2017/2018 Balsa Build Along, SIG HOG BIPE ELECTRIC CONVERSION

[AkimboGlueGuns]

It would be roughly equivalent to a sport bipe (think acrosport/star duster,) and the pilot does make the plane appear to be about that size, so I'd say it's about right. Chopping the shoulders should make it just about perfect. Love the way this build is shaping up. Keep at it.

 

[TexMechsRobot]

Based on some quick math and the assumptions:

1. that the Sig Hog Bipe would be about the size of a PT-17 Stearman and
2. that the average height of a male pilot is 5'10"

we have the following chart with all measurements in inches.

 

[nhk750]

So, my guy is about right. When I perform shoulder surgery on him, he will be hollow. I think I will just make the fuse side high enough to hide this, or should I glue some plastic sides to seal him up again? I don't work with plastic much...

 

[AkimboGlueGuns]

2. that the average height of a male pilot is 5'10"

I might skew that a bit. I barely fit into my C152 at 6'4" ;p

 

[Joker 53150]

I was figuring my Astro-Hog to be somewhere between 1/5 and 1/6 scale, and when it came time to put a pilot in it I just 3D printed one, and made it a few times until I was happy with how it looked. I call it "TLAR Scale". (That Looks About Right Scale)

 

[nhk750]

Problem

I am working on the cabane mount area and per the Sig instructions they say to glue on the fiberglass cloth over the top of the cabane and wrap the edges of the cloth around the edges of the mount and glue. In their picture it shows them using thin CA, but I have always used epoxy or epoxy resign to work with fiberglass cloth. So, I thought I would try the CA...arggggg!!! that was so stupid, my eyes were watering I felt sick from all the fumes and it made a big mess and worked like crap! So after it dried, I epoxy coated the bottom of the mount to smooth things out then sanded the top of the mount, per the instructions, to smooth the top flat. It came out ok, but the edges are all loose and airy (I'm not sure how to describe it) Now I am going to have to wait until I build my top wing to see if I have enough clearance to epoxy the edges and possibly the top to make everything nice and smooth. Jeezz, using CA is the worst idea ever on fiberglass....I guess this part wont show to much so I shouldn't stress about it...

Here is a copy of the instructions with the picture.

 

[Joker 53150]

CA on fiberglass is ok for some stuff, but if this is structural I'd prefer epoxy. How thick of cloth did the kit include? You may get better results with a thinner cloth that conforms to edges/curves better.

 

[nhk750]

I just got home, here is a couple of pics. It is really thin fiberglass cloth and the top came out ok, but the sides need some epoxy or something and I did epoxy the bottom as it was really bad. I think epoxy works way better than ca for fiberglass. I need to build the top wing and see how the mount fits in there before I mess with it anymoe. I think Sig chose ca for speed in building, but I really have a dislike for CA as it kills my eyes and I only use it when I really need to. Epoxy doesn't bug me though and I really like Titebond II, but I dont think it will work on fiberglass cloth.

 

[nhk750]

Build update

Got some good progress done this weekend and worked on the electric conversion engineering. Battery tray is mounted, motor mount is modified and the ESC mounting area is ready to accept the ESC. Here are some pics.

Making the battery tray. 3/32" ply, I used the Dremel to cut out the battery strap slots. I kind of mutilated it a bit, I was tired...


Installing the battery tray. I lined up the center of the battery with the motor thrust line, but it sat to high so I had to drop it down a little. I did leave enough room for a bigger battery also if I decide to go that way some day.


Battery tray mounting complete. I used balsa 3/8" angle epoxied in to strengthen the battery tray mounting area.


The business side of the tray.


Glued in some minicell foam for a battery pad and anti skid. I have some nice battery straps coming to hold it all down. You can see some slots cut in the foam for zip ties that will hold down the ESC mounted on the bottom side of the battery tray.


This 6s 4500 fits easily and I made sure to have extra room for a larger battery someday.


I decided to move the ESC as far back as possible for CG balance. After reviewing weights on gas/nitro motors and other types of builds people do, I think this is a good idea. If it is tail heavy I can always put in a larger battery. I also have a few inches to move the battery if needed. I am guessing at this point, but I think it will turn out pretty good.


The ESC has some minicell foam under it to help secure it when the zip ties are tightened. I may cut an access hatch in the bottom of the fuse for future access in case of service needs or a zip tie wears out.


I cut the motor mount shorter to fit the plans and the fiberglass cowl. I also decided to add a washer on the left side mounts for a slight bit of right thrust. After much review and even a reply from SIG, they say a little right thrust wont hurt, so now is a good time to add a little before I trim and mount the cowl.

 

[nhk750]

Cowl mounted

Moving right along this weekend. Got the cowl mounted after cutting and sanding out the holes in the front using a Dremel cutting bit, grinding bit, and sanding drum attachments. My round hole for the motor came out ok, but not perfect. Pretty good for a first timer working with the Fiberglass Specialties cowl. Looking pretty sweet with the prop and spinner mounted!



Looks pretty cool backlit, almost transparent. Seems a shame to cover up that beautiful Scorpion motor...


Nice tight clearance with cowl and spinner. Using a turbo cooling spinner to force air into the motor and cowl. The bottom of cowl has an induction slot to hopefully force air into the fuse and cool the ESC mounted in there.

