Quick Gate Question

Silly boy,

This has nothing to do with engineering. This question has only one solution and it should be obvious even to a bookish chemist such as yourself.

Let me explain. There are two words here that say it all, and will relieve you of any blame in the future. Those words are: "She wants"

No amount of scientific data, reasoned explanations from experts nor graphs and pictures will ever overcome "She wants".

She knows what she wants, and that's all there is to it.

">2 feet apart" and that's it.

Dear Rocknroll99,

Grow a set of big ones, and then tell her that the closer the diagonal strut pieces are to 45 degrees, the stronger and stiffer the gate leafs will be, even if this increases the horizontal spacing distance between the two backer boards.

Blame me if you have to....even show here this post. Ask here what is more important here: longevity, stiffness, and strength or pretty? From the street side, you're seeing mostly the vertical pickets and not much of the backer boards and diagonal stiffeners.

As an alternative to the wooden stiffeners in each gate leaf, use 1/4-inch threaded stainless steel rod with a turnbuckle located in the center and anchorage hoops at the ends for the wood screws......then paint it white like the rest of the picket fence. You'll hardly notice the diagonals then!!!!

Important tip! When installing the SS diagonal rods or wood struts, make sure the lower end is at the bottom where the gate leafs come together, and they end up at the upper backer board and leaf hinge. This arrangement will induce tensile loads in the diagonals and will permit turnbuckle adjustments up and down of the leafs where they meet!

I have these arrangements at all of the wooden fence gates on my property...one gate is 12'foot wide.......soon (next week) I'll be replacing the 550 feet of 6' wooded stockade fence that's nearly 20 years old and will be employing this very gate design in several locations for access to the back yard.

Good luck growing a set of brass BB's and convincing your "Better Half" my friend! LOL

===Signed,

CaptMoosie, Structural Engineer/ LPE

Ignoring the marital advice, I agree with this comment. Here are three suggestions to deal with the technical issues. I am not going to distribute marital advice. After 25 years of marriage I still haven't figured it out.

If you add additional fasteners at all the connections of fence pickets to horizontal braces, and space these fasteners apart at each connection, they will help resist the moment caused by the hanging gate.

Another option is to forego the wooden brace (which as previously stated is in compression) and add a wire element from the top of the gate near the post to the bottom of the gate at the edge that contacts with the other gate. This arrangement will put the wire in tension. Wire in tension is much stronger than wood in compression. If you add a threaded coupler to the wire, then it is also adjustable. So over the years when the gate sags you can tighten the coupler and lift the fence back up. With the wooden brace, all future adjustments have to be made by removing the brace and repositioning it. This wire element can be (should be) painted white. If the angle is low that is okay because wire in tension is so much stronger than wood. You will want to make sure the wire to wood connections at either end of the wire are sturdy.

If you like the wooden brace but find the length of the gate is not conducive to installing the wooden brace at an angle that will resist sag due to moment (i.e ratio of height of gate to length of gate is relatively small) you can add two or more braces to the same gate. That is, connect a brace from the bottom of the gate near the post to the top of the gate near midspan. Then connect another brace at the bottom of the gate near midspan to the top of the gate at the edge where the gate contacts the other gate. This creates sort of a truss. Wish I could draw this to explain it.

Anyways, I hope these ideas assist you.

If and only if you've already fabricated the gate the way you thought was correct do you have any argument at all. But you will still lose this argument. I recommend that you ask her to help you fabricate the gate the way she wants the gate built. This way she will be working with you. As complications happen in this fabrication, she'll be there to decide how to resolve the complications. The only way you might win this aesthetic discussion (argument is too confrontational ) is if her preferred design falls apart. If this happens you want her to have been with you during design and fabrication process.

Your actual problem is not a structural design, chemistry or any other engineering problem. The problem is an ancient societal problem that happens at times between any two people (living?) together of any combination of sexes. She was upset enough with your approach that she mentioned her displeasure. DO NOT DISMISS THIS COMPLAINT.

rocknroll99,

I will confine my comments to engineering aspects of the problem as I am not an expert in 'de man and de woman' aspects.

If each leaf of the gate weighs 'W' and has length 'd', the moment on the support post is Wd/2. If the supporting hinges are centered on the horizontal boards and are separated by height 'h', the horizontal reaction top and bottom, 'H' is H = W*d/(2*h).

If the diagonal brace makes an angle β with the horizontal, the compression 'C' in the brace is C = W/(2sinβ).

If the weight of the gate leaf is carried equally by the top and bottom board, the vertical reaction at the post will be W/4 on the top hinge and 3W/4 on the bottom hinge.

As the gate is opening and closing frequently, perhaps being slammed periodically, it may be wise to multiply all hinge forces by a factor of 5 when designing the fasteners.

I like the diagonal the way it is. The diagonal is in compression, and a barn makers trick of setting the diagonal into a notch in the horizontal will be even stronger. All too often builders will expect fasteners to hold loads that proper engineering would put on the lumber. The wood should do the work, the fastener only keeps it from falling apart.

As far as spacing between the horizontals. if they are too close together, the pickets will warp all over the place, and the fence will not be straight along the top or bottom. The only way to win this one is to find one done her way and see if it stays straight. Once the pickets warp, the whole fence will have to be replaced.