Single-seat ultralight puddlejumper: the "Carbonmax"

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plncraze

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That is cool! When you talk about design you always share a lot of experience. Thanks for keeping it "real." LOL!! It looks like you could do all your lay ups on a table then vacuum bag it down and then build the aircraft from the pieces. Do you cut your carbon pieces before (as fabric) or after you mix/cure the pieces? Marske's manual has the calcs for doing fabric covered composite wings. The "Irv Culver" airfoil (RIFPIB) would be fine for this performance envelope. The air will forgive you. When you "ballpark " structures do you usually start with a three layer 45-45-0 or is this excessive for carbon?
 

cheapracer

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Look at motorcycles. How many of them are only practical single seat
The motorcycle analogy is a good one. .
Show me all the single seat motorcycles on the market guys ... That's right, next to none, people won't buy them. Yes, very rare you see a sports bike 2 up, but the silly little seat is there, as are the second set of footpegs, because it's what people want.


* If you squint your eyes a bit, you see that one wing is about 7/8" further forward of the other. That lets the wings be mirror images of each other but still allows the wing spars to overlap inside the fuselage. Do not confuse symmetry for balance.
A number of planes have offset wings, the RV12, and the Morgan is about 50mm/2".

Meh, planes aren't symmetrical anyway unless you have 2 counter-rotating engines or props.
 

Hot Wings

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Show me all the single seat motorcycles on the market guys
Note that I qualified my statement with the word 'practical'. ;)
I'd have to agree that most sold do come with the 'provisions' for 2. I removed the back pegs from my Triumph 675. Just dead weight with the aftermarket single place saddle. :cool:
This trend is not limited to motorcycles. I see it with 2, AND 4 place, ATVs too. Most get used solo.

I think where we disagree on the single vs 2 place market is that the existing market believes they need 2 place because we haven't done a good job of convincing them that they would really be better off with a single because that is they way they actually get used.

If you don't want to spend the time educating your market - and that gets expensive or time consuming - than you build what the market believes they want. This IS the safe way to a profit.

But this is all thread drift. Boku is investigating ways to produce a single place plane. I think it's a great idea. The market may not.
 

Pops

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Powered with a 1/2 VW with an alt, and starter with extended wings.
Or, built light with a bare 1/2 VW .
Where are you going to put the fuel tank ?
Keep on talking.
 

plncraze

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The Starlite was an incredible design. The designer had worked professionally in aviation and said all the materials on it could make it through certification. A new one would be nice.I
In the subject of a second seat look at Chris Beachener's V8 Special. The passenger's knees were his armrests. But you could take someone along.
 

plncraze

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BoKu, there is a stress report for the Mini Max on the lonesome buzzards site. It is for the original version with the mid wing. It had pine spars with ply and 6061 wing fittings.
 

Pops

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I think this little airplane could be very popular if done right.
Example-- One of my neighbors is a retired airline pilot that owns 4 airplanes. When a friend of mine that has a Mini-Max with 1/2 VW on it with over a thousand hours on it , flys the 50 miles to my field and back home, my neighbor shakes his head and says, '" I think I'm doing something wrong, He has more fun on almost no money than anyone I have ever seen".
That is what people will see in this airplane. Fun little modern looking airplane that most people with a pilot license can afford. Most fun for the buck.

Dan
 

plncraze

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Pops, your neighbor is right. At some point the cost gets so high it just kinda ruins it. Remember the Frank Christensen quote about his Cavalier Mustang "The cost of the gas going into the engine was louder than the Merlin." It isn't fun if you're broke when you're done. Your SSSC is cool too. Affordable materials from the cabinet shop with an affordable engine.
 

Bill-Higdon

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Bruce crossed the Rainbow Bridge, and his estate shut down the web site, no longer sells plans, and will not entertain someone buying the rights and continuing support. I have a set of "Early Builder" plans. It's well thought out.
Frtom the BK1 flyers group on Facebook, there' still activity outside of what Bruce had done, and some reports of errors he wasn't interested in correcting if I remember it properly
 

proppastie

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what they were doing:
Selling books and design software. Claim to be able to design with CF as if it were a homogeneous material. Considering the level of (or lack thereof ) of stress expertise I am not sure there is any advantage for someone like me using their system.
 

harrisonaero

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A friend that is a really good pilot and has owned and flown numerous kinds of airplanes (ag planes,Tri-Motors, warbirds, antiques, numerous experimentals, etc.) said he'll never own another single seat aircraft because you don't have someone to share the experience with and you're too tempted to do low level aerobatics and/or buzz jobs. A good compromise is something like a Just Aircraft Escapade where the GIB doesn't have controls and straddles the pilot like a motorcycle.
 

BoKu

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I finally had time to do some experimenting with the construction techniques for the CarbonMax aft fuselage. The overall idea is that we'd make and sell the skins for the compound-curved forward fuselage and cowling, and builders would make pretty much everything else themselves. That results in a sleek, curvaceous airframe while keeping up-front costs down and maximizing sweat equity in the finished product.

The concept for the aft fuselage is that you cut cradles out of particle board or whatever 3/4" material you have at hand, and use them to enforce the contour at each end of a piece of thin aluminum sheet. Then you constrain the remaining edges of the sheet with straight pieces of aluminum or steel tubing. The result is a clean, smooth ruled surface between the cradles.

You use these assemblies as female molds to make the three aft fuselage skins. For the lower skins, you first make one side, then you reverse the cradles and make the other side. And after that you use the sheet in a different set of cradles to make the upper skin. Actually, you probably make the upper skin first. Anyhow, you use the same piece of aluminum sheet and the same steel rails to make the molds for all three skins

After fabricating each skin, and before demolding it, you create ring stiffeners and longitudinal stiffeners by hot-gluing down 3/4" diameter rods of pool noodle foam and skinning them over with one or two plies of carbon tape.

Here's my test mold. The cradles are a couple of random curves that go a bit beyond 90 degrees. The length is about 26", of which we're using the middle 24". The actual aft fuselage would be more like 84" long, with more substantial side rails to constrain the edges.
20200223_152604.jpg
The back side of the test mold.
20200223_153702.jpg
Here I've waxed the test mold and sprayed it with an in-mold primer to control pinholes. The primer here is just Rustoleum gray from the hardware store.
20200223_153714.jpg
And here we've laid up a test part consisting of three plies of cheap 8oz carbon, 0/90, +/-45, 0/90 and bagged it down with low-dollar consumables.
20200223_172132.jpg
Next weekend I'll add the stiffeners and break it out of the mold to see how it looks.
 

sming

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Great job!
2 questions:
- 8 oz/yd² is ~270g/m² for us european, right?
- how do you join the molded pieces ? That's something that still is a bit of mystery to me, how just tape around a butt join is enough structurally ? (my bible are the mike arnold videos, and it goes rather quickly over the subject "the aft fuselage is taped together and next... we have a complete airframe!")
 
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