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Old Jan 28, 2013, 05:49 AM
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Bradford West Yorkshire, UK
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Wonder why on "Old school" drawings used in industry, there was always a note "DO NOT SCALE"

Regards Ian.
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Old Jan 28, 2013, 06:21 AM
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United States, MD, Elkton
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Originally Posted by Circlip View Post
Wonder why on "Old school" drawings used in industry, there was always a note "DO NOT SCALE"

Regards Ian.
You devil !-I wonder if they were telling us to accept "close enough" even then ?

I made a couple of attempts to draw the 'perfect plans' and gave up in disgust.
Double checking measurements got different lengths from right to left,as compared with left to right!

As much as I want accurate plans, I'm not the man to produce them.
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Old Jan 28, 2013, 10:20 AM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
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Plans - fascinating subject indeed.

Well recall drawing 'real' ones - I did 'technical drawing' at grammar school back in the early 1960s, so was well used to the good old ways by the time I got to designing model aircraft.

Got one of them new fangled CAD things around 1990 when we'd bought this wacko device called a 'PC' and my drawing board - a real one with sliding parallel motion and all - suddenly got used mostly for laying print-outs on.

Oddly enough, have strong suspicion that it takes longer to draw a CAD plan than one done with pencil, paper etc on a drawing board, though I was unable to get a government grant to research that supposition

Plan accuracy? Well, in theory, if you CAD draw a right wing, get it all sorted and mirror image it, you should get a left wing the same length. Not arriving at that was quite easy back in the day of pencils and rulers, it seems. Wings get to be the worst, on account of they're the longest part of most plans and come in left and right sides.

When you get to a plan, CAD or hand-drawn, that you buy off someone, it's likely been through three phases. I'm basing this on how I draw my designs up, so may be completely wrong in some cases, before we start!

One - you draw up all the big bits, then figure out the little bits off those sections. In the case of CAD, these are amiably scattered around a file and can be addressed, moved, diddled with and/or changed completely as the need and wimsy takes the designer.

Two - build the durn thing. At this time, you find out if the little diddly bits actually fit! There's a fair bit of scooting between building and drawing areas/rooms/buildings here. The worst case goes: print out diddly bit. Fit to intended location. Find it doesn't fit. Say 'durn it' or thereabouts. Head to plan. Redraw diddly bit to really fit. Re-print. Re-cut and fit.

Three. The plan is now a range of bits, big and little, with the really big familiar bits like wings and tailfeathers. Now the trick is to get them all into a format that can be printed at the local Kinko's/wherever in the magazine's building plans are printed or suchlike. If that sounds bad, try getting them onto either side of a full sized pull-out plan layout. At least with a 'for sale' plan, you are mostly limited by paper width and can go longer, or even multi-sheet.

Doing any of that last on paper was really, really fun. Aeromodeller magazine back in England - the original version, not the new one that's coming out now - had a draftsman who figured out how to get larger models onto full sized freeby pullouts by drawing big bits diagonally on the sheet size and also drawing what amounted to two plans, one atop the other, in contrasting colours on each side of the sheet. I still have one of my designs done like that in my files and it almost makes my head hurt!

Big points when building off a plan? Make sure things will fit before lashing into making a ;kit of parts'. Doesn't matter how simple or complex the model is, the bits have to fit and while a 1/4" extra wing chord overall will not cause your creation to spin off the take off roll and destroy itself, it could cause the completed wing to not fit into your equally completed fuselage.

Scale? Who mentioned scale? First off, if your 'drawing' is one of those scratty three views on the builders' website or promo pamphlet, chances are it was doodled up by hand to go on the website etc. It is very unlikely to be accurate As one who's flown (and won) the odd scale comp, the trick is to assemble your documentation, make sure your model is going to look like it and then paint it to resemble your best colour photos or paint detail.

