Leading and trailing edges .... how to form them.

[toto]

I have a couple of dancing wings balsa kits and I've been looking through the instructions , as you do , to see what's involved in building these kits.

 

They look reasonably straight forward ........ until ...... you come to shaping the leading edges and where they show that you have to cut free the aileorons from the main wing. This is a bit scary, to me anyway as there is a real chance the whole kit could be ruined if you get it wrong. 

 

I have been scouring utube etc trying to find build videos to see how folks have approached this to see their technique but to no avail. I am lucky in the respect that the actual size of the sections being worked on are relatively small compared with bigger large scale models so there is far less materials to be removed/ shaped but it still intimidates me somewhat.

 

Can anybody guide me to a decent demonstration of this type of task being done ? 

 

I have not started the builds yet but would like to do so to give me a project whilst I progress my " flying lessons / training ".

 

Thanks for any assistance

 

Toto

Edited April 14, 2023 by toto

[Andy J]

You could cut a ply template to the correct profile but I have always done it by eye using smoothing planes ranging in size from 12 to 4 inches and good old sand paper stuck or folded around a long section of timber.

A couple of pencil reference lines drawn onto the front will also aid to keeping your balsa removal consistent.

[Engine Doctor]

A nice fresh razor saw will cut ribs etc easily and cleanly . Measure twice cut once .

[toto]

Yes,

 

I did watch one video on a large scale build where the guy used a small modellers plane and sandpaper blocks to form the leading edge profile. He also used the pencilled centre line technique as mentioned. I'm just questioning my carpentry abilities in terms of accuracy. I'm pretty competent with tools etc but I must admit, there is a bit of an art in the precision of this particular task.

 

I guess I'll just need to give it a go. I'm not sure if the leading edge section could be removed and replaced with a fresh section if I make a mess of it or just how true this needs to be ..... if reasonable is good enough not to effect the flying characteristics of the model.

 

As far as the razor saw goes, I'm assuming we are talking of the removal of the aileron section. The picture I saw when thie was being referred to showed a guy cutting along the balsa wood wing panel using a scalpel blade. I would have thought that the aileron would have been better made as a separate section altogether rather than having to cut it from the main wing section. Maybe there is method in the madness that is a little beyond my experience / understanding at the moment.

 

Oh well ....... in for a penny ...... in for a pound.

 

Thanks gents

 

Toto

[Graham Bowers]

Youtube is your friend, it took a couple of minutes to find this:

 

It can be quite intimidating making some cuts however there is very little that can't be rescued if a mistake is made. However one way to reduce the chance of mistakes is to practice new skills before putting them to use on your airframe. Even if that means buying some extra balsa to make test pieces.

 

My approach is to use the right tools for the job as improvising mostly adds to the risk of things not going to plan.

 

And as ED alluded, don't make sawdust / shavings until you're sure your assessment of the cuts is correct.

 

[Engine Doctor]

Re cutting the ailerons. If the cut isnt quite straight dont worry to much. The aileton and the recess it sits in can be sanded square then lined with appropriate sheet and sanded to a perfect fit ready for hingeing.  

For leading edges i use a philips modelling plane to remove most of the unwanted wood then finish with glasspaper glued to a wooden block. You can use a template although i usè the mk1 eyeball to get the shape following on from the line of the ribs . Never use glass paper on its own to shape as you will get a wavy finish once happy with shape a rub over with fine abrasive/glas paper to finish.

Good luck . Its fun learning and very rewarding when done. 

Some pics of you build will help identify the task your asking about.

Edited April 14, 2023 by Engine Doctor

[Mark Turner 12]

Use masking tape to protect what you don’t want to sand,  I quite like my perma grit block also after initial razor plane shaping.  You can also rough shape the trailing edge before fitting, or if you are worried get some preformed le and te from a model shop or slec.

Edited April 14, 2023 by Mark Turner 12

[toto]

Ahhhh, pre formed le and te .... now that may be the safer option.

 

However, if you never try ...... you'll  ever learn .... and always wonder. I will give it a try. As I said, the size of the section is not huge and it doesn't call for massive amounts of materials to come off.

 

The video in the post above ( I think ) is the one I watched previously ( I recognise the image and will watch again later ). However, the subject matter is a larger scale and I would imagine a slightly harder job as there is more material to come off and .... 2ith the scale being so large, imperfections will be magnified accordingly.

 

Again, many thanks for all the responses suggestions and links etc.

