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Old Feb 11, 2012, 10:50 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
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Quote:
Originally Posted by madbomber View Post
Also....Sundancer, could you explain your wing a construction in a bit finer detail? I was planing on making it scale to the FF plan....
I'll try MB. Since this was going to be a radio model - as is yours - the wing was liable to be subjected to rather more stress than would a F/F one, so I strengthened it up a little. The main changes from the plan involved extra sheeting at the centre, a stronger and longer dihedral brace and two additional 1/8" square top spars (the main purpose of these was to "balance" the spar structure - with just a bottom spar wings tend to warp or bow upwards, but they also gave a little extra strength for next to no weight).

First step is to make a 1/16" ply template of the wing rib and cut out the required number of ribs. Then the centre section ribs, where the sheeting will be, have 1/16" removed from them top and bottom so the sheeting will be flush with the surface. Now cut out the dihedral brace from 1/16" ply, accurately cut the three pieces of the main spar, assemble them with the dihedral brace and leave to dry. Cut to size and pin down the bottom centre section sheeting (deviation from plan - no bottom sheeting on the original) and pin and glue down the centre section leading and trailing edges, the assembled spar and the ribs, then the top 1/8" spars if using them. Leave to dry.

Building the rest of the wing is now just a matter of tipping the wing to the right and assembling all the right hand panel over the plan, being careful to get good joints where the leading and trailing edge join the centre section, pinning the spar down over the drawing and fitting all the ribs, then the top 1/8" square spars if using them. When dry, tilt the wing the other way and repeat to build the left panel. When all dry add soft 1/4 inch sheet tips and sheet the top centre section as shown (NOTE the grain on all surface sheeting runs spanwise). Add some corner gussets (right angled triangles of 1/8" balsa with the grain running parallel to the long side of the triangle)where the leading and trailing edges join to the centre section and at the tips and when everything is dry, sand to a finish.

The pre-assembled spar ensures that you get the correct (and equal each side) dihedral. I think the F/F dihedral of 3.1/2" a side can be reduced to 2.1/2 inches for radio operation, but this is a matter of choice, the original 3.1/2 inches will work fine.

Hope that helps, it really is a very simple wing.
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Old Feb 12, 2012, 12:58 PM
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madbomber's Avatar
United States, CO, Denver
Joined Apr 2011
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Sundancer,

Does it matter much where top spars are located? I see in your build log they look to be equal distances away from the larger, bottom spar. Can I just pick something that looks close to yours and be ok?

Also, for the dihedral brace, did you mark the plan at 2.5" and draw a new template for the dihedral brace?

Also, not having a large enough pan to soak the bottom longeron, I ended up using the bathtub...:

Do I need to pin the bottom longeron to the plan and allow it to dry before gluing the vertical spacers to it? Im concerned about trying to glue dry wood to wet wood.
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Old Feb 12, 2012, 01:13 PM
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Just a photo of progress so far. Already found a small mistake. Got a pin mixed in with some glue in the crack of the top longeron.
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Old Feb 12, 2012, 01:22 PM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
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Quote:
Originally Posted by madbomber View Post
Sundancer,

Does it matter much where top spars are located? I see in your build log they look to be equal distances away from the larger, bottom spar. Can I just pick something that looks close to yours and be ok?

Also, for the dihedral brace, did you mark the plan at 2.5" and draw a new template for the dihedral brace?

Also, not having a large enough pan to soak the bottom longeron, I ended up using the bathtub...:

Do I need to pin the bottom longeron to the plan and allow it to dry before gluing the vertical spacers to it? Im concerned about trying to glue dry wood to wet wood.
Hi MB

The extra top spars on mine are located 1 inch and 3 inches back from the leading edge.

Dihedral brace; yes, that is how to do it.

Yes, pin both bottom longerons down and let them dry before building the fuselage sides. When you build the first side cut two lots of spacers as you go, then when the first side is dry, remove the pins and lay a sheet of polythene over it and build the second side directly on top, using the pre-cut spacers - makes sure you get two identical sides.

