Right outer wing surface

Started on the ribs for the outer wing surfaces. The second ribs require a 19 reamer and a 20 drill bit due to the AN365 bolts/screws used as fasteners. Luckily I had those from earlier.

Stacking the main spar

Started stacking up the main wing spar. I definitely need some more and longer sheet holders. Even the 1/2 inch is too small. I have to order these, and leave the main spar for the time being after I have deburred the edges etc. 

Aft outer spars and main inner spar

Finished outer aft spars. Started on main inner spar.

The other outer spar

There was too few 470 5-9 rivets. If it is an error from Sonex or if ACS has put a finger on the scale I don't know. Luckily I have a rivet cutter so I took a few 5-16 rivets and cut them to correct size.

Outer wing spar

Riveted the outer wing spar.

The other one is primed and left to dry overnight. Started with the aft spars. Deburred and bent the flange to correct angle.

Left outer spar updrilled

Updrilled the right outer spar

Rather straight forward, but I wish I had the Drill Doctor when I reached the steel. I hope I stacked them right though.

Stacking of outer spars

Finished with dimpling and priming the mating surfaces of the vertical tail. Can't rivet the skin before Lasse has been here. Started stacking up the main outer wing spars just to understand how it is going to be. I wonder if I got enough long clecos to do this. Also the main webs was very water stained, probably during transport or storage at Sonex (Indoor in Norway the humidity is way too low for any water staining). Water staining is the most common kind of crevice corrosion in aluminium. Water staining will make the aluminium even more corrosion resistance, but it also makes it harder to get coating to stick.

Ordered a bunch of CherryMax rivets for the ribs on the Horizontal tail, the spar and aft rivets will be solid. There really is a huge difference in diameter of the holes that are drilled with #30, deburred the "old way" and dimpled and the ones that are drilled with #31, deburred the correct way and dimpled with the "tuned" dimple dye. Dimpling is a much more straight forward process when using solid rivets.

Also ordered i Christmas gift from my wife, a Drill Doctor 500X from ACS Germany. It seems to me this 6061 T6 is much harder on the drill bits than 2024 T3. When I get this Drill Doctor I will always have super-sharp drill bits which is the most important thing regarding hole quality and to minimize burrs. The 500X will sharpen anything, high-speed steel, cobalt and TiN.

up-drilled the vertical tail

When the electricity came back after the hurricane Ivar had come and gone I updrilled the vertical tail using 31 drill bit (and 30 for the tip).

Vertical tail skin and tips

Pilot drilled the hinge and the rest of the skin and tip. The skin was still too tight around the tip, so I trimmed the skin a bit. Still it was too tight, so I had to trim the tip as well. This time I only trimmed it so a thin fibre glass was left. After I reinforced it on the inside with two layers of glass cloth and epoxy.

Vertical stab tip

Drilled pilot holes for the fiber glass tip. Filing the inside front and trying to push it as far back as possible should allow it to fit without having to cut it up in the front.

Flaps and vertical tail

Finished the flaps and riveted/bolted the vertical tail.

Found out how to achieve correct holes so the CCC-42 rivet stems don't get pulled through. First I filed my 120 degree dimple die (used in a C or squeezer) a bit more so that the male end enters fully a hole drilled with a #31 drill bit with no friction or without having to use any force. Then I revisited what is actually said about deburring of holes that is to be riveted. In the book "Standard Aircraft Handbook" by Larry Reitmayer it says that burrs under either side of the rivet is no concern, but should be removed if the sheet is not to be used immediately to not cause scratching when stored or injury to personnel. Drill chips between sheets should be removed. Removal of any "appreciable" amount of material from the edge of the rivet hole should not be done. Although I have not removed any appreciable amount, I have used a normal rotating deburring tool. So, with the trimmed dimple and deburring with a glove, a perfect rivet with a #31 dimpled hole.

Since Lasse has not yet shown up, I have yet to rivet the skin on the horizontal stab. The h-stab has #30 deburred and dimpled holes, and none of those rivets will actually fit correctly. I still have the choice to use solid rivets and Cherrymax. I will see.

