# diagonal member of a fence gate



## bigmike2258 (Feb 2, 2008)

hi everyone

I am building a fence gate with a 2×4 rectangular frame….....inside dimensions are 29 hi x 46 wide….........i am trying to figure out the best way to make the diagonal brace, but i can't come up with the answer…....is there an easy way to calculate that….......it's not as easy as calculating the hupotenuse…....that didn't work.
help would be greatly appreciated
P.S.--- i am trying to make 2 parallel cuts on the 2×4 29 inches apart…..but what is the angle?


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## Karson (May 9, 2006)

Bigmike:

I'd draw the gate on a piece of plywood and get your angle cuts for it. It's more accurate than doing it by math, if you are not into that type of calculations.


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## bhack (Mar 19, 2008)

Bigmike
I agree with Karson. That pencil get dull sometimes.


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## JohnGray (Oct 6, 2007)

Make the frame and lay it on the 2×4 and mark your angles.


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## North40 (Oct 17, 2007)

Build the rectangle frame, lay it on your workbench, and make sure it's square. Then lay the diagonal member (rough cut long) on the frame and take your marks right off the frame.

You probably already know this, but as a reminder for others who might read this thread: the diagonal is supposed to run from the bottom on the hinge side to the top on the latch side of the gate. This way the weight of the gate pushes down on the brace. If you run the diagonal the other way, the weight pulls down on the hardware, which is likely to cause loosening.


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## dalec (Oct 3, 2007)

Peter,

I hadn't thought about the layout of the diagonal relative to the hardware. It makes sense. Thanks for the information. Never know when this info will come in handy.

Dalec


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## brunob (Dec 26, 2006)

I agree. I'd build the frame then mark the diagonal.


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## bigmike2258 (Feb 2, 2008)

thank you all for the help…........i built the frame and then laid a long 2×4 across..marked it….cut it…....and it fit quite nicely….......i am not exactly sure what the brace is supposed to do….......i think it redudes racking and keeps the two rales parallel…......it is only fastened to the top and bottom rails…..again, thank you all for the help.


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## Catspaw (Dec 15, 2007)

assuming all joints and fasteners are tight and stay tight, the forces on the hinges are the same either way you put the diagonal. I know nobody will believe it, but it's true.

I'm thinking the placement as stated above probably compensates for the fact that things probably won't stay perfectly tight and it works alittle better that way.

either way, scribe.


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## North40 (Oct 17, 2007)

Catspaw - you are exactly right. If the joints and fasteners did not fail, the orientation of the brace wouldn't matter … in fact, you probably wouldn't even need a brace. But since wood changes shape and nails and screws may back out and joints can fail, the method I mentioned above helps the gate maintain it's shape when it's no longer new.


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## grumpycarp (Feb 23, 2008)

Two issues here. To find for the length of the diagonal (hypotenuse) the Pythagorean theorem is in play. Side A squared times side B squared = side C squared or in your case 54.3783 or there abouts.

If your #s don't work it is because your pulling them from the wrong place. Outside rather than the inside for instance. I don't know much but on the following I will be firm, the Math is never wrong. The work that has gone before is.


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## North40 (Oct 17, 2007)

I agree the math is never wrong, and the calculations would be pretty simple if you were trying to find length "A" and angle "B" ...


... however, you are trying to find length "C" and angle "D", which are difficult to calculate until you know length "E", which is difficult to calculate unless you know angle "D" ...


... there's a reason why woodworkers have relied on story sticks for so long!


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## grumpycarp (Feb 23, 2008)

If you think about it you will see that all the answers are already in your diagram. Just keep reducing, or enlarging the triangles. Find for the triangle. If you have the length "a" and angle "d" then its a trig function.

Also if you actually have the angle "d" then your cut is the reciprocal of "d" (I think thats the term) If "d" is 35 deg then the cut would be 65 deg (to net 90) the thing that hangs people up is it is measured "heel to toe" or "long to short" points.

I use story sticks all the time to transfer layout, etc. But, it is often easier to do the math when dealing with large systems, like roofs, where the mass of objects doesn't really allow for the "Cut on er till it fits" method. A 20 ft. 4×14 LVL rafter is a bugger to put up and take down, takes a lot of time, costs big bucks and annoys the crane operator. So the math. And it's just as easy to do it with the small, plus it gives an extra goof proofing layer to the exercise. I like to have my pinch sticks match what my numbers tell me. Then I know I'm still square as well.


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## ronstar (Mar 29, 2008)

You're close. The hypotenuse angle is 32.23 degrees for 29" height 46" width. This is the inverse tangent of 29/46. The hypotenuse distance is 54.38 inches. but you need to calculate the additional angle for the width of the 2×4 (3.5"). So for an additional 3.5" over the 54.38" hypotenuse, take the inverse sine of 3.5 divided by the 54.38" hypotenuse. This equals 3.69 degrees. So the total angle is 32.23 + 3.69 = 35.92 degrees


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## dirtclod (Oct 31, 2007)

I agree with everything Peter O said. I've built a number of gates for cattle. They're much more durable than what you can buy at a local farm center and can hold even determined animals in tight quarters. Just watch what happens even to a new/heavy gate that a 1200 lb cow tries to go over on the latch side when the diagnal brace is running down from the hinge. It's not only the hardware - it's the compounding of hardware. The brace compresses against the ends and picks up the hardware that hold the ends on. Therefore the brace, its hardware, and the hardware holding the ends on all work in unison. An analogy is to brace a free-standing wall with spring boards that are nailed at both ends on only one side. It holds well as long as the wind is blowing the wall toward the brace, but fails miserably when the wind blows the wall in the opposite direction.


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## North40 (Oct 17, 2007)

Grumpy - well, that was kind of my point - the original poster didn't know angle "d", and since knowing where the heel of the brace is depends on knowing "d" ... well it gets complicated. The math is certainly do-able (as ronstar showed us), and necessary in your example of large, heavy construction items, but for a gate member it seems a little much. I offer as evidence the fact that our guy already had his brace cut and installed while we were still talking about how to figure it!


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## douglas2cats (Mar 31, 2008)

Math Smath (my college major). Lay it on there an mark it but also set a bevel guage too for setting the saw cuts.


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## Catspaw (Dec 15, 2007)

i don't know….maybe if you used a GPS system you might get it.

scribe doesn't lie.

neither does a cad program.

it still doesn't matter which way you brace it….but…with respect to and in conjunction with what dirtclod was saying, you have to fasten the brace with fasteners that are perpendicular to the lines of force. if you do that, either way works just as well.

has the gate been built yet?

make it out of metal and weld it.

personally i prefer a force field generator…...still looking on ebay for one….they can be really expensive.

actually, a "math for woodworkers" forum might be kinda cool.

then we could figure out all those hippopota-mouses.

trig. is based on circles not triangles…another thing nobody will believe.

(lotsa overtime lately….i'm just in a mood. just feeling silly and thot i'd try to be funny.)


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## Grumpy (Nov 9, 2007)

BigMike, You can only build it a bit at a time. When you come to putting on the braces you will be able to measure where they fit & the angles will be obvious.


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