# Drawing without dimensions ?

Discussion in 'General Experimental Aviation Questions' started by kirbylee, Jun 30, 2019.

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1. Jul 1, 2019

### 12notes

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You're assuming things that you lacking the context to condemn them. The hole dimension could be (IMO, probably is) the 1/4" dimension. The first page of the build manual could have a diagram which explains the convention in the drawings are done, it might not be standard, but as long as it's consistent and this and any similar drawing are full scale, there's nothing wrong with it. If these things are true, there is zero searching for dimensions elsewhere in the plans, everything you need is there.

Everything I am stating could easily be wrong, too, but I find that unlikely, we don't have the rest of the plans, or even know what aircraft it is for, so let's get some more information before condemning them.

Kirlbylee, what aircraft is this for? Do you have the full plans and build manual, or are you just evaluating a scan of a page or two?

2. Jul 1, 2019

### FritzW

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This isn't an Airbus, it's a homebuilt. Homebuilding implies (at least it used to) that the builder has some degree of mechanical aptitude.

Nowadays I guess it depends on the builders comfort level with (and ability) to figure out the "head scratchers" on their own. Some builders need to be spoon fed a flawless set of drawings showing every conceivable detail and an 1-800 to call every five minutes when they need their hand held. ...some can handle figuring out the little details on their own.

The Legal Eagle plans are a good example of a really crude set of drawings that builders use to build really good airplanes. Millholland probably drew the plans on his kitchen table and he sure as heck didn't have (or need) a "boss" to approve the drawings. ...the drawings work fine but they're not for builders that need a lot of hand holding.

3. Jul 1, 2019

### 12notes

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I thought the drawing style looked familiar, I just looked it up and this is from the affordaplane drawings, and R2 is a full size drawing.

I was wrong about the 1/4", it is a misplaced edge distance for the holes (which are rivet holes). The drawing for R1 (on the previous page) has it in the correct place, between the lower holes and the lower edge. The white box in the lower left corner covers a similar dimension on a different part on the same page, my guess is it got moved and to insert it and not moved back. More of a "typo" type error than a problem with the plans.

The plans are ok, I'm not so sure about the affordaplane design itself, though.

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4. Jul 1, 2019

### proppastie

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Enough is there if it is in CAD or PDF. Just print so 7/8 dimensions are right, cut and paste on to the aluminium. Many newer process do not have demensioned drawings. It is all digital even the quality control with computerized mesuring equipment. I bet most of you guys still have your sliderule.

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5. Jul 1, 2019

### TFF

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Legal Eagle plans are crude. More like sketches with dimensions. It builds one of the best UL planes you can, if you are after a regular airplane UL size. Someone has converted them to CAD so all the parts line up. Too bad that if you build some parts from one and some from
The other, stuff does not fit.

Vans made building an airplane accessible to anyone. Follow the directions and get an airplane. Before then, homebuilt plans were an idea that had to be executed by someone who could make it work. Everyone expects Vans no matter what you are really buying. It’s really the anomaly along with a few others. Mainly planes designed in the CAD era. Offering a new design today, no way with the average dreamer expecting it to build its self.

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6. Jul 1, 2019

### Angusnofangus

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At the aircraft manufacturer that I recently retired from we used this method for developmental parts all the time. Glue a full sized drawing on the material and go from there. Hard part was cleaning up the part afterward.

7. Jul 1, 2019

### proppastie

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Best I found is rubber cement. ..peel it off ....rub off any still on the part with my thumb or rag......Does not distort paper like white glue will. Only problem is mylar will not let it dry.

8. Jul 1, 2019

### Tiger Tim

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R2 looks to me like a gusset of some kind, perhaps the best way to find the mystery angle is to just measure it off of whatever it joins during construction. In most homebuilts the builder is making one copy and everything is bespoke, just make this stuff to fit.

Havin said that, I hope the hole size and edge distances are specified somewhere.

9. Jul 1, 2019

### BJC

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I’ve used varnish to temporarily attach full size paper templates to wood. Doubt that it would work well with metal parts. BTW, it is useful to include straight lines with dimension ticks on paper templates to use to verify that the paper didn’t change dimensionally from the varnish or glue.

