Making a 15ft radius dish part 2 of 2
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- Опубликовано: 13 апр 2017
- I'm making a radius dish for sanding curves into the profile of guitar braces and for using as a clamping caul for the braces.
In this video I do the actual routing, having set my rig up in the previous video. I also use an elegant piece of mathematics to show that my dish is perfectly spherical.
Part 1 is here: • Making a 15ft radius d... 
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So glad I found your channel.
Great videos Susan.
Okay, that was awesome. Great video.
loove your shoes lady!!
also really liking your part two video.☺ i like the way you think.👍
That's class! Top marks :)
amazing
I use a dry rot hardener on MDF after I have routed and sanded the bulk of the MDF what the wood rot liquid does is harden the MDF really well once dry I give it one more sanding and then another coat of the hardener with a final light sanding once it has dried the only one I can think of Earls here in Australia you will have to find out if you can get it there or something similar but it does work well on the MDF it gets rid of that spongy feeling that MDF gets when carving
thank you
A beam sticking out above a 1st floor window like a Dutch house would get you to about 20ft, and with a pulley on it would be handy for getting that piano upstairs.
What an awesome project Susie! Thanks so much for sharing. I'm a joiner and I work with MDF a lot and I agree it probably wouldn't be best for this application. As you're building something that is effectively a tool, a hardwearing surface is key. Possibly a higher grade plywood, like a birch plywood with no voids would be good. Another Idea might be to consider a plastic material. Cutting boards make good tool surfaces. If you're able to get one thick enough and cheap enough (Google is your friend) then they cut well with normal woodworking tools.
+Alex Howard Nice ideas Alex. I've purchased some MDF already so I'll try that first. I'll varnish, sand, varnish the surface to see if it stabilises it. One idea I've had suggested is to use thin MDF and bend it into a spherical surface, held with screws. I'll try routing thick MDF and we can all see how durable it is when varnished.
Susan Gardener MDF tends to get softer on the inside the thicker your material is. Laminating thin sheets might get you far better stability.
BTW: Really love your work, your videos make me smile every time 😀.
Awesome, will be very interesting to see how the mdf works out. Something else I've tried in the past is to use car body-filler. If you make the cuts, leave it in position whilst you smear the filler on nice and thick, working it into the mdf pores, then take the final cut again and you can get quite a passable surface. Also, I've noticed that thinner mdf can be more dense, laminating will probably give more solid material. Once again, thanks for sharing, looking forward to the next instalment! :-)
MDF soaks up so much varnish it isn't funny. After 10 coats of PU it was still sucking it up. There's a sealer you can put on first but I haven't tried that. Your drum sander must generate a lot of wood flour. Mix that with glue and you can fill the voids in the plywood.
+MattOGormanSmith I had thought about the wood flour filling, but I'm a little wary of getting a spherical surface true - laziness might win out here :-)
Hello Susan. I have worked with a material called "REN" (Polyurethane Tooling Board) I don't think Ren is a brand name but more of a material name. But it is a Polyurethane Tooling Board used in mold building industry. You would use it to machine on CNC machines to make a model of your part. It comes in different density and can be coated like with lacquer to give a smooth finish the coating would just keep any glue from sticking to it. I don't know if available in the UK. Look it up online it may work for your model. Very stable product.
Nice work Susan.
I missed an opportunity there didn't I, I should have started with first.
Symon Fobbester You'll get over it lol.
On your larger radius dishes you could use a horizontal plane rather than a vertical, just bolt a cable to wall on one end and router on other.
My MDF radius dishes have lasted for years. What happens when you make a dish from MDF is that the machined surface has tension released and the board cups. Screwing and gluing a backing board sorts this out.
That's a pretty cool project, and several thousand times more elaborate than anything I think I would ever undertake for bracing, but I like that you strive for perfection.
A little comment on your test though: Even if the test bowl doesn't rock there might still be low spots in the surface of the dish.
If you want to check it even more accurately then you could do it in a dark room, put a bright electric tea light (or something similar that is squat, stable and shines its light in all directions equally) roughly in the middle of where you put the plastic bowl down. There's probably going to be a thin sliver of light coming out all around the edge of the bowl but if there are spots that let out considerably more light then that's a low point.
+PikkaBird it was pretty accurate- I did check the edge of the bowl and it was flush to the dish everywhere- you can just about see that in the video. I like your idea of putting a light inside the bowl though - I'll try that on the next one, where I suspect I'll have some issues.
Oh I absolutely trust that the result was perfectly fine, it was just a suggestion to take a little more of the guesswork out of the equation and maybe speed up the test.
I am definitely looking forward to seeing you use the dish and get on with your guitar project.
Sue-perb!
Who needs a CNC to create great curves!!! lol Nice video as always.
Wow! It totally worked... Just watching you build this made me want to make one for you on my CNC and send it to you! Lol I wonder what the postage would be from Texas to the U.K. for that thing? 😀
+bucknaked31 My method's more fun though :-)
look at chris pollucks not sure his name is spelled right but he uses a long compass method. mabe you can do that for the bigger radius dish.
Susan, would particle board have worked better or is there a reason not to use it ? If that's your design it's brilliant.
Dan
Very clever and logical way of testing the result.
I noticed that when you started carving, router did not do very smooth job, but cut very randomly. Was there some slack or recoil or what caused the issue?
+Ostap1974 if you randomly push the router into the work it tends to grab and do a climbing cut along any edge it establishes. It's much more predictable to work in straight lines going against the rotation of the bit. You really have to follow the same rules that apply when using the router in more conventional ways.
Instead of MDF why not a plain poplar or pine board? Or if size is the issue, several 10" wide (which I think is a fairly standard width) boards glued edgewise, with several more glued on top of them in perpendicular orientation. Then you'd be carving into a uniform material.
Not many people have a 40 foot ceiling to play with, their must be an easier way to do that, although I cant work out how. good luck on your bigger ones. It seems a hard way of getting the back of a guitar the shape you want it.
+John Fithian-Franks but I'll be sorted for many guitars to come!
Nice work. I presume you'll make a virtual pivot linkage for the larger radii?
+Jon Allen I wondered about that but tried to figure it out myself and failed. Do you have a link on how to do it? Can you do a true sphere that way?
Any vertical 4 bar linkage will give a virtual pivot in a plane if the upper and lower bar are of different lengths (side bars equal lengths). (so eg the top outer edges of your router cradle for the bottom bar and a shorter, fixed upper bar). You then rotate the workpiece as the router cuts to give the 3rd dimension.
Been doing some playing with my lego technic, and its not quite as simple as I first thought. I'm sure its very close to an arc around the centre position (which is how you'll be using it, just a few degrees off vertical), but deviates at larger angles (from my playing >20deg from vertical becomes noticeable)
OR ...
Use a string compass to mark an arc of the appropriate radius. Use this to make a wooden template (Like a "D" shape. If the template rests on its curved face on any two fixed points and is moved left and right, an attached tool will describe an arc of the correct radius. (and as before, rotate the workpiece under it for the 3rd dimension)
OR ...
Pantograph mechanism with appropriate length linkages to trace the 15' radius to the larger sizes.
I'll stop now :)
👏🏻👏🏻😬😬
Go have a word with your local fire station and see if they will let you use their practise tower or hire a scaffold tower or scissor lift, maybe do a deal to film at a hire shop and get free use.
+Jim Porter That's the next level of engineering up from a windsurfing mast! I have some other methods to try first :-) Nice ideas though
Turning lead into gold would be much easier..lol