Littlest BiStik

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kdc914
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Joined: Tue Feb 09, 2021 7:54 pm
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Littlest BiStik

Post by kdc914 »

After realizing the challenges of my other idea, I decided to pursue a project that I had actually prepared for - a biplane based upon the Littlest Stik. Last year at Fall S.M.A.L.L. I purchased a Littlest Stik kit and and extra wing kit for it. When I told Doug my plan for it, he included a set of Q-Tee cabanes. Using my experience in building the fuselage of a Honker Bipe along with the Ed Larsen's EXCELLENT pictorial instructions of the Honker Bipe, this project theoretically has a reasonably high chance for success. Given that the Littlest Stik build is well documented elsewhere in this forum, my build photos and commentary will focus on the required changes to make it a biplane. Having already built a low-wing version of the Barnstormer, I am familiar with building a Stik design "upside down." Fingers and toes crossed...
kdc914
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Fuselage mods part 1

Post by kdc914 »

As a biplane, I have to invert the Littlest Stik fuselage as one would a Barnstormer to make it a low wing. The difference between the two is that the Littlest Stik has 5 degrees of downward thrust built into the shape of the fuselage sides whereas the Barnstormer does not. Therefore, an angle gauge and judicious application of Xacto blade is in order.
The first photo shows the unaltered side panels with notes indicating what must happen to them.
LittlestBiStik_fuselage1.jpg
The second photo shows the angular difference.
LittlestBiStik_fuselage2.jpg
The thrust angle mod completed.
LittlestBiStik_fuselage3.jpg
Next: re-engineering the wing saddle for what is now the LOWER wing.
kdc914
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Fuselage mods part 2

Post by kdc914 »

OK. so now we tackle the saddle for the lower wing. Here's where the Box-o-balsa-scrap shines. Sometimes being a packrat comes in handy. ;) Every conceivable shape and thickness just waiting to be used.
20240130_095115.jpg
First we fit the odd angle
20240130_094627.jpg
Then we cut/sand that flush and edge-glue more stock to accommodate the new curve
20240130_095711.jpg
Now we take our newly created wing profile gauge and, measuring carefully to ensure zero incidence, draw out the desired new saddle
20240130_125427.jpg
20240130_125946.jpg
And, after a bit of carving and sanding (my favoritest thing EVER :evil: ), VOILA! I'll go back and add some extra for strength around the saddle and then we're ready to assemble the fuselage.
20240130_153148.jpg
kdc914
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Joined: Tue Feb 09, 2021 7:54 pm
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Fuselage mods part 3

Post by kdc914 »

Having completed the mods to the sides for an inverted fuselage, it's time to assemble. As with any project involving modification, I usually outsmart myself at least once and screw something up. Today I did it twice. Neither mistake was particularly bad but still annoying.

Everything in place. Fortunately, I remembered to flip the forward and middle former bulkheads before gluing them in.
fuse_assembled1.jpg
fuse_assembled2.jpg
close up of the assembled lower fuse mod for the wing saddle
fuse_lower_mod.jpg
And here's where the oopsies come in. I had to flip the forward and middle formers (not really, but yes from the standpoint of which way is "up"). In so doing, I thought I needed to do that for the aft former as well, so because one end is longer than the other I made a flipped image of it. Of course, I didn't realize that was incorrect until AFTER thoroughly gluing it into place. Not TOO terrible a mistake. At most, this will cost me slightly less than 2g of total weight for the carbon fiber stiffeners on the aft pushrods - that will now have to pass through the large hole rather than the small guide holes they were intended to use.
oops_mid.jpg
The other oopsie was a failure to RTFM. The last few WN kits I built called for gluing the aft end of the fuse sides together. This one does NOT, at least, not the way I did it. Easy enough fix with very careful application of the balsa saw.
oops_aft.jpg
And now it's beginning to resemble an airplane!
Fuse_lower_wing.jpg
kdc914
Posts: 156
Joined: Tue Feb 09, 2021 7:54 pm
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Wing mods1

