Project 5 build thread

[alexM]

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I cleaned up the shop (mostly) and set out my sawhorses two days ago. My digital tape measure and digital level came in handy for setting up the wing fixture. I fixed one to the garage floor with Bondo and once it kicked off I got the second one leveled, oriented by the book and also fixed to the floor with Bondo. Yesterday morning I checked all the measurements again and they were spot on. Both sawhorses were level, my 156" dimension was not even out 1/32" and the diagonal was within 1/32" out. For some repurposed studs I'm pretty happy with it.
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With that all checked I cut some lumber for the index blocks which attach to the saw horses and the 1/2" pieces which serve to stagger the spars at the inboard rear end and to set the washout. By afternoon I was removing screws from the spar crate. I tested out my fixture and then got busy with a scotchbrite pad cleaning up the outside of the tubes. It was one of those nights where you are about ready to shut off the lights and decide to see what kind of effort it will take to prep the spar inserts, and next thing you know it's 1am and they're done.
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During an afternoon break I went to the local building supply place and bought 14' of 3" PVC pipe (had to buy a 10' and 4' piece), a coupler and two end caps. Armed with knowledge of the "tennis ball trick" I included a big pet store in my errands. I thought it would be great to find some smooth rubber balls instead of tennis balls, and fully expected to strike the mother load. I was to be disappointed however, and the best I could do was some overpriced tennis balls.

Around dinner time I slapped more Bondo on the feet of both sawhorses and used some PVC pipe adhesive to bond the coupler and one end cap in place. Then I vacated the shop while all the fumes cleared out.

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Today I explored the tennis ball thing. I wanted to slosh the inside of the tubes with acetone. The balls leaked pretty badly and acetone will just laugh at any attempts to tape it. I just lived with the leaks and had a big tub at each end to catch the leaking acetone, which I filtered and used for the initial sluice of the next tube and fresh acetone for the second. I retrospect I should have started by cleaning up the insides of the tubes because I had cleaned them externally to a beautiful uniform appearance.

Once all four spars were cleaned inside I mixed up a big batch of my Henkel Bonderite etch solution. One at a time I etched the spars, and two at a time I etched the inserts in my big PVC tube, sloshing continuously for 4 minute cycles.

The inserts were the last thing etched and the first things I ran through the Alodine process. They came out looking pretty nice. The spars came out splotchier than most parts that I have Alodined. Until this job I have been able to run them directly from etch to rinse to Alodine without drying the parts. The instructions say that if you don't dry them they might not be uniform. Working alone and needing to get all the way through etching all the parts before I could Alodine them made the job challenging. And lest anyone think they're splotchy or terrible they look fine, just not perfect. They didn't pick up quite as much color as usual but again, no real impact on the treatment process.

The lack of uniformity has no impact, and I'm used to seeing parts like this. They were treated with etch and Alodine so the job is done. I was pretty worn out by the time I cleaned up. Actual hands on time (not including the tennis ball acetone task) was about 2.5 hours. Damn glad I'm not building a biplane.

Tomorrow I'll start the process of sliding the inserts into the spars.

[Freedom2]

Alex, Good job on your video!!! enjoyed it!! I'm just curious what your thinking for some final weight numbers of the Verner with accessories added? (approx)

[alexM]

Thank you.

It's been a while since I looked at the exact weight but, comparably configured, it weighs somewhere between a Rotax 912 and 914. And I have read recently that the 912iS weighs 30 pounds more than a 912ULS (straight from the interwebs with no reference to back it up, so take that for what it's worth).

The CG of the Verner will also be closer to the firewall so at this point I'm not worried about overall weight or CG. After scouring threads from the heavy engine crowd I see no reason to sweep my wings forward 1 degree. This engine is much lighter than the other popular radial available. The Verner is direct drive and uses a magnesium crank case, which accounts for the weight difference.

Anyway with the hp and torque figures I should have better performance than a 912ULS with no significant loss of useful load, no CG issues and a fuel burn not remarkably worse.

An amusing thing about the engine straight from the installation manual: Engine preheat not required down to -5C.

Considering the part of the world the engine comes from that shouldn't be a complete surprise.

[alexM]

I only had part of today to work on the wings, but next up on the list was a step that has been looming for a while: Getting the spar inserts into the spars.

I followed the directions in the manual where it says to chamfer and deburr the tip end of the spars. With everything theoretically ready I gave a sigh and went about sliding the first insert into the tube. And it didn't want to go in. The manual is very clear that you do not force this. I grabbed some wood and all the big clamps I own and put some squeeze on the tube but it didn't improve things enough.

So I pulled the insert back out, cleaned everything up and took a break. I used the search tool to find threads on dealing with the inserts and I read both the series 5 and 7 manuals. I triple checked my surface finish, deburring job and then I used a clean rag on a long string to drag through the inside of the spars to get any possible. I ended up using my Kitfox supplied Scotch brite pad to make a a few passes over the surfaces that would contact the inside of the spars, cleaned everything REALLY well with fresh acetone rags, then lubed up the contact surfaces just a bit. That whacks my ability to slosh some epoxy in here later but the Alodine was still largely intact and the lube

The result was an insert that slid into the spar without fighting me. Finger pressure only, and a pusher stick with a mark for when the insert would be 70" from the root end and 32" from the tip end.