I once blew a scale comp with a Sopwith Pup on account of my documentation showed the aircraft I had modelled to be in an ugly brown-ish colour, which anyone should have known (especially me, bragging at the time) was nothing like any sample of PC10 in the world. So I painted it in my best try at PC10. One of the judges was kind enough to nudge me in the bar later that day and point out that I'd have scored really high if I'd painted my model in ugly brown like my documentaion, despite what we all knew about PC10. Which was the standard topside paint colour used on RFC aircraft in WW1, if you're baffled.

Unless you're entering scale comps, which few can afford or manage these days, just make sure your plan matches up on things like wing and tailfeather tip shapes and anything really obvious. If you want to see how bad a scale model can be, look at cheap Chinese BARFs of Piper Cubs and Spitfires - it must take real effort to be THAT bad.

And so back to building - a 50" span large scale model of Joe Bridi's Kaos, for electric power. Guess who drew up the plans - and fouled up the wing dihedral brace?

D
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Old Jan 28, 2013, 11:15 AM
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Spoken like a true gentleman.

Dereck- thank you for the input. You get it- and as Andy Kunz said, Close enough is worth shooting for.

We're teaching the tentative builder that a few mistakes can be repaired, and so WHAT? if every part doesn't fit without some alteration ? Most parts do their assigned task with aplomb.

I'm not capable of cad filing anything,so my well varnished drawing table and I spend a lot of time with each other.

I learned mechanical drawing so well, I can't erase it to make room for modern tech.(I don't really want to-)
Mike Hudak spent a day drawing a 3" wheel into his computer memory.I didn't..
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Old Jan 28, 2013, 11:58 AM
The Prez....... again
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United States, IA, Rockwell
Joined Jul 2011
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I am experiencing a set of plans that are supposed to be "very scale" and true to the original airframe outline. While this may be true, I did not verify this as I want a "stand off scale" plane. Or as some would say "close enough"

The parts on the plan do not fit one another. Wing ribs are way off kilter, formers are a different size from one part of the plan to another, spar slots not in the correct location and the list goes on. It is to bad because while the construction is a bit different, the plane is well designed and it actually builds fairly easy. If the parts fit each other, it would be an EXCELLENT first scratch build.

The airframe was featured in an old, (sometime in the 90's) RCM magazine. It appears to me the designer supplied a first version of the plans to be offered for sale. Were updates ever even made to the plans??? Maybe the designer and the person who "inked" (what ever that means) the plans had issues. Maybe the inker (is that a word ) was incompetent???

In any case it is proving to be a challenge beyond the actual construction of the model itself.

Ken
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Old Jan 28, 2013, 12:19 PM
Just Me
United States, OR, Salem
Joined Apr 2006
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Originally Posted by epoxyearl View Post
.............Mike Hudak spent a day drawing a 3" wheel into his computer memory.I didn't..
Not sure why it took so long to CAD up a 3" wheel, but that being accepted, if his rendition is/was stored correctly, it's his for life and with a few clicks of the mouse can be any size he wishes......

As you can tell by the statement above, I am now a so called CAD lover. However, in my past (dating back more years than I care to dwell on) I have many times been confronted with a blank sheet of vellum on my board, a triangle ruler, a T square, a 90 degree triangle, an eraser bag and my first real lead holder, a Faber-Castell Locktite, in my hand and a vague idea in my head of where I was going with those tools. (this after having graduated from doodling on a paper sack with a #2 pencil on Mama's kitchen table.....with the magazine under so as not to scar the table top....lol)

Then I was introduced to CAD in the late 60's or so. Expensive, slow and not too user friendly. I hung on to that lead holder etc. for some time.... Although I still played at developing some rudimentary CAD skills. As CAD got more advanced and more affordable I also advanced in my useage of same. I've finally stored that lead holder in a place that's been lost in my failing memory, but I can do a presentable plan using my laptop and mouse. And best of all, 2D CAD is now available free. And, for the plans and building I do, that's "good enuf"......

Always fascinated by the stories that come to life in threads like these.....keep coming with the great posts......
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Old Jan 28, 2013, 04:05 PM
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United States, VA, Arlington
Joined Dec 1996
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Snag with CAD is you can do all these party pieces!

