Is a 2x8 top frame enough?

Tuffloud1 · 08/21/2019, 11:01 PM

I'm questioning whether or not my 2x8 with no center brace on the back top frame of my stand is sufficient. I'm worried about deflection, not a total failure.

Tank is 72x28x30, 262 gallons

550 pounds empty

I got info from one of RocketEngineer’s threads that a 2x8 header will work.

Here are pictures of the measurements from the middle of the 2x8 before and after I filled the tank with water 7 inches from the top.

Should I reinforce it better?

Tuffloud1 · 08/22/2019, 02:08 PM

Anyone? Not sure what happened to Rocket Engineer.

I tried sending him a PM months ago, haven't heard back.

mcgyvr · 08/22/2019, 03:24 PM

I would not be worried...

Tuffloud1 · 08/22/2019, 04:26 PM

Quote:

Originally Posted by mcgyvr

I would not be worried...

So 1/16" is nothing to be worried about?

I assume that it will deflect even more over time (years and years).

mcgyvr · 08/22/2019, 04:28 PM

If it concerns you just sister another 2x8 on each existing...you wont even see it..

Tuffloud1 · 08/22/2019, 04:39 PM

Quote:

Originally Posted by mcgyvr

If it concerns you just sister another 2x8 on each existing...you wont even see it..

I guess the question is, why should I not be concerned about the deflection if it is already showing and the tank isn't totally full?

From my understanding, you want 0 deflection because we are supporting glass.

wrott · 08/22/2019, 07:34 PM

Isn't it 2 X 6'? What size are the planks, 2x6"?
And I would put a couple of 2x4s in the middle to secure it.

mcgyvr · 08/22/2019, 07:35 PM

Yes zero is ultimate but rarely achieved.. Some deflection is ok and the glass/joints can tolerate some...

1/16 over a 6ft span should be safe.. Sintering another board or adding a center support wont hurt and will reduce deflection..

Tuffloud1 · 08/22/2019, 07:57 PM

Quote:

Originally Posted by wrott

Isn't it 2 X 6'? What size are the planks, 2x6"?
And I would put a couple of 2x4s in the middle to secure it.

It's a 2x8 but realistically 1.5x7.25.

I can't put a middle beam in as I am putting a 60 inch sump down there.

Tuffloud1 · 08/22/2019, 07:58 PM

Quote:

Originally Posted by mcgyvr

Yes zero is ultimate but rarely achieved.. Some deflection is ok and the glass/joints can tolerate some...

1/16 over a 6ft span should be safe.. Sintering another board or adding a center support wont hurt and will reduce deflection..

Would 3/4 ply glued and screwed work well?

mcgyvr · 08/22/2019, 08:17 PM

Quote:

Originally Posted by Tuffloud1

Would 3/4 ply glued and screwed work well?

To what/where?

Why not put the sump in place then add a middle support that could be removed if needed

Tuffloud1 · 08/22/2019, 08:28 PM

Quote:

Originally Posted by mcgyvr

To what/where?

Why not put the sump in place then add a middle support that could be removed if needed

3/4 ply glued/screwed to the face of the 2x8 (sistered).

I don't want a center support. Makes maintenance a nightmare.

mjenk430 · 01/01/2020, 10:23 AM

Tuffloud1,

What did you end up doing for your stand to reduce deflection? I am currently designing a stand for my new 300 gallon (72"x36"x27") and don't want a center brace in the rear for sump access similar to yours. I also don't want a super tall top support to maximize space under the stand. I was considering using a doubled or even tripled 2x6 at the top for the clear span. What are your thoughts based on your experience with you stand?

cvrle1 · 01/03/2020, 02:22 PM

RE is active on the other site, so he can be reached there. I did talk to him about center brace few months ago, and he said that 5 foot is basically limit of center vs no center. Since my tank is 5 feet, and I used 2x6 for the top, I added off centered brace. This way I had some extra support, but had enough room to fit a sump in without issues.

08/22/2019, 02:08 PM	#2
Tuffloud1 Registered Member Join Date: Feb 2014 Location: The People's Republic of California Posts: 600	Anyone? Not sure what happened to Rocket Engineer. I tried sending him a PM months ago, haven't heard back. __________________ The inherent vice of capitalism is the unequal sharing of blessings; the inherent virtue of socialism is the equal sharing of miseries. — Winston Churchill Current Tank Info: 110 gallon freshwater, 90 gallon reef tank in the works

08/22/2019, 03:24 PM	#3
mcgyvr Registered Member Join Date: Sep 2003 Location: North Carolina Posts: 20,050	I would not be worried... __________________ Who me?

08/22/2019, 04:28 PM	#5
mcgyvr Registered Member Join Date: Sep 2003 Location: North Carolina Posts: 20,050	If it concerns you just sister another 2x8 on each existing...you wont even see it.. __________________ Who me?

08/22/2019, 07:34 PM	#7
wrott Registered Member Join Date: Mar 2004 Location: Alabama Posts: 2,912	Isn't it 2 X 6'? What size are the planks, 2x6"? And I would put a couple of 2x4s in the middle to secure it. __________________ OK, but where does the meat go! ------------------------------------------------ 120g SPS, 125g mix, 56g FOWLR, 20g qt

08/22/2019, 07:35 PM	#8
mcgyvr Registered Member Join Date: Sep 2003 Location: North Carolina Posts: 20,050	Yes zero is ultimate but rarely achieved.. Some deflection is ok and the glass/joints can tolerate some... 1/16 over a 6ft span should be safe.. Sintering another board or adding a center support wont hurt and will reduce deflection.. __________________ Who me?

01/01/2020, 10:23 AM	#13
mjenk430 Registered Member Join Date: Jun 2012 Posts: 7	Tuffloud1, What did you end up doing for your stand to reduce deflection? I am currently designing a stand for my new 300 gallon (72"x36"x27") and don't want a center brace in the rear for sump access similar to yours. I also don't want a super tall top support to maximize space under the stand. I was considering using a doubled or even tripled 2x6 at the top for the clear span. What are your thoughts based on your experience with you stand?

01/03/2020, 02:22 PM	#14
cvrle1 Registered Member Join Date: Nov 2000 Location: Surrey, BC Posts: 454	RE is active on the other site, so he can be reached there. I did talk to him about center brace few months ago, and he said that 5 foot is basically limit of center vs no center. Since my tank is 5 feet, and I used 2x6 for the top, I added off centered brace. This way I had some extra support, but had enough room to fit a sump in without issues.