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Rib Plotting by Computer


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Many things are more expensive for at least a while. Covid has disrupted all sorts too. Not just wind turbines. 

 

CW ailerons are 1.25 in wide, so you could get two from a 3" sheet, if you're planing and sanding. 

 

As for the shavings on the floor, they're just the bits of wood that didn't look like an airplane...

 

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Hi Nigel

According to the plans ailerons are 1.5" wide, which is why I said 4" sheet.  Anyway, still stand by what I said. Aileron stock is expensive, but the alternative methods don't save too much either.

Guess we'll just have to get used to these prices. Can't see them coming back down, even after Covid threat becomes manageable and the chinese start making rotor cores out of foam.

Such is life

Jeff

Edited by Jeffrey Cottrell 2
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10 hours ago, Jeffrey Cottrell 2 said:

According to the plans ailerons are 1.5" wide, which is why I said 4" sheet. 

 

I really should check my figures.

 

That said, you could adjust the ribs and make them 1-1/4", they'd work just fine.

 

Built up is an option, but, give or take, they'd use a whole sheet of 1/16 per aileron anyway - back to about £3 a throw.

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We have been used to cheap materials - back in the 70's, 80's etc balsa was cheap but radio items dear.   People then often had only 1 model rigged up and perhaps another stored away, now everyone ( except me!) takes a car load of planes each  with motor & full radio gear.   Model plans have not evolved to minimise on materials but ready built models have by being built from cheap moulded foam etc.

I don't see much alternative to balsa for LE,TE and ailerons so we have to use balsa.    It's interesting that we don't really pay for the bulk of balsa but for the sawing and sawdust waste.  A sheet of 1/16th costs 2.40 pounds while 1/8 costs 2.88 and 1/4 3.84.   So 1/16 th isnt a quarter the cost of 1/4 you might expect.    Means there is less point in trying to build cheaper using 1/16 each side of an air space or a bit of foam.    Cheap building is possible by making models built up from strip vintage style but by cutting your own strip from sheet and cutting tapered stock using a razor plane.    The heap of shavings on the workshop floor may not be waste but actually saving money!

 

 

We have strayed from the original point - have you found a way to use Profili or get your rib shapes Jeff?

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Yes we're in effect paying for machining as much as raw material. 

 

Don't forget liteply as a possible rib stock (especially if the ribs are drawn in a cad program they can be laser cut straight from the computer files).

 

Or, foamboard. Works fairly well for ribs and is very very cheap. 

 

All the above may inform what the ribs look like so not totally off topic kc.

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On 22/09/2021 at 18:56, Jeffrey Cottrell 2 said:

Hi Adrian, thanks for the quick reply.

Did have a look at the site you linked to, but it seems only to be a way of plotting an individual aerofoil according to your needs.

Might be missing something, but I couldn't see it being used to plot intermediate rib profiles, from root and tip templates.

Am I getting this wrong?

Jeff

I use the website to load co-ordinates into a CAD program. I then cut wing cores using a homemade CNC foam cutter.

If you were creating a tapered wing then I guess you could draw the plan view of the wing and measure the chord at each section. By changing the chord on the website it would give you a plot of each individual rib. 

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8 hours ago, kc said:

We have strayed from the original point - have you found a way to use Profili or get your rib shapes Jeff?

Hi kc

Seem to be being beaten at every turn.

Posted the question on RCGroups as well, and got a reply from a guy called Harry in Toronto of all places. He is obviously fluent in using Compufoil.

Managed to look at the Chili Wind plan, sorted out the nearest aerofoil, tweaked that in CF till it matched and printed out the intermediates, all in one evening.

Cracked it, says I, not so.

He e-mailed me the pdf and I printed it out here, only to find the rib lengths were off. Not by much, about 15mm on the root overall length, but enough to spoil it.

Been in touch and he tells me he did a test print before he sent it and the length was spot on, so the issue is at my end. just can't figure out where.

He suggested I take the file to a print shop and get them to do it, but I live in a small town and do not have a local print shop. Nearest big town is Eastbourne and I'm sure they would have one, but not looking forward to taking the car in there.

Ho hum. The battle continues

Jeff

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Hi Dad_flyer

Thanks for the thought but I don't think it's that.

The guy in Toronto did all his measurements in inches, because that's what the plan is in. On his test print he measured exactly 12" for the root chord, which it what it should be.

The pdf is designed to fit on A2 sheets. I don't have an A2 printer, so I did it with my A4 printer in 'Tile' format. Done this many times with plans downloaded from Outerzone, and it's never let me down before.

can't help thinking the problem is at my end somewhere but can't think where.

He suggested I go to a local print shop and get it done in A2, but I don't have a local print shop (small town) and the nearest one would be in Eastbourne. Not the easiest place to get the car into, even on the best of days.

 

Jeff

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You want to drive the car inside the print shop !!?

