Wing Jigs - Mklll

Bronze member

Hi again,
The favourable response to the previous posting on these jigs shows there is interest. So here goes for the Mk 3 (Thankfully for you guy's although it did reach a Mk 4 'universal it was never put into practice Rolling Eyes

)

Before we get going however I have been made aware that the previous posts were too long and contained too many pics which evidently caused some of you problems in opening the post. Apologies for that - I had no idea that would happen. This time the posts will contain around 3-5 pics and I'll break the posts down after this first one.
One last thing, apparently it's not normal to interject in someones tutorial - well how do you respond to questions and explain something a bit better - I have asked for that to happen on this thread so please interject whenever you wish but please keep to the topic - I've been warned Wink

Okay, The previous jigs had served well but there was always this need to ensure the TEs were parallel in section.
It also meant that some wings would have to have a big change in spar layout/structure which sometimes as designed is very characteristic of the model. The one thing the method did give however was consistency and a wing that though it has to be said could be a bit lighter was structurally very sound.

Then Tom Morris came up with his idea of separate blocks with cutouts in that held the LE and TE. On the face of it this seemed something long waited for but the big requirement was a, to be able to cut those support blocks accurately to fit the LE and TE sections and b, when they were in place it appeared that it was going to be difficult to get the LE sheeting in place with the blocks holding the LE proper. Thinking about this rather novel approach proved the inspiration for this one then.

The basis of this version is that the wing is built around the plane (no pun etc) that ideally all stunt wings should be built namely the centre line passing through the section chordwise and spanwise. To do that the ribs have to be located as near perfectly on centre line as possible. The rib sections are generated as before - a block of 1/4 thick half ribs from which to make card masters. The reason for the half ribs is that when drawn around the section is as symmetrical about its centre line as you can be with a pen. by doing it this way you are eliminating that posibilty for error from top to bottom

Here are a few better pics of achieving fairly accurate ribs to those drawn on the plan

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That last one is a bonus for this post Laughing

you can probably see from these where this is going. Next thing is how to get the slot in in the right place.

BTW as you can see this jig was set up for an Intrepid XL and a Tempest It came after the Thunderbird jig which was a more technical wing to build and proved this system - for me - as the most easy to use and set up yet. There are a lot more pics of this set up though - the T'Bird ones will be in there at some stage however.

Any questions please ask.

Bronze member

Hi guy's, Look I'm not to bright on these things - I have totally missed the point about the discussion board Embarassed

and have just seen all the new comments that have been moved there so disregrd the above on 'questions' if there are any please use the discussion board. Sorry about the confusion - back later with the next stage.

tug

Bronze member

Hi again folks, time to get on to a bit more.

As you've no doubt worked out, this method requires supporting the ribs about their centreline and in this case on a layer of thin balsa. We'll come to the support later but first the ribs need to have a cut out put in at LE and TE as centrally as possible. For this we need a fixture - a piece of kit that will do this repeatedly and consistantly from rib to rib without error.

Once again, nothing elaborate is required other than to be able to cut a bit of contiboard and some careful aligning........

I use 3/32 balsa for the support in the wing and cut a piece of hard wood about an inch wide and eight long to this thickness to make a sanding stick using double sided sticky tape and 120 grit garnet paper. (I don't recommend 'sand' or 'glass' paper - this has a habit of shedding its grains which though not important in this case will put quite nasty scratch marks in the balsa when flat sanding- not good when finishing off). If you can't get a piece of hard wood cut this thick then use hard balsa but seal the edges before applying the tape.
(Normally I push the block or stick onto the tape then cut along the block edges to remove the surplus. Peel the backing paper off then push this down onto the abrasive paper and cut along the edges again. Finally use a block to sand the cut edges of the paper into the block sanding at 90 degrees to the edge).

By 'sanding' it in, the rib cut out will be very consistent in its width so now we need to get it on the centreline.

Cut two pieces of contiboard (the top rails) just longer than the longest rib - you need to have the finished edge (of the CB as supplied) on one side - about 3" wide (not critical)
Then another piece (the base) about 2" shorter and about or a little more than the width of the two pieces laid side by side. Lay the two rails on the base with an overhang at one end then, with the sanding stick held tightly between to 'size' a 3/32 gap, tack the rails to the base with thin cyano.
Remove the sanding stick and slide it vertically between at each end - it should be tight enough to allow vertical movement but without sideways slop. If not snap apart and do it again. Once happy run cyano in the joins wiping any surplus off. This is the basis of the fixture.

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In use the rib is laid on the jig and kept central by two simple aids made from balsa which in turn are held central by those two guides of 1/4 sq at the 'sanding end and by the slot at the other. The guides must be equidistant from the slot and its probably best to fix them to the rails first before attaching the rails to the base.