 

[Joker 53150]

Wow, that is a MEAN looking spinner! If you go in nose-first that baby is going to penetrate the ground in a major way!

It may just be the angle and it's just my opinion, but the spinner looks a little narrow for the cowl. Did they give a recommended size? I went without one on mine as it looked more old-school and matched the look I was going for. That cowl certainly looks better and more contemporary.

With the trimming on the fiberglass cowl, are you wicking in a little thin CA where you cut/grind/sand and expose raw fiberglass? I seem to recall the instructions saying to do that, but haven't done it on mine yet.

 

[nhk750]

It is the recomended size at 2.5" and the cowl cutout matched it. I did grind the hole a little larger though as Im new at this. I didnt see anything in the instructions about sealing the cutouts, but it does mention prepping the glass for paint carefully and cleaning very good with the recommended solvent. Since this plane is going to have 1,500 watts of power, I thought the spinner would give it that look of power and its fan will help cool things hopefully.

Did a little more work last night and am now ready for the battery hatch manufacture. I have some ideas and had to sleep on it. Hopefully will have the hatch done tomorrow then the electric conversion part will be done and I can get back to the conventional build parts of this model and turn my brain back off.

This picture shows the hatch former sitting against the right former in the pic for reference, so dont get confused by this picture. When the hatch is complete I will have better pics.


This pic shows the super thin ply being glued to the former for durability when the hatch is removed and installed.


I cut out super thin ply and glued it to the formers I made for my battery hatch. This will keep the surfaces from wearing out as the hatch is used as I think the balsa wouldn't hold up by itself over time.

 

[nhk750]

Battery hatch update

I know this thread is growing, but I like to be thorough as during my research on building this plane others were not. Guys would say "built the battery hatch and installed" but, they wouldnt tell you how they did it and that frustrates me because then I have to think and thats a lot of work...Anyway if someone needs to build this plane I hope my detailed build thread will help them along.

Almost done with the battery hatch and here are some pics.

I measured, accounting for the thickness of the sheeting, the base to fit with a little room for covering on the front and rear. Then cut out with my jig saw. Used 3/32" ply. I kind of copied a design I saw on the internet.


Good fit. In this pic you can see my false bulkhead I built against the firewall. The cowl will cover this area so I wont be sheeting it but will use covering instead. I just needed something for the battery hatch to mate against and I am still debating about using a dowl or magnet for the front of the hatch.


My ply is slightly warped, so I pinned it down with magnets for the assembly in hopes it will be straight when done.


Got the stringers in and sheeting will be next then the magnetic attachments.

 

[Joker 53150]

That looks just Ike I did with the hatch for my Hog, but yours is much cleaner and wasn’t hacked out of glow fuel soaked balsa!

 

[nhk750]

That looks just Ike I did with the hatch for my Hog, but yours is much cleaner and wasn’t hacked out of glow fuel soaked balsa!

Haha, thanks, if you look closely mine is hacked out too as I'm using a Dewalt heavy duty jigsaw to do fine detail work. I'm lucky I didn't cut a few fingers off as I disregarded all saftey rules to cut it out. I really need a scroll saw if I continue to scratch build parts.

 

[agentkbl]

or a laser cutter.

 

[nhk750]

Bending balsa.

Finished the battery hatch and bent the sheeting around my frame using Windex, then a combination of Titebond and CA to glue it down. I thought I would try some CA on the bottom edge of the sheeting to save time, but Titebond works so much better. CA just sucks sometimes as its hard to sand and then it didn't stick as good as the Titebond II. Lesson learned, have more patients. I haven't mounted the magnets yet, but have a plan for a magnet in each corner (4 magnets, 4 corners), then use screws on the mating surface. I cant use a dowel in the front as the clearance wont allow its use, next time I would angle the rear former so the hatch would slide into a dowel. The extra magnets will add weight, unfortunately. I also made a simple access hatch for the bottom fuse to service battery straps and the ESC. Hopefully I haven't added to much weight with all these modifications.

Finished hatch frame test fitment.


Finished battery hatch.


Battery in finished battery tray compartment with fancy 300x20mm battery straps.


Battery hatch in place.


Bottom access hatch that will be held in place with servo screws.

 

[Joker 53150]

If the power on your Hog is anything like mine, the extra weight from magnets, multiple battery hold-down straps, etc will never be noticed!

 

[nhk750]

Oh ya, lots of power with a Scorpion pushing 1,500-1,700 watts!

 

[nhk750]

Electric conversion finished!

Ok, I finally finished the battery access on this and that will wrap up the electric conversion. The battery hatch magnetic attachment and tray are done, the ESC mounting is done, the motor mount is done, the cowl is fitted, the bottom access hatch is pretty much done, and I am ready to move on to the rest of the build per the instructions. I can turn my brain off now and just read and build...

I used a Retro RC latch kit for this part. 1/4" latch kit and then epoxied them to some balsa and to the fuse for strength.


I Used the screws included in the kit in the ply hatch base and put CA on the threaded holes then reinstalled the screws. I had to countersink the hatch base so the screws would sit level with the base. The basswood rails are for alignment when the hatch is installed.


This should look sweet after I cover everything and paint the cowl as the hatch lines up nicely with the cowl! I have no idea about my color scheme yet or what type of covering yet. Probably will try Ultracote on this one, or maybe the HK stuff as it works really good.