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cheapracer

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I should have mentioned earlier what I am attempting here to lower cost and build time on the newly named "Sabretooth".

I title it the BJC method, Better Jalopy Challenge.

The outer fiberglass skin is flat, duh, but the inner fiberglass molding forms vertical and diagonal bracing.

The inner is adhered to the outer while sandwiching the longerons in the process, as in this very loose depiction ...

Image4.jpg

Image5.jpg


Got a late mid arvo start today, but happy to get a side done before dinner anyway, the first layer always being the hardest of course. Rinse and repeat tomorrow for the other side.

Hmm let me see, it's the left side you're looking at.

In case you're not sure what's happening here, I made a pattern that became a mold to make a pattern to become a mold to make a mold to make parts, simple eh!


Image7.jpg


Image6.jpg
 
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cheapracer

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So need to get serious about the rudder and dorsal fin now.

I have looked at various methods but most of the methods used to take a vertical surface from a horizontal surface don't really grab me, so I have made a vertical surface to begin with simplify and put fastener loads in shear rather than pull.

I have simply split the rear section of the turtle deck, added a spine, which adds a lot of strength anyway, and will take my fin/ruder vertically from the sides of the spine, built a basic mockup of it today and works well, looks something like this



rudder 1.jpg
 

cheapracer

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So starting mapping it all out today, testing rudder shape with an old bit of blue fiberglass, should get a result in a few days time. You can quite clearly see the spline here and the gaps are because it's only got a couple of rivets holding it all together, as is the entire turtledeck also only held on by a few rivets ....


Image8.jpg

Image9.jpg

Image10.jpg
 

cheapracer

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So there's all these little things being done that will suddenly all come together over the next couple of weeks I hope, and that will go from looking like I'm doing sweet nothing at the moment, to suddenly advancing forward in great steps.

I did a dummy run with the tail design today after many, too many, iterations trying to find a simpler, cheaper way.

Came down to, for the moment at least, a pretty simple, almost 2 dimensional in feel, aluminium design that's stupidly easy to make, and due to some importance in alignment, even has "matched assembly holes". First run ever had it assembled in less than an hour with mistakes and adjustments (pre cut and bent parts).

The tail is sitting 50mm~2" too high as it needs to be slipped in down through the rear/rear tutledeck yet, as described in the 2 previous posts above
 

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cheapracer

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So today I assembled the vertical stab onto the rear rear turtle deck sheets, again as per post #62 above, and threw it on, it's so stupidly easy you even question yourself if it should be so easy.

I need to make a few minor changes, one example is my 'spine' is too short, needs to run all the way to the tail post (the spine has that green foam in it for support to drill and rivet against).
 

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cheapracer

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In the end I not only increased the length of the spine, I ended up running it the complete length of the 2 turtledecks, from the top of the roll bar (and a real roll bar too for your safety), to the bottom of the tail post.

Dang it made it easy to hang the dorsal fin, rudder and rear turtledeck from, as well as adding strength to the complete structure for a weight penalty of under 1kg/2lbs.

It also makes it easy to align the front and rear turtledecks as can be seen here, very smooth junction between them with just a couple of rivets at this time, happy about that.
 

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cheapracer

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This is a fake photo-shop to represent somewhat the aprox psychical size and proportions of my craft.

I did this to understand how I can best achieve a simple flat wrap canopy for cheapness and ease of replacement at home. Of all the canopies I have tried in 3D and photoshopping, I am happy with this representation ....
 

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cheapracer

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So a lot has happened over the Xmas break...

So a few weeks ago I was looking at the sides of my project and was thinking that every single vertical and every single angle brace was of a different length and had a different angle cut on each end, along with every single gusset to carry them to the longerons was also individual, although I quite like the design it is a bit of a headache to consistently reproduce and maybe for others to build with consistency.

This is especially important with a jigless, self aligning design. Too many alignments required raises the risk of a disturbance in the force.

