34" span Chipmunk- House of Balsa- build.

[Frank v B]

Bought this from Simon H. just before the December meeting.  Will see how far I get before my knee surgery on Feb 9.
During my recovery I will be covering the L19 Bird Dog.

span- 34"
length- 28.5
weight- less than 2 pounds
power- TBD but it will be "enough plus 25%".  I usually build until I see the weight, size and prop clearance, then start calculating the power to see what would fit.
colours- still to be decided.  "Don't make a decision until you have to".  The decision will be influenced by the colours on hand.

Frank

[Frank v B]

Gentlemen...I started my engine.

Triple checked...there are port and starboard fuselage sides.   

F.

[GuyOReilly]

Gentlemen...I started my engine.
Triple checked...there are port and starboard fuselage sides.   
F.

@Frank v B you have passed the first of many steps in becoming a Master Builder: 2 different sides!!
Good luck with the other steps. 

[Frank v B]

canopy structure assembled.

F.

[Frank v B]

Something that looks like a fuselage.
Note: to make sure the two formers are square I taped triangles to the formers (photo 46).


F.

[Chappers]

Hope your recovery from knee surgery is going well Frank..

[BJROB]

Hey. Frank the build is looking great. Keep the rebuild on the knee up too. The two will flying soon enough.

[Frank v B]

Back to building because:
.... the pain from the knee replacement surgery 3 weeks ago is slowly subsiding.
.... the pain and frustration from the new modelling disease (RPAS, TCARS, AGL, etc) is setting in.
Can only sit at my workshop desk for a max of 30 minutes because I cannot elevate my leg and my back starts to hurt.

- finished the cockpit top
- did the wing doublers for the landing gear (plywood to balsa ribs).
- laid down the trailing edge and leading edge spars.
- set the ribs in place.

Good news- the smell of balsa dust is a better pain killer than Oxycodene! .  For me balsa dust is more addictive.

Frank
ps: went from 13 pain pills a day to 2 (extra strength Tylenol) in the last week.

[Polecat]

Frank   Good to see you are getting back into the balsa dust, I am laid up as well, with feet and legs swelling and have to set down to build. I agree with you on this crap that is going on with MAAC and TC, who would ever think this would have happened.
As for pylon racing this summer, I am planning a race in June, just hope I am well enough to put it on and hope to see you at it.
Our club field should OK as we are well out of a no fly zone, with only one registered flying strip about a good 5-6 miles away.

[Frank v B]

How to curve balsa wood along the grain.

This wing is built a little backwards per the instructions because the airfoil has a Phillips Entry (flat bottomed behind the main spar but semi-symmetrical ahead of the spar).
The wood has to curve up to meet the leading edge.

Solution- 3 passes of a wet paper towel over the leading edge sheeting and the wood curved immediately so I did not have to use clamps.  Pins were fine.  Clamps can dent/crush this light balsa.

Photo 1- the wing pinned down so the glued trailing edge sheeting could dry straight (overnight). Note: the bottom leading edge sheeting is not glued to the ribs or LE yet because it has to curve up.
Photo 2- three passes of the wet paper towel (on top) and the balsa curved completely into the rib. Note: the wing is held up-side down in the photo. You can see how the water yellowed the top of the wood.*

I believe in miracles!

Frank

*Note: when bending balsa, the curl will happen opposite the wet surface.  In this photo the wet wood at the top wants to expand.  The dry wood under it does not so it curls away from the moisture.
If you wet both sides, the wood will stay straight.  The curls cancel out.

[Frank v B]

Second wing half.

Deviation from the instruction manual...again.

per instruction manual- build two separate wing halves then butt-join them and add fibreglass over the joint. Problem- there is no continuity between the halves.

per my method
- build one wing half minus the front top (LE) sheeting, place it on the plan and put 2 pins at the center rib.  Lift up the finished wing to the required 3" dihedral at the tip.  Build the second half directly to it flat on the board at the root.  Reason- do not have to build accurately and the center joint will be perfect without any trimming or sanding.  Been there!
- ditch the 2 small hardwood landing gear blocks.  Replace it with one long one that becomes a dihedral brace at the same time. Much stronger.

Photo 02- note the finished right wing with the two pins at the root and the red thing propping up the wingtip at 3" dihedral per plan.
Photo 06- note the two small landing gear blocks that came with the kit versus the new long, continuous one above them. 

Frank               

[Frank v B]

Photo 1- all thumbs beginner- put my thumb through the wing sheeting trying to remove a pin.  What a Klutz.

Photo 2- wing taking shape- note the continuous landing gear block acting as a dihedral brace as well. It is wrapped in dental floss and 5 minute epoxy to stop it from splitting.  It is still loose.  Will secure it to the ribs, top, bottom and sides before the top sheeting is installed.

F.

[Frank v B]

Installing the landing gear.

Did not like the plans so did the reverse.  These are torque rod landing gear.  Drilled the hole into the hardwood block/spar closer to the center line. The plans showed them on the outboard end.  Inboard is thicker and much less likely to split on one of my bouncy landings.

Note: this plane was originally designed for an .049 gas engine which always meant a slower dead-stick landing.  As an electric we can do a smooth power-on landing (if you are Glenn).  Any bounce will have more energy behind it.  That's why all the extra time spent on strengthening the wing and landing gear.

The landing gear was to be slipped into a hole drilled into the hardwood landing gear block.  This leaves it open to splitting the wood on a hard (normal?) landing.

Trick: I use a piece of brass tubing and glue the tubing into the hole.  Because it is a larger diameter, it spreads the load on a larger surface. Also, after many landings, the hole will never wear larger and start the Lg leg moving back and forth.

Photos show the brass tube, inserted into the wing hole and then landing gear in place. 
I have done this on all my scratch-built airplanes including my 60 size pattern plane.  It works well.

Frank

ps: sorry for the messy background in the photos.  I do this on purpose because it keeps Andy busy mining the background of every photograph. 

[Chappers]

Lookin' good!

[Frank v B]

Finishing the wing.

Sand the rectangular profile leading edge.  Trick: mark the very leading edge with a magic marker at the tip and the root.  Connect the two dots with a steel ruler with a magic marker.  This means you can sand to it from the top and the bottom.  Leave the line showing.  Then you know you have not scalloped the edge.  When the profile looks good and smooth, sand the marker line away.  It will through most light (white) covering if it is not sanded.  Photo 37

Cut the CA hinges.  I cut them into rectangles (left pair)  Trick: cut the four corners off on each hinge. (right pair). It makes the installation much easier because the corners will not dig in. Photo 40.  Do not glue them in until after the covering is finished.

Finished wing- photo 48- it is a very strong wing!!  Good.  I know the pilot.

Next power calculation and motor selection and installation.

Frank