BJC

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10. Jul 1, 2019

### wsimpso1

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We still do not know the angle from the plans. Sloppy,drawings.

11. Jul 1, 2019

### Hot Wings

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It's a perfectly acceptable method for development parts and hand built homebuilt aircraft. But the modern homebuilder doesn't have the skills that were normal in years past and expect "tab A to slide perfectly into slot B" especially if they have purchased a CNC cut part that has "slot B" and are expected to build "tab A".

Wsimpso1 also pointed out that from the manufacturers side poor plans also translate into increased work load for the support staff - if such is provided.
I'm right in the middle of a project to turn a set of old school aircraft plans into modern readable CAD accurate drawings. The better job I do making them accurate and easily readable the easier the build will be for the plans purchaser and the less likely the builder will make a mistake that compromises the integrity of the design.
In my case the airplane was designed by an aircraft engineer and has proven to be a safe plane that meets it's claimed performance numbers. The version of the plans for the amateur builder, while they have enough information in conjunction with the build manual to build the plane, require quite a bit of study. If the plans had been better organized and didn't require a lot of cross checking there might have been more than a hundred or so built.

"Clarity of formulation is essential in my profession" ... Spock

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12. Jul 1, 2019

### lvaero

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What kind of QA does this company have? We can try to assume that this is an oversight if a singular dimention is accidently omitted, but this is pretty awful.

13. Jul 1, 2019

### 12notes

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Since the plan is full size, we know exactly what the angle is. There isn't a number printed on the plans, but the angle is known, it's right there in front of you. There is zero need for a number to make the part.

14. Jul 1, 2019

### 12notes

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I built a "light table" (actually, I piece of leftover acrylic on two crates with a clamp lamp underneath it), then traced the plans onto white contact paper. Stuck just fine to the metal, and protects the parts until you remove it. Peels off easily.

Alclad also has a protective plastic, so I've even printed a wing rib on a plotter and used 3M spray adhesive. Since it was actually stuck to the plastic protector, I just peeled it off with that.

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15. Jul 1, 2019

### mcrae0104

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So much for stone knives and bear skins. #cityontheedgeofforever

16. Jul 1, 2019

### 12notes

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I'd like to point out that these are plans for the Affordaplane, plans that cost $3.95 when I bought them a few years ago, although they are$20 now. I'm not sure why exactly you're picking on the quality here, there are way more expensive plans that have less detail. But, sure, let's demand they redo all of them because R2 has an misplaced number that R1 doesn't, and that it doesn't have all the dimensions for CNC cutting on a part that's supposed to be traced and cut by hand, determined from by your opinion based on viewing 1/4 of one page of the plans. I'm sure that'll sell enough additional plans to pay for the draftsman.

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17. Jul 1, 2019

### ScaleBirdsScott

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I'm amused at the variety of perspectives on offer here.

For me, I'd see the use of fractional nomenclature as the first and primary indicator that this set of plants is 'notional' at best. Actual shaping, angle-finding, layout, and so-on is up to the builder to suit. (Other indicators being the mentioned stacked dimensions and just the extra THICC lineweights) and so for these types of plans while I'd assume some construction standards and material choices have been made for you, the formal rules are out the window; the designer expects you to do whatever one must to get something that works, whether it's tracing or printing out templates, using cardboard to plot out what you think makes sense and tweaking from there, it may be that whole assemblies are just a sketch and you're left to figure it out in your own way at assembly time. And that's fine, if one is interested in and willing to go to the mat to take on this type of project. If these are plans made by a one-man operation, showing how to make a super-inexpensive ultralight, then that seems about right. IF these are from plans to build a twin-engine cabin class cruiser with retracts and stressed skin construction, then it really does stretch incredulity that such a vehicle could be reasonably built without adherence to more disciplined and well-laid out plans by an average builder who is relying on following said plans.

So it's all about scale, expectation, etc.

