Wing Build/Fuel Tank Install

[Maverick]

I am building the wings on a KF5. I had the wings built on my first build but, on this one I am doing the wings myself and I've run into a question that I don't really find the answer for in the manual, either hard copy original or the Kitfox, Inc, web manual. It has to do with sequence of the build. I have the spars, ribs, compression struts & brackets done and ready but, the manuals don't make it clear when to install the wing tanks.

There is a series of instructions for fitting the wings to the fuselage for rigging and placement of the strut brackets on the spars. Do you install the wing tanks before or after this process of fitting the wings to the fuselage? The manual seem to imply that it is after the wing rigging is accomplished but, it also seems that there are things that might need to be done before the wing tanks are installed. Does anyone have any words of wisdom on this question?

[bholland]

I purchased my kit with quick build wings that were pre rigged. I put the fuel tanks in myself which was one of the last things done.

[jiott]

I built my own wings and the tank install was one of the last things to do, after rigging to the fuselage and after installing the #1 rib.

[Maverick]

Just what I needed to know. Thank you.

[Maverick]

New question: I am reading the instructions and I find something a little confusing. I've got a call in to Debra but, I thought maybe others could share their knowledge on this question.

In marking the ribs for location on the front and rear spars (see attached PDF) the instructions are to use a half inch spacer between the end of the rear spar and the jib stop thereby offsetting the rear spar outboard 1/2". (done).

Next the language below the wind diagram showing the distances from wing root outward states: All rib center line locations are referenced from end of rear spar. Locations along the front spar are the same as rear spar plus 1/2".

The way I read this, using the rib location for rib #3 is 37-1/2" from root end of spar. Then the front location would be 38" (37-1/2" + 1/2" = 38). I marked these all using the rear spar dimensions plus 1/2". Then I started trying to fit the drag braces and found that they will not fit. In order to make them fit, if I slide the front of the rib on the front spar toward the root end 1/2" then the drag tubes fit as described in the instructions. What am I misunderstanding?

[Geowitz]

Nevermind, I was thinking of the wrong thing...

[David47]

I've built my own wings for a 7 SS and I checked the dimensions for rib placement against your 5. They are exactly the same and my drag braces fitted with no problem - drag brace length adjustment was achieved by sliding the brace tube in or out of each end fitting and then riveting them in place. I'm assuming you have a similar arrangement for your drag struts. It gets a bit tight, but they should fit. Maybe try again.

Info: The distance, centreline to centreline, between end ribs for any two bays containing a drag brace is 35.5" in each case; e.g. between #3 to #5 = 35.5", #5 to #7 = 35.5" etc.

[Maverick]

I spoke with John McBean at KF, Inc. and he said that my measurements were correct. I gave him the length of the drag struts and they were 3/4" too long so I followed the assembly instructions and cut the drag tubes down as needed so everything fit together. Left wing glued together today. Thanks all.

[Maverick]

I have my left wing ribs and drag braces installed and glued up and am thinking about the next steps, i.e. hanging the wings on the fuselage to rig the location of the strut braces and the wing root hole locations in the spars. In working, it seemed to me that I was frequently catching myself hanging on the rear of the ribs and wondered if there is any reason not to put the trailing edge on the ribs before moving forward. I think of this a means of strengthening the ribs and preventing me from catching something on the ribs while in the process of installing the wings.

Can any of you out there that built your wings any advise on when to add the trailing edge pieces now or later?

[efwd]

I have pre-assembled wings and they were nearly completed with the exception of the bay behind the fuel tank. In that light, I have now idea why completing the trailing edge would be a problem. I don't recall if I closed the trailing edge before or after the tank went in.

[aviator79]

Can any of you out there that built your wings any advise on when to add the trailing edge pieces now or later?

Have you installed the tanks and #2 partial ribs? You need to install the tank to install #2 rib, which you'll need to install before the trailing edge piece between ribs 1 and 3.

I can't think of a reason not to install the trailing edge on the rest of the wing, but I also had quickbuild wings, so my advice is unreliable.

