The XPB Stage 1 underway.

[bexrbetter]

Well after another late night moving holes around in 2D CAD, off to have the final sideplates cut so I can start moving on from there, might be some minor glitches but will know by the end of the day, or at least tomorrow hopefully.

 

 

[Marty_d]

You're a machine Bex. Hope at the end of this process you have a great system that sells well.

 

 

[pmccarthy]

Bex, thanks for this interesting coverage. Here are three fuse ideas from my 1909 Janes All the Worlds Aircraft (facsimile). :)

 

 

 

 

 

[bexrbetter]

Well I am very satisfied with most of the results today, things are working out both in directions I intended and opened directions I might not have seen previously - really a case necessarily innovating due to being frustrated by not being able to follow original chosen paths.

 

Will be clearer by the end of the week what I am doing, sadly I couldn't get a good picture as I was on my own later when I thought of it and it wouldn't stand up by itself on the table so you'll just have to take what you get today.

 

Those 2 rear vertical braces are held in by the yellow tape you see, onto sorting the braces out for real tonight.

 

I am very pleased how far below target I am with weight presently to the tune of 15%.

 

 

 

[bexrbetter]

So I am very happy with a trial run today assembling a side using the modules I designed.

 

PLEASE NOTE that I am currently using stainless steel for the inner skin modules, as shown, as it is tough and durable while I develop my system - if I run with this system then of course ALUMINIUM will be used. Sorry I have to shout but there's some people who just look and decide what they see is what it is.

 

So stainless now while developing, but will use aluminium later - ok, that's clear?

 

I want to mention with great pleasure how simple and darn fast the build procedure is here with NO measuring, NO centre-punching (no hammering of course), and all self jigging.

 

Simply lay a module down on top of the tubes, align by eye and feel along the edge of the tubes, drill a hole in a couple of corners, cleco or temp rivet to secure, and then merely drill away with all the pilot holes already pre-drilled (laser'ed), de-burr and rivet. Lay the next module on the next section of tubes overlapping the first module and repeat 6 times from front to the tail. Took me and the sidekick 5 hours to build what you see here from scratch including deciding all the lengths of the verticals, making a few mistakes and pulling the odd module back off a couple of times needing to drill out rivets (no problem with the stainless, tough as). I drilled all the holes but only popped a rivet every second hole.

 

I will make some sort of video of the procedure in the next few days.

 

Will fit some diagonal braces tomorrow morning.

 

 

 

 

[SDQDI]

On those inner skin modules they look like stainless, wouldn't it be better to use aluminium?

 

JUST KIDDING!!!!!

 

 

[Kiwi303]

I'm guessing the stainless sheets are the thin cheap generic stuff the supplier had in stock for less hassle than ordering in airworthy known-composition reputable aluminium with the attendant pricing? The chromium steel used in kitchens as splashbacks there instead of tiles in low end homes?

 

No point in using the good stuff for a Proof-of-concept mockup I guess. Not when those pennies saved can be used to buy a beer or ten.

 

 

[Deskpilot]

Not knowing the final design leaves me thinking 'what an excessive use of 'material' . You building a plane or a tank? ;-)

 

 

[pylon500]

That's some serious overkill!

 

Even if this was going to be fabric covered afterwards, this is WAY too much material.

 

You will also find that, suddenly it's quite hard to flex the sides in!!

 

If you're fully skinning the outside, you only need a couple of verticals to support the outer skin, and they only need small simple triangles to brace them.

 

There's a reason that the small triangles are all thats used, it's all thats needed....

 

If fully skinned, diagonals are pointless, the skin will do that, and you may remember that the diagonals on a curved frame do not stay on the skin 'plane', so you can't rivet to them anyway, or were you planning on gluing with Sikaflex like Gary...?

 

 

[bexrbetter]

I'm guessing the stainless sheets are the thin cheap generic stuff

You guessed wrong, they are expensive 316 marine grade I ordered in. They are almost Chrome Moly spec. The main wing carry plates probably will be 440C stainless which is stronger than 4130 ChMo and the Russians use quite a bit of it in their fighters.

 

Not knowing the final design leaves me thinking 'what an excessive use of 'material' . You building a plane or a tank? ;-)

Might look that way but the weight is under target even with the stainless. There's pleanty of air to be added yet, waiting for the FEA results to come in.

 

The laser time costs money and no point in putting in every lightening hole at the moment.

 

At the end of the day the scales don't lie and that's all that matters.

 

 

[Kyle Communications]

What sort of weight are you aiming for empty? If it was a 600kg MTOW then if you can get it finished empty at 300 kg that would be fantastic. A lot of aircraft are 330 to 350 empty and 250kg isnt really enough for big buggars like us aussies. Its ok for the asian and european runts of the pack but not of most aussies at 100kg plus each. You need to be able to carry at least 70 odd litres of fuel preferably 100 litre

 

 

[bexrbetter]

Even if this was going to be fabric covered afterwards, this is WAY too much material.

