Frank's Bill Evans Scimitar Pole Star .45 size electric conversion

[Frank v B]

Mark and I are team building a Pole Star each.  His is a short kit but it is very short with minimal instructions. On top of that we are converting it to electric which was not an option when this plane was designed.

Executive Summary- A Scimitar is a stabilizer-less airplane, overpowered and very simple construction...if you know how to build.  The Pole Star is a .45 size 50" span airplane yet the plans show a K&B .65!!

My version is different from the plans:
- electric.  I will use an E-Flite Power .46.  No decision on whether to use 4 or 5 cells.
- the firewall was moved forward about 1 1/2" to put the prop in the correct place.
- the sides and top on the plans are 1/4 balsa.  I had 10 sheets of 3/16" balsa so I made the formers 1/8" wider and 1/8" taller.  Benefit: larger battery bay.
- my version has a built-up double-tapered wing versus the foam one in Mark's short kit.

The balsa wing build will be covered separately on another Build post-  https://temac.ca/smf/index.php?topic=8918.0

We had a state visit from Rob Dickinson who immediately decided to build one too.  He will be using my wing rib templates once I finish with them.

If you discount the yakking and BS, Mark built his fuselage in two hours.

The first photo shows the two fuse sides mated to one central 3" wide balsa sheet to reduce waste.  The highest fuse point is less than 4".

Frank

[octagon]

I have fixed/finished all other projects and was looking for something new to build. In talking to Mark Satin, he mentioned that he and Frank VB were going to build something a little different from the norm called a Scimitar,which comes in a variety of different forms, twin, biplane and many more. The more I thought about it the more I kind of liked the idea. So, with a kind delivery of some 3/16th balsa from Frank today, I started working on it. Mark lent me his extra set of plans so I could get a set copied for myself. As Frank mentioned, it is a straitforward build, but was designed 30 or 40 years ago and for Nitro. I think it is quite overbuilt for the needs of a modern electric system so I will try and lighten where I can. I got the sides cut out and a couple of the ply formers fabricated this afternoon.

[Frank v B]

Motor in place.  Even though I moved the firewall forward one inch versus the plans, it was not enough.
Made some stand-offs using the aluminum bushings supplied by my old Brio 10 kit.  Adjusted to a proper height by adding washers to the top and bottom with 5 minute epoxy.  Note that the washers were sanded on both sides to get oils off them.  The washers give the standoffs a bigger footprint so they will not crush the plywood firewall during one of my classic and forgettable landings.

Frank

[Frank v B]

Shaping the fuselage

Used a razor plane (see photo) to rough shape the fuselage.  Used the tri-stock as a guide on how far to go.
It took half an hour to produce the shavings and get it roughly to the correct shape.  The rest will be hand-sanded.

The fuse is completely boxed in.  Will only be able to install the nose gear after I cut the battery hatch in the front.

Frank

[Frank v B]

Hand sanded the rounded fuselage after the rough planing.  I did this by grabbing a piece of sandpaper and curving my hand.  A sanding block leaves ridges.  This hand sanding leaves a smooth finish.  Total time 5 minutes.

The X-mount was very tight so had to Dremel (sand) clearances in the balsa to drop the motor in.  That would make it impossible to line up the stand-offs.  Used a dab of 5 minute epoxy on the bottom of each stand-off, put a Dollar store pointed skewer through it, put the point in the screw hole in the firewall and dropped each stand-off down.  The photo shows the skewers in place until the glue cures.

BTW- glueing the stand-offs to the X-mount was not an option because they stuck out beyond the X-mount.

Frank

[Frank v B]

How to make a plywood nose ring (F1) around a spinner.

Step 1- take a piece of plywood larger than the nose area.  Drill a hole in the middle for the prop shaft.
Step 2- glue the plywood to the balsa nose and install the spinner properly.  Wrap tape around the spinner at the backplate to protect it from sandpaper.  Let the glue cure (yep, 5 minute epoxy!).  I used balsa wedges to add pressure to the plywood so it would not slip while it cured.
Step 3- rough cut the plywood with a razor saw.  Make a pencil mark around the spinner backplate.
Step 4- rough sand the nose toward the spinner backplate.
Step 5- Remove the spinner and prop adapter and cut the inside of the backplate large enough to remove the motor.
Step 6- fine sand the balsa nose up to the pencil mark on the nose ring.
Step 7- fine sand the inside of the nose ring (used a Dremel and sandpaper).
Step 8- fill the inside edge so it does not delaminate.  I used 5 minute epoxy mixed with micro balloons*.  Micro Balloons turn epoxy into a light weight white paste that will stay in place on vertical surfaces without running.  Applied it with my index finger. The photo of the Micro Balloon container shows the mixed epoxy in a cup in the bottom left hand corner.

The whole process took less than 20 minutes and is very accurate ...without me having to be.