Flaps

Drilled pilot holes in the flaps and hinges

Rivet binding strength

Spent this evening on investigating different ways of drilling for the countersunk rivets. Some info can be found here and here. The issue is mainly what drill size to use, #32, #31 or #30. I made three samples that I wanted to tear apart in the vice. It all went well until I found out the very hard way that my vice is very good for pushing things together but terrible at pulling things apart :-) (when pulling, the big bolt just comes out not taking the rest with it).

Then I tore them apart using a flat screwdriver and found that the aluminium sheet broke before the rivet fastener. Doing this I mounted them flat standing in the vice, so that one part was in the vice and the other part including the rivets standing on top. I then got the idea of using a hammer sideways, parallel to the surface, to get a torsion (and shear) load around the rivets, that will then be felt as shear on each rivet. So I took what was left of the samples and made new rivet connections. This time I used straight forward 30, 31 and 32 drill bits. I used my squeezer on the 30 and 31 holes and the "simple" pulled dimple die on the 32 hole.

The result was that I had to bang from side to side and totally bend the pieces out of shape to get them apart. The #30 drilled eventually separated because the shop end of the rivet got pulled through the hole. The #31 drilled did the same, but the plate also got torn up. The #32 drilled separated because the sheet broke while the rivet bonding was intact.

So what is the strongest? For all the samples the aluminium plates had to be hammered way past yield strength back and forth several times. The pieces also got bent, which means there was tensile stress in addition to shear stress. So who knows? The #32 sample seems to have the strongest bonding, but it was also the easiest to brake apart, so it could very well already be fractured from the previous abuse with the screwdriver. Besides, #32 holes are totally impractical because a 1/8 cleco won't fit and the 3/32 cleco is too loose. The only possible way is to match drill to #40 or slightly larger, then un-cleco, drill up to #32 and dimple in one go because the 1/8 clecos fits the 32 holes after dimpling. Using solid rivets is also an option of course, they are not nearly this sensitive regarding exact hole size.

All in all, when the pure pull test didn't work out, I didn't really get that much more knowledge other than knowing that the rivets are not likely to pop out of the aircraft unless the aircraft is bent and twisted beyond recognition, no matter what drill size is used. However, the ball on the stem is never pulled through when using #32 drill bits for whatever that is worth.


Also tried to polish the Topgloss BR with Biltema rubbing by hand. The result was surprisingly good. Really nice and shiny and smooth.

I then tried to polish it with Jotun Hardwax and also some old car polish I had laying around, but then it got all milky. The tech sheet says that polishing the Topgloss BR may cause milkyness, but not Hardwax, the tech sheet is obviously wrong.

If I can rub/polish this polysiloxane paint this easily, I probably also can roll on some polyurethane just as easily and hopefully be able to polish it without getting this milkyness. I begin to suspect that this polysiloxane Topgloss BR has been rushed out into the market before it is fully usable.

Right aileron

Left aileron

Finished riveting the left aileron. The led was cut according to the plans. The plans suggests that the led is over sized and need to be trimmed. My led on the left aileron needs to be enlarged, and this is with no paint on! Still have not decided paint or no paint, so fine trimming of the led counterweight have to wait in any case.

Aileron and flaps

Trimmed and drilled the led counterweights. The led sounds easy to work with, but is actually very laborious and difficult. Destroyed two drill bits and I hope my vixen file is still OK. Deburred, dimpled and primed the ailerons, but the primer was still a bit moist here and there, so I let it cure overnight.

Started with the flaps, the last moving surface. Cut to correct shape and measured up the position for the ribs.

Right aileron hinge

The holes for the aileron hinge also stiffens up and shapes the aileron. I almost did a huge mistake here because the ribs, only at the root and tip, pushes the two bent halves a few mm apart. When the aileron is laid upside down and I tried to push with a flat hand at mid span, the surface will come too far down. When released the aileron will have a nice banana shape. What I did was to push the edge down with a file to get the lower surface flat on the table, then hold the hinge in place with my thumb and the other finger at the trailing edge without pushing the surface down. It ended up 100% straight.

