aftcg

My Feedback: (1)

I've built 4-5 planes. All .40 size. All but one from kits. All of the ribs in the wings in those planes had cap strips on top and bottom.

I'm building a larger plane that will have ten ribs in each wing and each wing will be about 40" long. The ribs are about 18" long, 4" tall and 1/8" thick. Obviously, the monokote will be resting against the 1/8" edge of the ribs unless I add 1/2" cap strips on ribs.

Are the cap strips necessary for a rib that is 1/8" thick? What do they do for it?
Thanks for the help.

Josey Wales

My Feedback: (61)

The cap strips strengthen the wing and make the ribs rigid. Put them on the top of a rib and then try and twist the rib lightly. Now put the cap strip on the bottom and try the same thing and you will see the difference..

Cactus.

My Feedback: (1)

cap strips do as much for strenght as shear webbs for me...
also help keep the back of the wing inline with the front

Balsa Master

yup, you need em, think of a building, ever seen a skyscraper built our of sheet metal, no its all I beams.

Sprink

Its not until you are getting to 25 size planes and below that you can start to think about not using them. however they do make the attachement of covering easier and nicer with them than without

linclogs

I've seen some kits that had cap strips ONLY on the top. It depends on the wing sheeting - obviously, if the wing has sheeting on the top and bottom (leading edge and trailing edge), then you'd need capstrips on both sides. Unless the ribs were notched so the sheeting met the tops (and bottoms) of the ribs without capstrips. I've seen them designed like that, too. But if I had a choice, I'd go with capstrips both top and bottom as the wing will be much stronger and have greater torsional strength. Also gives much more surface for the covering to stick to.

aftcg

My Feedback: (1)

Thanks for the replies.

Does it matter if the cap strips are made of balsa or basswood (or other hardwood)?

Again this is an 82" WS 16# plane.


Also, probably an obvious question, but do I put the cap strips on every rib or some other combination?

Josey Wales

My Feedback: (61)

Ive never seen cap strips made of anything but balsa but I could be wrong..Yes you want them on every rib..

greenboot

My Feedback: (1)

The wing will always look much nicer with the cap strips. Also it gives you enough area to make a seam in the monokote. I alway put stripes on the bottom of the wing so I need the cap strips for that.

Tom