# Aaaaargh, what am I doing wrong??? Please help!



## TrimTheKing (20 Feb 2010)

Hi all

I am trying to design a bed for my daughter and I have found either a c0ck up on my part that I can't find where I'm introducing, or a 'featuer' of SketcUp that I can't understand.

Below is a 2D output of the head/foot boards and so you understand the processes I have done I will explain.

I have created the legs as components then flipped the foot board ones on their red axis and the rigth hand side ones at both ends on their red axis.

Next I have used the protractor to rotate the legs outwards by 5 degrees and back by the same. So effectively the tops of the legs point out at a diagonal from the centre of the bed. Still with me...

Now look at the measurements (bearing in mind that at no point have I modified the squareness of the legs to each other)!!!

This is causing me an issue because now when I try to add the side rails and put the curve in them, because the adjoining sides of the side rail are not square it causes an issu.

Can you help???  







Thanks in advance.

Id this explanation doesn't make sense let me know and I will try and make it clearer.


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## mr grimsdale (20 Feb 2010)

Doesn't make much sense!
Are you trying to splay the legs in 2 direction? Differences of 1.2 mm are not worth the bother - will be invisible.


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## xy mosian (20 Feb 2010)

TrimTheKing":2urs5xzb said:


> Next I have used the protractor to rotate the legs outwards by 5 degrees and back by the same. So effectively the tops of the legs point out at a diagonal from the centre of the bed. Still with me...



Sorry not with you at all. If you have rotated the legs, I assume about a vertical axis, outwards and then back again. Why should the legs point out at a diagonal from the centre of the bed. If they are in fact pointed outwards then surely the dimensions will be different, inner surface to outer surface.

Trying to understand 

xy


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## TrimTheKing (20 Feb 2010)

xy mosian":1k9joqwp said:


> TrimTheKing":1k9joqwp said:
> 
> 
> > Next I have used the protractor to rotate the legs outwards by 5 degrees and back by the same. So effectively the tops of the legs point out at a diagonal from the centre of the bed. Still with me...
> ...


Sorry, it was tough to write. Imagine the legs being vertical, looking at the footboard from the foot end of the bed. The lags cant out at 5deg so the gap is wider at the top than it is at the bottom.

Next I have also canted them towards you by 5 deg, I will do another pic now...


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## TrimTheKing (20 Feb 2010)

mr grimsdale":1qym7uxt said:


> Doesn't make much sense!
> Are you trying to splay the legs in 2 direction? Differences of 1.2 mm are not worth the bother - will be invisible.


I appreciate that in a build sense, but to make the side rails in sketchup the faces between the two ends don't match so you can't click the side rails into place and the model goes wonky.

The really weird bit is that if I can't the legs out from one perspective first them the the other then the discrepancy is between the short sides.. If I cant them the other way round then the discrepancy is between the long sides...

I am going to export some more pics to try and explain...


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## xy mosian (20 Feb 2010)

Ok! So the bounding rectangle at the leg tops is bigger allround than the bounding rectangle at the bottom of the legs?  

Could this be done with the scale tool?

xy


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## TrimTheKing (20 Feb 2010)

Here we go, this is the end of the bed, the line is the vertical





And here's another view





And here's from the side





And another





Yep xy, your explanation was much better 

Not sure about the scale tool, the bit I can't understand is why this discrepancy comes in because unless my mind has gone completely, what I have done should make no difference whatsoever to the squareness of the respective faces to each other...

The real problem is that when I draw the side rails in place, then add an arc to the bottom, because the face is slightly out of whack it won;t allow me to push the face of the arc through to the other side, it goes mental...


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## xy mosian (20 Feb 2010)

OK! I have managed to reproduce the effect. I think, bearing in mind I know nowt. That it is an axis problem. I am trying to align the axes with the long corner of a leg, but I've forgotten how. How about adding the curve detail, to the rails, before rotating the legs? Now you may have some extending of the rails to do once the rotation is done but that seems to work. 

As for the difference in the dimensions. Well it would be nice to know what is causing it, but hey! this is wood perhaps the simple answer is to make it and put it together.

xy


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## SketchUp Guru (20 Feb 2010)

Mark, send me the SKP file so I can see what you've got. Well sort you out. Check for a PM.


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## TrimTheKing (20 Feb 2010)

Thanks Dave, will send it over now.

xy - Thanks for your help, will let you know what Dave comes up with.


