Winter? Build...Avro Anson

[Frank v B]

Bill,

re: your "Three bottles hardly captures the frustration of trying to get things to line up."

OK.  Cue the two-four!

Frank

[Wingnutz]

Made a crude jig to check the alignment of the wing centre section. Last time I tried to build a tapering semi-symmetrical wing was before I attended TEMAC build classes and I ended up cutting the bottoms off of all the ribs, building it on a flat surface and gluing the rib bottoms back on afterwards.
Think I've learned something at build classes and I'm gonna try this one "off the board"
Laser cut ribs make life a lot easier. I still feel better jigging the whole thing before anything gets glued. My crude jig consists of a 2" sheet of pink foam, slotted white foam sheets to hold the spars level at the centre, equal height foam blocks just inside rib 6 and squares to get the engine bearers vertical once the spar centre is horizontal.
Frustration index down to two Canadians today...saving the two-four for a bad day!
I have some more beer in the fridge so if any of you experienced builders see potential potholes, LMK...I'm not against opening another...or two.

[Andy Hoffer]

The folks at the Boeing plant in Seattle will be envious!!   

Andy

[Wingnutz]

The folks at the Boeing plant in Seattle will be envious!!   

Andy

Andy, you're right! I can wash down the balsa dust as I'm working...the Boeing crew doesn't even have balsa dust or balsa dust throat soother and I'm glad they don't...I fly in one of their airplanes from time to time!
Had to see how the wing and fuse will go together...something to do while I make the final decision on how to make the wing outer sections removable. Once I start gluing, options for removable sections get stickier
Plan calls for a one piece wing of just over seven feet and a fuse just over six feet. Since I would prefer not to separate wing and fuse for transport...wait a minute...if all the electrics except the rudder and elevator servos are in the wing...maybe separating for transport wouldn't be all that bad...now, will a seven foot wing fit imy Escape?
Glad I wrote this...made me do some thinking!

[sihinch]

I see it is a true "Canadian" twin, now!!!!

[piker]

Hey Bill.  I like the twin power   

As we discussed last night, I found removable tips to work well, but they add an extra challenge while building, probably more weight with less strength, and unsightly seams in the wing.  IF you have enough length in your vehicle for a one piece wing, I would always suggest that route.  The exception being where the wings plug into the fuselage from either side.  The fuselage WITH a 4' wing root still attached, will take up more space than a one piece wing laying along the side of the fuselage.

I know you were thinking that keeping the center section on the plane would simplify assembly, but as you point out, everything BESIDES the tail servos can be fastened to the wing and go with it when removed with only a simple disconnect of a couple of servo wires.  That's how my two, multi motor flying boats are set-up.  I leave 6" extensions plugged into the servo Rx for easy plug ins.

[Wingnutz]

I see it is a true "Canadian" twin, now!!!!

Definitely Canadian powered!

[Wingnutz]

Hey Bill.  I like the twin power   

As we discussed last night, I found removable tips to work well, but they add an extra challenge while building, probably more weight with less strength, and unsightly seams in the wing.  IF you have enough length in your vehicle for a one piece wing, I would always suggest that route.  The exception being where the wings plug into the fuselage from either side.  The fuselage WITH a 4' wing root still attached, will take up more space than a one piece wing laying along the side of the fuselage.

I know you were thinking that keeping the center section on the plane would simplify assembly, but as you point out, everything BESIDES the tail servos can be fastened to the wing and go with it when removed with only a simple disconnect of a couple of servo wires.  That's how my two, multi motor flying boats are set-up.  I leave 6" extensions plugged into the servo Rx for easy plug ins.

I agree with everything above...however, my daily driver would be hard pressed to carry a seven foot wing.  But, I haven't given up on the idea of one piece wing...so nothing's glued...yet...
Test fitted ribs 7-15 on the left wing. If the wing becomes three section, the break will be at rib 10, (flap/aileron intersection) ...so plan is, the carbon tubes can remain one piece, or act as sleeves if the wing is split into three pieces, with an inner carbon tube transferring load from the outer wing to centre section.
Challenge was to get a friction fit hole for the carbon tubes and have the laser cut ribs line up to create 2 degrees washout at the tip. Washout starts outside the nacelles and I set things up to create 1 degree washout at rib 15.
Jigged the ribs on a piece of 2" pink foam, and sharpened a piece of brass tubing to cut the holes...
Ended up re-drilling the drag spar holes. The hole for the tube was too close to the slot for the 1/4" square spar and the ribs split as they were fed on to the carbon tube.
Will bring the wing to class to get some advice tonight.