Not that I am not intrinsically changing or even want to change the design, indeed all the dimensions and major components remain unchanged, just making the side frames simpler, faster and more accurate to build for everyone, especially me!

I had also been considering an idea for a while now, and that was a simplified box shear web running the length of the fuse with appropriate further structural additions, something like this that for a start uses 30 identical lengths, all cut at 90 degrees and no gussets (single shear web instead), a safer and far less complicated bet than 20 (40 doubled up) all unique tubes with not only different lengths, but also different angle cuts on each end, combined with individually unique gussets. Something like this..


submarine.jpg

Seaman.jpg

shear web sides.jpg

shear web sides 2.jpg

.. more ....
 

cheapracer

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... continued ...

So I actually found the whole sides a bit awkward to maneuver around the bench so made the decision, a **** good one as it turned out, to split them into 2.

shear web sides 3.jpg

Also did some optimising over the last week and did some weight checks, appears I've knocked 6 kgs out of, I was expecting a couple so has come as a pleasant surprise.

Putting it all together again now towards this ..

B1.jpg


So finished those sides this morning, and started screwing, rather riveting, the rear halves together.

This involved first joining the tail, then merely bringing the halves together to the roll cage, clamp, drill through the lasered pilot holes, clean and rivet. All self aligning and self jigging without measuring anything.

I am extremely pleased with the ease and speed they go together, not to mention the result.

One of the good things is that now because I split the sides, is that the entire rear half, and entire front halves of the fuse will be able to be built independent of each other and bought together at a later stage as required.

There are homebuilders who lack building or bench space, and this will be ideal for them.

As there are no rear half central laterals installed yet, it's why there's little "curve" to it at the moment. Those laterals will push it out further in the middle later ..

RH 1.jpg

RH 2.jpg

RH 3.jpg

RH 4.jpg

RH 5.jpg

So tomorrow start on the front halves ..
 

cheapracer

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So this morning I had the side panels lasered and folded. Bit hard to see but all the pilot holes are there so you just pop the drill through without measuring or mucking around.

The panels fit snugly so you just simply line them up, push them on, then drill away. All these panels are sitting their on their own.

All the measuring, scribing and pin punching work has been completely eliminated, and of course the laser is deadly accurate and makes left and right sides alignment near perfect.


sp 1.jpg

sp 2.jpg

sp 3.jpg

sp 4.jpg

sp 5.jpg

 
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cheapracer

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Soooo....

Over the weekend I redesigned the wing box for some good reasons, as well as ever, simplicity, speed and cost.

Yesterday and today busy building it.

The theory is simple, tapered wing ends into a tapered hole, self locating and aligning. I just got enough of one partial wing finished tonight and it works a treat, fits so **** good that I actually am concerned about taper stiction, I had to wiggle it quite a bit to get it back out!


wing box 3.jpg

wing box 4.jpg

wing box 1.jpg

wing box 2.jpg



.. and also putting the front half back onto the rear half, note the carry through tubes that someone was concerned about. Also note there is a substantial outer joining plate not shown yet.


join 1.jpg

join 2.jpg

join 3.jpg
 

cheapracer

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So this is what the wing is looking like (in progress), note I use a folded C channel shear web, besides a little added strength, it's main function is as a jigging entity that keeps the assembly dead straight ...

WK3.jpg

WK1.jpg

WK2.jpg

WK4.jpg


Annoyingly the rear turtle deck front skin was a little too short (25mm/1") and I had to make a new one. So I decided to make it just one piece and rivet to the spine as you can see here.

Good thing is the entire rear turtle decks and tail can be assembled on a flat bench or floor in one piece as you see here then simply added to the frame as the one piece, of course I've set it up so that's all also self jigging. It's so darn easy.

R turtle and tail 1.jpg
 

cheapracer

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For those curious, I have been on holidays for the last 3 weeks in 90 to 110 degree heat wave in Australia.

Start back tomorrow on this.
 
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