No it's not following any known drafting standards, there's no GD&T for light-years in any direction, and in some applications this is worse than just having no drawing at all and just saying "make a thing that fits"

On the other hand at least it's not literally on a napkin, and people have done plenty with less.

So to answer the OP, yes it would be nice to have all dimensions laid out. But, at the level of detail this set of design sketches has been rendered at, very likely those missing dimensions are missing because one is to "locate to suit at installation" (a term we used a lot at a company retrofitting subs) and so providing them would just make it more confusing when one part ends up needing more or less angle for 'optimal' fit.

The challenge really is passing along design intent, and that's where maybe an overall assembly, and a method for arranging the elements of the assembly, would inform the builder where to put the given bracket and give them some idea of what to base the angles on.

What I'd usually do is provide a dimension in parentheses as "reference" and maybe include a note when required to clear up any intent.

Last edited: Jul 1, 2019
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18. Jul 1, 2019

### wsimpso1

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So it is OK with you guys that the designer gives you a drawing that you might be able to use, but if you build pieces as shown it might be useless too, and you are left to do the parts design anyway. That has a big problem - You are allowing yourself to be made into the designer of the airplane pieces and possibly of the assemblies - are you qualified to be an airplane design engineer?

As long as you guys tolerate crap, some folks will supply crap. Alternatively, if some of you ask for better, some of these folks will start fixing their stuff, then the rest of the market will have little choice but to do better work too.

Billski

19. Jul 1, 2019

### 12notes

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No. What I'm ok with is a proven, repeatable, often used, and consistent method that has produced usable parts on thousands of aircraft for decades. Every single Hummelbird has been built from plans with parts like this, I haven't seen any questions about how to make them, and I've gone through every post on the builders group back to 1999. I don't think there's s single part that states the diameter of the rivet holes on the Hummelbird plans, but I know to use a #30, it's just not necessary to repeat it everywhere. The edge distance on the R1 is marked on one set of holes at 1/4”, do you really think it's a mystery what the edge distance on the other set of holes should be? Do you really have any question what the misplaced 1/4” dimension is on R2 after you've seen R1? The Hummelbird plans are not unique in having parts drawings like this. These parts are not difficult to make, there isn't any math or design needed, just make the part and move on. While you can screw it up if you try, you'd have to intentionally do so, those of us trying to build a plane instead of prove a point have no problem.

What I'm not ok with it the idea that requiring industry standard regulation drawings for nothing but pedantic reasons would do anything but remove 75% of plans from the market. There isn't going to be a rush to undertake the time or expense of redoing the plans, they'll just disappear. There are so many designs that never had plans drawn that some of us wish we could build, anything would be better than nothing. Complaining about simple, working methods because they don't meet your high standards for professional blueprints isn't helping.

It's a gusset with 6 rivet holes on a \$3.95 set of plans. The part takes less than 10 minutes to make. Get over it, move on.

20. Jul 1, 2019

### wsimpso1

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Oh, I am over it. I am not building an airplane where the designer thinks it is OK to have his customers redesign features as they go. I already encouraged the OP to send the plans back and get a refund. You are the one in a tizzy because I am willing to call "Crappy Work" when I see it and encourage other folks to request fully defined designs from the designer.

If you go back to my first post on this thread, I did describe how to infer most of what is needed from this drawing. I do understand that you can make-do on this part. If we are willing to infer (that is a word for "educated guess" and is closely related to "take a risk") on the hole sizes and edge distances, we are still hoping that someplace else in the plans the angle between the mating parts is defined. If the angle is not defined somewhere, we are stuck with scaling from a sketch that may or may not reflect the intended angle. Do the plans say anywhere that scaling is acceptable or that the sketches provided are acceptable patterns for making parts?

As to building R2 and looking at R1, if they are the same, why the separate part numbers? They are most likely different somewhere important (justifies a separate part number and sketch), so you should probably be careful extending what is in R1 to R2...

Now we can get to the big issue - Given that this simple part is poorly defined for the builder, the builder had better be on the look out for others that are not so easily figured out and be able to get acceptable answers on those issues too.

Have fun guys.

Billski

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