Had to try the Topgloss once more as well. This time I rolled on a thicker layer, then use a foam brush to smooth it out. It became better, but far from OK on an airplane. High gloss and brush and roller is not a good combination no matter what the advertising says. Also sprayed some transparent coat on a piece of aluminium that was sanded with 1000 paper. Looks a bit cool, but I'm not convinced.

Aileron

Drilled holes for the ribs in the ailerons. A bit fiddling to make it all fit with all the cutouts.

The whole paint stuff is strange. When I oiled my floor in the new shop I used something called "concrete oil" for indoor use. The name is very misleading because it is no oil at all. It is an acrylic emulsion (latex paint) that soaks the surface and penetrates down into the concrete. When cured it binds the concrete together as well as making a smooth surface and is of course water proof. It is also used as a primer for epoxy floor paints. I am very satisfied with the result, it does exactly what it advertise.

This "latex paint" on airplanes is also an interesting thing, but confusing. I have looked at typical Norwegian house paints and there is no such thing as latex paint. What they call latex paint in the US can be vinyl paint, PVA (Poly Vinyl Acetate) or an acrylic emulsion, all water based. It can also be a mix. In Norway I have only seen PVA and acrylic emulsions. The difference is that the acrylic emulsions are superior to PVA. PVA is typically used on ceilings, and as cheap wall paint. Most acrylic emulsions are indoor paint. There are some acrylic emulsions for outdoor use, but most are alkyd paints, some are also acrylic hybrid water thinned alkyd paints. For vinyl paint I have only seen this primer I am using, but that is alkyd based, not an emulsion, not a "latex paint" in any shape or form.

This Stewart Systems looks interesting. My neighbor meant I could simply put a transparent cote directly on the aluminium sanded with 1000 or something sand paper. That could look very cool, but will it stick?

Aileron

Sanded down the test sheets. I will try to polish them in 14 days and see how that goes, not very optimistic though. Graham Smith at Sprite Aviation could tell me that they use rollers, but only on matt and  satin finish, never on high gloss. Makes sense to me. He also said they mix their own paint because the viscosity is very important and it varies with the actual pigment (color).

Cut the aileron led counter weights with my hand saw. That was several hours of hard labor. I wish I had a band saw.

Topgloss BR

Rubbed down the test sheets and sanded with 400 wet sand paper. I found that the rubbing down was unnecessary because wet sanding with 400 did the trick rather easily. It became really smooth. I thinned the paint with 10% thinner (Jotun number 7), but that did not help one bit, in fact I could see some spots where the thinner dissolved the first coat and the vinyl primer.

The only solution I can see is to apply one more coat (no thinner this time), and then sand with 400 and or 800 and polish the surface. I will apply that coat tomorrow, and try some other brushes as well, a foam brush maybe, and then sand it and leave it for 2 weeks to cure properly, and then polish. If that doesn't work I will dismiss Topgloss BR altogether, also for my boat.

I also tested the paint with acetone and the thinner, Jotun thinner number 7 which is 75% Xylene  and 25% Ethylbezene, and alcohol. All three dissolved the paint very easy. I hope this is because it is not cured yet. The paint is fully dry in 6 h, but is supposed to take at least 5 days to cure at 23 C. The thinner also dissolves the vinyl primer easily, while acetone requires some work. The "Quick" spray enamel paint withstands the thinner, but is affected by acetone a bit better than the vinyl primer. What a mess. In any case it shows that latex paint is not such a bad thing, very strong and flexible. The thing with latex paint though, is it can withstand almost anything except Xylene.

Also received the faulty ribs and spar from Sonex today, so I can start on the vertical tail, once I finish the ailerons.

I had hopes for this Topgloss BR, high tech Polysiloxane that is supposed to be specially made for brush and roller. So far it seems pretty much unusable. I painted my fiber glass canoe some ten years ago with a 2k paint using a brush only, and the finish is 10 times better than this Topgloss BR.

  

Tried the Topgloss BR

Lots of pigment in there and it is glossy, but the finish is nothing to be impressed of. I used the correct roller and finished off with a broad soft brush, as described in the manual. The problem is it is way too viscous to be smooth. Right now it seems back to polishing if not the second coat becomes much better tomorrow evening. Maybe some thinner will help, but to me it seems like it cures too fast.

