Finally got a cowl made. 3D rendering in Sketchup and generating gcode from it was a new experience for me.

Made the cowl by importing another J3 cub from the library of models available at Google. Pulled the cowl from it and scaled it to fit the EO Cub and then converted it to an STL file with a Ruby plugin.

Using a trial copy of MeshCam, I opened the STL file and sliced the cowl into 4 separate layers of .75" thickness and generated the gcode for the MK1 style of gantry.

During cutting, the Planet-CNC DIY USB controller encountered feed rate problems processing the files. For some reason it slowed down to .15 ipm twice on 2 separate files. The feed rates varied substantially throughout the cutting of the parts but did complete. I was not particularly happy with the quality of the cuts so I decided to monkey with the MeshCam settings.

On the second set of cuts, the ones attached, I increased the feed rates to 30 ipm for the rough cut processing, 75 ipm for the finish cut, and 100 ipm for a pencil cut. The first set of cuts were made at 30 ipm rough, 10 ipm finish and no pencil cut.

I switched to Mach 3 for the second set of cuts and cut the parts again and this time the feed rates remained constant throughout the cuts.

These cuts came out extraordinarily well. MeshCam did a great job in producing a finish that only required a small amount of sanding with 300 grit sandpaper to prepare the parts for vacuum forming.

The 4 slices were cut from Dow 3/4" Blue Foam and glued together to make the full cowl. I mixed up a bit of Durhams Water Putty mixed with lite spackling and water to make a paste to fill in any cracks and sanded the mold after drying.

Then using the Phlatformer, pulled a couple of cowls for mounting on the cub.

Both pulls resulted in creases that are not objectionable, but not perfect. Could be the part is just too tall for the 12x12" plastic sheet. Maybe if the surface area were bigger, the creases might not form? Dunno, this is another new area for me. At any rate, the cowl came out very well considering this is my first attempt at something like this. It was a bit difficult getting the plastic off the plug, but with persistence, I was able to finally get it loose without destroying the plug.

Tomorrow, I will experiment with mounting the new cowl to the cub having already covered it in Ultracote for Park Flyers. I still need to dress it up with windows and decals. Should be ready for its maiden and picture taking later in the week. Attached files sliced cowl_slice_1.stl.cnc (334.3 KB)Â sliced cowl_slice_2.stl.cnc (329.9 KB)Â sliced cowl_slice_3.stl.cnc (225.9 KB)Â sliced cowl_slice_4.stl.cnc (201.6 KB)Â

 

That is incredable...
I can't wait to get my MK and be able to stff like this...

 

Flashsolutions, could it be that the creases are do to the facts that the plastic cools before it has a chance to be pulled properly around the plug? Maybe a secondary heat source could help but I don't have any idea, yet, how to do it.

 

Almost done... still need to make a front windshield and mount aileron servos. Cowl is on crooked, need to remove tape and afix it on straight. Hoping for maiden Friday if all goes well.

Attached files

 

And I am giving this one away... Oh well, maybe I will build another one for me.

 

Looks great and i bet it flys just as good...

 

Just a note, You will need to add carbon fiber to the LE and TE as the wing will fold in half if you don't do this. Trust me i found out the hard way

 

I used 3/16 basswood for the leading and trailing edge. It fit perfectly into the grooves that were provided. They were glued in with Gorilla glue, taped to prevent seepage. The wing is very strong. I do however, still need to add struts, mainly for looks, but also for support.

 

Sounds good, and the struts look the part too.
Matt

 

Finally got to do a maiden of the completed Cub. The weather cooperated for a change.

I had installed two 3/8" Bolts on the firewall to try to get the CG where it belonged. I was still a bit short but decided to give it a shot anyway.

Yep, tail heavy. Just what I was afraid of.

Landed somehow, not very graceful at that, but on the ground with nothing broken.

Took the battery out and taped it to the bottom as far forward as practical.

Looks like that is the sweet spot. CG now 25 to 28% of the chord.

Airborne and flying well! I put ailerons on this one, although they are slow to react, the rudder turns the plane well.

Some last minute updates to the SU file to move the hatch further forward, added holes for bamboo sticks in the wing saddle area so I could eliminate rubber bands and have a bolt on wing. Just glued a piece of lite ply with a 8/32 nut embedded in it to the rear bulkhead and added a piece of 1/64 wood laminate for supporting the screw to hold the wing in place.

Took out the cowl parts from this version since they are pretty much useless anyway and because I am using a vacuum formed cowl. Added some landing gear wire covers and a few other minor edits to what should be the final version of the SU file. Attached files EO CUB Rev 7.skp (3.9 MB)Â