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## xy mosian (20 Feb 2010)

As a last note. I have found, in my own bumbling way, that I have had most success drawing the parts as I would make them, then adding them to a model. In this case making a model of the rails and adding them as components to the assembly. Rotating as required. 

xy shuffles off in the presence of a MASTER  , but watches with great interest from the shadows.

xy


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## Jake (20 Feb 2010)

What happens if you chop the bottom of the legs off so they sit flat on the floor?

Oh, ignore me, I've misread the problem.

Oh maybe I haven't! Here:






You can see the inner faces of the legs are "longer" than the outside faces, i.e. stick up further (in that orientation). As they are canted outwards, they travel further in the directions they are canted in, so the inner face corners will be further apart than the outer face corners.

I think.


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## Chris Knight (20 Feb 2010)

I don't think this is SU, but rather your understanding of geometry.

Imagine the head and foot of the bed laid flat on the floor, it's clear that the inner corners of the tops of the legs will be further apart than the outer corners.


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## SketchUp Guru (20 Feb 2010)

Mark, if you sent the file, I haven' seen it yet. Maybe the e-mail is being sent via surface mail?

Chris may have hit your problem on the head already.


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## Steve Maskery (20 Feb 2010)

Spot on, Chris.

Mark, to get your rails to behave, make them longer than necessary and then Intersect with Model. The ends will then match your legs correctly (after removing the waste, of course).
S


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## TrimTheKing (20 Feb 2010)

Dave - On baby duty so had to run away, just sent it now.

My brain isn't working, I've looked at both Jake's and Chris's explanations but it's not going in.

The faces of the legs that face each other down the length of the bed are square to each other so regardless of how long the corners are, providing they are the same at each end surely they will have the same distance between them over the length of the bed?

Sorry for being dumb here guys but it just doesn't seem to be logical to me


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## TrimTheKing (20 Feb 2010)

Scratch that last one, of course it makes sense that the longer ones will be further away because of the canting away from each other. They wouldn't if they were only canted outwards along the headboard but because of the double cant it does. That makes sense now 

The bit I still don't understand though is why depending on which direction I cant the legs in first moves the discrepancy around???

Also, this shouldn;t make any difference to the rails being placed on the faces should it because the faces are the same length at the point in which I am trying to plant them?

Now I'm confusing myself even more!

I think Steve's explanation of drawing them too long and intersecting will be the answer but I'll wait for Dave's expert guidance.

Cheers all for helping.


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## Chris Knight (20 Feb 2010)

Intersection and deletion of the unnecessary geometry will enable you to draw it but as you will appreciate the side connecting pieces would have to be cut with angled faces at their ends to fit precisely. Once you have drawn them, then of course you will have a component you can examine in isolation.


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## SketchUp Guru (20 Feb 2010)

See if the following images help describe what you're seeing. I used 25° as the rotation angle for both directions.

First Rotation:





Second Rotation. Notice the black protractor.





The results of that second rotation. The horizontal guidelines are parallel to the green axis. Note where the top one comes out of the leg. This shows that the leg is indeed twisted relative to the axes.






If you make the second rotation about the green axis, thus:






Then you won't get the twist. Notice the guideline. It lies on the face of the leg.






In the shop, you would build the headboard or footboard laying flat with the legs splayed out. Then you would tilt the entire assembly. This would result in faces being oriented as you need them to be.

Or did I miss something?


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## SketchUp Guru (20 Feb 2010)

Have to run to celebrate the mother-in-law's birthday but I have more to add. Back ASAP.


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## TrimTheKing (20 Feb 2010)

Thanks Dave

I still don't get the rotation bit (brain just isn't working today), but I think from the other answers I have worked out what the issue is.

From these pics you can see that I have decided to keep the 5deg splay on the side rails too and compensate for the angle by angling the inner rail that the slats will rest on.







As per Chris' post, because I have marked up the guide points from the bottom edge of the leg (which is obviously at a 5 deg angle) the the inside faces of the rail are higher thus bringing in the small (0.22mm) gap you can see here.






In reality I don't think this tiny gap will make any difference at all to the build process but if anyone can offer a better way to do these side rails then I would be most happy. 

Dave - As you say, when I build it I will build the head/foot boards flat and introduce the angle later, but I think I will still encounter this problem when I cant them backwards, or am _I_ missing something (highly probable)...


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## Chris Knight (20 Feb 2010)

I think you wil find it easiest if you do as Jake in fact suggested and that is to trim the feet flat with the floor after your first rotation. This will give you the correct edge to make the second rotation around.