Frank

*micro balloons are microscopic glass beads that mix with paints and fillers without absorbing the medium.  It can be bought at a Fibreglass supply shop.  It is used in racing sailboats to smooth out through-hull fittings without adding weight.  It can be shaped, moulded and sanded.

[Frank v B]

A quick battery hatch.

Step 1- draw the outline of the battery hatch with a pencil
Step 2- Cut the long edges on an angle.  This way the hatch will always fit and always sit in exactly flush with the rest of the fuse.
Step 3- make the front and back cross cuts.
Step 4- take out the hatch and add a balsa tongue and glue it to the front side*

Done in 10 minutes- start to finish.

Frank

* on hatches, I always put the tongue at the front and the latch/magnets at the back.  This way the wind will never pry open the hatch in flight.

[Frank v B]

That's enough for the fuselage.
Now the wing.

Mark's wing is foam.  Mine has to be built-up.

To follow this "How to build a balsa double-tapered wing" follow this link https://temac.ca/smf/index.php?topic=8918.0

Frank

[Frank v B]

Back to the fuse:

- cut the wing saddle into the balsa fuse sides to match the wing.  Installed plywood wing saddle doubler on both sides to strengthen the fuse.  Epoxied in place.  Used the green Dollarama clamps to hold it while the glue was drying.  Used the wing rib-shaped plywood cut-out on the balsa side to make sure the clamps did not dent the balsa sides.  See first photo.
- drilled the wing dowels- into the wing and the fuselage.
- installed  wing hold-down plate (plywood), drilled and tapped them for the nylon 1/4-20 wing bolts.
- installed the rudder servo.  I always use wood cross-braces to help strengthen the fuselage.  See photo.

F.

[Frank v B]

Fin/rudder

Cut it from pieces of 1/4" balsa per plan.
2 changes: 1) I did not curve the bottom of the rudder.   It looked a little too Jules Verne for me.  2) I left tabs on the bottom of 2 of the 3 fin pieces .  I plan on cutting a slot in the fuselage top so there is a strong gluing surface. The middle section of the fin does not have the tab so it can keep the top strong and continuous in that section.  The plan showed the fin glued to the surface with 1/2" triangle stock added on the surface on both sides of the fin.  The plan looked a little too utilitarian for me.

Frank

[Frank v B]

Fitting the fin/rudder

[octagon]

I like to make an inside curve in the trailing edge and then bury the higdges deep into the aileron. This means you can get a very close gap between the leading edge of the aileron and trailing edge of the wing, as the centre of rotation of the hinge is actually inside the leading edge of the aileron. The hard part of the whole thing is getting a strait groove in the trailing edge. I used my drill press and one of Dura Grit's tools to create the channel. It makes a great job of it and so easy. Anyone building is encouraged to consider tools from Duragrit. The tools just make every aspect of building so much easier.
The ESC is burried deep in the fuse, and I was concerned about getting enough airflow to cool it, so I decided to simply have it open to the air on the bottom of the plane. I cut an opening the same size as the ESC and that should be good I think.
Last bit of business for the day, attach the grooved trailing edge pieces to the wing, and fashion a fairing block behind the wing to blend into the fuse.

[octagon]

More work today. I was very happy with the wing saddle joint I achieved by using micro balloons.I mixed them with epoxy, spread it on the bottom of the saddle and installed the wing after coating the top of the wing with plastic cling wrap. Left it for an hour or so and removed the extra that squished out. Good tight gap. I also like to imbed the hinges into the leading edges of the ailerons so the centre of rotation is behind the leading edge. this allows for a nice tight gap. This plane has a lot of wing!

[Frank v B]

Hinging a larger airplane.

I prefer plastic hinges with hinge pins.  I modify them so they are removable.  The bent pins are just temporary.  Will show you later how I install them permanently but so they are still removable in case of a re-build.

Steps
1) Cut off one end of the hinge pin and pull it out. Photo 00
2) Take a straight pin and bend an angle into the ball end and insert it into the hinge.  Photo 01, 02
3) sand the flat plastic portion of the hinge on both sides of the hinge, top and bottom.  Purpose is to rough it up to remove mould release and add bite to the glue.
4) mix epoxy and put some on the hinge slot.  I push it into the slot with the back (dull) end of a used #11 blade. Photo 03
5) add a drop of oil (or wipe on vaseline) on the hinge at the hinge pin to stop epoxy from sticking to the hinge pin area.  Wipe off excess oil without spreading it onto the hinge tabs.
6) wipe epoxy onto both sides of one hinge tab and push it into the slot.  Stop pushing it before it reaches the final spot.  Wipe off the excess epoxy that builds up on both sides before it hits the hinge pin area. Photo 04
7) push it fully into the slot.  Photo 05

Objective: the hinge pins on all hinges should be accurately in line so you can pass a single piece of piano wire through all hinge pins without bending it.  If they are not in line it will bind.

F.

[Frank v B]

Sneak Peek

Assembled.

Still have to install the LG, power plant, control rods, canopy, hatch hold-down, etc.

F.