The XPB Stage 1 underway.

[Old Koreelah]

It’s always better to put the pilot before the navigator.

 

 

[pmccarthy]

Mosquito was a bit like that.

 

 

[Rastus]

I'm staggered no-one has thought of this before. 

 

Kookaburra two seat glider 

 

https://images.app.goo.gl/XmHa1xwuaha3Za579

 

 

[bexrbetter]

I'm almost ready to jump in and make engine noises!

 

Look at all those lovely pre-matched holes ...

 

 

...off to the fold shop tomorrow.

 

.

 

 

[Marty_d]

I like it Bex!  Good work.

 

The rudder / fin appear to be straight "slabs" with a square LE & TE - is that correct?

 

Any washout in the wing?

 

 

[bexrbetter]

 

The rudder / fin appear to be straight "slabs" with a square LE & TE - is that correct?

 

Any washout in the wing?

 

 

 

Fin/VS is 'slab' sided, but LE is of course aero rounded, TE is 'tapered to a point' rudder.

 

Later there will be a slight curvature to the sides of the Fin/VS, but first i wanted to make the part to see how much curvature I could force on it with the 90 degree flange on the bottom.

 

Not everything is shown on the 3D, not everything shown is how it's going to be exactly. The 3D CAD to me is merely a measuring tool, and a very accurate one, as you well know.

 

I actually came back to add an edit but the edit function had timed out (too short a time here Admin)

 

It read....

 

PS: Graphics are crappy, if you want better, go join a computer CAD group, but for those who want to see a real plane get built, watch this space ...

 

 

[bexrbetter]

Fold shop today ..

 

The Boys at it ..

 

 

The result ..

 

 

Dunnya just love pre-matched holes ..

 

 

Trial fitted the "Bex Rib-Fit System" now patented in Nigeria (got a great deal from some Prince there)

 

The silver speckly stuff is oil based paint, I think it's a good enough anti-corrosion joint sealant.  Silver speckly because it's what I had. 

 

 

 

Oh, and I bit the bullet today and ordered some 7075T6 for wing and HS spars. 

 

"Ouch" said my wallet, it ain't cheap, but cheaper than the Titanium I wanted to use, and much cheaper than Carbon Fiber, but fact is I wouldn't know what I was doing with Carbon Fiber anyway, so moot point..

 

So tomorrow will be a few thousands twists of a drill bit by hand to de-burr, and some trial fit-ups.

 

 

[OldBird]

https://alloytester.com/

 

Oh! Wow! What a resource!

 

You're de king, man. Coff.

 

 

[M61A1]

Oh, and I bit the bullet today and ordered some 7075T6 for wing and HS spars. 

 

Why? Very strong...Yes, but brittle, cracks easy, corrodes easy and fatigue life is limited. Not a homebuilder friendly material. 

 

I'm thinking along the lines of your signature line......just imagine how easily a homebuilder can find ways to mishandle that material.

 

 

[bexrbetter]

Why? Very strong...Yes, but brittle, cracks easy, corrodes easy and fatigue life is limited. . 

 

 

 

 

 

You could say the same for Carbon Fiber too, and yet numerous craft out their with carbon wings/spars.

 

7075 has 3 times the strength, 3 times the elongation of CF, and most importantly for a wing and spar, massively stronger in compression than CF (all composites are weak in compression), one of the critical factors for material choice in a wing/spar - yet plenty of successful CF winged planes flying, just as there is plenty of highly successful planes flying with 7075T6 wings and spars.

 

The reason: It's called "Engineering", and I assure you I am over-engineered in this area, I am paranoid about 2 things: Wing failure and roll over protection.

 

I can show you 6061 spars that have failed, I can show you wooden spars that have failed, I can show you 2024 spars that have failed ... and I mean under normal conditions. 

 

 

I'm thinking along the lines of your signature line......just imagine how easily a homebuilder can find ways to mishandle that material.

 

 

 

They won't be handling it, spars will be complete. There's other safety measures in place, but when we get there ..

 

 

[johnm]

 

 

 

Trial fitted the "Bex Rib-Fit System" now patented in Nigeria (got a great deal from some Prince there)

 

thank you Bex - your patent certificate has been posted tomorrow 

 

 

[onetrack]

Trial fitted the "Bex Rib-Fit System" now patented in Nigeria (got a great deal from some Prince there)

 

 

 

Hot off the press, from our paparazzi with the long-range telephoto lenses, we've got "sneak" photos of Bex's latest product release......

 

You'll all notice Bex's continuing accent on "low cost componentry"...

 

 

 

[Marty_d]

Dunnya just love pre-matched holes ..

 

I don't know.  Never had them!

 

But seriously.  Looking good.

 

I'm kind of with M61 on the 7075 for wing spars.  Not that I'm an engineer of any sort and I have a plane-building sample of... 1, almost.

 

But if the professional designers at all the LSA aluminium aircraft factories use 6061 in the spars, as long as it's the right thickness and capped, it'd do me. 

 

 

[bexrbetter]

 

 

 

But if the professional designers at all the LSA aluminium aircraft factories use 6061 in the spars, as long as it's the right thickness and capped, it'd do me. 

 

 

 

"All" Marty?

 

"ALL" did you say Marty?

 

While it can help to pass the time away while eating breakfast, the sides of Corn Flakes boxes are not actually a reliable source of information.