As said the centralising 'aids' are just made from hard balsa The larger pad holds the 'cutting' end and has two symetrical curved pieces cyanoed to its lower face.

The exact shape of the curves is not critical infact these were cut free hand but they must be symmetrically shaped and equi-spaced on the pads and about the slot. The cut out in the larger pad is unimportant - it's just clearance for the sanding stick

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To use the rib is laid on the rails, TE to be cut first. The tongue of the smaller pad is run into the slot and the rib pushed up to it. The larger pad is then slid in between the rails pushing toward the the smaller pad to centralise the rib. The sanding stick is slid into the slot and the cut out sanded into the rib - you can mark the rib how far to go but in practice this is an eyeball job after the first couple of ribs.

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As mentioned the TEs are done first then the smaller pad is repositioned with the tongue vertical to centralise the TE cut out and the exercise repeated for the LE cut outs.

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Dont be put off by the thought of this extra work. I assure you that, with the Contiboard cut, making the fixture and aids took about 90 mins or so. Putting the cut outs in the ribs took about 20 mins - and it's all there ready for the next model. Much less time that it takes to describe Rolling Eyes

Apologies for showing you this again - but it will save you going back to look.

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That' it for tonight the jig is next - don't forget, any questions just ask,
Regards - Tug

Bronze member

Hi again, time to get on with the next stage then.......

Before we can set the jig up two items are required - a set of blocks to support the LE and TE that are all the same height and the LE and TEs which are a composite of three pieces of balsa - I know Shocked

but dont panic about the weight just yet.

First the blocks. Contiboard in itself is a very uniform thickness and for our purposes can be considered as consistently parallel. It also cyano's to itself very well. Ideal then for making support blocks but not so ideal for sticking pins in. The blocks then have a lamination of firm balsa on top - not too hard, just firm enough to take a pin and hold it well.

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As you see here the blocks have two lams of balsa to get the height required. The piece of balsa packing the block is laying on is to make sure the balsa projects in front of the Contiboard (CB from now on). Cheap CA is good enough for this op BTW - save the ZAP for the structural stuff.

The TE and LE are made from (in my case) 3/32 sheet cut to a width that will provide an inner shelf for the ribs to align with and an outer area that supports the wing by pinning it to the blocks.

These pics show the make up. It is simple to do against the side of a piece of CB. Section can vary depending on the size of model in this case LE is 1/4 x 1/2 (Can be wider if LE is thicker) and TE 3/16 x 1/4.

I took these following four pics tonight as there were none of this part on file so it's a bit of a jury rig and the sizes are what were to hand but I'm sure you can see what's required.
To do, the central 'support' piece is held with a down wards pressure (there's a piece of packing in this shot) at the same time pushing it against the CB and pulling the side TE/LE piece tight to it - sounds difficult infact it's 'easy peasy'. With it all tight tack it with a small spot of thin cyano and move it forward about 2" and tack again continuing until one side is done. Don't overdo the cyano - just enough to grip it. Now reverse it making sure the side pieces are in line - yes you would be right on that Rolling Eyes

- and repeat. Remove and now run cyano down the inside edge - no need to do the outer edge as there will be a capping applied to that much later in the build. You can easily do a 30" strip in less than 5 mins.

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The strips, now in a cruciform shape, are very stiff but quite light and remember, a high proportion of it will eventually be removed.

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At last we can now get on to the jig itself - I say at last but in reality it should not take much more than a few hours to get to this stage - a couple of evenings at most.

Draw out the TE line and rib positions as shown for the previous jigs then cyano the blocks with that projecting edge exactly over the TE line. You can see here that the blocks are set against a straight edge which is positioned against some balsa triangles tacked on the TE line. (The second (red ink) lines rib on the board are for the other - 'Tempest' - wing)

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With these in place the TE section can now be pinned down with the lower side piece tight against the blocks then by using the centre and tip ribs to set the spacing the LE support blocks are set at the centre

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and at the tips

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Further LE support blocks are tacked in place ensuring the LE is straight by holding a straight edge against it as you tack the blocks in place. Incidentally that is all you need to do with the blocks - just tack them - there is no need for lots of cyano.

Here we are ready to go

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That's it guys we've over run the quota for tonight Wink

- hope this is useful to some one.

See you later - Tug

Bronze member

Back again guy's.
I did sit here and do the following on Wednesday night but the 'puter developed a big sulk and got slower and slower on opening the preview until finally it clogged - one click and I lost the lot Crying or Very sad

Out last night so here goes for a second attempt.

