Nose ribs

[wapati-bull]

My question is do I use 1/4” plywood for all the nose ribs or just the ribs that have a but joint of the nose skin thanks, Dave

[Theodore]

All, some guys add extra ribs made from rigid foam (closed cell)

[Kamcoman77]

.

[914pete]

The extra foam ribs were 1.9oz. total weight. I did a test gluing an extra one to a scrap piece of spruce using T-88 on one leg and Titebond 3 on the other. Both worked great but the Titebond was stronger. I still haven't decided what product to protect the spruce with but I tried Spar Urethane on the base of one rib and it didn't affect the foam at all.

[wapati-bull]

Thanks guys, my full sized pattern says that nose ribs are 1/4” plywood. Then in the text it states to put the nose skin butt joints on the 1/4” ribs,  so I wondered if they were all the same. Great pictures.

[Aaron]

Likewise to mentioned earlier all of my nose ribs are 1/4" birch aircraft ply. Personally I would not use anything thinner than 1/4" from both aspects of strength and gluing area of the nose skin. That 'D' section is critical to having a rigid wing that won't wash in and out on you while you fly. I wanted to share what I did for the ribs where my nose skins butted together. I glued some scraps of 1/4" square spruce cap strip left over from making wing ribs around the perimeter of the 4 butting nose ribs (2 per wing). Once dried I sanded to profile. Some might criticize but I liked the idea of negligible extra weight and additional gluing surface considering you get only an 1/8" per nose skin on that rib, and thats considering a perfect world where you actually make everything surgically straight (remember this is a legal eagle we're talking about not the apollo 13 :p ). I attached a couple of photos from my build process to help visualize. Hope this helps!

You might notice that my rib is offset an inch. I did that so that I can maximize the use of my sheets of plywood, otherwise the outsidemost leading edge sheet will need to be greater than 48", just a logistical thing, saved about 80$, only an issue for a perfectionist...

Also note that I really wish I would have put those rigid foam false ribs in there, now I have long spans of unsupported 1/32" plywood just asking to crunch a hole thru it. You don't need them to fly but they make good sense for protecting the integrity of your leading edge when the airplane is unattended, or the knuckle dragging pilot puts an elbow thru it trying to fuel (I'm not going to brag but I haven't done that...yet...)

[mike ketteman]

To save some weight,get a sheet of 3/8 balsawood and put some strips on the ribs that nose skins join on.

[Tom H]

Regarding the foam nose ribs:  this idea came about because builders were reporting that their leading edge was distorting as weather changed.  Large dimples or depressions were forming between the plywood nose ribs.  It was felt that adding a foam rib (or two) between the plywood ribs would add support to the plywood with little weight penalty.

This was discussed a bunch years ago on the site, if any of the old conversations can be found.

[Chuck in Indiana]

Regarding the foam nose ribs:  this idea came about because builders were reporting that their leading edge was distorting as weather changed.  Large dimples or depressions were forming between the plywood nose ribs.  It was felt that adding a foam rib (or two) between the plywood ribs would add support to the plywood with little weight penalty.

This was discussed a bunch years ago on the site, if any of the old conversations can be found.

The foam ribs would be a good idea. I didn't do it, and when it gets really cold, there are a lot of depressions in the leading edge. I'm pretty sure it won't really affect the way it flies, but you can feel them when you rub your hands over them.

[DA Miller]

From reading the posts on the forum several have reported that the dimples in the leading edge skins do not affect the flight characteristics. They just look ugly. I am not going to put the foam ribs in my LE-XL.  I am going to thoroughly soak the leading edge skins in warm water before installation. Once again from forum posts the thinking is: the skins will have a maximum water content so when the weather gets hot and dry the leading edges dry out and shrink getting tighter, when the humid weather returns the skins go back to the tightness of when they were originally installed. Hence no dimples.  If the skins are installed dry (low water content) then when hot humid weather comes the leading edges get soggy and lose their tightness and develop dimples.  Or so they say.  We shall see

[Chuck in Indiana]

I wet mine..

[DA Miller]

yeah, when I read that you developed dimples when it got cold I wondered how that fit in with my theory. It will be interesting to see how the dimples act when your plane goes through a seasonal cycle.  Keep us posted

[pappyadkins]

I didn't follow the plans here... I placed my nose ribs every 12". I used 1/4" ribs every 48" (at the splice only) and the rest were 1/8" ribs... It added very little weight & very little nose dimpling.

[Chuck in Indiana]

FWIW.. I'm not sure how much good false ribs will do. I wet mine at installation and they were perfect until the first Winter. I *did* install a false rib between number 2 and 3 because Keith, I think, said people were cracking the leading edge there (!) at installation. My photo app is acting up, but I have a picture at that location, and there is a dimple right next to the rib. There is a rib bay with no dimpling at all, and two in the next bay. That was the same piece of plywood, by the way.
No matter. IMHO, the air molecules that are sliding by at near supersonic speeds  most likely won't notice.
Edit: here's the pix..
first bay with a false rib

one bay with no dimples, but a small one right next to the rib

A false rib would have helped this bay, but not the next to it

[DA Miller]

chuck, I'm starting to think that this issue of dimples in the LE plywood is in the realm of "black Magic". From previous posts, I was led to believe that the dimples occurred when the weather got hot and humid and the PW got soggy and loose hence the dimples. Now it seems that your dimples occurred after cold and low humidity winter weather.  Do you have any thoughts on what's happening here?   FWIW I'm going to wet my LE PW with no false ribs and take what ever Comes

[Aaron]

I can attest, my LE will have dimples when I open the hangar doors to go flying, all it takes is 10 minutes in the warm sunlight, by the time I am started up, found my earplugs, and ready to climb in, the leading edge looks like I just covered it yesterday. With warmth they retreat, with cold they appear. It indeed seems contrary to common sense, however I wonder if maybe the nose ribs expand/contract at a greater magnitude than the skins? Doesn't seem right but that is all I can think up at the moment... I would love to hear any other wild theories, maybe somebody can bring some light to why the wood seems to contract in heat/humidity and expand in cold/dry.

Maybe an interesting note, I installed my skins on a hot and humid day, thinking about expansion and dimpling, thinking that the skins, if anything, will dry further preventing dimples until I could get them varnished. It wasn't 48 hrs from the day I applied the nose skins that the first dimple appeared. :/ Chipped my pride as up to that point I thought I made some pretty nice looking wings... she still flies so beggars can't be choosers! Out of curiosity has anyone applied the "D" skins in relatively cool dry climate? Curious to their experiences with dimpling compared to mine.

[Chuck in Indiana]

No, Possum, I'm clueless, my usual modus operandi.  Of course this plywood is considerably thinner than "normal" leading edge plywood, but the same method of soaking the outside and clamping securely to the nose ribs should apply.
FWIW, my shop is air conditioned but the still uncovered wing that is sitting in the wing rack in the hanger is worse if anything. Black magic probably covers it, although foolishly I didn't check the phase of the moon when applying the leading edge. 
I've seen old airplanes where it looked like the driver had shut them down each night by taxiing into a tree and they flew ok. Not to worry..be happy.

[DA Miller]

your posting gave me the chuckles

[Chuck in Indiana]

That's a good thing. Life is too short to be serious all the time.