It gets easier once you realise that you don't have to put the material sizes onto your own plans - I use a stock range of wood sizes anyway, so its not like I have to think hard here. Another is that you don't have to make a CAD initial build plan pretty - putting on fancy dancy hatch fills to tell you that your sides are made out of balsa is kind of 'unintelligent donkey' level.

I do have fairly close doodles of my servos, though I still check that whatever I'm using fits before cutting up servo mounts - especially as my aileron servos always go into wing ribs. No, I don't have various sizes of Hitec and Futaba logos in memory to go with servo drawings either!

Back in MD, I still had a parallel motion drawing board until late 2009, when we approached slimming down into a condo from a town house with a full basement. One week, I found a old BARF wing in a corner of the shop, taped a sheet of paper onto my old board, drew around the wing's section - it was parallel chord - and drew up a fuselage for a tailless 'design' around that wing. Figured it took me way less than if I'd have scanned that section into CAD and drew up an incredibly detailed fuselage. Instead, I mostly doodled up the sides, figured an internal width, made the formers to go with it all and built the thing. Took about a week from thinking 'mmm - what can I do with that wing?' to flying the thing.

Unfortunately, it was obvious there was no floor space in life ahead for a drawing board that had gotten gainfully employed for a week in the past ten years, so it and some even older drawing instruments shuffled off to better homes when we packed up and moved to the 'extremely cold, constantly windy and far too overstuffed with politicians city' AKA Chicago.

It hurt too. You're talking about a guy here who has metalworking and car repair tools that out-do his recently celebrated 25th wedding anniversary by many years. I think the record is held by a pair of dividers from when I was a coppersmith - somewhen before 1971, when I joined the RAF.

An essential part of plan building that you don't get radically away from the design's major elements. Incredibly enough, a 1/4" difference in wing panel lengths will have far less effect on life than a couple of degrees of upthrust on the firewall that the prototype didn't have, to idly think of an example.

Structurally, it's always good to stick to the drawing too - one must assume that the prototype(s) survived a fair amount of flying built like that. Those who think a Kadet Senior should have enough power on board to be able to hover from the parking lot to the pits with a 12 pack of beer lashed atop the wing may want to rethink some structural points though.

On a smaller scale - let's say you're building something with skinny little stringers all over the fuselage - scale or vintage / OT free flight, effect's much the same. If the plan is hand-drawn, it is virtually impossible to accurately draw a 1/8" square stringer slot by hand, especially if there's a lot of them. So, mark up a common point for each of those slots and cut them out using a short sample of your stringer material as a template to cut around. Much the same applies to wing spars fitting into slotted ribs too.

And now back to making my K-E-os plan fit my prototype build

D
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Old Jan 29, 2013, 08:00 AM
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Oh the luxury of the F/C Lead holder (crutch pencil) and then the dedicated "Pentel". Never had the ACad until being taught after leaving the board. First three days, the compewker and monitor nearly went out the window, teecha said "worst people to teach were Draughties with years experience", then it "Clicked". still use a pencil on bits of paper to hold up to camera on Skype cos I can sketch a solution while talking but for a serious drawing "offset, mirror, scale, erase and SAVE are your friends.

Diazo printing had its problems but hanging a print up to dry due to wet developing was a sheer bloody nightmare, we had it tough.

Regards Ian.

HMMMMMMM Inkjet printers do that.
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Old Jan 29, 2013, 08:17 AM
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Would any of you cad users want to engage in a thread to help us learn how ?
.
I do my plans with a pencil, paper, and a new idea.

Great satisfaction is a return for helping others...Some of those helped say 'thank you', even...

I do not know where to start...Give us the most basic program capable of developing a plan...Please nothing fancy to start, unless advanced is the better choice.
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Old Jan 29, 2013, 09:05 AM
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Illinois
Joined Sep 2001
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I use my TurboCAD system (been using it since it was DOS-only) pretty much like an electronic drawing machine. I do the same constructions I learned with pencil and paper even though many are automatic if I wanted to learn how. Sometimes my parts don't fit perfectly, but usually are close enough for sandpaper

One of my friends is a draftsman for a ship design company in Oregon. He "builds" the model in CAD, and when he's done the parts fit perfectly, even when he does compound curve from a single sheet of wood. He's the kind of guy I would want teaching me, not me teaching somebody who knows how to draw on paper. You wouldn't learn anything!

