Creating a Use Once Plan

[Martyn K]

I was asked during the AcroWot build blog to show how to create a simple plan from which a built up wing can be produced. I have noted my method here, I am not pretending that this is the best way, but it works for me. So a simple step by step guide to produce a single Use Plan - i.e. a plan that will be disposed of when the wing is built. The plan is simply an alignment aid, it will contain any structural information such as u/c blocks braces etc. Keep it simple and this will take about 30 minutes to produce

1. Preparation

I am assuming that the plan will be drawn onto paper that is taped to the building board. It is essential that the long edge nearest to you is straight and free of any bumps. While you are checking this, remove any glue blobs, solder splashes etc from the top of the board. Get it as smooth as possible.

I use cheap wrapping paper, taped down using masking tape. There should be sufficient paper to leave a space all the way round.

You will need:

• an accurate board as described above
• a square - within reason, the larger the better
• a pen
• a sketch of the wing (or fuselage) - salient measurements noted.
• a couple of rules of different lengths
• a pen or better a pencil with a sharp point

I have used a pen here so that the lines show up better in the photograph

2. Drawing the first vertical datum

Use the square as shown with a straight edge against it. Assuming that you have sufficient space for the full wing, draw a vertical line in the centre of the papered area. Make sure that the square is had against the long edge and the rule is hard against the square. DRaw a line and mark it as DATUM or C/L - make sure you are clear what it is for.

If you are only planning one half of the wing, draw the datum at the right for a left wing or vice versa.

3. Mark the Outer Limits (Wing Tips)

Measure out from the Datum each way and Mark the extremities of the wing tip(s). For this wing, it was 29" from the Datum. Make sure the rule is parallel with the building board baseline.

4. Draw the Tip limits

Using the same method for the Vertical Datum, draw a vertical line showing the boundary at the wing tip. You should now have 3 vertical lines on the paper.

5. Mark the positions of the ribs

This wing has rib spacing of 3.222". Using a cheap plastic ruler, I drew a line on the ruler at what looks like the correct amount - just over 3.2" and marked out moving the ruler along as I went. A BETTER way is to start from the datum and measure out 3.22", 6.44", 9.66" etc to prevent compounded or cumulative errors. However, if you are within a couple of mm when you get to the outer point then it should be accurate enough (mine was).

Next part follows

[Martyn K]

6. Draw the ribs in

When you are happy that the spacing is correct, use the method outlined above and draw vertical lines representing the rib positions... For this wing you should have 19 vertical lines.

7. Mark the box boundary

We only have one edge that we can trust but need to mark a line parallel with the baseline of the building board.

Turn the square through 90 degrees and then measure from the edge of the square and mark the upper boundary of the wing. Repeat for the tip limits (the same distance - we are drawing a horizontal datum here). This should allow sufficient space for the wing to be built plus a bit spare - I allowed an extra inch on top of the 12" root chord.

Join the dots with a straight edge and you will have a 3 line box with the rib positions marked up.

8. Mark up the Leading Edge

Measure back from the horizontal Datum that you have just drawn the sweep at each tip plus the a second line the width of the LE. Allow for any taper that your design has and clearly mark the Leading edge area.

We now have the LE marked up and will work backwards from there.

9. Mark the spar and false TE position

Using the tip rib and the root rib, we need to mark the rear edges of any spars. we only need one edge marked. Align the rib centrally over the rib position line. Place a dot on the plan at the TE and at the position of the spars (assuming that they are the same top and bottom, if not - just the lower spar). Note that you are marking the front of the false TE.

Where a line joining the dots intersects with the rib position will be the lower spar position. As this is a straight taper, it is a simple matter to link the root and tip ribs and this will give you the position of the rear edge of the spar. If the upper and lower spars are in a different location, then use a square to draw the intersection point from the pencil point on the plan.

Draw in the front of the TE as well.

10. Annotate your plan

Make any useful notes on the plan now so you are clear. Things you may want to include are measurements for the taper for the LE or TE, roughly mark up where any braces are etc - but no detail - its just an aide memoire.

Finally - check and recheck all the measurements before you start pinning and gluing

That's about it, hope that was useful

 

Martyn

Edited By Martyn K on 04/01/2014 19:17:00

[Bob Cotsford]

Excellent Martyn, I've on occasion done something similar but left out the paper - just drawn up the wing straight onto the board using a fine marker pen.

[kc]

I think many people will find that useful. It might help to put the model name on the drawing and save it, if its saved you wont crash and need it , if it's not you will!
It's worth saying that those carpenters try squares are not square on both inside and outside edges but engineers squares are. ( different British Standards the man from Marples told me) Better still for this use is a draughtsmans Tee square which are probably thrown out due to CAD.

[Monz]

All my plans of late are single use: Draw it on paper, cut it out, build it, toss it

[Martyn K]

Bob - when i was building only free flight models i never bothered with a plan - i just lined ribs up against a pinned down trailing edge and used a trig square for alignment. very simple with a parallel chord wing and no flaps or ailerons.
Kc - the carpenters square i use is square on both sides i checked it against my engineers square when i bought it second hand. Its doubly useful because it is actually a mitre square so can also check for 45degrees as well.

Martyn

Ps just spotted a typo in the sub heading. The word 'not' is missing which changes the entire context of the message.

[David Tweddle]

Posted by kc on 04/01/2014 20:12:36:
I think many people will find that useful. Better still for this use is a draughtsmans Tee square which are probably thrown out due to CAD.

KC got a good one from Ebay adjustable. Brill price too also some flexi curves (French).

David