The ribs can now be positioned one by one on the LE/TE support 'shelf' aligning them over their respective stations and gluing them as you go working from the tips toward the centre. Get the bellcrank assembly made and use this to position the centre ribs to ensure a good fit of the bellcrank platform. Before this is fitted lay the spars across the ribs in their correct positions and temporarily pin in place. Cut each rib each side of the spar to mark the ribs then remove the spars and cut out the slots, finally sizing them with the spar slotter previously made.

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Slotting the individual ribs like this is a bit fiddly but not difficult though it pays to provide some support underneath the rib directly beneath the cutting pressure - I used a small tapered piece of balsa - but it does give a good fit for the spar and allows the fitting of it without any induced stresses. With the spars and spar 'reinforcing spar' in and dry, the bellcrank can be tacked in position and checked for free movement all round and then consolidated with strip and plenty of cyano as previously mentioned.
The wing is then finished as before - TE sheet, LE and centre section sheeting and finally the cap strips. The LE support blocks will need their tops planing away to allow planing and sanding of the sub-LE strips for fitting the sheeting. With this all done the LE sheeting is trimmed back to the sub LEs and the wing is ready for turning over

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I'll break this post here so that there are not too many images and continue with another.

Back in a while

Bronze member

That worked okay Very Happy

so heres 'Part two'

These show the finishing of the top surface

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The wing has now been turned over. Because of using the same rib profile on the assymetric planform the angle of sweep back is very slightly different on both panels. The LE support blocks need to be trimmed slightly to allow the wing to sit but this will not affect the further use of the jig.

Pin the wing down as before and repeat the exercise Smile

Please note the hammer and chisel are not requisite tools Embarassed

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Here are a couple of better pics of the spar slotting. Note that the shelf between the ribs on the inside of the sub LE and TE has been trimmed out to leave just a gusset shaped support. Not essential but a little less weight to carry Wink

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This is going much better tonight so I'll post this and see about a few more pics.

Bronze member

A few more pics of the slotting
The rough cut, note the two 'nicks' at the top of the slot ...

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then sized by sanding....

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and finally the fitted spar.

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Before sheeting the lower surface there are a couple of things to attend to first.
This shows a hinge block in place ready for the TE sheet...

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And these, a couple of views of the spar webbing. Note the extra webbing set at an angle in an attempt to bring the line pull forces down the spar line and also the extra thick riblet sanded to final shape in situ to finish the sheeting on. I don't normally web more than a couple or so bays beyond the centre sheeting.

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Incidentally I don't know if any one else does this but I always fit 'stop blocks' to limit the bellcrank travel - one can just be seen in the second from last pic behind that centre riblet. They prevent over movement of the bellcrank and subsequent strain on the control linkage and, more importantly, the hinge system.

Heres the finished wing removed ready for the tips to be fitted.

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Removal of the outer shelf supports are only done when absolutely certain it does not need to go back in the jig again - once they're removed that's it Rolling Eyes

And finally for tonight, just in case you have any lingering doubts I'm sure you'd agree that this is not bad for a wing built on a home made jig

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Well that really is it for tonight. You'll no doubt be glad to hear that there just a few pics left showing the T'Bird wing and building those wingtips in situ. If you are still interested after that and can stomach a bit more theres a few on setting the wing into the fuse and aligning the tail using a Contiboard (what else Laughing

) building aid.

Sleep tigh - I will Very Happy

Bronze member

Here we go again then - eyes down for a last look. Phew - thank gawd for that I hear you say Laughing

These last few pics show the Thunderbird ll wing under construction using this 'central shelf' and slotted rib system.

The T'bird came before the Tempest/Intrepid jig born of the desire to get those built up tips true to the wing section. I am more than satisfied that this was achieved hence the follow on.
There are not many pics of this wing but what there are give a good idea...

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As you can see these are tacked into strategic positions between ribs and keep the whole tip area very flat indeed. These tip blocks are tacked very lightly as when the wing is removed they also need to be repositioned due to the assymetric planform. They are very easily knocked off with a light tap from a hammer, a quick sand of the area to knock down any cyano build up and retacked in the new position once the wing is back in the jig.

Incidentally the spars which curve downwards into the tips were not stressed 'bent' in but had a curve induced in them by rubbing the inner face over a hot surface - in this case a small baked bean tin with both ends cut off and held in a vice with a small candle inside.
This gets very hot and will shape a gentle curve into balsa by sliding the spar across the required length and applying a gentle downward pressure.

Finally a pic of the finished wing. Sorry about the jump from building to finish but that's all I can find on the T'Bird - but I'm sure you've got the gist of this by now though Wink

Well guy's that's it on the method I use(d) to build a wing. If you want a bit more on aligning the wing and tail to the fuse let me know.
There is a just little bit more to add but I think that is best suited to the discussion thread which I'll do tomorrow

Hope this is of use to someone somewhere

Regards - Tug