Andy
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Old Jan 29, 2013, 09:11 AM
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Have a read in the CAD/CAM section Earl , everybody has their personal favourite. I've used three and the prime choice for me (Being a Yorkshireman) is it has to be FREE.

ACad (NOT free) is heavy to drive.

Doublecad (Free) is a bit easier. From same people as Turbocad, just a later version.

Draughtsite (Free) similar.

All are "lifts" from ACad but the main problem is that you need to use them regularly. My foray was ACad, twenty years ago and except for one or two drawings back then I didn't use it much. Got back into it using Doublecad and after a couple of days it started to come back although the commands were slightly different. The "Kids" are using three d now, so I'm out of that loop.

Regards Ian
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Old Jan 29, 2013, 09:18 AM
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I'm off to see the Wizards...don't 'cha see, I couldn't even comprehend where to go !
Thank you.....watch me grow.
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Old Jan 29, 2013, 10:05 AM
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The problem with CAD is the same as it was with earlier hand drafting. It's the paper, the plan itself. Great, totally accurate while it's in the damn maching. But as soon as it's printed for real world use, it is subject to all the same problems that plague it. Admittedly it starts out closer, and CAM parts are brilliant, but the paper expands and contracts. I suppose the plan could be printed on mylar (my favorite stable drafting medium) but paper is so much more convienient and available. Dare I say universall?

I have tried to learn CAD, several times. It's simply not for me.I will stick to my drawing board. Im going to try to incorporate more real aircraft bulding practices in my modelling of larger scale subjects. That is start building ,not OVER a plan, but FROM a dimensioned plan, establishing rib spacing etc. in a fixed space.
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Old Jan 29, 2013, 11:27 AM
Just Me
United States, OR, Salem
Joined Apr 2006
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Originally Posted by epoxyearl View Post
I'm off to see the Wizards...don't 'cha see, I couldn't even comprehend where to go !
Thank you.....watch me grow.
On your trip be sure to stop by this sight...

http://www.3ds.com/products/draftsight/overview/

They have a free 2D version that quite closely resembles AutoCad. I started with ACad but when obtaining a new laptop with Win7, my version of ACad would not install.... The price of a newer version of ACad was prohibitive on my retirement income so I started down the same path you are now on. Finding DraftSight was like manna from heaven. And FREE manna at that.....

As DraftSight mimics ACad in most functions, I had no problem making the transition. Your drafting skills will be of great help to you on acquiring even newer Cad skills.

Word of caution, don't expect your journey to "CadLand" to be the same as a stroll down LollyPop Lane...it'll take time, a little effort and you'll have many questions along the way. Your trip will be riddled with trial and error (remember those days of scrubbing through your drafting medium while correcting errors.....Oh....I see, you never did that...lol). Well, that doesn't happen with Cad. You can "erase" as many times as you wish and still no "hole" in your paper.....

If you choose to pitch your tent with DraftSight, I'll be happy to help if/when I can....Good Luck on your journey and don't stumble into the briar patch.....

Don
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Old Jan 29, 2013, 11:38 AM
Just Me
United States, OR, Salem
Joined Apr 2006
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One thing I've tackled recently was writing a script for drafting into CAD any airfoil (or for that matter, any shape) that I could secure or develop a .dat file for.

As I'm just a neophyte at scripting, this script works but is not very user friendly but it does do the job. What the script does is read a .dat file, draft that shape into my Cad program, stores it as a block into the memory of the file I'm working on. This block has an overall length of 1" (chord line in the case of an airfoil). That block can then be inserted and scaled to the required chord dimension with just a couple of clicks of the mouse. Not very impressive for a constant chord wing but really shines when you're developing ribs for a tapered or elliptical wing.....draft on fellow Cadders.....
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