The only good thing seems to be that it sticks to unprimed aluminium just as good as the primer.

Primers

I have to write this down before I forget. I have tried a whole bunch of primers now. Monopol wash primer, Monopol Strontium chromate epoxy primer, Scanox rattle can (no longer available), Biltema aluminium primer, Duplicolor aluminium primer, Duplicolor plastic primer, some old zinc chromate primer, Jotun Yachting rattle can Vinyl primer and Jotun Yachting canned vinyl primer. I have also tried rattle can top coats.

Biltema and Duplicolor gives a very nice finish and are very easy to use. They look really nice, but when testing physical and chemical strength they are extremely poor. A drop of acetone will destroy large areas.

The Scanox (quick) rattle can is a bit more difficult to use, but it is much stronger physically and chemically than Biltema/Duplicolor.

Monopol wash primer is really good. It is for professional use. But the surface is porous and therefore it must be covered with something. As a primer for outside top coat it is probably as good as it gets. But it really is not something to use inside the house, the VOC content and odor is beyond belief.

The Strontium Chromate Epoxy is the best overall. Extremely strong, yet only 10-20 micrometer thick, and can handle even Acetone in moderately amounts, and is totally corrosion proof. But, it is not for the house due to VOC and toxicity and it is a lot of work.

The old zink chromate rattle can is easy to use, but it is thick and not very strong. It is also practically impossible to get.

The Vinyl primer is a bit difficult to use from the rattle can. But when cured over night it is very strong, and it even handles acetone to some extent, not nearly as much as the epoxy, but remarkably well. It is the only one together with the epoxy that is 100% waterproof. It can also be brushed on, and this is really practical when priming only the mating surfaces. In addition it can be used everywhere, on all substrates, and it is non toxic. And of course, it is part of Jotun Yachting system with the Polysiloxane top coat and is available everywhere around here. I just hope the rolling of the polysiloxane turns out OK.

Ailerons, primer and top coat

Bought Topgloss BR (Polysiloxane) at COOP along with some rollers and other stash. Then I went to the drug store and got some 60 ml syringes so I can accurately mix smaller amounts of the Topgloss. The syringes were surprisingly inexpensive, 3.5 NOK or about 0.4 Euro a piece.

Finished deburring the cutouts in the ailerons and measured up all the rivets for the ribs. Then I scuffed a test sheet of aluminium to test the Topgloss. I primed half of it with the vinyl primer and left the other half, just to find out how the Topgloss is with primer and without primer. I let it dry until tomorrow. The sheet is actually a faulty piece of RV horizontal stab skin. I really miss my old priming booth when testing all these primers and coating.

I haven't heard anything from Jotun about using Topgloss BR with no primer, so I just have to try it and see how it goes. If this works out, I will coat the whole plane with Topgloss instead of polishing. I'm not too keen on coating the whole plane with this vinyl primer with rattle cans though. If a primer is needed, then my old Monopol wash/etch primer gives a really smooth and thin coat, if it is compatible with Topgloss. But it is also possible to thin out the canned version of the vinyl primer and spray it on with air and achieve the same thickness as the wash primer (30-40 micrometers). Theoretically a 35 micrometer primer covered with a 35 micrometer Topgloss BR gives a total added weight of approximately 2 kg. This weight penalty is nothing when knowing that the polysiloxane is better than any polyurethane out there. In the cockpit I can also use Topgloss BR, hopefully with no primer.

Then the whole plane will be "Pegasus Grey" with tips and cowling in "Draco Red" and maybe with some trimmings in Draco Red as well.

Cut the openings in the ailerons and Polysiloxane

Cut the openings in the ailerons, only deburring left. Also bought a new orange from Hagmans. It was a bit more difficult to get a good finish, but the amount of pigment was abysmal also here. 4 coats of orange, and I still can easily see through it, it's ridiculous. Obviously I am doing something wrong here.