Further tip; when you come to joining the sides make centre reference marks on the formers, draw a centre line on the plan view and join the sides over this to make sure you get the fuselage dead straight - it is very easy to build in a bend or twist if not careful.
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Old Feb 12, 2012, 01:23 PM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
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Quote:
Originally Posted by madbomber View Post
Just a photo of progress so far. Already found a small mistake. Got a pin mixed in with some glue in the crack of the top longeron.
Good to see it's in progress!
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Old Feb 12, 2012, 01:40 PM
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Thanks for the help, Sundancer! This sure is enjoyable! The wood feels nearly dry so I'll give it a bit longer.

Im going to make a foam trainer for one of my friends so while I wait I'll get the plan for that printed out.
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Old Feb 12, 2012, 04:46 PM
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When cutting the vertical spacers, is there a trick to making square cuts? Or to match the angles of the cuts on the plan? Im trying to do it by hand and I keep getting tiny gaps where the angles of the longerons and the vertical spacers meet up.
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Old Feb 12, 2012, 05:14 PM
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Some more progress. First side framed up and drying.
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Old Feb 12, 2012, 08:00 PM
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Your doing well.
What motor? I don't think you have mentioned that. A real proper motor or electric? And is it to be Freeflight or RC?
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Old Feb 12, 2012, 08:26 PM
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Quote:
When cutting the vertical spacers, is there a trick to making square cuts? Or to match the angles of the cuts on the plan? Im trying to do it by hand and I keep getting tiny gaps where the angles of the longerons and the vertical spacers meet up.
I cut them slightly oversize, then use an emery board or small sanding block to adjust them to the final length and angle.
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Old Feb 12, 2012, 08:31 PM
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Originally Posted by gossie View Post
Your doing well.
What motor? I don't think you have mentioned that. A real proper motor or electric? And is it to be Freeflight or RC?
Thanks for the kind words. I am going to go with electric. My friend who will be receiving the plane for his wedding gift has electric equipment, no gas setup for him. I dont know what size it will be though, so any advice in this department is appreciated. It will be 3 channel RC. I considered making it 4 channel...but I suppose this model isnt suited to ailerons.


Quote:
I cut them slightly oversize, then use an emery board or small sanding block to adjust them to the final length and angle.
Thanks for the advice. I am getting started on the other side now so I will give that a shot.
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Old Feb 12, 2012, 09:11 PM
Balsa Flies Better!
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An old Don Srull trick was to make sure that all parts are a drop in fit-not snug and use Titebond for a little gap filling. I use Titebond II because it sets up quicker and is a bit more flexible. This trick is very helpful with wing ribs on the trailing edge of the wing- the stresses in the wood that's pressed into place have a tendency to cause warps over time. I've either gotten lazy or just do this as a matter of course now.

Sam
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Old Feb 12, 2012, 09:39 PM
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Not going to get much more done tonight, Im afraid. I soaked another strip of wood for the other bottom longeron but after attempting to pin it in place, I removed it and started soaking another strip that was less stiff. Im afraid the stiff piece that I first attempted to use will warp the side after I unpin it from the board. Looks like Ill get the top and bottom longerons pinned and they will dry overnight. I wont have any more progress till after work tomorrow.

Also, I am beginning to wonder about the quality of my T-pins. This is the building board I have:http://www3.towerhobbies.com/cgi-bin...?&I=LXVZ63&P=7 Some sections accept a pin easily while others take a bit more effort. I seem to be bending a lot of T-pins though. Is my building board to hard or did I just buy poor quality pins? The pins were the least expensive ones towerhobbies had for sale. Those magnetic building boards sure are starting to look nice.
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Old Feb 13, 2012, 02:14 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
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Quote:
Originally Posted by Bargle View Post
I cut them slightly oversize, then use an emery board or small sanding block to adjust them to the final length and angle.
What he said!

Get the angle right at one end of the strip, lay strip in so it overlaps the other longeron and look down vertically on it, mark strip, cut slightly on the generous side (Xacto type razor saw is the best tool as you can cut vertically more consistently with this) and then adjust that end only by gentle use of the sanding block.
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Old Feb 13, 2012, 10:41 AM
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Owl and Sundancer, what size of motors did you guys use? I looked in your build logs but didnt see a spec.
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