How would you make a barn star?

[Agent_zed]

Hi,

I was thinking of making a 'barn star' (one of these if you don't know what they are https://en.wikipedia.org/wiki/Barnstar#/media/File:BarnstarProud.jpg) for decoration on the mantel, as I don't have a handy barn to affix one to.

They are often made of metal but I've seen them made of wood. Metal is relatively easy to do but I was thinking about the wooden version and wondering how on earth I'd cut all the angles.

There must be a trick to it.

Any thoughts how to do this safely? I'm assuming using a table saw.

 

[ChaiLatte]

Throw some proportions on the picture to which you link and we can 3D model it and tell you the angles.

Call the diameter of the circle that passes through the points 1. Then you need to supply the diameter of the inner circle and the height of the centre (so give us two numbers that are between zero and one).

You could cut everything square and use a jig on a sander to form the bevels.

 

[niall Y]

A way to do it from the point of view of making it easy, would to fabricate all the points by first mitring their edges and gluing them together to form a series of tent like structures, slightly over length.

The slope can them be marked on base and cut and planed away to form the sharp points. Reinforcement in the shape of triangular pieces , can be added to stiffen the structure of the separate pointed arms.

These pointed arms can them be marked and mitred with their internal mitres on a chop saw. If you have slightly over length pointed arms, then you can have a few practise cuts to get it right - bearing in mind that any discrepancy in the angle will be amplified by a factor of 10, In fact it might be expedient to fit these onto an accurately drawn plan. ( just as with building model aircraft ).

 

[Agent_zed]

This is the metal example I've seen https://www.instructables.com/Metal-Barn-Star/ which hopefully gives some ideas of proportions.

I hadn't thought about it til you mentioned that where all the points intersect will be a vertical cut. I was thinking it was more complicated at that point.

I think planing or sanding would take too long.

I've been thinking it though a bit more and wondering about cutting all the centre vertical angles then on using jig on a tablesaw that holds each piece of the star at an angle so that the centre of the point to the outside edge is cut and with the blade tilted over it should cut the correct angles. Then turn it around to do the other side. If that makes sense.
It could be screwed to the jig from underneith to hold it in place.

 

[niall Y]

That sounds like a goer, if you screw the individual pieces to a large board to keep your hands well away from the canted blade. You can then run it off the fence, The only problem will be that the off-cuts might rest on the blade and fire off at you - so best wear a visor.

 

[ChaiLatte]

Once you decide on proportions (proportions, a scale model, no need to use absolute measurements), you could make the star from folded paper and measure the dihedral angles. You can also make a tetrahedron of 1/10 of the star, which will also help with the set-up for cutting.

You could also 3D print one of the same proportions and measure the same. You could slice up a 3D printed item and use it to set the blade angle in the saw.

 

[stuckinthemud]

The basic shape for each arm is a simple diamond meeting to form The “solid” centre as a pentagon. Shouldn’t be hard to draw at full size by stepping dividers around a circle to create that hexagon. Lots of videos out there but one short cut is to divide the circumference (3.4 x diameter) by the number of steps (5) to give the measurement for the dividers.

 

[ChaiLatte]

Shouldn’t be hard to draw at full size by stepping dividers around a circle to create that hexagon.

Hexagon, pentagon, tomato, potato.

Where I live, we must be on hard times as my local pi's are only 3.14, not the full fat 3.4 ones you have.

There is an exact compass-and-straightedge construction for a pentagon (72 degree angle), known for 2000 years.

 

[Cabinetman]

If you were to draw a circle then without altering your (beam) compass mark off around the circumference it will give you all the points. Schoolboy geometry, eventually it comes in handy!!
I live most of the time in Pennsylvania and know those stars well, often on Amish Barns, they’re the ones who speak in a German Swiss language with English as a second. They aren’t allowed by their religion anything very modern, so you see them driving around in horse drawn buggies, covered over like black boxes ( but with LED lights on the back) no buttons allowed so all the men have homemade trousers and braces. All the men have beards but no moustaches and they all wear straw hats. The women wear print dresses and bonnets.
No Electricity allowed and life is quite hard especially for the women who are chosen for child bearing and hard work, definitely not looks. ( think about Darwin’s theory and the effect is noticeable):
They are very self sufficient (and successful) and come the great reset life will probably go on pretty much the same. The women are now allowed mobile phones but only for emergency use after a tragic attack recently.
Some have specialised in furniture making and it’s quite highly prized, but rather ashamed to say I know very little as to how they go about it! Time I found out.
Ian

