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Drawing without dimensions ?

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kirbylee

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drawing RDR FITNG.jpg drawing RDR FITNG.jpg I keep running into plans with drawings like this one that doesn't tell you the height or the angle. Should a person be expected to figure it out? Wouldnt it be much easier to write the dimensions?
 

Hot Wings

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View attachment 86397 View attachment 86397 Should a person be expected to figure it out?
I was taught, way back before CAD, that the guy in the shop should have to do no adding or subtracting in order to make the part - no matter what reference he chose to use. I was also taught in the shop to never scale from the prints.
Life being what it is we have to put up with poor plans such as you show. In this case you have no choice but to scale from the plans or find a matching part somewhere else in the plans and hope the missing dimension is given there.
IMHO if the plans are this vague, unless the plane has many built and flying, it's a good indication of TLAR engineering and is one not to build.
 

wsimpso1

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My first response is send the plans back and demand a refund... These awful drawings are from which airplane plans?

On several levels, I have a hard time with what you are showing me.

First flaw is chained dimensions. Establish a datum - a point of reference, then dimension from there. Start at the bottom left hole, first hole to the right is 7/8, second hole is 1-3/4. Do the same thing going up.

Next flaw is the drawing does not show a reference line for the holes. Are the ones along the bottom on a straight line? is it horizontal? Terrific! Show us so we will know. How about the ones extending upward? Are they on a line? At what angle? Showing us either the angle or how far to offset each hole to the right from the datum would allow us to know how to lay this part out.

Next flaw is what size to make the holes?

Last easy flaw is what edge margin and radius to use beyond the holes?

Adding that up we have six diameters undefined, three radii undefined, positions of all six holes and all three radii undefined. Then there is chain dimensioning, which is a lousy way to define things - three more defects. Thickness does not appear to be defined either, but may be that is somewhere else. Maybe the hole sizes and radii are defined elsewhere, but I got 21 drawing defects on a simple part. And they sent this out on the www for us to look at?!? UGH!

Now you could be an incredible nuisance to the tech support line for this outfit and perhaps drive them to make their individual drawings useful. I like that approach because doing dumb stuff like this should hurt them. My worry over this, is that tech support either knows your pain but have no way to get the drawings fixed (management failure) or tech support and the drawing guys are the same ones and do not even understand what is deficient about the drawings (technical failure).

Let's see what we can do for you anyway. Yeah, detective work:

In business/industry, we would sometimes have a finished drawing that seemed incomplete because specs and standards are referred to and the part is made from a blank described on another drawing. So, is there a blank someplace else with other dimensions?

Airplanes often use standards. Are those holes for bolts or rivets used at assembly? Find the size of the fasteners used in those holes at assembly. Ron Wanttaja helped us with a useful summary on a lot of this: http://www.wanttaja.com/shopsheets/

There are standard drill sizes used to finish holes for each size rivet, and the final size drill only goes in when the parts are clamped together with Clecos. Use a smaller drill when making the parts, but lay it out knowing that your rivets use a standard size drilled hole when built. Then we use standard edge margins related to the drilled hole size D. If we have a line of rivet holes, we usually leave 3xD between centers of rivets and 2xD from center of rivets to edges of the part.

Now to those angles. I bet that the gusset you showed us attaches two very specific things together later on. Look at where R2 is used... Are there any specific layout directions for the members that R2 connects together? They may tell you the angle between two parts or give lengths and offsets or slopes. Yeah, you might have to do some shop math (I know, some folks never got friendly with trigonometry, but we can help). If you have two tubes at X degrees to each other held together with two copies of R-2 and two lines of rivets, I bet the gusset needs to be at X degrees too.

This may seem an awful nuisance, and maybe it is, but I suspect that you will greatly improve your grip on the big picture of how the airplane goes together when you do some of this paging back and forth, and that is invaluable. At least when your builder buddies show up to help, you can take then back and forth between parts and assemblies and seem knowledgeable while you show them why you can not figure out what the designer intended...

Fallback plan is you call tech support and tell them about how the drawings are little better than dog poop allowing you to make the part and you need to know the angles and hole sizes and edge margins and radii at the corners of this part and this part and this part and ... Make a list, then follow up by emailing the same questions to both tech support and to the guy who signed the drawing...

Have fun.

Billski
 
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Jay Kempf

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Love the stray 1/4" off to the side. I am guessing that is from hole center to the edge and it is for all holes. Bad drafting for sure.

There may be missing context which is not a good way to completely understand the part. But if there is an assembly and I surmise that this is a bracket for putting aluminum tubes together say in a truss tailboom of a fuselage, then the angle might be on the fuselage part of the drawing. Chain dimensioning is not good if you are trying to machine two mating parts but lesser draftsman that weren't trained use them all the time. If this is just to position rivets on gusset then it is technically harmless. So if we could see whole plan set we might be able to do detective work and put the whole picture together for you. "R2" is the clue here that will go to a note on an assembly page with some other dimensions that will get you there.

