[cockney steve]

I may be talking total carp here, but, AIUI, the Aloominum sheet is actually coated effectively, main sheet is " A " and it's coated both sides with " B "
Hence, raw . cut edges (and holes) all expose the "core" metal. used to use "Scotchbrite" wheels over 50 years ago, when they first came out....for removing weld-discolouration on Stainless- Steel, yacht-mast fittings, preparatory to mirror-polishing. deburring S/S would strip a wheel down to the hub in seconds.I would think it a bad move to use such an aggressive medium on any sheet Alloy on an aircraft.

I also believe that the RAF discontinued polished- aluminium aircraft when they found out just how much gets polished away, over a period!

The "laminated "sheet has pure aluminium and alloy. I suspect the core is alloy and the outer surfaces , pure aluminium? Anyone know more??

[Rob L]

... I suspect the core is alloy and the outer surfaces , pure aluminium? Anyone know more??

Bless you Cockney Steve. You are correct, mostly. Many sheet alloys (like 2024T3 sheet) are so prepared. But others are not coated so (weldable ones, and the billets used in Airbus wings, for example). Search in the Aircraft Spruce Website, they have a good description of many of the aluminium alloys used in light aircraft construction.

The reason for using a Scotchbrite wheel is purely for deburring already cut surfaces.
Scotchbrite pads are used for providing a light mechanical key for primers.
Personally, I use a Scotchbrite pad and then etch prime and then epoxy prime, before topcoat. But that's just me.

Hope that helps.

[G-JWTP]

What primer Rob?

G-JWTP

[Ian Melville]

I've just heard from mission control that it's not advisable to engrave. Either use tags or permanent marker.

I did cringe when I read that comment. As a newbie builder, I wondered if it was me that had got it wrong.

I have a stalled project(CX4) that when I restart will need a decision on how to protect from corrosion. Advice out there is very mixed, but I am getting a feel for it now. All the bits are now in storage and I have a wooden restoration on the go at the moment (slowly), Jodel DR1050.

Despite the lockdown, I still don't have the time. Considered as a critical worker in IT and expected to still be out and about.

Stay Safe
Ian

[kanga]

What primer Rob?

..

<classicist from early age> Kennedy's Shorter Latin ? </>

[PeteSpencer]

What primer Rob?

..

<classicist from early age> Kennedy's Shorter Latin ? </>

Ah the shortbread eating primer: I remember it well.

[patowalker]

What primer Rob?

..

<classicist from early age> Kennedy's Shorter Latin ? </>

I was 'primed' by a dictatorship.

[Rob L]

What primer Rob?

G-JWTP

Personally I use a solvent-based acid-etch primer. And a solvent-based epoxy primer.
I'm not wholly convinced by the water-based primer (That RV and Boeing stuff), it sets up corrosion very quickly on any steel, like the cores used on Cherry rivets).

I'm not sure that answers your question, though.
Rob

[cockney steve]

Thanks @Rob L I was pretty sure I read about it on this very Forum - but the link should prove interesting. I restored my first motorbike @ 16 y.o. it had been brush -painted with black house-paint (a James Comet, 2-speed ,98cc Villiers ) Automotive paint was all Cellulose back then. stripped and repainted with brushing-Belco and I used a spraygun that fitted on a cylinder vacuum-cleaner,with the hose plugged into the "blow" end! grey primer, maroon topcoats and sky-blue side-panels to the tank.

Eventually, I got better gear and learned about getting colours mixed by trade-factors and making vast savings buying thinner by the gallon....also, slow thinner compensated for poor equipment and technique and allowed "orange-peel" to flow -out! Some years in, I learned of Sikkens Isocyanate-based 2-pack paint. The high-build primer had a Phosphoric-acid based catalyst and passivated surface-rust on ferrous substrates. Top-coats , when mixed, had several hours' pot-life ...I once went to bed and then remembered I'd left the spraygun, unwashed, on the bench at work! got up, dressed, back to the Garage and tipped out the paint, dismantled and washed the gun.....back home about 1 AM ! When all the concerns started about volatile organic solvents (VOC's) water-based was developed. Never used it, but i'm told the basecoat is very soft and relies on clear-lacquer overcoating for durability and hardness....water-based on bare steel just goes against all I ever learned about protective coatings Strangely, the modern HVLP guns for applying it, work in exactly the same way as that vacuum-cleaner powered gun some 40 years earlier!. I still use 2-pack and see tractors I painted 10 years ago, left out 24/7,still shiny,still rust-free.

