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Old 04-16-2012, 05:35 PM   #1
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Which beam is stronger?


Hi,
For my kids playset I am trying to overbuild the swingset portion.
I see many designs with 4x6 as a swing beam. I saw a DIY swingset with 4, 2x10's bolted and glued together.

The only thing that bothers me is that 10" is quite a long way to drill through with my basic tools and drillbits.

I was thinking a more manageable 4x6 to drill through (not as critical to have it perfectly centered either).

To beef up the 4x6, could I sister a 2x10 on either side? Would the beam act as a 2x10 in the downward movement??
I am hoping to have the strength of a 2x10 without needing the precision, and the dill bit, to drill thru a 2x10.
Thanks!

This is what I was thinking....
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Old 04-16-2012, 05:39 PM   #2
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Which beam is stronger?


Yes what you are proposing would be stronger than a 4X6. would not be as strong a 4-2X10's.
Beams are much stronger in depth then width.

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Old 04-16-2012, 05:56 PM   #3
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Which beam is stronger?


I suspect you could also considerably stiffen the beam by laminating (glue-n-screw) exterior-grade plywood (10" nominal continuous strips) to the 2x10s in your design. It will only increase the beam width by 1" or 1.5" but make a big difference.
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Old 04-16-2012, 06:20 PM   #4
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Which beam is stronger?


Wouldn't it be difficult to precisely drill thru a 2x10 for a carriage bolt with a handdrill and typical drill bits?
Or am I fretting over nothing?

Wouldn't 4, 2x10s be as strong (vertically) as 6, 2x10s or 2, 2x10s??
I thought the vertical dimension was the important part?

My purpose is to get typical available lumber, i.e. a 4x6, and not need to buy a specialty drill bit to go thru a 2x10. Plus make it a strong beam.

Would the plywood strips help because they are sheets with opposing grain laminated together?

Thanks!
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Old 04-16-2012, 07:34 PM   #5
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Which beam is stronger?


Quote:
Originally Posted by D270
Wouldn't it be difficult to precisely drill thru a 2x10 for a carriage bolt with a handdrill and typical drill bits?
Or am I fretting over nothing?

Wouldn't 4, 2x10s be as strong (vertically) as 6, 2x10s or 2, 2x10s??
I thought the vertical dimension was the important part

My purpose is to get typical available lumber, i.e. a 4x6, and not need to buy a specialty drill bit to go thru a 2x10. Plus make it a strong beam.

Would the plywood strips help because they are sheets with opposing grain laminated together?

Thanks!
Your idea will work due to mass because u cant precisely drill through a 2x10 n by the way u can never over do a project especially if it for your kid(s) cuz u obviously want to keep them safe but just a tip if u do go through with it finish boxing it up with plywood or something jus do it covers the bolt and makes it look nice ya no
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Old 04-16-2012, 07:42 PM   #6
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Which beam is stronger?


A simple cheap 1/2" paddle bit would do the job and for what your doing it does not to be precise as you suggested.
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Old 04-16-2012, 08:17 PM   #7
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Which beam is stronger?


Quote:
Originally Posted by D270
Hi,
For my kids playset I am trying to overbuild the swingset portion.
I see many designs with 4x6 as a swing beam. I saw a DIY swingset with 4, 2x10's bolted and glued together.

The only thing that bothers me is that 10" is quite a long way to drill through with my basic tools and drillbits.

I was thinking a more manageable 4x6 to drill through (not as critical to have it perfectly centered either).

To beef up the 4x6, could I sister a 2x10 on either side? Would the beam act as a 2x10 in the downward movement??
I am hoping to have the strength of a 2x10 without needing the precision, and the dill bit, to drill thru a 2x10.
Thanks!

This is what I was thinking....
How is 4-2x10s...10"?
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Old 04-16-2012, 08:49 PM   #8
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Which beam is stronger?


Quote:
Originally Posted by Joe Carola View Post
How is 4-2x10s...10"?
Because he building a swing he's goin to bolt it so he wanted to drill it upward not through you understand so his idea of sistering 2 2x10s on each side of a 4x6 is good enough cuz it will be solid and hold a good amount of weight n will last for his kids for a long time to come
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Old 04-16-2012, 08:52 PM   #9
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Which beam is stronger?


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Originally Posted by joecaption View Post
A simple cheap 1/2" paddle bit would do the job and for what your doing it does not to be precise as you suggested.
Ya but me personally would use 1/4" because some of the hook or whatever you would call it I can't really find a huge selection But 1/2" would to if you can find one
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Old 04-16-2012, 10:37 PM   #10
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Which beam is stronger?