[piker]

Cool!

Did you sharpen the brass tube before drilling?  If "yes", did you sharpen/taper on the outside of the tube?  If "yes", the act of sharpening on the outside creates a smaller diameter hole cutting edge, with the area further up to tube at the original outside diameter.  As you plunge the brass tube further into the hole the larger diameter forces the wood away, causing the split.  Is that what happened?

Best option, is to taper on the inside of the tube.  It won't split the ribs, but it jambs the blanks in the tube pretty good.  I find I can't cut through vary many layers without stopping, removing the tube from the drill press, and clearing the blanks from the tube by pushing them out from the other end.

[Wingnutz]

Cool!

Did you sharpen the brass tube before drilling?  If "yes", did you sharpen/taper on the outside of the tube?  If "yes", the act of sharpening on the outside creates a smaller diameter hole cutting edge, with the area further up to tube at the original outside diameter.  As you plunge the brass tube further into the hole the larger diameter forces the wood away, causing the split.  Is that what happened?

Best option, is to taper on the inside of the tube.  It won't split the ribs, but it jambs the blanks in the tube pretty good.  I find I can't cut through vary many layers without stopping, removing the tube from the drill press, and clearing the blanks from the tube by pushing them out from the other end.

Rob, always glad for your input...thanks.
Yes, I sharpened the tube...first on the inside, but as you suggested, in my testing, the blanks(9) jammed in the brass tube...firmly!
Then I tried sharpening on the outside...the blanks didn't jam as badly, the test balsa didn't split, but the brass tube didn't cut very well and ran out of steam on the third balsa sheet in the test stack...
so, I cut some teeth in the brass tube and it cut much better.
I still spit one rib trying to feed it on to the tube...partly because the hole was too close to the spar slot and partly because o.d. of my brass tube is a few thou larger than the o.d. of the brass cutting tube.
I'm using carbon tube battens out of old windsurfing sails as the joiner sleeves and the joiner inners and they don't match the brass tube o.d.s .
Gonna flip the plan, set up the right side ribs and drill.

[bfeist]

Just caught up on this build thread. It's looking fantastic! Those big beefy wing ribs are a thing of beauty.

Ben

[Wingnutz]

Just caught up on this build thread. It's looking fantastic! Those big beefy wing ribs are a thing of beauty.

Ben

Thanks Ben...it's supposed to be scale so any applause or boos for appearance belong to the designer...
Measured the root rib, top to bottom and it's almost 3"... you're right...beefy!
I'm going to build the wing in one piece with the carbon tubes in place...I'll decide whether to cut it later...so, I need a bigger build surface...
Went to Home Despot and bought a sheet of 2" pink foam, 2'x8'x2" foam to build the wing on...my table's only 6' and the 7'2" wing hangs over both ends...
Also went to A&J and bought spruce spars and leading edge, cut the ribs for flaps and then test-fitted everything on one side, most on the other...still no glue

[Wingnutz]

Almost ready to start gluing, but before I do, I need some advice from all you aerophysicists and aerodynamic engineer types.
My latest cogitation revolves around dihedral...how much and how to measure it with a semi-symmetrical wing.
My photo shows the recommended diahedral and my measurements at the LE and under the deepest part of the wing.
LE dihedral measures at about 30 mm and measured under the fattest part of the wing is about 52mm...neither meets the plan specified 70mm...
1. Where exactly should I measure to establish dihedral?
2. How important from a stability point of view is hitting the recommended 70mm?

[Andy Hoffer]

Hi Bill:

Here is an excerpt from Airfield Models which I have always found to be an excellent source of RC info:

"Dihedral is an angle raising the centerline of the wing tip above the centerline of the wing root.  Many plans show the dihedral measured from the bottom of the root rib to the bottom of the tip rib.  This is incorrect.  Dihedral is correctly measured from centerline to centerline."

Here is the link:

http://www.airfieldmodels.com/information_source/math_and_science_of_model_aircraft/formulas/dihedral.htm

Andy

[piker]

I would always measure under the lowest point as compared to the lowest point at the root, resting on the bench.  I think your plan is showing at the LE , only as a clear way to show at which rib the height should be measured.