 

[stuckinthemud]

Everything is better with pi . I stand corrected, too tired for mathematics, quite correct, pentagon, hexagon for 6 pointed star, pi is an infinite number starting 3.14159. 3.4 is very wrong, clearly forgot the tenth, don’t use it! Round it to 3.14 though you may still have to fudge things a little bit…and yes, there are many ways to construct the shape, and I actually enjoy the process, but some don’t and the divide the circumference is a great short cut, especially if you don’t have a protractor nearby, whereas for a hexagon, stepping the radius around the circle is much the quickest way…..,

 

[Orraloon]

As everyone is pointing out its geometry innit. 2 circles on the same center. 360 divided by 5 to get angle between the points. Decide on thickness of disc and everything slopes down from the common center point. After marking out my choice of weapon would be a japanese pull saw. Please dont try it on a tablesaw. Very dangerous and as its a round blade I cant see it as even possible.
Well now I am going to contradict myself. There is a flat 2D one you can do in the tablesaw made from 5 bits of wood.

Project Idea: Barn Wood Star | Andrew Morgan
Regards
John

 

[Agent_zed]

As everyone is pointing out its geometry innit. 2 circles on the same center. 360 divided by 5 to get angle between the points. Decide on thickness of disc and everything slopes down from the common center point. After marking out my choice of weapon would be a japanese pull saw. Please dont try it on a tablesaw. Very dangerous and as its a round blade I cant see it as even possible.
Well now I am going to contradict myself. There is a flat 2D one you can do in the tablesaw made from 5 bits of wood.

Project Idea: Barn Wood Star | Andrew Morgan
Regards
John

hmmm, that doesn't look too bad as just a flat version. Might try a few different versions and see what comes out best.

With a tablesaw I'd use a jig and each piece would be screwed down so shouldn't be dangerous as hands will be well away from the blade. The only bit that might cause an issue is the offcut but standing to the side should mitigate the danger of being hit by that.

 

[stuckinthemud]

Just for completeness, since tinternet is forever, I tried for hours this morning to step a compass around the circumference and failed until I realised you open the compass to 1/5 distance as measured on the circumference, not as a straight line - 11.3cm along the circumference is not the same as 11.3 cm off a ruler

 

[Deadeye]

Just for completeness, since tinternet is forever, I tried for hours this morning to step a compass around the circumference and failed until I realised you open the compass to 1/5 distance as measured on the circumference, not as a straight line - 11.3cm along the circumference is not the same as 11.3 cm off a rulerView attachment 184629

Have a look at this - it's a more accurate way than I think you used?

 

[Richard_C]

As everyone is pointing out its geometry innit. 2 circles on the same center. 360 divided by 5 to get angle between the points.

For any regular polygon in a flat circle the sum of the External angles is 360, so what you need for the internal angles is 180 - (360 / number of sides). For a pentagon it's 180 - 72 = 108. Do a sense check for yourself by working it out for a triangle, square and a few others. Triangle is 180 - (360/3) , so 60. Square is a special case, external equals internal.. Internal angle of an 18 sider would be 170.

Halve the angle to make the cuts. Back to the square example, 2 pieces cut at 45 give you a picture frame.

Can't help with any 3d ishness, too hot for brain to function clearly. In anything more than 2 dimensions.

 

[stuckinthemud]

There are many, many, ways to plot a pentagon but most use a protractor. Not every workshop has one to hand. This method only needs a way to draw a circle (circle, piece of string, mug, bucket - anything circular) and a ruler to find the diameter and count around the first arc of the circumference. It is in fact very accurate when you take time to do it right, plotting off a protractor is not as easy as you might think. As part of my indulgence this morning I constructed, using ruler, compasses and protractor, off a straight line, off a centre point (72 deg) and around the circumference (108 deg). None were as satisfactory as stepping off at 1/5 of circumference.

Anyway, draw your diagram, based on a pentagon to produce the star. Cut out one of the arms to give a kite or diamond template running from the centre of the star to the tip of the arm. Cut out 5 of these from your chosen timber, grain running along the length, not across. Plane a slope from full thickness at the inner end to a few mm thick at the outer tip. Mark a centre line along the length. Chamfer each side to a few mm thickness. Join the parts and finish

 

[Limey Lurker]

Does this help?

 

[stuckinthemud]

That’s useful, I’ve not come across that before, Thankyou

 

[HOJ]

Managed to draw one, no idea how to make it though.

 

[John Brown]

Not 3D, but may be helpful in some way...