Post by kdc914 »

Given that this bird will have twice the wing area of the normal Littlest Stik kit, I confirmed that lower wing loading meant I didn't need to use all the shear webs, thereby saving precious weight. After I completed the first wing, Dale Womack suggested saving even more weight by fitting the shear webs between the spars rather than in front of them. I did that with the upper wing. According to my presumably very accurate laboratory scale, I should have only saved a few tenths of a gram, yet the difference between the wings was a whopping FIVE grams. I can only attribute that to differences in wood density and/or moisture content.
Wing_compare.jpg
Because of the inverted fuselage and battery placement, I need to put the landing gear in the lower wing rather than the fuselage. To do this, I borrowed from the method used on the Skylark and Sky Tiger kits - building a box for the wire to slip into adjacent to a wing rib. My only regret is not thinking of this BEFORE decking the lower wing. I should have extended the forward upper decking further beyond the inner rib to form the top of the box.
The rather complicated wire bend required to make this feasible
wing_gear_bend1.jpg
wing_gear_bend2.jpg
Next, I crafted proof-of-concept braces from relatively thin balsa
wing_gear_brace2.jpg
And here's how that looks with the wire in place
wing_gear_brace4.jpg
And finally a ballpark idea of the finished look. Now to go back and craft the outer braces in thicker balsa or ply. Then I'll quadruple check alignment and epoxy it all together
wing_gear1.jpg
wing_gear2.jpg
wing_gear3.jpg
kdc914
Posts: 156
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Tail mods 1

Post by kdc914 »

Because I hadn't previously included the full-span trailing ailerons in the calculation, I had to revise my total wing area from 160in² to 170in². This new area measurement was used to create the new tail feathers, shown below with the kit originals on top for size comparison. At 29in², the horizontal tail is 17% of total wing area and a bit over 1/3 of wingspan. Not wanting to get too deep into geometry calculations, I used my calibrated eyeball to get the size of the vertical tail. Hopefully, it's enough.
Tail_mod.jpg

Well, by gosh and by golly, it's starting to resemble an airplane!
general_idea_view.jpg
Now, onto the cabanes. And then, even more [deleted string of expletives] SANDING...

.
kdc914
Posts: 156
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Tail mods 2

Post by kdc914 »

The kit came with 7/64" balsa. My LHS didn't have that so I had to use 3/32". Given the extra area, that will help offset some of the extra tail weight. Here are the new tail feathers in 3/32" with the lightening holes cut. I used a quarter for the holes on the horizontal stab, a nickel on the vertical stab, and a dime on the rudder.
Tail_mod2.jpg
The original 7/64" tail feathers weigh 4.1g. My new 3/32" ones weigh 5.6g. Only 1.5g extra weight for the significant extra size. Not too shabby - IF they are strong enough. NOW on to the cabanes...
kdc914
Posts: 156
Joined: Tue Feb 09, 2021 7:54 pm
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Cabanes part 1

Post by kdc914 »

When I ordered the Littlest Stik kit with an extra wing, I told Doug my plans for it and he graciously included a set of S-Tee cabanes. After playing around with those for a bit, I realized that I would have to recreate the saddle pieces for the upper wing anyway so I set the S-Tee parts aside and decided to do my own cabanes, using the example from my partially completed Honker Bipe. Step One was a trip to my local hobby shop for wood. I got both Balsa and Basswood.
Cabanes1.jpg
The S-Tee cabanes from Doug are 9/64". My LHS doesn't sell 64ths and was out of stock on 5/32" so I sent with 1/8". Given that I was going with a material 1/64" smaller than what is presumably recommended, I opted to go with Basswood since it (theoretically) should be stronger.
Cabanes2.jpg
Here is the mostly finished saddle and rough-cut vertical struts.
Cabanes3.jpg
Pretty decent fit. Still some sanding to do on the upper wing AND the saddle BUT...
Cabanes4.jpg
Now I have to figure out the vertical strut lengths, angles, and placement.
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