 

Yes I know, just could not resist that one, sorry.

 

I am following this thread as I have been interested in software for rib plotting, for future use.

 

Also 3d printing...

 

Stepper motor driven hot wire foam cutter...

 

Never throw away a printer, the bits it's made from are so so usefully.

 

Saving hard for new modern computer ( tiny windows 98 has outlasted 4 xp PC's, but can I get a printer for it ! ? It's 24 years old now, 25 in december ) printer, scanner and 3d printer...

 

I'm still making ribs via pack method.

Edited by Rich Griff
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29 minutes ago, Rich Griff said:

Stepper motors, drive belts and sprockets, shafts can make very good punches, varoiuse other bits and bobs...recycle the plastic parts apart from the flat bits...

This is way beyond me. If I had one and it broke it would go to the tip, otherwise I would end up with a house full of junk, or door stops. 

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Maybe your printer is set to 'fit' to the page?   Or not set to 100percent?   Or just try printing at A4 without Tile - it may just print onto 2 sheets A4 like Profili does.

Or get a friend to print out for you.   Or ask one of us to print out the root rib and see if its OK.

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Rich Griff -  start a separate item about your computer and probably the computer experts here will advise.    When I asked a question about replacing my wife's computer I was advised to get Linux Mint and try that on the Windows computer.   I did that and bought a memory stick with linux Mint for a few pounds and it just works and I can open that or go back to Windows  ........  but my wife wanted  Windows because she knows that well.    So didn't save buying a new Win computer but Linux just works so like Windows that it seems the way to modernise an old computer.   

We use our broadband Wi Fi to connect either computer to the same printer - maybe that will work for you and  connect your old computer to a modern printer.

Edited by kc
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Hi kc

How we got from computer printing ribs to how to re-cycle old printers, I don't know. Talk about thread drift!!!!!

Anyway, thanks for bringing us back to topic.

Here's what I have.

On the top of the pdf page is a box labelled zoom. I have that set to actual size. As an experiment I tried setting this to 110% but it still printed to the same size. Obviously that affects what you see on the screen, but not what is printed.

When I click the print icon on the pdf page, it does include a scaling factor which I tried at 105% but printing from that page only gives me a print small enough to fit on one A4 sheet. Whether it's 105% bigger than what's shown on the screen, but it's far too small to use.

To enable tile printing I have to go to the dialog box for my printer, but that doesn't include any scaling.

So far, I'm lost.

Got in touch with the guy in Toronto and he did a test print which came out exactly right, so the problem is at my end. Don't have a print shop local, so it would mean a trip to Eastbourne, which I don't relish.

Did look at a couple of online printers, who only quote 50p or so for the print, but when you add in minimum charge, shipping etc comes out closer to £10.

Quite happy to pass on the pdf if someone on here could print it out and check. Might highlight where the problem lies.

Other than that, considering going with what I have and building the wing some 3/8" shorter in chord.

After all, wouldn't see that when the model is 400' up.

What's your thoughts?

Jeff

 

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Jeffrey, if you have the pdf file why do you need to drive anywhere? Just email the pdf as an attachment to a commercial print shop and I am sure they will post you the prints at reasonable cost.
If the files are the correct size don’t change the scale on the pdf. Your problem is your settings when you select print (as you suggest). As someone else said, you probably have ‘fit to page’ rather than ‘print actual size’ selected. It is not a scaling issue.

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Hi Piers, thanks

Couple of good thoughts, but neither applies.

I did try a couple of on-line printers. True, they only wanted about £1 to do the print, but when you add in minimum charge, shipping and handling etc it comes out to more like £10.

Ok if I knew this would solve the problem, but I still don't know where the issue lies.

Also, once I get a correct size file I will cut the templates out, stick them to the balsa and cut round them. Assume I goof with one (not unknown with me) and need a new template, will I have to go through the ordering and cost process again?

As regards my settings.

I have set the size on the pdf to 'Actual Size', then I tile print on A4. Prints on to 4 sheets which I the sellotape together. Don't think 'fit to page' applies here.

When I go to my printer dialog box, I have the choice of either scale printing or poster (tiled) but not both, so I don't think it's  scaling issue.

Thanks anyway

Jeff

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I wonder what you opened the pdf in?   When I open a pdf in Adobe Acrobat Reader DC   ( which I think is the latest free version ) and load a pdf of -for example the Chilli  plan- and choose print I select the following boxes

Poster

Tile scale 100 percent

overlap .005 inch

ticked cut marks

and I think thats what I did to print my full size Chilli Wind plan - it certainly came out at 300mm ( maybe a few mm overlap error)

So do you get those options in Adobe or do you have something other than Reader DC?

In addition there is a set of options and one of those I chose Properties- Plain-Borderless off- Paper Quality-Main tray.    Could one of those options be wrong on yours?

Edited by kc
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