For spars 2 and 3 I went straight to the debur check, acetone rag pulled through the inside, then a light lube and they went in no problem. Spar 4 started out the same as the 1st spar so I pulled it right back out. I ended up needing to use the Scotch brite pad again, followed by another super cleaning and light lube. It went in on the second try.

Tomorrow I'm hoping to lay out the strut attach fittings. This part has been renting space in my head since the beginning. Seems like something that could be done wrong, so it's time to get careful and RTFM.

[Freedom2]

Interesting, looking at pics at previous installs it actually doesn't look like alot of accessories to be added compared to other engines. I'm assuming this engine was not a radial option at the time kitfox provided a fwf package for the Rotec as it seems like a better prospect especially for weight! I'm still on the fence of which engine to go with in my IV. Trying to find that happy medium between power to weight ratio. I'm excited to eventually see your install as there is nothing like a radial!

[jiott]

Your procedure for getting the inserts into the spar pretty much mirrored what I had to do. I was having trouble and called the factory; they recommended thorough cleaning/deburring, slightly pinching the spar to an oval shape and using baby oil as a lube. I had already done the other things, but the baby oil was the final solution. I also wanted to slosh epoxy primer inside, so I first sloshed acetone to dissolve the baby oil, then sloshed the primer-seemed to work well. I would recommend you do this two step sloshing BEFORE you glue the spars and wing ribs-much easier.

[alexM]

Your procedure for getting the inserts into the spar pretty much mirrored what I had to do. I was having trouble and called the factory; they recommended thorough cleaning/deburring, slightly pinching the spar to an oval shape and using baby oil as a lube. I had already done the other things, but the baby oil was the final solution. I also wanted to slosh epoxy primer inside, so I first sloshed acetone to dissolve the baby oil, then sloshed the primer-seemed to work well. I would recommend you do this two step sloshing BEFORE you glue the spars and wing ribs-much easier.

Great advice, thanks. That would be quite a show sloshing an entire wing around.

So far I have the inserts in all four spars, one pair of them have the 4 rivets (2 top and 2 bottom) near the center of the hole pattern and my left front spar is fully riveted - except the area under the lift strut attach fitting of course.

Heading back out to the garage now to get through the left rear spar.

[alexM]

At this point I've drilled and riveted the spar extrusions for one wing and set them aside. Tonight I started on the other pair of spars, which already have the inserts in place. The second set seems to be going quicker because I've got some practice. Before dinner I had them clamped into place with the shear web of the extrusions vertical, rubbed my 4' scale to mark the center line and laid out my staggered 2" hole pattern on what will be the bottom side of the second wing.

I captured some of the first set of spars in my second video:



If videos aren't your thing that's fine. Short version: The manual has you lay out lines which are 19/32" from the line you made on top of the spars. It includes a tolerance of +/- 1/32, which in my book rounds down to 9/16". Next you lay out a staggered 2" hole pattern on those offset lines.
When you look inside the spar you'll see there isn't a ton of edge margin there. Wow it would suck to drill into the spar/insert and have it at the edge of that extrusion, right? So staying to the low end of the tolerance just seems like a great idea.

Sticking to the 9/16" dimension has a free bonus. The forward strut attach fitting is supposed to roll towards the trailing edge and the manual wants you to temporarily put the forward strut attach by aligning the witness hole in the strut fitting on a 9/16" line to accomplish this. Well I've already gone one, so I'm good to go.

This won't be news to any of you who have already built their planes but for the newcomer, the strut attach fittings are put in their future location so you can trace around them and then NOT drill the holes in the 2" staggered pattern where it passes under the strut attach fittings. There will be plenty of holes drilled into the spar/insert later.

Starting with two holes on top and two holes on the bottom you debur, then rivet the holes with 1/8x1/4" SS rivets. Once the center of the insert is locked in place you clamp the tube to keep the insert located and to minimize chips building up between the surface between the inner wall of the tube and the outer face of the insert.

Keep at it and you'll soon be looking at something like this:
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I shined a light into the inside of both riveted spars and saw that the edge margins are just fine.

[alexM]

A brief update.

A few days ago I completed drilling and riveting of all four spars. No foul language and no extra holes. I didn't make an exact count but it's very close to 200 rivets by the time you complete top and bottom of all four spars. My Milwaukee 12V rivet gun has worked flawlessly, so I have no wrist cramps to complain about. I didn't even need to swap batteries on the rivet gun.

I immediately began setting up my sawhorse wing fixture and incorporating both 1/2" spacers, then got out my ribs.

I still haven't sloshed the spars to get out the chips or the lube used to get the inserts in place but that didn't stop me from sliding a few ribs into place so I could see how they fit. Right away I learned the rivets in the rear spar won't slide over all those rivets. I will need to file two small notches inside the hole in the rib where the rear spars go, so they can slide into place in over the riveted sections.

I've done some internet searching and found some smooth rubber balls which should have much better gap sealing properties than the tennis balls I used when I cleaned/etched/Alodined all the pieces recently. Once those arrive I'll get the spars cleaned out and make up my mind about sloshed with epoxy.

In the meantime I've got a bunch of ribs that need inspecting and sanding.

[jrevens]

Alex,

The ball idea sounds good & will probably be better than a fuzzy tennis ball for sure. I started out trying to use balls and found that sealing the ends with plastic wrap and rubber bands worked better.