Need measurement help - Woodworking Talk - Woodworkers Forum
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post #1 of 9 Old 05-01-2016, 09:32 AM Thread Starter
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Need measurement help

Hello! I am building a tennis backboard out of wood and need help determining how long the base supports should be and also the angle and length of the leg supports. The "backboard" is a 90lb 8' x 4' sheet of mdf. I'll be using 2'x6's for the base. The total height will be 6'10". It will sustain force of a tennis ball being hit against it and I want to make sure that it will not tip over! I've attached a drawing-sorry for the unprofessional quality! Thanks in advance!
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post #2 of 9 Old 05-01-2016, 09:45 AM
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It's difficult to say how long to make the base pieces. I'm assuming this will be used outdoors. Under normal circumstances you could make it 16" and it would not turn over. Wind will be the issue. Under a high wind 8' may not be enough. I think I would glue and screw the frame together and use a base 48" long. This should be enough that it will only turn over occasionally and strong enough it can just be stood back up. The highway department puts sacks of rocks on the bases on their temporary signs. If you could do that it would cut down on the wind turning it over.
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post #3 of 9 Old 05-01-2016, 09:51 AM Thread Starter
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I will have locking casters under the supports to roll in and of my garage. Wind should not be an issue! Is there a rule of thumb for base length to height? Thank you!
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post #4 of 9 Old 05-01-2016, 10:04 AM
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Indoors or outdoors?

Wind is definitely a factor if it's on casters per your drawing:


It's tippy enough just standing there with 90+ lbs 3 ft above the floor. I doubt if the force from a 100 MPH tennis ball would have any effect, since it's just a split second application, not continuous unless it has a propensity to tip from the gitgo.

Casters will make it more difficult to hold down with weights, unless they are sandbags. You shouldn't need more than one 40 LB on either front leg. JMO. a WAG.:smile3:

I would move the legs inward on either side to about 16" from the edge to stiffen the particle board. The "feet" should extend front and rear about 24" for maximum stability.... another unsubstantiated guess, just based on some real world experience moving 4 X 8 sheets of plywood and particle board in the wind.... You may want to put a rudder and some steering wheels on the unit AKA Red Green style, in case it gets moving down the road, you can jump on and sail into town, wind powered.
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The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #5 of 9 Old 05-01-2016, 10:04 AM
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I think 48" would work fine for you then. If there is anything you could do to make the bottom heavier that would help. Right now the design is very top heavy.
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post #6 of 9 Old 05-02-2016, 01:39 AM
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MDF is a very bad choice. Your design won't work. You will need a frame to attach the sheet to, not just the sheet nailed to two uprights. Tennis rebound walls are not flat, they usually have a dual curve so the balls bounce off correctly rather than go down. Have you considered a rebound net, inexpensive and a lot better than than what you have drawn, no offense! http://www.tennisexpress.com/oncourt...bound-net-6515
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post #7 of 9 Old 05-02-2016, 06:58 AM
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Quote:
Originally Posted by Hammer1 View Post
MDF is a very bad choice. Your design won't work. You will need a frame to attach the sheet to, not just the sheet nailed to two uprights. Tennis rebound walls are not flat, they usually have a dual curve so the balls bounce off correctly rather than go down. Have you considered a rebound net, inexpensive and a lot better than than what you have drawn, no offense! http://www.tennisexpress.com/oncourt...bound-net-6515
Quite interesting. I did not realize that there was such a thing. Is it a tightly strung net so that the balls are returned to the player?

If this net has a realistic rebound it would be far more practicable than a big heavy backboard.

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post #8 of 9 Old 05-03-2016, 09:42 AM Thread Starter
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Never say never! The concept drawing was just that, concept! The project is almost complete-just need to finish the paint! There's an 8 degree back slope consistent with most portable equivalents on the market. My daughter is used to hitting on the flat walls you would find at most tennis clubs, so she's enjoying the deeper loft return. Casters lock in place and held the board in place with no problems! Thanks to everyone for input!
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post #9 of 9 Old 05-03-2016, 10:05 AM
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I would also add, a bit in hind sight, that the length of the "supports" is dependent on how much weight you can get down low. Thus, lowering the center mass. the force from wind and tennis balls would then sort of "act" through the center of mass. So, if you find your current board to be a bit unstable down the road, adding some weight down low can only benefit you.
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