 

I will do a hit of a build thread when I start this to let you see how I get on ....... " warts and all " 

 

I do have a more relaxing ARTF carbon cub to kick into shape first which will be coming soon now that my workshop has been significantly cleared for space.

 

Cheers

 

Toto 

[toto]

Apologies .... the vide is a different one ..... thanks 

[Gary Binnie]

For the leading edge, plane and sanding block. My model building standard improved by using larger sanding blocks (less likely to introduce dips/hollows). I use a 12" block that I originally bought from the Balsa Cabin. Below is a screenshot from a Multiplex glider instruction manual, the middle two images indicate planing and the lower is finishing with sandpaper. As it is a lifting section there is no centre.

 

Ailerons and flaps are often built as part of the wing to ensure continuity of the aerofoil section and to maintain any washout (wing twist) that has been built in.

These photos are from a recent build of a Chris Foss Phase one glider.

 

1. The wing is complete and the ailerons needed to be cut out, the pencil lines and shaded area shows what needed to be cut.

 

 

2. The skins were cut top and bottom spanwise and these strips were removed, I deliberately used little glue on the ribs where the skins needed to be removed.

 

 

3. With the strips removed the ribs were cut with a razor saw (vertically in the centre of the exposed portions).

 

 

4. The ribs were then carefully cut back and the faces sanded level ready for closing/facing strips.

 

 

5. Facing strips applied, the ailerons on this glider are top hinged, wing is inverted.

 

 

[toto]

Wow ..... a brave move ....  quite a bit of cutting through every wing spar. Especially trying to maintain uniformity on every cut.

 

Nice clear reference photo's. I'm getting the picture. Thanks for the images as they give a very clear idea of what's involved.

 

Cheers

 

Toto

[Gary Binnie]

Measure twice, cut once!! Fresh scalpel blade to cut the skins, steel ruler stuck to the wing with masking tape to ensure it doesn't slip then several light cuts. It doesn't matter if the ribs are cut into slightly, in fact it helps to some extent. Pins can be pushed through from top to bottom to double check that markings are accurate and the end faces will be vertical.

 

These are photos from an Xtra Wot foam wing, same technique without the wing ribs, it has a balsa trailing edge which I think was supplied as a rectangular section.

 

1. Cuts marked out.

 

 

2. Making the end cuts, the bare foam is covered with a facing rib.

 

 

3. Sanding the facing strips level with the veneer skins, has to be done with the aileron in position and sanded spanwise with a long block to avoid dips. It's good practise to sit the wing on the foam bed that it was shipped in, built up wings can use foam beds from other model builds, there's usually one that fits (I throw nothing away!!).

 

 

 

[Gary Binnie]

I missed a photo from the Phase One build.

 

The razor saw is used to separate the ribs which leaves 'stumps', a line is drawn on each rib stump from top skin to bottom skin using a 6" ruler then each stump is cut off as close to the line as possible. I used the razor saw for this, what is left can be easily sanded off.

 

[toto]

Neat work.

 

I have the tools .... just require the bottle. Ha ha 

 

As you say, measure twice ( or more ) cut once with the correct, sharp tools. What could possibly go wrong. Oh yes ... and a steady hand.

toto

[toto]

Admittedly .... you are giving me a little confidence here. Not rocket science but a skill never the less. Good photographs like these always help as if you can see / picture what folks are trying to explain, it helps ten fold.

 

Thank you kind Sir

 

Toto

[Gary Binnie]

It helps to stick your little finger out while cutting with a scalpel (like drinking tea at the Ritz!) and make sure fingers holding the steel straight edge are slightly back from the edge (or you will loose their tops!).

 

If the skin has any grain then arrange for the knife to cut against the grain instead of with it as the knife will wander.

 

With foam core ailerons sometimes ply is let in for reinforcement at the control horn, with built-up wings wedge shaped balsa sections can be inserted before facing to do the same job.

 

If you are nervous about doing a particular job you could practise on a scrap model or build a short section of wing to sacrifice.

 

These photos show the reinforcing for the hinge points and control horn on the Phase One.

 

 

 

 

[toto]

Very good. I like the idea of providing the strengthening blocks for the wing furniture. I'm sure the dancing wings kits will have provided for that but I'll note it down to check. They could always be added from scrap balsa or hard wood section. I have a bit of a stock that I use in other modelling hobbies / tasks. 

 

Toto

[Gary Binnie]

I can think of just a couple of tips with trailing edges.

 

If you sand a trailing edge strip to section before gluing it to the wing/tailplane it will curl up to the side that has been sanded.

