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Bracing my MDF box ?


momofx76

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I thought that resin would help with stiffening my mdf box for 2 15's but I noticed one of the seams got a hairline crack in it today. Will bracing with a 3/4" threaded rod (side to side, front to back) and some 1" dowels (top to bottom) help strengthen this box after fixing it? Will this also help with spl? Thx!

Box is tuned to 38Hz and approx. 7.7 cu. ft. net with triple 6" aero's

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Pics?

Resin alone will do nothing for the strength of the enclosure

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Yes bracing will help. Will you gain db, maybe a few tenths.

Resin by itself does not add any strength

Edit: not sure why you would use dowels when you're already using all thread

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Hey thanks for the pics. I was gonna use dowels for the top to bottom because the box sits flat agains the trunk floor. I guess I could use something to raise it up a little and go with the allthread. Also I noticed you bolted them on the inside too. I just bolted the outside - is that ok or do I need to bolt the inside as well?

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pretty sure the bolt inside(nut) is to keep the walls from bowing/ to stop you from over tightening the all thread and cause bowing

Hey thanks for the pics. I was gonna use dowels for the top to bottom because the box sits flat agains the trunk floor. I guess I could use something to raise it up a little and go with the allthread. Also I noticed you bolted them on the inside too. I just bolted the outside - is that ok or do I need to bolt the inside as well?

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pretty sure the bolt inside(nut) is to keep the walls from bowing/ to stop you from over tightening the all thread and cause bowing

Hey thanks for the pics. I was gonna use dowels for the top to bottom because the box sits flat agains the trunk floor. I guess I could use something to raise it up a little and go with the allthread. Also I noticed you bolted them on the inside too. I just bolted the outside - is that ok or do I need to bolt the inside as well?

This..

First time I used all thread and didn't use a bolt on the inside it bent the shit out of the wood before it added any structural support.

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Not trying to argue but if Resin alone dries hard then if it's applied to inside and outside of box to seal it then why wouldn't it reinforce it somewhat? Even if it's only the slightest bit. I'm not suggesting adding it to reinforce alone but if sealing the box with it anyways I would feel after it dried hard that it would take more pressure to flex the sides of a sub box than without it. Maybe it doesn't do enough to matter?

Granted it would never take the place of actual bracing whatever you you might choose.

EDIT:

My sub box is 90% done, below is a link to the thread of the design of it. Used 3/4" MDF and running 4 - 15" RF T2 subs. Would you guys recommend threaded rod bracing front to back and side to side for my box or do you think it's not needed? My box seems Very similar to the pics. posted above is why I am asking.

http://www.stevemeadedesigns.com/board/topic/170750-custom-box-4-15-tahoehelp/

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Not trying to argue but if Resin alone dries hard then if it's applied to inside and outside of box to seal it then why wouldn't it reinforce it somewhat? Even if it's only the slightest bit. I'm not suggesting adding it to reinforce alone but if sealing the box with it anyways I would feel after it dried hard that it would take more pressure to flex the sides of a sub box than without it. Maybe it doesn't do enough to matter?

Granted it would never take the place of actual bracing whatever you you might choose.

EDIT:

My sub box is 90% done, below is a link to the thread of the design of it. Used 3/4" MDF and running 4 - 15" RF T2 subs. Would you guys recommend threaded rod bracing front to back and side to side for my box or do you think it's not needed? My box seems Very similar to the pics. posted above is why I am asking.

http://www.stevemeadedesigns.com/board/topic/170750-custom-box-4-15-tahoehelp/

Resin has little to no linear strength (flat surface). It's strength is in curves. It's like rebar and concrete. Rebar is super strong when being pulled but extremely weak when compressed while concrete is extremely weak when stretched but extremely strong when compressed. Even though concrete is super hard it has no real strength when laid out flat that's why side walks and driveways crack so easily. Adding resin to the inside of a box is like making a driveway of just concrete, it makes the surface smooth but doesn't add any strength that the ground (wood in this case) under it doesn't already have.

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