Single-seat ultralight puddlejumper: the "Carbonmax"

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BoKu

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IF - you used the same diameter...
The backer rod worked great right out of the bag, and I don't see any compelling reason to do different. I concur that by carefully choosing the rod diameter, it might be possible to make incremental gains in stiffening effect per unit mass, but I think that there are more fruitful places to apply attention. Ya gotta pick your battles wisely.
 

daveklingler

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Hi Bob. Just thought I'd bump this thread to find out whether you've worked any more on this project during the coronapocalypse.
 

daveklingler

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I now have the aft fuselage mold waxed, primed, and ready to lay up the skins.
Looking at those photos, I became curious about how you laid up the mold itself. :)

A big piece of acetate?

EDIT: Just went back and skimmed through the thread, and guessed it might have been a sheet of aluminum.
 
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BoKu

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...EDIT: Just went back and skimmed through the thread, and guessed it might have been a sheet of aluminum.
Just so. It is constrained to defined profiles at each end, and to a straight line along the edges. The actual profile is probably a little off in the middle, but that doesn't matter enough to worry about. The layup will be two plies of 8oz carbon vacuum bagged with a few stiffener profiles bonded on afterwards. Then I will use external tapes along the top and bottom (exactly as I said I _wouldn't_ do) to bond the right and left together. After that, I'll start figuring out the tail surfaces.
 

plncraze

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Considering that some folks take years to build a plane this is moving quick. Have you got an engine yet?
 

BoKu

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Considering that some folks take years to build a plane this is moving quick. Have you got an engine yet?
Nope, I'm leaving for last anything I'd have to spend cash money on. My plan is to make visual progress quickly, and see if I can rope in some development partners to help share the burden of powerplant development. What I'd like to do is use an industrial engine of about 25 HP, and develop a PSRU with a prop extension of 8" or so to make the nose look at least sleek-ish.
 

plncraze

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If you are an EAA member look for the Stewart reduction drive in the Sport Aviation archives. Stewart, of Foo Fighter fame, (alliteration points) designed a neat little redrive.
 

BoKu

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If you are an EAA member look for the Stewart reduction drive in the Sport Aviation archives. Stewart, of Foo Fighter fame, (alliteration points) designed a neat little redrive.
Can you help me narrow it down a little? What year or decade am I looking for? What airplane did he use it on?
 

Vigilant1

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Nope, I'm leaving for last anything I'd have to spend cash money on. My plan is to make visual progress quickly, and see if I can rope in some development partners to help share the burden of powerplant development. What I'd like to do is use an industrial engine of about 25 HP, and develop a PSRU with a prop extension of 8" or so to make the nose look at least sleek-ish.
The B&S 810cc can be run direct drive, gives 30hp, and has provided good service on MiniSport SD-1s. No PSRU cost, weight, and torsional vibration mysteries. The available modest prop extension and a large-ish spinner helps with the otherwise blocky profile. And both Spacek and our own TiPi are working on heads-down versions that can clean up the lines even more.
 

Victor Bravo

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Bob I agree with direct drive. It is not likely that you (of all people) will build anything with a lot of drag 😁 You can save 6-8 pounds and hundreds of dollars, a beautiful combination in this type of endeavor.
 

dog

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What I'd like to do is use an industrial engine of about 25 HP, and develop a PSRU with a prop extension of 8" or so to make the nose look at least sleek-ish.
[/QUOTE]
Is there an industrial V-Twin that runs a dry sump
and can be mounted inverted?
With a PSRU mounted it would be as "sleek" as
a piston set up could manage.
It all depends on how important the "sleek" specifaction is.
There are a huge number of possible candidates in that power range,many of which will have very
similar dimensions and weights,so you have the luxury to wait and be picky.
It will be interesting seeing what you choose.
 

Victor Bravo

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a PSRU with a prop extension of 8" or so to make the nose look at least sleek-ish.
There exists an interesting and unique opportunity for a prop extension, because the V-twins have a dozen or so threaded holes built into the front side (PTO) of the engine, for mounting the engine to various equipment. Those holes appear to be valid hard points with good structure around them.

So you could make a little welded tube or sheet metal pyramid that mounts to the engine itself, and supports a thrust/radial bearing a foot in front of the engine, and relieves the crankshaft of all of the propeller flight loads. This would be a bolt-on item. No need for a reduction unless you're fixated on low speed thrust.

Turning a V-twin upside down is a poor return on investment IMHO. The amount of engine work, fiddling, redesigning oil flows, playing with oil scraper rings, and everything that goes with it... likely not worth it.

The case for a low power V-twin airplane is mostly made by simplicity and cost, both of which are lost if you try to turn an upright V-twin into an inverted Daimler-Benz.
 
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