When I made alloy yacht-masts, we used Chobert aircraft rivets which had little blanking-pins in the centre-holes. Pop-rivets were alloy, closed-ended and then a plastic plug was driven into the hole where the "pull-nail" had broken-off... we also had Monel ones, these were open-ended and the broken-off head of the "nail" would drop out of the rivet....last job was to tip them all out before sealing the mast! A pipe jointing compound was applied to any stainless fitting before it was attached to the spar and also to end-caps (aluminium castings) which would seal them as well as preventing electrolytic corrosion. There were parallels with aircraft -building. ..In fact, we used a company at Rochford aerodrome ( London Southend, nowadays? ) to make skin-sections for an experimental wing-mast. (C- -classCat. )- It was so effective, the boat would go to windward with no sails set! Happy days!

[G-JWTP]

Right,

I'm thoroughly depressed with the state of things, covid, redundancy, debt and the rest of it all!

But there is an upside,

5 uninterrupted weeks of building!

So I left you with wing ribs in the last update.

I took the completed rib and put it together with 51 of its mates and various other assorted pieces of green aluminium and you get a wing skeleton x2.



There is a fair amount of personnel design that goes on when you build an aircraft. You have two wobbly 13' bits of aluminium that need to be supported so you have to design and build your very own rack to hold them.

So I've made the insides of the wings the build 'gospel' said now is a good time to fit the electrics/lights etc. So you do. This is the stall warning gadget.



So wing skeletons done.
It's flapperon time.

So I did those!
.

This now sits on its side waiting to be 'inspected'. ( Remember the older Chap!).

So I thought I'd get on with some more.

I opened the 'Fuselage box'! That looked a bit complicated.



Then I opened the fixings. Things were not looking good!



On wards.

You take bits like this



Then put them together like this.



With lots of them you get this.



And a few more and you get this.



Then this.



And finally



So tomorrow I'm having a go at 'longerons', what ever they may be!

Stay safe.

G-JWTP

[Rob L]

...Then I opened the fixings. Things were not looking good!

G-JWTP

Why not, pray? They look well marked up?

[G-JWTP]

One bag contained about 40 different types of nut.
Lock, squeeze, castleated, nylon lock, normal, and a few others that cause head scratching.

So if you can tell by looking the difference between a -08 and -52 by looking ,you're very good.

Me, I Google the number and look for a picture.

G-JWTP

[Rob L]

...So if you can tell by looking the difference between a -08 and -52 by looking ,you're very good.

Me, I Google the number and look for a picture.

G-JWTP

Google works too! I can indeed tell the difference between a -06 and a-08 screw or a -N03 or -N04 nut (or most other items*), but then I work in that industry; are they not as well marked up as they appear?

Rob

*I'm more used to the old AN- designations, rather than the newer MS- designations...plain washers and crush washers and "O"-rings are a nightmare! Fortunately, the Aircraft Spruce on-line calalog(sic) still uses both!

[G-JWTP]

Some of the bags contain a lot of one thing like a 3/32" rivet and so on.

Most however contain about 6 or 8 completely different things, of which you may end up with 3 things left over.

I think to make things easier accross all their kits they just standardise the bags, so bag no 3124 may be used on a RV-12 and a RV-7

G-JWTP

[aerofurb]

Have a look in the front of the Kit Assembly Instructions (can’t remember which Section) - there’s a very handy guide to the various fasteners, especially the various rivet types...

LAS website is another good source of info as they have pictures!

Looking good though