I am sure a lot of people in the ultralight world are not trained to aerospace engineering drafting standards. It is what it is. It's probably not worth debating or fighting with the drafter as they aren't going to have the experience to understand you. You just need to get the part done. If there is a forum for this design point this stuff out and leave a record so no one else has to go through this.
 

gtae07

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Agree with Billski. That is awful. I can see circumstances where "print it, check the noted dimensions, and then cut it out and use as a template" would be appropriate.

I've seen plans with overall decent dimensioning but a couple of real forehead smackers. The dimensions were complete but done in a way that wasn't clear and made it real easy to goof up the part. After the second try I modeled the part up and triple checked it, then printed my own dimensioned drawing.
 

Pops

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Lots of very bad airplane plans been sold on the market. The little simple Baby Ace has a great set of plans. All plans sold should be as good.
 
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12notes

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I have seen plans like that where the part is drawn actual size, you just simply trace the drawing onto material, cut and drill on the lines without bothering too much with things like dimensions.
Since the pictures are taken from a screen, they may be a scan of printed plans which were full size drawings. There are lots of parts like this on the Hummelbird plans, trace the part, cut it out, drill. Would be nice to have better plans, but it has worked so far.

Context within the full set of plans is key, but here's what I think.The 1/4" refers to the hole size, my guess this is spelled out elsewhere in the plans/build manual. Holes line up parallel to the nearest edge, center each line of holes to the the corresponding edge. Not ideal, but only takes a minute to measure and mark the holes, and, while not elegant and could be done better, this produces acceptable parts without much additional work.
 

FritzW

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I'm impressed with the experts who can judge a whole set of drawings by looking at only 10 square inches of them ...with absolutely no context to the rest of the drawing.

Yeah, these plans are pretty sloppy but I wouldn't rag on them too hard without seeing the whole set. You can take a tiny snapshot out of any set of plans and make them look bad.

Maybe the angle is obvious from the drawing right next to this one, maybe the 1/4" measurement is right next to a note that says "Edge distance". There's no way to know without seeing the whole thing.

EVERY set of homebuilt plans starts out with a few problems. Just let the designer know so he can update his drawings.
 
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TFF

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Humm bad yes. Unbuildable no. In the last twenty years, the kit plane industry has catered to the unhandy. Everything spelled out. The first five Pitts Specials were built without plans. S1C plans are OK, Tailwind plans are Ok, FlyBaby plans are OK. Great? No. All require head scratching but lots built out there. Heck a good number of FlyBabys and Baby Aces were built from magazine article plans done in a serial. Not full plan sets. The skill is gone from the general population and most people think they have to build an Oshkosh winner or it’s a failure. The real question is if the design is worth it?
 

Pops

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When I started building model airplanes at 8 years old , I also started scaling up the magazine drawings to build the models. Didn't have the money to order the plans.
Just saving my pennies to buy material at the hobby shop or order from AHC. If you don't know what AHC is, you are not an old model airplane builder :)
Most people today needs to be told how to do most anything and without instructions they just stop. No problem solving skills what so ever.
 

TFF

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Back about year 2000 when EBay was new, I watched in awe as they sold the contents of the AHC warehouse on EBay. AHC probably had been closed for 10 years and all that stuff sat quite until rediscovered when the sold the building. They had new stuff from the 40s, 50s,60s as much as my era of mid 70s-80s. It took over two years to sell the stuff and I never won one item. Pick the year you use to see the adds in the magazines and they still had it in stock. Crazy.
 

Pops

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Bought my first model engine from AHC. Saved my pennies until I had the $2.99 + shipping to order the Atwood .049 engine. Never received it, about 3 months latter my Grandfather's brother stopped by the house and had a little box with the engine that our mailman had dropped off at his house. Mailman road a horse the twenty miles each day and had another horse at another family members barn to switch horses half way. About 1950 he bought a WW-2 Jeep but still had to use the horse when he had to ford the creek when it was up, because the horse could swim and the jeep couldn't. I have swam the creek crossing many times with my horse when I was a kid.
 

TFF

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It was a big deal when that stuff came as a kid. On a horse, good thing you did not order a couple of big kits.
 

Pops

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Grandfather would have to hook the horses to the wagon or buggie and we would would have to take the 10 mile trip to the post office. 2 creek crossing each way.
 

wsimpso1

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I'm impressed with the experts who can judge a whole set of drawings by looking at only 10 square inches of them ...with absolutely no context to the rest of the drawing.

Yeah, these plans are pretty sloppy but I wouldn't rag on them too hard without seeing the whole set. You can take a tiny snapshot out of any set of plans and make them look bad.

