that come with the PBG carbon tubes are very thin, and are therefore very good as cutting tools, sharpened with sandpaper.
As noted above you have to do the job in stages, pulling out the cutting "tool" and remove the foam core. When you cut, you can "feel" when the core breaks inside the tube, this is when you remove it and clean it out.

On the other hand, if you want to use the inner tube, then I don't see why you could not sharpen this also, even if it is carbon.

Magne

nonstoprc

My Feedback: (90)

I should add to my previous post that if you use the wing tube to cut, you need to use the wing tube socket to "enlarge" the hole a little bit. Here are pictures of the tool I have used. Many thanks to Magne who pointed out the missing step.

VerneK

The forstner bit works great. Just make sure to have it spinning before you enter the foam. Obviously, you'll need a fixture that will guide the long steel rod that holds the bit. The fixture can be a square U channel with pillow block bearings that slide up and down for adjustment. The space between the walls of the U should be at least 4" to provide good lateral support. The hole won't be quite as clean as if you cut it with a hot wire but it will be clean enough. The down side is that it creates quite a mess so have a shop vac handy. The strength of the wing tube/socket assembly comes from the glue joints at the root and false rib. The foam only acts as a guide to keep the socket lined up.

I learned about this fixture from Aero Composites, a kit manufacturer back in the 70's and 80's. They were the first American manufacturer to have a kit with plug-in wings (Ivan Kristensen's Summit II). The advice someone else gave about boring the hole before the wing is cut is good and provides the best accuracy. Most of the forstner bits in the size range you're talking about have a 3/8" shaft so you'll need at least a 5/8" shaft and 3/4" would be better. The beauty of it is that you can cut a wide variety of sizes with it by just changing the bit.

Verne