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Thread: Project 5 build thread

  1. #151
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    Default Re: Project 5 build thread

    I took advantage of a clear bit of weather and flew today, so I only put in a couple of hours of build time.

    PXL_20210116_013900230.jpg
    When I got home my smooth rubber balls still hadn't been delivered so I decided to start sanding on my ribs. Man that is going to be an investment of time. I took most of an hour creating a rib shaped mandrel from some 2" pink foam. I figure it would offer the best support of the raw ribs for sanding and avoid any damage to the cap strips.

    It's a simple 2D shape so you sand it as shown, then flip the pink foam over and put the rib back on so you can sand everything from the other side. The inside is too small to run my 5" random orbit sander and the area between the rear spar tube and the trailing edge isn't even a candidate for a detail sander (multi tool). I used a rubber "taco" purchased at the auto body place and some 220 paper and found it doesn't really reach well behind the rear spar either. I probably spent 20-30 minutes on one rib and don't consider it done.

    The smooth rubber balls finally turned up about 9pm and while they're slightly larger than the ideal diameter they seem to fit pretty tight. I'll try them with some acetone tomorrow.
    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

  2. #152
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    Default Re: Project 5 build thread

    Well the smooth rubber balls showed up. I went straight out to the garage and tried them out, and they fit pretty tightly into the spar ends. While waiting for the balls to show up I should have been sanding ribs, but I under estimated the challenges of sanding the bare ribs.


    When I did my vertical fin ribs I slapped a 5" 220 disc on my random orbit sander and made beautiful parts in minutes. Well those are flat 2D shapes and ideally suited for that method.
    Once I finally wrapped my head around not being able to use any form of power tool I made 3 different sanding blocks out of 2" pink foam and used some self adhesive 220 discs cut to shape, along with one rubber "taco" sander.
    PXL_20210118_044611585.jpg
    I did four ribs earlier and hope to knock out four more (enough to begin one wing) by the end of the evening. I'll press through the ribs for the other wing while reading up on spar layout.

    The slosh

    Prior to beginning my work today I was thinking about doing the epoxy slosh in my spars when I realized I was no where near done drilling holes and riveting. The lift strut attach fittings have 42-ish rivets per spar, and there's the drag/anti drag link fittings several more. Ideally I would wait until those rivets had been pulled so those penetrations were epoxy coated as well.

    On top of that, if I were to slosh them I would be wise to mask off where the steel doublers at the wing root attach fitting bond in with Hysol.

    As much as I liked (user jiott) Jim's suggestion of sloshing now, I'm now in the camp of sloshing the wing after the strut attach fittings and inboard steel doublers are installed.

    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

  3. #153
    Senior Member jiott's Avatar
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    Default Re: Project 5 build thread

    I sloshed AFTER the strut fittings were fully attached. What I was trying to say in my post was to slosh before the spars were attached to any ribs or braces.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  4. #154
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    Default Re: Project 5 build thread

    Well now I'm even more confused. Don't the ribs have to be bonded on so I can mount the wings and drill up the strut attach fittings?

    I guess I need to RTFM a bit further out.
    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

  5. #155
    Senior Member jiott's Avatar
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    Default Re: Project 5 build thread

    You're right Alex; I had a brain fart. The strut fittings were not attached when I sloshed, just the internal I-beams.
    Why would the strut fitting rivet ends need epoxy-they are SS. The holes thru the aluminum spar get squeezed with Hysol so they are pretty well sealed up.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  6. #156
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    Default Re: Project 5 build thread

    My wing build is underway. I marked up my spars for the ribs 1 and 3-10, made my marks 1/8" on both sides of those marks, notched the holes in the ribs where the rear spar carries through for ribs 5-8 and got all the ribs lined up and in position.

    My kitfox order came with my new drag/anti drag weldments and tubes (plus the newer style flaperon hinges and doublers), trailing edge material and some other bits. My baggage compartment floor is on back order, but no rush there.
    PXL_20210130_235831185.jpg
    Today I did the layout for the drag/anti drag pieces. I thought this part would take at least a week but once I had all the pieces clamped in place with zipties it was about 2 hours until I had all 36 holes drilled to attach the weldments to the spars. I took everything apart and deburred, then reasembled everything.
    PXL_20210131_044230764.jpg
    I still need to layout and drill 5 holes at each location where the aluminum tube slips over the weldment.
    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

  7. #157
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    Default Re: Project 5 build thread

    Starting with the fitting near rib #3 I drilled one hole for each fitting/tube intersection out to rib #9, then started back at rib #3 to add a second hole. With Clecos in all the holes the entire structure was solidly locked in place.

    There are five holes required at each fitting/tube intersection, which was going to make it challenging to allow for drill & rivet gun access but because they were so well locked in I realized I could pull it all apart and drill the other three holes on my bench. I only drilled one extra hole.

    Then my plan became more clear. I would be able to bond/rivet a fitting in one end of each drag/anti drag tube, slide it through the slot in ribs 4, 6 and 8, then bond/rivet the other fittings.

    With all the holes drilled I deburred everything, carefully identifying each fitting and tube for where it went. I did my usual scotchbrite, acetone, etch and Alodine for each of the three aluminum tubes. Next I hit the Cad plating on the steel fittings with a coarse 2" scotchbrite disc just enough to get a good bonding surface.

    Next I mixed up 10 grams of Hysol, stirred in some micro balloons to help the steel to aluminum interface issue and got all six fittings bonded & riveted to the tubes. I Cleco'd everything back to the spars mostly as a sanity check that my plan was working. Everything looked great.
    PXL_20210212_043609488.jpg
    PXL_20210212_043605136.jpg
    My strategy now is to shuffle ribs back and forth while bonding/riveting the fittings to the spars. Where I thought I would have to bond all the ribs and fittings at the same time it is now clear to me that the only ribs I must bond in place are ribs #5 and #7, because they are trapped between a pair of fittings. I need to leave ribs #4, 6 and 8 floating where the tubes pass through so I can do this. Ribs #3, 9 and 10 are a slam dunk at any time after ribs #5 and 7.
    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

  8. #158
    Senior Member Eric Page's Avatar
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    Default Re: Project 5 build thread

    Wow, those are already looking like wings. Keep chugging along, and you'll have two wing skeletons cluttering up your shop before you know it!
    Eric Page
    Building: Kitfox 5 Safari | Rotax 912iS | Dynon HDX
    Member: EAA Lifetime, AOPA, ALPA
    ATP: AMEL | Comm: ASEL, Glider | ATCS: CTO
    Map of Landings

  9. #159
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    Default Re: Project 5 build thread

    PXL_20210213_044316546.jpg
    PXL_20210213_044309970.jpg
    Successfully riveted and bonded the drag/anti drag fittings and ribs #5 and 7 last night. Those two ribs are bonded just well enough to hold them so I can fillet around them when my Hysol mixing gun shows up on Tuesday.

    Not sure if the adhesive will be cured or frozen today but the hard part of installing the ribs is behind me.
    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

  10. #160
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    Default Re: Project 5 build thread

    I received my baggage compartment floor last night. I'm still waiting for my aluminum tube wing stringers which were shipped a week prior via truck. Those were supposed to arrive 3 days ago but now with snow on the ground, who knows when I'll see them (Not Kitfox's fault, just how shipping goes on a 13' long package).

    Couldn't help but notice that baggage compartment floor is, uh, substantial. Threw it on my scale and it is 4 lb 8 ounces. Seems overkill for what I'm likely to haul back there.
    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

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