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rtfm

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Well, today I spent fixing little CAD errors. Mostly not accounting for the thickness of the airframe members, like forgetting to cut out corner pieces in the bulkheads so that they fitted inside the fuselage. Took quite a while, so no building today.

Here's an example of how the fuselage can LOOK true, but is slightly out of whack.
1623562611080.png
Trust the CNC. I pulled the whole fuselage straight so that it lined up with the cowl base, screwed a few 20mm wood screws through the provided pilot holes to ensure the fuselage was square. VOILA!

Everything else lines up perfectly (except for the few CAD oversights, which have now been corrected. So tomorrow I'll be launching into "Day 4" of the build.

One of the very nice things about building a Fleabike is that it is completely repeatable. As I progress through the build, and fix the minor errors, these are incorporated into the next version of the CAD.
 
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WonderousMountain

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Your earlier wing construction method, with the foam ribs, and Straight
Panel went together fast & looked good, minus the cat-astrophe. What I
had wanted to see was a less ambitious plan toward greater performance.
An all aft tapered cresent wing, requires 25%-55% chord shift in spar local,
30% of Chord, or 25% if you start in 30% chord position. While this is not
A lot all things considered, it has driven you to add a whole 'nother set of
structural lengths, which will increase the build time & decrease simplicity.

You can definately do it, but is it worthwhile for appearance sake? Below,
is yet another planar drafting. I pulled the Chord widths from unit circle
Graph online - Desmos. Ten span positions, 4-3-2-1 as before. Percentage
within a percent or so. In my unsolicited opinion, the 5% chord reduction of
Section A0-A4 is no improvement over no taper. First section provides good efficient lift, reducing it's area, appeals to me none. Forward taper, a straight leading edge, inverse VB suggestion, requires 25%-15% on the 60% taper tip.
IMG_20210613_140138.jpg
To complete the thought, 5-10% is easier to achieve than 25-30% position.
It is for these reasons, that my preference goes to zero leading edge sweep. The same will be true of taper ratios in advance of that shown. A doublet,
spar wing is still a good solution to torsion & stiffness if required.

~CK LuPii
 
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rtfm

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Thank you LuPii,
I have software which does all the heavy lifting as far as wing design is concerned, so making changes is easy. I am in two minds (three?) about the best wing plan. One thing I'm reasonably settled on is that I'd like to avoid a rectangular wing if possible. Bear in mind, building a curved or tapered wing is no more difficult than building a rectangular one. The software sorts out the ribs, and the CNC cuts them. They are all equally easy to construct. So I'm left with two drivers: Aesthetics and aerodynamics.

I have to say, I rather like your wing plan LuPii.

I'm still about a week away from committing myself to a design, so if anyone would like to chip in, please feel free.

Regards,
Duncan
 

rtfm

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Sigh... Another non-building day while I try to figure out how to get the bulkheads in place.

There are two bulkheads just behind the firewall to secure the wing masts. Trouble is, if I fix the firewall in place, I can't get the bulkheads in. If I first bond in the bulkheads, there is no way to ensure that the fuselage is square (this is accomplished by aligning both the firewall and the cowl base.

I'm thinking that I need to fit the bulkheads, and bond one side in place - and fasten them with wood screws because there is no place to apply clamps. Once in place, I can fix the cowl base
 

rtfm

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I'm getting closer to a final wing design. This one is simpler by far. And the rear spar acts as the only spar for the wing tip, which is reasonable which has a dihedral of 15 deg BTW.

Numbers:

Front wing
Weight: 35kg
Span: 7.2m
Chord: 1250mm
Area: 6.8m^2

Rear wing:
Weight: 20kg
Span: 5.75m
Chord: 1000mm
Area: 4.37m^2

1623718656143.png
Typical rib:
7mm maroukis ply, 7mm deep. Weight of A1 rib (largest): 700g
1623719138656.png
 

poormansairforce

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I'm getting closer to a final wing design. This one is simpler by far. And the rear spar acts as the only spar for the wing tip, which is reasonable which has a dihedral of 15 deg BTW.

Numbers:

Front wing
Weight: 35kg
Span: 7.2m
Chord: 1250mm
Area: 6.8m^2

Rear wing:
Weight: 20kg
Span: 5.75m
Chord: 1000mm
Area: 4.37m^2

View attachment 111892
Typical rib:
7mm maroukis ply, 7mm deep. Weight of A1 rib (largest): 700g
View attachment 111893
Nice work but it strikes me that none of the x bracing in the ribs has any grain that runs from one end to the other. There is a reason holes are used with ply ribs.
 

