# Narfi's Scratch Built Zenith 750 Super Duty

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#### Victor Bravo

##### Well-Known Member
HBA Supporter
Carved foam and a couple of layers of glass cloth. Not very difficult to accomplish on non-structural parts.

OR... you could make the smaller ones out of plastic if you really wanted to. Use the "stretch forming" that the model airplane guys use for making custom canopies for R/C models. A couple of 2 liter soda bottles, a plywood form, and the oven in your house.

#### narfi

##### Well-Known Member
Log Member
2hrs.
Made the cutting and forming blocks for the two rear bulkheads. Could have probably freehanded them in less time, but if I mess one up during assembly and need to remake one, or inevitably damage one during the life of the plane, it will save me time in making a replacement and be a "quick" simple fix.

Total time spent building: 49 hours
Total Cost: $8276 Airplane + consumables + project specific costs:$5340
Tools, etc.. I will keep for future projects: $2936 #### narfi ##### Well-Known Member Log Member Friday the last of my aluminum came in and my wife helped me unroll and put it in the rack. I went threw my drawings to see which pieces to leave out on the table for the next parts and discovered a huge mistake I had made. The rear wing ribs are supposed to be .025 and I had made them from the same .016 as the tail ribs......... In all it's not a huge setback, a couple hours of work and 2/3s of a sheet of .016 aluminum wasted. If that's the worst mistake of the project ill be happy 4hrs friday night cutting all new rear wing rib blanks, nose ribs, and root ribs (all .025 this time) and the two rear fuselage bulkheads(one is .040 and one is .032) (Not counting the bulkhead parts, that is a full 4x12 sheet of .025 shown in the picture, all wing ribs from one piece) 2.5hrs and 3.5 hrs Sunday bending them all. 2 bulkheads, 14 rear wing ribs, 20 nose ribs, and two sets of two root ribs. The wing ribs are a larger front radius but it felt like the .025 forms better than the .016 on the tail pieces, the thinner stock wanted to fold more while the thicker could be (pushed around) easier with a brass hammer. My boy even came out to help bend some of the parts which made me proud. I had one flute crack out so needed to make one extra rib, but not bad for the mass production over the weekend. Just need to cut and flange all the lightning holes. That's all the parts I have from Roger to build so far, he is working on getting me the rudder drawings next. Total time spent building: 59 hours Total Cost:$8276
Airplane + consumables + project specific costs: $5340 Tools, etc.. I will keep for future projects:$2936

#### narfi

##### Well-Known Member
Log Member
1.5hrs cut the lightning holes in all the ribs, nose ribs and root ribs. Need to clean them up and flange them now.

Total time spent building: 60.5 hours
Total Cost: $8276 Airplane + consumables + project specific costs:$5340
Tools, etc.. I will keep for future projects: $2936 #### TFF ##### Well-Known Member You are probably going to have one of the more ideal builds because you are kitting the plane before assembly. Makes it look effortless, instead of slogging through one section at a time. Very nice. #### Victor Bravo ##### Well-Known Member HBA Supporter Congratulations on getting your son involved in the build! That alone is worth a million dollars. The cracks in the edge of the rib flange are 90% likely to be because you had a rough edge on the rib blank before pounding the flange over the form. One extra minute for each rib spent in front of the belt sander will greatly reduce that. You want a very smooth edge on the cut edges of the rib blanks. Not shiny polished, but smooth so you cannot see any marks on it, and with a slight rounding of the edge (round enough that you can't cut your hand if you slide the rib blank through your fingers). The Homebuilt Help guys had a video on ways to accomplish this using a Scotchbrite disk mounted in a bench grinder. #### bifft ##### Well-Known Member The Homebuilt Help guys had a video on ways to accomplish this using a Scotchbrite disk mounted in a bench grinder. Agree that deburring is a big part of avoiding cracks. I find that using a smooth file is just about as fast as the scotchbrite disk and doesn't tend to catch and bend sheet like the disk can. I prefer the file for sheet and the disk for extrusions. #### akwrencher ##### Well-Known Member HBA Supporter Nothing like a good sharp file. Just keep the aluminum cleaned out of it frequently..... They get gummed up fast and can scratch the material. #### PagoBay ##### Well-Known Member Besides Mark Pensenstadler's build series on the Zenith SD, just found another that is on Episode 16. Builder grew up on Alaska and lives in Wisconsin. Just an FYI. #### narfi ##### Well-Known Member Log Member Thanks, I've been watching his videos as well Still sore from our villages annual "Turkey Bowl" having lost so much weight this was my first year really running and catching instead of just playing on the line. Felt great but I'm guessing I'll never be young again 2hrs cleaning up the holes and 1 hour flanging all the holes. The plywood separated on the smaller die, so epoxied it and have a few of those holes left but will be just 15min or so. Landon came out to help but couldn't get enough oomph on the mallet so we tried a couple with clamps, learned about leverage on making handles longer but still not practical so he watched me beat the rest out with the mallet. He likes visiting at work and trying out the different cockpits and getting ideas and dreaming. Total time spent building: 63.5 hours Total Cost:$8276
Airplane + consumables + project specific costs: $5340 Tools, etc.. I will keep for future projects:$2936

