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Single-seat ultralight puddlejumper: the "Carbonmax"

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stanislavz

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Thanks for the kind offer. I will see if I can get profiles of the parts I made, as opposed to the parts I designed.
Waiting for profiles. I will privide some examples, of not straight joint for sections.

Just an arbitrary example :

Section is elipse 1000x600, 2500mm length as base.

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And by combinig it with other, more tapared and "bend" (tail section is not at centerline, but lower or upper)

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We can get pleasent and intesting shapes. But you will need two molds, for each side. But - they could be cut from large eps block with no effort.
1588162997652.png
 
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Jay Kempf

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Bob, if you've got key sketches, I can follow along in Solidworks just for yucks. Would take much time to build an as built document for you. Might come in handy later on and could be fun to learn along with you.

Now back down to the hangar to make another set of wing skins for me. Starting to dial in my rig. Using 3D printed parts where you are using your pool noodles. Seems to be working. But I have it all in 3D so easy. Not working to your scale yet but getting there.
 

stanislavz

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Option for cutting tapered parts with cnc, but without full garage size machine : 1588170798567.png
And three pieces are nicer than two :

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Cutting paths :
1588170894409.png
 

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Vigilant1

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Option for cutting tapered parts with cnc, but without full garage size machine
For those interested in the article Stanislavz posted describing a single-person point-of-convergence foam cutting tool (originally written by Paul Moreli), the attached file contains a (rough) translation of the original French text into English. See the original file for the drawing.
 

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daveklingler

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Or if one has a MakerSpace anywhere nearby, quite frequently said space has a large CNC router table that can route out compound curves fairly easily, eliminating the need for hot-wiring a series of tangent planes.

One of my local MakerSpaces has one of these:


Elsewhere on HBA, there are discussions of the use of the Lowrider CNC homebuilt CNC router table to do the same. I've printed out all the plastic pieces for Lowrider CNC table, but I have yet to create the space to hold it. I'm going slightly larger than 4x8 so that I can route right to the edges of full-size sheets.

 
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stanislavz

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Or if one has a MakerSpace anywhere nearby, quite frequently said space has a large CNC router table that can route out compound curves fairly easily, eliminating the need for hot-wiring a series of tangent planes.

One of my local MakerSpaces has one of these:


Elsewhere on HBA, there are discussions of the use of the Lowrider CNC homebuilt CNC router table to do the same. I've printed out all the plastic pieces for Lowrider CNC table, but I have yet to create the space to hold it. I'm going slightly larger than 4x8 so that I can route right to the edges of full-size sheets.

I have not seen any amateour build cnc router adequate z axle travel. It is doable. But you need something at least 3.6 * 1.2 * 0.6m travel.

But as shown up here - you can build parts in no time. Same should apply to molds too.
 

Jay Kempf

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You don't need a large capacity router to do slices and glue them together. You just cut up the task in the CAD beforehand. I do it quite often. I can build molds any size I want but I have to reduce the mold to panels that can fit my machine. I am currently doing 8' and 10' dimensions out of 4' x 4' x 12" of machine travel. Eventually I'll build a bigger one but right now I see no need.
 

harrisonaero

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Not hijacking Bob's thread but it applies... I have a big 4-axis CNC hotwire that would make short work of a lot of the foam cores. Don't use it as much as I use to so should probably let it go to a new home. Travel of 4'x4'x8'. If you don't just do aero work then you can pay for it pretty quickly doing architectural forms (tapered columns, etc.) or movie props. PM me if seriously interested (don't have time for tire kickers). Bob- you could supply the cut cores with your kits :)
 

Jay Kempf

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No, 8' is two panels machined separately. 10' is three. Cut up the part in the CAD, cut the molds separately, assemble them on a nice flat table. QED. Any sized part can be done that way. Requires some CAD knowledge. A lot of CNC machinists do not get to design the parts they are tasked with making and don't have CAD and design skills. Many do but not all. Many ways to skin the cat.
 

Jay Kempf

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Boat guys build hulls inside out with a lot of 2D formers and strips. Then they put foam over them and then glass. Some put the foam on the formers and strips and call it a mold and infuse inside that. They don't have a CNC machine the size of a 50 or 100 foot hull. Imagination is the limitation.
 

