Rib Question

[johnf]

Point of interest: Someone mentioned needing to resize the rib template due to shrinkage. I'm guessing the 25" was short. I just looked back to see when I received my plans. It was back in May 2007.

Yah! A little procrastinating here, however I'm a real estate broker in South Florida. The market dictates my spending.

Anyway, when I received my plans I took them to a local blueprinting company to make a copy for a backup/working set. I explained the importance of 'Actual Size'. The manager stepped in to handle it himself. Once the plans were scanned into the computer he adjusted the template and former pages to actual size and test printed a few while adjusting until, for example, the rib layouts measured exactly 25" on center of spars when printed out.

I then had those pages printed onto the thickest Mylar he had, as I would be cutting them up for actual layouts. This is a trick I learned with RC model planes.

Mylar for 2 reasons.
1.) No shrinkage
2.) Sturdier than paper. Better to work with as templates.

It's now been 4 years, most likely to the day. The Mylar has been sitting rolled up on a shelf in my garage. Did I mention South Florida? Heat/humidity? I laid out the rib plans just now. No real curling to speak of as they laid almost completely flat with a little curling on the ends. The dimension on the rib for on center of the spar is exactly 25". I do mean 'exactly'.

Thought this might help.

See ya

[Nick]

Great tip, John. I'll remember that for my NEXT plane

Nick

[johnf]

Due to heat and humidity extremes here in South FLA, maintaining flatness of any fixture when working with wood is a concern of mine. My cabinet maker friend and I built a box out 3/4 oak ply to hopefully maintain flatness for however long it is that I'm building ribs. Once the box was built the bare wood was as flat as wood will ever be. After gluing on the Mylar template, there is about a 3/32" bow from tip to trailing edge. Could be expansion of wood from glue, could thick glue in various locations, etc. Anyone have to deal with this? Is the bow a major concern, or will this true out during construction? Obviously I can built another box and template, but if this is not any concern I won't waste the time

[jwhanson]

Hi John,
Don't get too wigged out on some of this or you will never get done. We just plotted the airfoil out on a plywood table top, glued some locating blocks on and
built the ribs. Your ribs will be somewhat flexible and can be lined up straight during the assembly to the spars.
John Hanson HC-012.

[dougm]

I agree with John. The ribs have a fair amount of flex in them when completed so I seriously doubt the 3/32 bow will make any difference. As John said, if there is a bow you can straighten it on assembly, but again, I doubt you'll see any effect from the jig.

Don't make a science experiment out of it... if you are really concerned build one as a "practice" rib and see how it turns out. I think you'll be fine.

[johnkerr]

The process does not need to be elaborate, beyond the spacing for the spars. Now is the last time the ribs will be measured. The picture someone included above appears to be an eligant approach to rib building with the duplex capacity and screw clamps. EAA Tips for Homebuilders has an excellent video on rib building. Other examples are even more imimalist in approach. Some adaptability of the jig is desireable because there are at least 4 different configurations of the "standard" rib plus the smaller tip ribs. You probably won't want to build discrete jigs for each.

[johnf]

Thanks for the feedback. It's why I asked. No big concern.

Thansk again,

[womenfly2]

John, where did you get the full size rib drawing from I see on you jig table?

[dougm]

The full size rib drawing is in the plans. I also have it electronically along with the cad drawings for most of the flat steel parts.

[womenfly2]

I will have to check my CD, I only remember pictures of the build, which seriously needs updating.

Could someone e-mail a copy, ribs & fittings? Use my PM an I will forward my address to you.

Blue skies,
Keri-Ann

... rib material and spars on order!