#### Victor Bravo

##### Well-Known Member
HBA Supporter
What's that... a Norseman?

Log Member

HBA Supporter
Ahhh, my mistake

#### narfi

##### Well-Known Member
Log Member
30min
Epoxied the male plug back together and flanged the last of the holes. Very last one and the plywood on the male plug failed in a new layer (not my epoxy joint)
Not sure if there is more flanging to do that size or not, but if there is I will probably make a new male piece from solid wood instead of plywood.

Called Roger this morning and he is still waiting on Rudder drawings for me, so I'm on hold for a little bit.

Total time spent building: 64 hours
Total Cost: $8276 Airplane + consumables + project specific costs:$5340
Tools, etc.. I will keep for future projects: $2936 #### narfi ##### Well-Known Member Log Member I got the blueprints for the Rudder from Roger this week but in the middle of making a storage bed w/ bookshelves and secret cave for my son so probably cant start till next week. Ordered the 3/4x3/4 angle I needed, just a few inches needed for the rudder but Roger told me I would need roughly 20ft for the entire project, I bought a 25ft stick cut in half. Also have some 1/8" aluminum coming, will need some for the rudder horn. total for that order$275 (including $30 delivery) Ordered Some aluminum prep and some primer =$252
I decided to just go with primer I know, PPG 910-704 Super Koropon, it sprays easy, goes on super thin, and produces a hard chemical resistant shell.

Total time spent building: 64 hours
Total Cost: $8803 Airplane + consumables + project specific costs:$5867
Tools, etc.. I will keep for future projects: $2936 #### rbarnes ##### Well-Known Member The 750-SD plans are on Google drive now. I got my link to all the CAD drawings stored online the week before Xmas. #### narfi ##### Well-Known Member Log Member The 750-SD plans are on Google drive now. I got my link to all the CAD drawings stored online the week before Xmas. Yes, the CAD 3d pictures of parts and the Assembly instructions manual, but not the blueprints for actually making the parts correct? All the stuff for the kits, but not the info for scratch building which isn't finished yet. #### narfi ##### Well-Known Member Log Member Finally got most of Landon's bed made, still waiting on some magnets and hinges, and will need to paint it (black then scuffed up and clear coated for the old distressed look) once reassembled in his room. For not knowing anything about carpentry and making it up as I went along I am pretty happy with it, just not with how long it took Was able to start on the rudder yesterday, took about 5 hours to make 7 parts and decide that I needed more dimensions/info to make the rest. Tapered spars are easy, just make them a few inches too long each direction and then cut out the right size from the middle when done. I borrowed a neighbor's 12ft brake and it's got some quirks, not sure if it's just old or needs some adjusting, it bends sharper on the ends than the middle and doesn't clamp over center, the clamp arms need to be 'balanced' in the clamped position and it's a pain getting both clamped without one springing open. I got pretty close on my angles for the spar and doublers and just tweaked it a little with the hand seamer back at the tent when done. The hinge brackets were easy as was the little spar fairing and angle tab. Was my first time cutting sheet metal with the ulfa knife and it worked really well, though took quite a few passes for the .040, the thinner sheet cut really easy. I sent Roger an email listing the rest of the dimensions I need for the ribs and skins and horn. Will give him a call as well. Total time spent building: 69 hours Total Cost:$8803
Airplane + consumables + project specific costs: $5867 Tools, etc.. I will keep for future projects:$2936

#### Victor Bravo

##### Well-Known Member
HBA Supporter
If you are scratchbuilding, have you researched the home-built sheet metal brakes that have been developed for stuff just like this? There are even home-brew brakes that mount to the edge of your bench.

One trick to remember is that for MOST of the stuff, like your fin spar in the photos, the "depth" of the brake only needs to be an inch or less - the width of the riveting flange. Meaning you don't have to come up with a brake that allows a bend in the middle of a 4 foot wide sheet. Which means you can clamp the hold-down bar using C-clamps all the way across the bar.

#### Rockiedog2

##### Well-Known Member
HBA Supporter
I like that kid...