BoKu

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Last night we finished bonding the aft fuselage shells together, and this afternoon we went up to the shop, stripped out the interlocking teeth, and weighed the aft fuselage. The weight was about 11.3 lbs, well within my Part 103 budget for that part of the fuselage. We also took a bunch of silly photos of it.

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We also demolded the tailwheel spring, which turned out to be somewhat of a failure. The 1/2" OD solid rod we molded from carbon tow is so nearly completely rigid that it would be useless as a spring. I was not expecting that sort of modulus from such a rudimentarily molded part. I'll probably end up sanding it down to an oval cross-section in order to get some springiness out of it. Once I'm happy with the spring rate I'll wrap in some BID to encapsulate the tows and give it some torsional stiffness.

I'm not sure what's next. I'll probably start getting foam cores cut for the tail surface leading edges, and maybe start making the pan molds for the ribs of the elevator and horizontal stabilizer.
 

Dillpickle

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[QUOTE="We also demolded the tailwheel spring, which turned out to be somewhat of a failure. The 1/2" OD solid rod we molded from carbon tow is so nearly completely rigid that it would be useless as a spring. I was not expecting that sort of modulus from such a rudimentarily molded part. I'll probably end up sanding it down to an oval cross-section in order to get some springiness out of it. Once I'm happy with the spring rate I'll wrap in some BID to encapsulate the tows and give it some torsional stiffness."

I set aside some compound bow wood/fiberglass limbs to play with as possible lightweight tailsprings. There is an old bow or 6 in every pawnshop on the planet for 25 to 50 bucks
 

Grimace

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I am working on an ultralight glider with a similar approach to things. One thing to consider is the molds. If you are looking to sell 100 planes a year, molds make sense. But if you are looking to build one plane easily, molds do not. I am currently working on using flashing (roofing sheet metal available at Home Depot) to create a mold of a seat in 2 dimensions, which can be used to make a carbon fiber sandwich structure. The difference is that the mold can be made easily in a garage using simple sheet metal... And thrown in the trash when you are done with it.

IMO, the problem with most affordable composite planes is that they either rely on complex molds in the hands of the designer/owner which makes it a financial risk if you don't buy a full kit right off the bat, and really only makes financial sense if you have the backing of a manufacturer to provide the kit, or else they are moldless construction and require a lot of time-consuming finishing work. By contrast, using 2D molds for composites lets people build the molds simply in their garage, while still taking advantage of the greater strength and properties of CF. Just something to consider in terms of taking composites in a new direction.
 

akwrencher

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I'm really enjoying following this build, it almost makes me excited about composites, which is saying a lot! Can't wait for the next installment.
 

Bill-Higdon

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Today we stripped the consumables and added the longitudinal stiffeners to the first aft fuselage half.
Stripping the peel ply:
View attachment 95414
I marked the stiffener locations in silver Sharpie, then hot glued backing rod to the longitudinal sharpie marks:
View attachment 95415
I saturated a ply of carbon with visqueen on one side and peel ply on the other. The peel ply has 4" diagonal lanes marked on it:
View attachment 95416
Then I cut strips along the lane markers and pasted them down over the backing rod. At the end of each strip I peeled the peel ply back for an inch so the strips can overlap cleanly at the ends. Because I'm cutting them out of a rectangle, the strips at the end are shorter than the rest:
View attachment 95417
After that we let it be to cure. Hopefully we'll go back up to the shop tonight to put in the orthogonal stiffeners.
Bob,

I like the use of "Backer Rod" and hot melt glue as a form for the stiffeners, in my "misspent" younger days I was involved with making some molds in the middle 70's. Our stiffeners molds were made by spiral cutting PVC pipe so it looked like "spiral wrap" this was glued down to the molds we didn't use hotmelt glue so that was a pain then resin impregnated cloth was laid over it. The backer rod costs less money is a lot faster to source & apply
 

stanislavz

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Last night we finished bonding the aft fuselage shells together, and this afternoon we went up to the shop,
Have you thought of using same technology - single skin/mono skin with reinforcement for wing construction build in female mold? In place of solid core foam or three layered construction ?

Especially in a case of doing it lancair 320 style - D box and upper portion of wing in one piece/ mold. with reinforcement along span. Like in any big metal wing :)

Of course - its may be too much metal thinking, but i would give it a shot.

It may be better to full foam wing due to much lesser amount of sanding. Better to standart technology - less steps and only visible joint, under main spar.
 

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