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## mr grimsdale (20 Feb 2010)

It's the same problem as the trestle I've got here.
You have to choose between square section posts which won't project square on plan, or rhombus section posts, which will (if you've worked it out right).
Or just bodge it in the old fashioned way.


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## TrimTheKing (20 Feb 2010)

waterhead37":14o7yto2 said:


> I think you wil find it easiest if you do as Jake in fact suggested and that is to trim the feet flat with the floor after your first rotation. This will give you the correct edge to make the second rotation around.


That's part of the problem Chris, I don't want the feet flat on the floor. I intend to have a round bun foot on the bottom of these so the angle need to stay, but I think I can bodge what you suggest by putting in a guide line on the drawing to take out the angle before making the measurements for the rail.

I'll give it a try now...


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## TrimTheKing (20 Feb 2010)

mr grimsdale":4ro832f3 said:


> Or just bodge it in the old fashioned way.


You got there just as I was typing, I think this is going to be the way to go


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## SketchUp Guru (20 Feb 2010)

Square section legs, no bevels on rail ends. I drew the front face of the rails and used Push/Pull to give them thickness. No bodging and no need for Intersect


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## mr grimsdale (20 Feb 2010)

Some subtle angles at the rail/post joint! The rhombus section post would make things neater in appearance i.e.you wouldn't get the toe in - it'd be square on plan.
Hmm 2nd edit I've edited this once already.
A third option is to have one pair of sides flat with simple angles between post and rail, and the other pair toed in with complex angles.


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## Chris Knight (20 Feb 2010)

Smart work Dave!


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## SketchUp Guru (20 Feb 2010)

Does it make sense?


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## Chris Knight (20 Feb 2010)

err - no...Basic geometry is still the issue I am afraid just as Jacob has described. It's the sawhorse problem.

Here's a section of your approach - ortho view.


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## SketchUp Guru (20 Feb 2010)

Video coming.


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## SketchUp Guru (20 Feb 2010)

It's still processing as I post this link. There's no sound and I used a couple of different methods to to make the rails but both amount to simply drawing the face shape and pushing to thickness. The ends fit against the legs with no bevels, no intersect, etc. The legs are not deformed from their square section, either.

Notice that the second rotation in this example is done after the three parts are made. Also note the rotation is parallel to the red axis. 

In the shop the ends of all of the rails could be cut cut with a simple 5° mitre. The blade would be left vertical. Assemble the foot board and head board. They'd lay flat on the bench. Then they would be assembled to the side rails as with any other bed.

http://blip.tv/file/3244819


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## TrimTheKing (21 Feb 2010)

Thanks Dave

I ended up doing what you have done with the rails, drawing one face and push/pull earlier today. Problem is there is still the tiny gap I posted earlier.

Is that because I left the rotation as it was and haven't done it the way you stated?


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## SketchUp Guru (21 Feb 2010)

Yes, I think that's the reason. In my earlier screen shot examples the leg was rotated 25° and you can see how close to the edge the guideline comes out of the face. At 5°, it would be much closer.

I think this is a good example of doing in SketchUp what you would do in the shop. I would assume you don't plan to but a compound bevel on the ends of the rails. Rather you would cut them with the blade vertical and just put a 5° angle on them. The legs would lay flat on the assembly table while you are joining them to the rail. Then you would stand the foot board and the head board up so they are leaning out at a 5° angle and install the long rails.

I wouldn't draw the legs laying on the ground plane but I would avoid the second rotation until after the foot board/head board is assembled as I did in the video. I think this makes it easier to understand where the axis of rotation should be, too.


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## Chris Knight (21 Feb 2010)

Dave,
Thanks for helping me get my head on straight! I finally realised that my thinking was being driven by the error of measuring from corners of the *tilted* bedposts. Intersecting a plane parallel to the floor and dimensioning from the contact points with each side of the posts showed that the distances were equal.

And of course , the section of the leg parallel to the floor is a rhombus but that is irrelevant.


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## mr grimsdale (21 Feb 2010)

I think that if you aim for rhombus section posts (square on plan) your construction will be easier (post and rail faces will be in the same plane with simpler angles at the joints) and the end product will be visually improved - will _look_ square, without the little toe-ins at the corners.


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## SketchUp Guru (21 Feb 2010)

Chris, I'm glad that helped.

With the foot end of the leg cut off at the floor, the resulting rhombus has angles of 89.6° and 90.4°. I doubt that most people would be able to see that it isn't square. Certainly no one would notice there's any toe in/out.


