2020-2021 Buildclass model suggestion; build and discussion

[Michael]

Preparing and applying the bottom-forward fuselage sheeting was the first (minor) problem I found. 4 laser cut parts are glued together to form this piece, but when test-fitted to the fuselage, it was not a good fit (see photos). The fix was easy; I simply glued in 3 very thin spacers to suit. Then the part fit easily, was held in place, and thin CA glue was dropped in along the joints. 15 minutes work.

[Michael]

Battery tray and velcro glued in, and front top sheeting assembled and glued on. There is a bit of sanding and bending required, but still easy stuff.

So far, this is fun!

[Michael]

Nose block glued on and shaped.

[Michael]

Fuselage construction is done. Tail is fitted in the slots but not glued (until after covering). It can still use an overall light sanding.

[Michael]

Wing center-section.

I built this following instructions very carefully. While it was not difficult, it took me more than 2 hours. I fitted (and sanded if necessary) each piece carefully, before gluing. The parts-fit is precise, but I had to check and double check each joint to make sure I got it right. As long as read and followed the instructions, it went well. There are several plywood pieces in this assembly.

[Michael]

Wing construction:

First major (not so terrible though) problem with the kit. 2 balsa strips (24" x 3/32" x 1/4") were missing. I had extra scrap lying around, so I was able to cut strips, but this was annoying and inconvenient.

I built both wing halves at the same time, making sure specific parts were built correctly for the right and left sides.

I followed the instructions carefully, but not careful enough. I still installed one of the servo-bay-openings upside down. I was able to cut it out and re-glue it in properly, so I remind anyone interested, dry-fit over and over, and make sure it matches the plans and instruction photos, before gluing.

(The photo of the aileron servo opening shows the correct positioning; plywood face up to the inside of the wing.)

Anyway, basic construction of both wings took about 3 hours. Sanding is still required, and the ailerons have yet to be built.

[Michael]

Ailerons built as per the instructions and plans. Leading edges cut/shaped/sanding as per instructions. Hinges temporarily installed (this took most of the time), and wings joined/glued to the center section. I used 15-minute epoxy here because I wanted time to position the wing to make sure everything was straight, and then I taped things together so they would stay in place as the dried. I used medium and thin CA for all the gluing so far.

[davidk]

Using 15 minute epoxy and medium and thin CA are the nice bits to know about.  Could you explain a bit where/why you'd use medium and thin CA?
Do the nylon wing bolts come with the kit?  Cheers.

[Michael]

Using 15 minute epoxy and medium and thin CA are the nice bits to know about.  Could you explain a bit where/why you'd use medium and thin CA?
Do the nylon wing bolts come with the kit?  Cheers.

Thin CA seeps quickly into a tight joint and balsa grain, and drys in less than 5 seconds (brands vary), but does not fill a gap.

Thin CA seeps more slowly into a joint and the balsa grain, fills a very slight gap, and takes about 25 to 30 seconds to dry (brands vary).

Epoxy is heavier, fills larger gaps, and takes 5 to 15 minutes to dry, depending on the type of epoxy used.

Also consider, CA seeps into soft and light balsa better than in hard and heavier balsa or plywood.

So, in areas of exceptional tight fit and reasonably light-soft balsa, I use thin CA. Sometimes a structure or a joint is held together so perfectly, that simply dropping a few drops of CA on the joint locks everything in place.

Where hard balsa or plywood is part of the joint, or if I want to build  up a small amount of glue outside the joint for extra strength, or if I need to apply glue and then put the pieces together (I need a few seconds to glue the pieces together), I use medium CA. These glue joints need to be held or taped or pinned together until the glue dries completely.

Once glued with CA, it is basically impossible to undo the glued joint. Make sure things are in the correct position BEFORE applying CA glue.

These kits can successfully be built with white glue, but it will add many hours to the project.

I use epoxy where I want much more strength and more time to work before the glue dries. I used 15 minute epoxy when gluing the wings to the center section, as I wanted a couple minutes to do the work, and time to tape the pieces tightly, slightly repositioning the parts, to get everything to line up as nicely as possible. If I had used CA, and then put the pieces together improperly, the entire model (or at least the entire wing) would have been ruined.

******

The nylon wingbolts, and any hardware needed so far in the construction, was included in the kit. I may buy/use some extra hinge material, since the pieces I'm using are fraying quite a bit, that when final assembly is done, the hinges may be worn out (the fibers, that are layered over the center plastic part of the hinge, that absorbs CA glue, are falling off).

[davidk]

Thanks Michael, this is really good information.

Do you use a CA accelerator... or is not needed?

[Michael]

I have not needed CA accelerator in this construction, so far.

CA accelerator is a liquid that is sprayed onto a medium or thick CA joint to speed up the drying process. It usually expands the glue a bit and dries white.

[Michael]

Suggestions:

Make sure the #11 X-Acto is changed regularly. It's much easier to cut with a fresh sharp blade.

Make for yourself sanding blocks. I epoxy fine, medium and course sheets to hardwood blocks. It makes sanding easier, more precise, and faster.

[Michael]

Tip floats.

Take some time to cut out parts if they don't slip out easily. Use a sharp #11 X-Acto blade/knife.

Built as per the instructions, with no significant issues. I did notice that the parts fit (see first image below) did not match the drawing on the plans. It did, however, match the photo in the instructions. It went together easily. Total time here about an hour and a half.

All built parts (not glued) together nicely at this point.

[Michael]

Motor pylon.

I found another motor that is more suitable for this model. Almost any brushless motor that is rated for 3 cells, 100+ watts on a 7" propeller will work, as long as the size fits.

I'm using the following, which is a quad motor and (30 amp) speed control. Anything similar will do.
https://www.seeedstudio.com/Emax-XA2212-12V-DC-1400KV-Brushless-Motor-p-1900.html

I needed about ¼" extension from the firewall to place the propeller in the right position. I cut parts out of plywood scrap from this kit. The modification was simple, and worked well. Don't be afraid of making minor changes to suit your needs.

[Michael]

Suggestion:

Buy small hex screws and a hex tool. This makes work much easier than with regular small screws and small screw drivers.

It's more expensive, but cheaper than Tylenol in the long term.