DIY Light Fixture Help

[ellebelle]

I am considering just buying a shell, but if possible I'd kind of like to make a hanging light fixture out of some of the leftover birch plywood I have.

Basically, I want something that will be a hard shell for my PFO parallel reflector. I want it to be in the shape of a trapezoid with the two longest pieces flaring out, and then the sides flat down.

Here is my concept, but I think I'm not getting the measurements right. Any help all of you DIY savvy people could give me would be appreciated. I want to go get my wood cut for this this weekend.

 

[LeslieS]

Lissa, if you make the top 12" and the bottom distance 14", it is going to be a very slight trapezoid. If you want the piece to look more like your picture, you should increase the difference between the top and bottom.

 

[FRY]

if the side on the end is10 inch then the 8 inch on the side is wrong its going to be longer then 10 inch ,allow for the slope and miter cuts

 

[ellebelle]

Okay, assuming that the width of the top piece is 10inches (I re-measured), the question is .... (drumroll)

How long do the sides need to be on the long pieces?

And how long do the sides need to be for the ends?

I feel like I learned this in geometry many years ago. :sad2:

 

[bad coffee]

how tall do you want the end pieces?

if the whole thing is 10", then your sides are 10" plus the cuttoffs for the angles top and bottom.

at 10" the angle is 5.71, btw

 

[meschaefer]

On the sides, is it 10 inches from top to bottom, or is the width of the side wood ten inches?

 

[ellebelle]

The top would be 36 x 10".
The sides would be 36 x ?"
The ends would be 14" x ? x 10".

Brett, are you saying that that angle isn't right? Or that that would be my add-on.

 

[ellebelle]

Wait, if the bottom is 14" and the top is 10", then the sides have to be somewhere around 10.2in ... right? but will of this work with a 45 degree mitre cut?

 

[bad coffee]

45 is way to steep of a cut.

If you're not completely set at 10" height (like you can go 1/4" either way) then cut your sides first. Set the table saw to 6 degrees and then cut your long sides with the angled cuts top and bottom.

Once you have them, measure from point to point and make your end height. cut the height of the piece, then measure from center top and bottom to find your side corners.

Or, you could just take a piece of wood, cut it 10 x 14. then take the top and measure 1" in on either side. Then connect with the bottom corner, and cut the trapezoid. Then measure for the front and back.

B

 

[ellebelle]

Here's the problem - I can't cut the wood myself. I have to take it to century lumber to be cut - that's why I'm trying to figure out all of the side lengths and angles exactly. I have a circular saw but I would not trust myself to use it. I certainly don't have a table saw.

 

[bad coffee]

if you make the front and back 10 1/2, they'll cover the top and bottom of the sides so you won't have to cut angles.

 

[meschaefer]

If the top is 10 inches wide and the bottom is 14 inches wide and the entire thing is 10 inches tall, then the width of the side needs to be 10.77 inches

The miter cuts wont be 45 degrees either, I think it will be a 9 degree miter.

Somebody else should check my math, its been a long time since I did this type of calculation.

 

[bad coffee]

pssst. the top is 12"

B

 

[jhale]

isn't this the hood I told you I would make for you?
I can't do it this weekend, but next week should work.

 

[masterswimmer]

isn't this the hood I told you I would make for you?
I can't do it this weekend, but next week should work.

I like Jon's calculation. :idea:

BTW Lissa, if you were to use 45 degree angles, then the calculation becomes VERY easy. You would use the Pythagorean Theorem. We use what's called a 3, 4, 5 triangle in construction all the time. One leg is 3", one leg is 4" and the hypotenuse is 5". You can use any multiple of this to come up to the desired lengths. THIS ONLY WORKS WITH A 90 deg and two 45 deg angles in the triangle.

 

[Aqua Pro Builder]

Here is the diagram you need, if I understand your requirements correctly. You can just show the lumber yard the diagram. I am assuming you said looking form the side: height must be 10", and bottom must be 14" and the top 10" wide. If not, tell be again what's the dimension and I can redraw another one for you.

I will be around 86st and York Ave tomorrow or Monday, If I carry a table saw as well. I can help you cut them.

 

[ellebelle]

isn't this the hood I told you I would make for you?
I can't do it this weekend, but next week should work.

You said you were really busy, and I didn't want to take advantage of your generosity :happysad:. So don't you roll your eyes at me! In my head, it seemed really simple - I just figure out the measurements, take it to the lumber yard (three blocks away) and nail it together. I have nails, and wood filler and wood glue and clamps and all of that stuff.

Was more difficult when I put theory into practice :sad2:

 

[ellebelle]

BTW Lissa, if you were to use 45 degree angles, then the calculation becomes VERY easy. You would use the Pythagorean Theorem. We use what's called a 3, 4, 5 triangle in construction all the time. One leg is 3", one leg is 4" and the hypotenuse is 5". You can use any multiple of this to come up to the desired lengths. THIS ONLY WORKS WITH A 90 deg and two 45 deg angles in the triangle.

That's how I came up with my side length in a previous post - 10" and change.

 

[jhale]

ok if you don't get it done this weekend lmk, it would take me about an hour to make.

 

[masterswimmer]

Lissa, not that you're using the method I described, but I need to correct my triangle angles. The 3, 4, 5 triangle only works on a 30, 60, 90 triangle. My bad :banghead:

swimmer