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## TrimTheKing (21 Feb 2010)

mr grimsdale":3d3snxk3 said:


> I think that if you aim for rhombus section posts (square on plan) your construction will be easier (post and rail faces will be in the same plane with simpler angles at the joints) and the end product will be visually improved - will _look_ square, without the little toe-ins at the corners.


This way way beyond my tiny mind now 
How would this work in practice Jacob? Posts cut with 2 sides at 5deg off square in one direction?


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## TrimTheKing (21 Feb 2010)

Dave R":ogov86cy said:


> Yes, I think that's the reason. In my earlier screen shot examples the leg was rotated 25° and you can see how close to the edge the guideline comes out of the face. At 5°, it would be much closer.
> 
> I think this is a good example of doing in SketchUp what you would do in the shop. I would assume you don't plan to but a compound bevel on the ends of the rails. Rather you would cut them with the blade vertical and just put a 5° angle on them. The legs would lay flat on the assembly table while you are joining them to the rail. Then you would stand the foot board and the head board up so they are leaning out at a 5° angle and install the long rails.
> 
> I wouldn't draw the legs laying on the ground plane but I would avoid the second rotation until after the foot board/head board is assembled as I did in the video. I think this makes it easier to understand where the axis of rotation should be, too.


Thanks Dave

I still can't understand why it goes out of square because I used the midpoint of the 2 bottom edges as rotation points so my basic understanding says it should still be square. I'm obviously wrong as your example (and my own errored findings show) but I really can't get my head around why.

Surely the axis of rotation is always just off vertical...

I'm getting that headache again 

PS Not watched the video yet, just going to make a coffee and will sit down and watch it.


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## SketchUp Guru (21 Feb 2010)

Maybe after watching the video, it will make sense. Coffee should help, too.


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## mr grimsdale (21 Feb 2010)

TrimTheKing":x67n5w8f said:


> mr grimsdale":x67n5w8f said:
> 
> 
> > I think that if you aim for rhombus section posts (square on plan) your construction will be easier (post and rail faces will be in the same plane with simpler angles at the joints) and the end product will be visually improved - will _look_ square, without the little toe-ins at the corners.
> ...


Yes - diamond shape (equilateral rhombus) with the long diagonal at 45º in plan across the corner if the splay is the same each way. Easier to do in the long run IMHO. 
Difficult to get your brain around I know. In fact I tried to do it by algebra and found I couldn't do school stuff anymore so had to go off and do an OU maths course (MST 121). I can do the trigonometry now, but only just!


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## SketchUp Guru (21 Feb 2010)

There is no need to make the posts anything but square.


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## mr grimsdale (21 Feb 2010)

Dave R":3eckaqmm said:


> There is no need to make the posts anything but square.


No need - but would look better and be slightly easier at the rail joints.
It's a classic text book problem - see the link to trestles I posted above.


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## TrimTheKing (21 Feb 2010)

Dave R":20zvg861 said:


> Maybe after watching the video, it will make sense. Coffee should help, too.


Certainly makes sense now Dave. I think my frustration was coming in because I initially did it the way you show but then couldn't tilt the legs and end rail at the same time, only the legs moved. Then it became clear on your video that I had only selected the leg components and not the rail too  

I was also using the midpoint as the pivot and not the axis which would have made it much easier.

I've been at this a long time, obviously couldn't see the wood for the trees.

Thanks everyone for your help on this, much appreciated. I only need to finish the bed, draw the table, wardrobe and drawers, then start making it all in time for baby to arrive in mid May.

No problem! 

Jacob - I am also interested in your rhombus thoughts, do you have any sketchup's of how it would look in practice, other than your link (that scared me when I read it first time)?


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## TrimTheKing (21 Feb 2010)

Another quick question guys (sorry!), is there a quick way to change the width between the head board posts while dragging the already drawn rails out with them? EG, so I don't need to redraw the rails again after moving the posts in or out?

The only reason I ask is that I'm not entirely sure on how wide SWMBO wants it so I'm basing it on a standard single, but wondered how easy it is to modify if she changes her mind...


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## mr grimsdale (21 Feb 2010)

TrimTheKing":17m36mro said:


> ...
> Jacob - I am also interested in your rhombus thoughts, do you have any sketchup's of how it would look in practice, other than your link (that scared me when I read it first time)?