 

Putting "LSA" aside just for a moment, a company called Cessna, the largest light aircraft manufacturer in history, does not use 6061, they use 2024T3.

 

Vans, who is actually the largest LSA manufacturer, by far with the RV12, don't use 6061 either, they go for the 2024T3 as well. Not to mention all their other top selling models that put them behind Cessna as number 2 light aircraft manufacturer.

 

Then there's Gruman who's first light aircraft had 6061, but they went to 2024 on the next model. Then there's Piper, Rans, .... quite a long list of light aircraft manufacturers who don't use 6061.

 

Oh, Zenith LSA low wings used 6061 ..... and their wings fell off. Mind you  a number of Vans RV3 2024 wings fell off too. Again we come back to engineering with the material, far more important, relative, than the material itself.

 

As for 7075, well Airbus, Boeing, huge numbers of military aircraft all use 7075 in their wings extensively, especially spars and top wing skins, because it's outstanding strength in compression that you need for a wing, it comes no better than 7075 and it's derivatives.

 

..

 

But hey, above all, one thing I have learnt over the last 20 years on the internet (I joined my first forum in 1999), is that you can not beat the Internet and social media with actual facts.

 

If 2 Members here pop their heads up and say that 7075 is bad, then there's plenty of others out there with the same thoughts spinning through their heads.

 

Due to that sole "Internet" factor after reading Marty's comment, I changed my order to 2024T3 this arvo.  So now I am protected by Cessna, Vans, Piper and many other famous light aircraft companies usage of that spec material, a clear case of social media triumphing over actual engineering.

 

..... not the first time, certainly far from the last.

 

 

 

[bexrbetter]

But anyway, back to the task in hand.

 

Only had an hour to spare today, but got to trial the very first parts ...

 

 

 

 

[bexrbetter]

Some more lower stringers in today, as well as corner gussets ..

 

 

A person was kind enough to suggest I run out and buy a cheap junk battery drill for de-burring, because they are weak and slow, ideal for the job ... and he was right, the drill bit is even heavier than the drill!

 

I'll get a better bit later for it, or cut the drill bit down.

 

Funny how you just get into a habit of doing things one way for decades, when there's better alternatives.

 

 

 

[bexrbetter]

So today I added the rest of the vertical stringers, and introduced the top skin assembly to the lower skin assembly.

 

 

 

Then I introduced the side skins

 

 

 

Savannah builders will recognise the design concept, and thanks to Member 'Kyle Communications' for some of the info that help it happen.

 

I went to see if the tail cone was all ok, then horrified to realise I couldn't put it on as the cone overlap inside the fuselage was larger than the tapered finishing end of the fuse! But was all ok, I managed to lift the corners of the side skins and slip it in, phew, I had in my head already started designing it!

 

 

 

 

Well not much I can do further with the tail end until my 2024 sheets arrive in the next few days for the HS spars.

 

But now the rear fuse has some form, I can get accurate measurements for the roll bar and look at creating the cabin area forward of the roll bar now. I already have a plan and basic design, I just wanted accurate proportions to work from.

 

I spent about 5 hours on this today, the pre-matched holes are just amazing in improving assembly speed, I even took a video!

 

 

 

 

 

 

 

 

[bexrbetter]

An arty farty shot. All the rivets were pulled by this stage.

 

 

 

[onetrack]

That video is just riveting.

 

I've never had pulled rivets, are they similar to pulled pork? 

 

That last photo looks like it belongs in the Guggenheim in Bilbao.

 

 

[bexrbetter]

Checked out the dorsal fin/VS today.

 

First the Fin...

 

 

Then we'll need a VS.

 

Notice the rivet box lower right hand corner is near empty ..

 

 

And stuck them together

 

Excuse that it looks a bit wavy, that's because I just ran out of rivets and only had a few to hold it together.

 

 

I've never had pulled rivets, are they similar to pulled pork? 

 

 

 

You gotta cook the rivets a whole lot longer ..

 

That last photo looks like it belongs in the Guggenheim in Bilbao.

 

 

 

I spent a bit of time and money on that, so not throwing it in the rubbish bin.

 

And just call it a "bin" like everyone else would ya.

 

 

[Blueadventures]

I think you need to buy bigger boxes of rivets ?

 

 

[bexrbetter]

I think you need to buy bigger boxes of rivets ?

 

 

 

Ha, I read that as in Jaws: "I think you gunna need a bigger boat!" .. 

 

There's a thousand per box. I thought I had another box to hand but I didn't, well I did, but I didn't realise those were 2mm longer dang narn it.

 

Anyway, grabbed 2 more boxes on the way home. Things are conveniently close when you live in a small country town of only 600,000.

 

 

[bexrbetter]

I can't seem to find time at the factory the last few days, house do this, house do that, but managed a couple of hours today.

 

The VS looks a lot better with some more rivets ..

 

 

And a whole lot better sitting where it's supposed to sit.

 

 

 

[Marty_d]

Looks as strong as an ox in that rear fuse Bex.  Hell of a lot more bracing than my 701.

 

With that wide rear fuse I'm guessing your rudder cables will be internal all the way?

 

 

[Thruster88]

Looks like the flight loads of the VS are being transferred into the fuselage bulkheads via 8 or 10 pop rivets. I realise it is not complete yet.