Maybe the angle is obvious from the drawing right next to this one, maybe the 1/4" measurement is right next to a note that says "Edge distance". There's no way to know without seeing the whole thing.

EVERY set of homebuilt plans starts out with a few problems. Just let the designer know so he can update his drawings.
OK, I can not stand it. I AM an expert on this, having been technical leadership in three different major companies in two different industries, neither of which were aviation related (Cars/Trucks and Guns/Ammo). Drawing defects are like rats and ticks. There is never just one - if you have seen one there are almost always lots more that you just have not seen yet. Drawings have to DEFINE what is to be made and make it possible to check the parts afterward too.

In this example, I can build a part exactly to the published print, and it will not look like what you want at all. The hole sizes and edge radii are not defined, the hole positions are each only defined in one dimension but not the other, part thickness is not defined. In short, I can build a part that 100% meets the print dimensions and is equally useless for building the next up assembly. The only hope it gives the builder is that he/she can call the support hotline and ask questions about how the R2 is to be built, and maybe get a copy of the print that actually defines this part forwarded... Yes, we need to call and complain.

If the seller let this piece of crappy part definition escape on such a simple part, I can only be worried about how bad the more involved stuff is. You paid the seller money to ship you an engineered design, right down to how to build the pieces, and this indicates that they did not ship what you paid for. Now maybe they really do know how to define their parts and did a great job everywhere else, but the OP say that this is an example of stuff he has been seeing. There seems to be more like this out there... Until a bunch of customers call the sellers and gripe about crappy definition of parts and demand our money back or explain that this sort of thing on their drawings is why we are not buying, they haven't a reason to fix it.

So yes, complain to the guy who signed the drawing and his boss. Maybe we can move the needle.

Billski
 
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Angusnofangus

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I agree, crap drawing, but that said, the worst of it is not saying what the angles are. Otherwise it is buildable with the information given, assuming the material specs are somewhere else. I've seen lots of drawings in my past career, some very clear (Boeing), and some barely decipherable, (Bell Helicopters). Mostly I dealt with repair drawings, not new parts. But the ones that took the cake were from a draftsman employed by a helicopter operator that I worked for who knew nothing about aviation or aircraft drawings. his drawings would include rivets and all three of the lines associated with a bend. I tried many time to steer him toward something that would pass for an aircraft drawing, but he just loved his CAD program that would put in rivets.Eventually he got replaced by someone who knew what he was doing.
 

Bill-Higdon

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When I started building model airplanes at 8 years old , I also started scaling up the magazine drawings to build the models. Didn't have the money to order the plans.
Just saving my pennies to buy material at the hobby shop or order from AHC. If you don't know what AHC is, you are not an old model airplane builder :)
Most people today needs to be told how to do most anything and without instructions they just stop. No problem solving skills what so ever.
AHC sadly gone the way of a lot of the old suppliers https://stunthanger.com/smf/open-forum/ahc(-america's-hobby-center)-who-remembers-it/:(
 

12notes

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Context is everything, you don't know what conventions were established elsewhere on the plans. I'm pretty sure I could build a part from those plans and have it match exactly what was needed. Unless you were trying to intentionally not make it fit, you could too. It may not be ideal to your standards, but this drawing, assuming it is full size, is perfectly acceptable to me. It is typical of what is found on the Hummelbird drawings, and those are the improved drawings made by Bill Spring. A bunch were built with even rougher drawings before Bill Spring redid them in 2001-ish.

This isn't major companies in industry, it's unlikely there is a boss, there is probably only the guy who designed the plane who also drew the plans. It's usually difficult enough to get a designer to release any plans, requiring him to take an engineering drawing course and redraw the plans is asking a bit much. If it's been built more than once, then these plans are probably adequate.
 

wsimpso1

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I get that the rivets are probably defined somewhere so we can get to D, but maybe they are not. You ain't lived until you have had to figure out what goes where by poring through plans tallying up how many bolts or rivets are used in various places to see how that lines up with the Bill of Materials.

Once you have D for the holes, then you can use the standard 2xD for edge margin and radii at the corners. But what angle will you use? Then you go back and forth through the plans to find out what angle the two pieces are to each other, which will be nice but time consuming. Or maybe you can scale or copy the drawing and hope it is right. I have seen drawings re-used with just the dimensions changed - scaling will make a part that does not fit. I do not like guessing and deductive reasoning when they should just tell us the dimensions and the part numbers.

With this level of inattention to part dimensions, I can only hope that the scavenger hunt through the plans will show you the rest of the dimensions. The alternative is to call to ask for the angle. And you gotta search or call for every little gusset and bracket in the airplane? I can not wait to see what surprises they have for us on other details. Then you gotta listen to them telling you that support is time consuming and expensive when they made the problem for themselves...

Billski
 
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