No sorry I don't do Sketchup. I'll get round to it one day. I'm still using a drawing board.
BTW it's not _my_ rhombus thoughts, it's classic text book stuff worked over by cleverer people than me.


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## TrimTheKing (21 Feb 2010)

mr grimsdale":1824wqc3 said:


> BTW it's not _my_ rhombus thoughts, it's classic text book stuff worked over by cleverer people than me.


Yeah, I appreciate that


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## SketchUp Guru (21 Feb 2010)

You can adjust the length of the rail with the Move tool if you select only the edge at the top end to move it. The thing to consider is that you'll want to rotate, in the proper axis of course, at the bottom corner of the rail.


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## wizer (21 Feb 2010)

Well I've just sat and read all four pages of this thread totally confused, wondering all along what the problem was. Watching Dave's video, this is exactly how I would have gone about drawing this design. So er, I guess that's a good thing. 

Anyway, Mark I like the design very much. I think it's going to look great!


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## TrimTheKing (21 Feb 2010)

wizer":1yyp9qi0 said:


> Well I've just sat and read all four pages of this thread totally confused, wondering all along what the problem was. Watching Dave's video, this is exactly how I would have gone about drawing this design. So er, I guess that's a good thing.



And it was the way I drew it, except I used a black protractor at one stage instead of the red one and that's where the issue came in  

Still, good to know it was a small error and my thought process was correct.



wizer":1yyp9qi0 said:


> Anyway, Mark I like the design very much. I think it's going to look great!


Cheers, just a table, chest of drawers, wardrobe and details on bed to do now and I'm happy!!!!

Also, I might be taking you up on that turning lesson earlier than anticipated as the legs need some round detail...


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## wizer (21 Feb 2010)

I don't think 'lesson' will be the right word. I can point you to the lathe and show you how to make shavings  :lol: 

Is the rest of the furniture going to have this splayed effect? I think it'd be cool in a chest of drawers. Not sure how a wardrobe would work tho :-k


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## wizer (22 Feb 2010)

PS: Much as it pains me to say it. I think a 'rod' will be essential when building this bed. It will be much easier to take your measurements from a full size drawing. If you have access to a plotter then it's as easy as pressing print  I did it on a couple of things I've built and makes live much easier.


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## mr grimsdale (22 Feb 2010)

wizer":14ztjr7o said:


> PS: Much as it pains me to say it. I think a 'rod' will be essential when building this bed. It will be much easier to take your measurements from a full size drawing. If you have access to a plotter then it's as easy as pressing print  I did it on a couple of things I've built and makes live much easier.


Why does it pain you to say it? The 'rod' is the essential key layout system which all woodworkers need to know about. (Ignoring that trestle rod which I linked to - that is complicated - but is essential, for roof cutting especially).
Working without a rod is like having one hand tied behind you i.e. pointless and difficult.


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## wizer (22 Feb 2010)

yes yes, shut up Jacob. Sense the sarcasm.


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## TrimTheKing (22 Feb 2010)

wizer":3kzplx0j said:


> I don't think 'lesson' will be the right word. I can point you to the lathe and show you how to make shavings  :lol:


That's more than I know now... 



wizer":3kzplx0j said:


> Is the rest of the furniture going to have this splayed effect? I think it'd be cool in a chest of drawers. Not sure how a wardrobe would work tho :-k


That's the plan, but let's see how it works out...



wizer":3kzplx0j said:


> PS: Much as it pains me to say it. I think a 'rod' will be essential when building this bed. It will be much easier to take your measurements from a full size drawing. If you have access to a plotter then it's as easy as pressing print.


I agree, I think it will be absolutely necessary, my mate has a plotter so it should be possible.

And I will need to actually _plan_ before I start, which will be a novel idea for me...


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## mr grimsdale (22 Feb 2010)

TrimTheKing":25xx7rv2 said:


> ...
> Still, good to know it was a small error and my thought process was correct.
> ...


Dunno I thought the thought processes were the problem - mainly the twice rotation. You only need to tip the post once; about an axis on the diagonal of the base of the post (or anywhere else you choose according to the design - but sticking to 45º will help a lot).


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## wizer (22 Feb 2010)

You probably won't want to hear this, but last night after reading this thread, I started thinking that some garden planters would looks good with this design..... :lol:


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## BradNaylor (27 Mar 2010)

I have to confess that if I was making this I wouldn't bother with getting the drawing right at all - I'd just start hacking at bits of softwood and nailing them together until I had some sort of prototype to make a rod from...


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