[David47]

I built my wings and installed the trailing edge from rib #3 out before the fuel tank went in. I did that for the very reason you’re talking about, ie catching my clothing on the rib most times I walked by. You can’t finish the trailing edge installation because you need the tank in place in order to set up rib#2 and get the lower surface profile sorted for the long unsupported cap of that rib, if that makes sense. You do the initial rigging of the wing to fuselage without the tank in place.

[Shadowrider]

I have the STI and it comes mostly assembled, but you don’t won’t trailing edge (at least between rib 1 to 3) until the wing is on the aircraft, because you don’t want to install rib 1 until it’s on the plane because the spars moves slightly. Then you glue rib one in place and then install the training edge. The trailing edge is left off from rib 1 to rib 3 until rib 1 is in place and that’s not installed until the wing is on the aircraft.

[Maverick]

My new tanks arrived and I've cleaned and tested them and am ready to install them. I am doing the left tank first (for no particular reason except it was the one on the saw horses). In reading page 40, step 7, of the online manual where it says apply structural adhesive between the top cap strip and wing tank edge on ribs #1 & #3 ribs. This is a little nebulous. Also, there is a gap between the tank and the #1 rib of up to 3/8" and up to 1/4" at #3 rib.
Can anyone elaborate on this step as to how to accommodate the gap, as in what keeps the structural adhesive in place while it sets up?

Also, the tank sits on top of the spar attach brackets. Does anything need to be done to the tank to accommodate the brackets of just let it sit on top of the brackets? See below:
23185
Thanks,
Maverick

[efwd]

Okay, here it goes. Many questions on this in the past. Be aware of the clearance you have for the fuel fittings and the finger strainer at the #1 rib. Some people have trimmed the tank edge at the #3 rib to allow the tank to be pushed out further to get the space for the fuel fittings. I notched the #1 rib capstrip so that the fuel fitting will spin. Im still not certain it is going to work. I question if I have adequate space to get the finger strainer out. Anyhow, whenever you trim from the tank flange you will need to do your leak test again on the tank. However you chose to do it, the next problem is getting the gap filled with structural adhesive. My gap was maybe slightly wider than what is in your pic. I just used painters tape and stuck it under the tank flange to the web of the ribs. I used flox in the Hysol and filled the gap. It won't be smooth and nice so use some Super Fil to allow sanding after its dry. As for the overlap on the spar. I left mine as yours appears to be. I used Super Fil to feather out the transition from fiberglass to underlying structure. I think I used a dremel to remove a little fiberglass at the point it lays over the rivets.

[jiott]

You can either notch or relieve the tank corner so the spar reinforcement doesn't hold the tank up.
I used some aluminum tape on the underside of the rib cap-tank flange to span this gap and then put the Hysol in the gap. I only did it at the #1 rib, and used some spacer blocks at the #3 rib because it leaves room for rib stitching.

[Dave S]

Access to the fitting and finger strainer isn't real good without some mods. As Jim O did, made sure the tank was positioned outboard in the bay as far as reasonable to get a little space. Temporary tape to support the hysol fill as Jim did works sweet. Nothing wrong with inventing a little access port on the bottom of the wing next to the rib either - using a similar aluminum cutout to the ones for the lift strut brackets - easy enough to support the fabric, fabricate a little cover panel and a couple screws to make life easier.:)

Photo attached:

[Maverick]

Next question: the manual says after you put a bead on the tank and place it on the spars, it says to clamp the tank to the spars until the silicone dries. I think that I could use ratchet tie down straps to do this but, is there a better solution?
Thanks for the replies.

[rcbif]

If you use ratchets, any gap between the spars and tank will result in the spars being pull in inward. Could be an issue, or could not be an issue....

I haven't done this yet, but I would make some wide wood blocks contoured to the spar diameter to give the clamps a level spot to clamp, and also distribute the load so you dont damage the spar.

[jiott]

When installing the tanks, you don't want to pull the spars in at all. What you do want to do is pull the tanks down so the front and rear flanges seat solidly on the spars; this is so the top of the tanks match the top contour of the wing ribs on both sides. It should not take a lot of force; I relieved just a LITTLE material from the underside of the tank flanges in a few spots to get a good fit; then no clamping was necessary.

[Maverick]

I was thinking of setting something on top of the tank to weight it down. It seems like that would do the trick but, I don't know if that would be a problem.

[jiott]

That should be fine, within reason of course.