Quote:
Originally Posted by D270 View Post
Wouldn't it be difficult to precisely drill thru a 2x10 for a carriage bolt with a handdrill and typical drill bits?
Or am I fretting over nothing?
You don't need to drill precisely through the 9-1/4" of distance in one single 2x10. Think of the four fastened 2x10s as a single block of wood. All that matters is that you start drilling through the top (or bottom) and you come out the other side, and that the resulting hole is mostly vertical. You're going to have a washer and nut holding the through-bolt in place.

Quote:
Wouldn't 4, 2x10s be as strong (vertically) as 6, 2x10s or 2, 2x10s??
I thought the vertical dimension was the important part?
Absolutely not. You're getting confused with the fact that increasing the depth of a joist or beam is more effective than doubling up. E.g., a 2x12 makes a stronger and more rigid joist than two 2x10s.

Quote:
My purpose is to get typical available lumber, i.e. a 4x6, and not need to buy a specialty drill bit to go thru a 2x10. Plus make it a strong beam.
You just need a long bit. That's not too difficult to find, especially in the age of the internet.
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Old 04-17-2012, 06:53 AM   #11
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Which beam is stronger?


Quote:
Originally Posted by ninjahero

Because he building a swing he's goin to bolt it so he wanted to drill it upward not through
Ok....all he has to do is buy a long drill bit.
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Old 04-17-2012, 10:42 AM   #12
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Which beam is stronger?


I do appreciate all the feedback. Lots of good perspectives. I mis-spoke when talking about 10" to drill through...all lumber is smaller, of course.

My thought about the lamination was what if I drill through the one 2x10 crooked and come through a seam?

Maybe it doesn't really matter??



Would adding anything to the width strengthen a beam in the downward deflection? I'm still confused...below is what I was talking about.
Thanks, lots to think about.

D.
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Last edited by D270; 04-17-2012 at 10:51 AM.
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Old 04-17-2012, 11:28 AM   #13
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Which beam is stronger?


Three 2 X 10's would be more then enough.
It does not matter if you hit a seam.
Just make sure not to drill where there's a fastner.
You will need a 12" long bit. A paddle bit would be less then $10.00 and would have a small enough shank that even a small drill will hold it. As you drilling keep back it out to clear the chips.
1/4" would not barly be strong enough for a plant hanger, use 1/2 instead.
You will need a lifting eye not a reguler eye bolt.
A lifting eye has a one piece eye, it's all cast as one piece.
A reguler eye eye bolt is just a streight rod that has been bend to form the eye and can open up over time.

Last edited by joecaption; 04-17-2012 at 11:37 AM.
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Old 04-17-2012, 11:29 AM   #14
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Which beam is stronger?


You are confused about the definition of the word strength. The strength of a beam refers to the load the beam can carry before it fails. Strength does not refer to the deflection of the beam, that is a different item. In typical residential applications, beam strength is computed based on the maximum allowable fiber bending stress on the beam, which means how much stress the edge of the beam experiences when the beam is loaded.

The strength of the beam depends on three factors:

1. The maximum allowable fiber bending stress. This varies with the species of wood, and can be as low as 800 psi, and as high as 2,500 psi, depending on the species. For most construction grade wood, the maximum allowable bending stress is around 1,000 psi.
2. The moment of inertia of the beam. The greater the moment, the lower the fiber bending stress, and the stronger the beam. For a rectangular beam, the moment of inertia is b*d^3/12, where b is the width of the beam, d is the depth, and the ^3 means cubed. so if you double the width of the beam, you double the moment of inertia, and the beam is twice as strong. If you double the DEPTH of the beam, the moment of inertia is 8 times as big, and the beam is 8 times as strong (but see note three for the whole story).
3. The distance from the centroid of the beam to the edge of the beam. Stress is directly proportional to the distance, so a beam twice as deep carries twice the stress; however, the moment of inertia is 8 times as big, so doubling the depth of the beam increases strength four times.


Conclusion is that sistering a second beam of equal size onto the first beam doubles bending strength. Doubling the depth of the beam increases bending strength 4 times. Note that this discussion is about BENDING STRENGTH only. These conclusion DO NOT apply to vertical and horizontal shear, torsion, and tear through of the nut holding the support. But this is not a course in structural mechanics, so let's leave it at this for the moment.
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Old 04-18-2012, 10:10 AM   #15
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Which beam is stronger?


Doesn't need to drill at all. Notch the center 2x10's will a saw before making the beam. Nice even straight hole.

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