I have mentioned a number of times now I am under target for weight.

 

At the end the scales and load test will tell the story.

 

What sort of weight are you aiming for empty? If it was a 600kg MTOW then if you can get it finished empty at 300 kg that would be fantastic. A lot of aircraft are 330 to 350 empty and 250kg isnt really enough for big buggars like us aussies. Its ok for the asian and european runts of the pack but not of most aussies at 100kg plus each. You need to be able to carry at least 70 odd litres of fuel preferably 100 litre

Yup, exactly.

 

Sub-320 is target and it's for bigger Oz and Yanks with over 6' and 100kgs asses in mind.

 

 

[Kyle Communications]

That will be excellent

 

100 litre = 71kg roughly so 529kg so anything under 320 kg would be fantastic. My Sav is 320kg

 

 

[Downunder]

Anything under 100 litres and you're not "in the game".

 

What I would like to see, is more fuel capacity than that so that "1 up" 130 or 150 litres can be carried.

 

I don't see why (max) fuel capacity is normally set and calculated by manufacturers in a 2 POB situation when most time flying is reported to be solo.....

 

 

[Kyle Communications]

The Sav has 140 litres....I usually only fill about 100 litres so 3 out of the 4 tanks. This gives me over 6 hrs endurance in actual fact closer to 7 hrs with my fuel burn in cruise. I also have 8 litres not counted in that for reserve.

 

 

[pylon500]

Anything under 100 litres and you're not "in the game".What I would like to see, is more fuel capacity than that so that "1 up" 130 or 150 litres can be carried.

I don't see why (max) fuel capacity is normally set and calculated by manufacturers in a 2 POB situation when most time flying is reported to be solo.....

Maybe we should have Jumbo's in RAAus, you can get a few thousand litres in them......

 

 

[bexrbetter]

Well not much to show that's much different than previous, but that belies the hours and hours that have gone in to detail and optimising - a lot!

 

Very happy with the results today and getting close to time to seal the deal on this stage and move forward to the next.

 

I was asked why didn't I remove metal on the 3rd module upper area (red arrow), well that's where your shoulder and elbow are and I didn't want to risk any possible sharp areas there, and discomfort otherwise.

 

 

 

 

[bexrbetter]

So after reviewing the FEA results, I made some minor mods still based on above, quickly cut them from some el-cheapo steel sheet, and was so happy with the result that today I got my first real inner panels cut from my 6061 T6 sheets.

 

It was the first time the laser guy had ever cut aluminium and was quite concerned but they came out just perfect, couldn't ask for a better finish and accuracy.

 

Could only get onto assembling it this afternoon, and didn't quite finish a side to take pictures of and, more importantly, get a weight from, but will tomorrow.

 

The correct assembly procedure has been interesting to figure out, do the wrong steps and it bites you a few steps further down the path - got it all figured now thanks to 2 simple throwaway tools made from $2 worth of 3/4" strap, and that has made a world of difference.

 

 

[Nobody]

Looking good!!! I like the construction methodology.

 

Just make sure that your fatigue design takes into account the laser cut edge condition, but I am sure you now that.

 

 

[bexrbetter]

Well I'm locked in, finally satisfied with what I have now. Weights are great, FEA says it's as strong as a bridge. Of course real load test later on will determine how accurate that is, and I will test to destruction.

 

The thing is since I went to the "Fish" (the double opposing curves causing the lens shape), it has allowed me to create a double tapered box girder, i.e. the boxed in top longeron and the upper fish longeron, which has quite substantially increased strength. Strong as a bridge and looks like one too! I like bridges so that's not a bad thing, something like this in theory ...

 

 

... and something like this in real life ...

 

 

 

You can see the ears for the diagonals that will look like this later on ...

 

 

I forgot I was doing a left side today and cut the sheet on the wrong side so you can see all the manufacturer's writing rather than the nice shiny side I usually try for, oh well.

 

Oh for all those comments such as "tank" and "too much material" etc, have a look at this ...

 

 

 

[bexrbetter]

Oh, and the above took me 4 hours by myself to build from absolute scratch, including cutting all the tubes to length (that would otherwise be supplied pre-cut). All holes drilled but only 50% riveted so add another hour.

 

 

[Marty_d]

Oh for all those comments such as "tank" and "too much material" etc, have a look at this ...

69 kg for one side!! What a tank. Too much material.

 

 

[rgmwa]

69 kg for one side!! What a tank. Too much material.

And still missing 50% of the rivets! Not looking good!

rgmwa

 

 

[bexrbetter]

And still missing 50% of the rivets! Not looking good! rgmwa

when i do the left wing it will be missing half it' s screws ....typical.

 

 

[fly_tornado]

you should be using solidworks it can simulate loads on your structure which will show you where you can remove and add strength