Vigilant1

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Nice work but it strikes me that none of the x bracing in the ribs has any grain that runs from one end to the other. There is a reason holes are used with ply ribs.
The X-bracing could have about 1/2 of the grain running fully end to end, depending on how the ribs are cut from the sheet of ply.
 

rtfm

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Day 5 (not day 4):
(I mis-counted the build days - I was too busy trying to finalise the wing design, and also trying to figure out how to put all the bits together, and lost track.)

After much head-scratching, I decided to bond the aft wing mast bulkhead by itself. I had to contort my arm to get in there, and I used T88 rather than West System which is almost like water. T88 is nice and gloopy, and since the bulkhead is almost vertical, I needed something which would mostly stay in place once applied. I used a tongue-depressor to apply the T88, but realised as soon as I'd started, that this wasn't the best way to get the gloop in there. A mini squeeze bottle would have been much better.

I'll see if I can get a picture tomorrow when everything is cured, but at the moment I have the firewall, cowl base and panels screwed in to ensure everything is square.

Build time: 1.5 hrs
 

rtfm

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I'm surprised at you. Looks can be deceiving. All of that plywood is Maroukis Gaboon ply.
Mourikis Gaboon BS1088
1623734924209.png
Okoupanel Gaboon Throughout Marine Ply BS1088
Sheet size 2500mmx1220mm
Premium marine gaboon plywood made from okoume wood throughout, glued with the highest grade of water proof adhesive. This plywood is lightweigh gaboon marine plywood, made to the highest quality standards and the equal of any gaboon produced anywhere in the world.
Mourikis SA are primarily producers of Gaboon throughout plywood. In business since 1924, the companies long experience means marine plywood which is quality controlled at the highest level at each stage of the production process.
Mourikis are proud of their premium Okoupanel Gaboon through-out marine ply. They have obtained qua;ity certification from KOMO (Dutch), and Lloyd's of London. Production meets the European CE marking requirements.
Mourikis SA purchase all their Okoume (Gaboon) logs only from sustainable and well managed forests, using only suppliers that meet the PEFC certification. Mourikis SA has FSC certification, which provides strong chain of custody certification for these plywoods.
 

BBerson

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This plywood is lightweigh gaboon marine plywood,
I don't have any info so just going by looks. It looks like a thick core with very thin skins. Not like aircraft three ply. I don't like the thick core "lightweight" plywood even for model use. Do you have data for this material used in aircraft? If the face skins are not oriented 45° it would hardly work to cut out the 45° diagonals.
 

rtfm

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BBerson,
I owe you an apology. The photo in post #521 WAS cheap ply from Bunnings. It was a mock-up to illustrate how the eye can deceive and how the bulkheads pull the fuselage square. I should have double-checked the photo before climbing on my high horse.

Here is a shot of the actual Gaboon I'm using throughout.
1623807578552.png
 

rtfm

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Day 6:
Today I drilled the holes to accept the embedded nuts and captured nuts for the cowl-base, control panel, seat and seat-back. Quite a tricky job to keep everything square. Then I screwed in both the embedded nuts and the captured nuts.

Next, I bonded the firewall and the fin-doubler to the turtledeck, and started bonding the aft bulkheads and the "vanity" roof and back behind the pilot's head.

Build time: 4.5 hrs
 
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BBerson

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...and shear webs are significantly stronger if the outer grain is on the diagonal?
But the grain is not straight 45° on the diagonal is it? (it would be if you orient the ribs 45° on the sheet) But then the capstrips would have incorrect 45° grain. I don't see a solution other than oversizing the cut width and load testing.
 

Victor Bravo

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But the grain is not straight 45° on the diagonal is it? (it would be if you orient the ribs 45° on the sheet) But then the capstrips would have incorrect 45° grain. I don't see a solution other than oversizing the cut width and load testing.
What about gluing 1/4" spruce or hardwood stick doublers onto the "diagonal" sections of the ribs for that localized load ? Yes of course this increases parts count and adds a few minutes for each rib, but it preserves most of the advantages he is trying to get out of using a big CNC to make the kit parts to their final shape, with no rib jig boards and a hundred little gussets in each rib. If you remember, on another design thread FritzW was piddling around with a 'tab and slot' rib that had little stiffener/doublers in the diagonals. Those were also plywood, but the majority of the grain could be arranged to maximize the compression strength of that little strip.
 
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