Looking a bit closer at Duplicolor web site what I have to do is first a plastic primer (also for fiber glass), then a white general purpose primer (white primer for bright colors), then the color itself (2-3 coats) and then a 2k transparent epoxy coat (2-3 layers) to achieve mechanical and chemical strength. This is not exactly straight forward and easy anymore, and with all those coats, it gets heavy. I begin to understand why people like Latex paint or real aviation products. The problem for me is that aviation paint products are practically speaking impossible to get. They can be sent from UK or USA, but the cost becomes ridiculous because they are labelled hazardous goods.

Anyway, I had a real eye opener this evening: Polysiloxane coatings. Going for the Jotun Yachting line of products, I only need one coat of Vinyl Yacht Primer (spray or brush) which I already have, and one coat of Topgloss BR, and it will last forever. Topgloss BR is a new 2k polysiloxane coat especially made for brush and roller. It is supposed to be completely smooth and shiny, even when applied with brush and roller, which in fact is the preferable method. Polysiloxane is superior to urethane in all aspects as well as being non toxic, no isocyanates. Polysiloxane coats are completely resistant to UV and oxidation. Generally a coat of polysiloxane is more corrosion resistant, more weather resistant, higher chemical resistance, more temperature resistant, and more glossy than the usual 2 step epoxy primer and urethane top coat.

The "old" Jotun Yachting method was epoxy primer and urethane top coat. The new preferred method is 1k Vinyl primer and a top coat of 2k polysiloxane. The Vinyl primer is preferred because it is smoother (but also needed for wood). So I wonder, on an airplane it should generally be enough with only a coat of polysiloxane with no primer or anything. In fact what the vinyl primer does is only to make a smooth surface for the polysiloxane top coat when using brush and roller, but it could also be that Jotuns formulation of polysiloxane requires a primer for adhesion? I don't know, but my guess is that using polysiloxane directly on aluminium would require 2 or 3 coats because it spreads so thin. And then it is faster and better to use the fast drying vinyl primer that is smooth and can be smoothed further by sanding. The spreading is incredible. 1 liter last for 30 square meters, film thickness of 30 micrometer. The older urethane top finish have the same film thicness, but only goes for 16 square meters due to higher VOC content.

I have read several places that people are using some new paint system and using only brush and rollers, Sprite Aviation for instances. This can only be polysiloxane coatings I guess.

So I ended up "Acetoning" all the orange paint off the tips. From now on there will be only polysiloxane coats on the Onex, with some Vinyl primer here and there (if needed). But this also means that I have to wait until I have more surfaces to cover because the paint is 2k. Another thing is that Jotun don't have orange, they only have a whole bunch of modern non-colors and "Draco Red". So Draco Red it is. Under the inner wing section and on the underside further back I will have some gray polysiloxane to protect the aluminium during the winter.

Measured ailerons

Cut the ailerons to correct length and measured up all the internal cutouts and ribs. Also deburred all the ribs and plates.

Changed the color from dark green to bright orange. Dark green is nice, but it's so dark that it only looks good in sun shine. Here in Stjørdal the sun is not something that is shining all too often, and then the airplane will look too dull and dark. With orange tips and cowling, the airplane will look similar in color to the picture of the Trial further down (or ordinary Sonex polished style with orange instead of yellow). I think that will look cool, also on rainy days.

The Duplicolor turned out to be really a turn down. The finish really is nice and shining, but there is too little pigment in there. It is literally impossible to cover anything if the prepped surface is anything but white, and when the Duplicolor plastic primer is transparent, there is a problem . The tip that was partially green is impossible to get orange, and the seems in the glass fiber (dark color) shines through. I am also skeptical about duplicolor aluminium primer. I tried to sand it, and it goes off in a couple of wipes. The Jotun Yacht vinyl primer on the other hand, is 10 times as durable and can be sanded to a smooth finish. I also tried the houshold "Quick spray" primer from Scanox, it is much more durable than the Duplicolor. At least the Duralac works really well, and that is the most important thing. The Jotun Vinyl primer can be put on anything, and it can be covered with 2k paint.

I put the dimple die in the drill and sanded it to #31 size, it took ages. On the rudder about 1/3 of the stems had to be sanded a bit. From now on all countersunk skins will be #31.