 

If trailing edges are sanded to a razor's edge the wood will be weakened and be prone to damage in transit to the field/slope and on landing. On a 100" span glider I would typically leave the trailing edge 1/16" or 2 mm thick, it makes no difference to the performance.

 

I've contrived a photo to show how to get round over enthusiastic accidental sanding. The lower piece of wood is the edge of the building board or an old MDF shelf, the upper piece of wood is the sanding block. If the trailing edge is positioned slightly in from the board edge a right angle triangle space appears and the sanding block can't reduce the wood to a point. If the trailing edge distance from the edge of the board is consistent then the thickness of it should also be consistent.

 

 

 

[toto]

These little tips can go a long way. I think it's a good idea  not to rush into the task but sit down before, assess what you are trying to achieve and conjure up a bit of a  methodology before starting. Maybe some of these tips could be In

clued as some kind of check list to see that you are adopting a sound approach procedure and at least giving the nest chance of success.

 

Thanks again

 

Toto

 

 

[Cuban8]

6 hours ago, toto said:

I have a couple of dancing wings balsa kits and I've been looking through the instructions , as you do , to see what's involved in building these kits.

 

They look reasonably straight forward ........ until ...... you come to shaping the leading edges and where they show that you have to cut free the aileorons from the main wing. This is a bit scary, to me anyway as there is a real chance the whole kit could be ruined if you get it wrong. 

 

I have been scouring utube etc trying to find build videos to see how folks have approached this to see their technique but to no avail. I am lucky in the respect that the actual size of the sections being worked on are relatively small compared with bigger large scale models so there is far less materials to be removed/ shaped but it still intimidates me somewhat.

 

Can anybody guide me to a decent demonstration of this type of task being done ? 

 

I have not started the builds yet but would like to do so to give me a project whilst I progress my " flying lessons / training ".

 

Thanks for any assistance

 

Toto

The wonderful Carl Goldberg kits that I loved back in the day and IMHO showed how a kit should be produced, used to supply a selection of jigs and sanding guides in their kits.

 https://www.rcgroups.com/forums/showthread.php?1300403-Creating-a-Leading-Edge-Sanding-Block

 

Came across the above which you might find useful. Not the same as the Goldberg simplicity, but might be worth a try or altering to your preference or particular task.

With care, a sharp razor plane, good sanding blocks and templates copied from the plan or Mk1 eyeball will work just as well though.

So many ways to do the same job in this hobby.

[Simon Chaddock]

+1 for using the Mk1 eyeball!

Get used to looking along the line of the wing and from the front and back to check all is true.

With practice If you can't see any deviation then there probably isn't any. 

[toto]

Nice link above. That looks like a pretty good shout for getting uniformity into the process. 

 

I'll have a ponder on that one. 

 

Thanks for the link.

 

Toto

[Gary Binnie]

The two sanding jigs on the right were assembled from ply parts in my Goldberg Ultimate 10-300 kit, the one on the left is a copy made by me.

 

The jig with 'E' and 'A' written on it was for chamfering the hinge faces of the elevator and ailerons, there must have been a rudder one as well?!!

Jig on the right was for sanding the symmetrical leading edge.

 

 

 

[john stones 1 - Moderator]

Hacksaw blade for cutting through ribs if your razor saws not deep enough.

[kc]

Shaping Leading Edge etc.   The trick with a razor plane or sanding block is to do one stroke along, then change the angle slightly and again, then do the same to the other side.  Then do the other wing top then bottom.   Keep doing one after the other so keeping everything a similar shape.   Most important point is the varying of the angle - never planing away to form a flat but always rounding in each successive stroke.  The plane is used along the whole length from tip to root along the grain.   Sanding also, but can be done along the rib shape at final stages.   All this applies to those fuselages shaped from large square blocks like balsa AcroWot and old aerobatic models too.

I find that a Permagrit block ( wedge block is all you need ) is great for shaping balsa and does it with less strokes than glasspaper which means there is more control.   Big plus is the dust seems larger and less of a problem.   Permagrit also sell a flexible sheet that could be cut and attached to a shaped block of balsa to shape LE.

 

It may not be a good idea to change the kit construction too much ......but the modern method of building up LE in 2 layers is easier for shaping.  1st layer is often 1/8th which needs just a little shaping and the 1/16th sheeting goes OVER while a cap strip goes on after and is shaped.   Less wood is wasted and its easier.   My diagram shows the construction on a typical model - Note the first (blue) layer is BENEATH the sheeting, the cap (black) is not.  Stronger joint too.