Bridge Deck Weight Capacity

[ERTF]

I have a Marine Trader 44. I'm wondering if 1800lbs is too much weight to be placed on a 3x5ft area of either the flybridge or "sundeck"? I'm not concerned about stability, just structurally is it plenty strong enough that i won't be overly stressing it?

I have a rain catchment system that yields about 100 gallons per 1" of rain. When we get heavy rain events, my tanks overflow. I spotted these water bladders for a very cheap price. Thinking i could unroll the bladder on deck before a heavy storm, divert rain into bladder after tanks are full. Wash clothes and pressure wash boat the next few days after storm. Then fold up bladder and stow.

 

[Mambo42]

You would be looking at 120 Lbs per sq ft and to me that sounds like a lot of weight for the fly bridge or sun deck.
But best option would be to contact a maritime engineer and have him/ her calculate the stresses on the boat. If you can still contact the yard that would even be better, but since I have no marine trader I cannot tell you where to find them.

 

[Circumnavigator]

That's nine people -- a high, but not unreasonable load on a fly bridge.


I would take your bags and fill them slowly, keeping a close eye on deflection -- how much the center of the area goes down. If it seems unreasonable, I might fab a 4x4 from under the deck to the next level down which you would insert only when the bags were filling. You might also think about putting them on the side decks, where the supports are closer on both sides.


Jim

 

[Mambo42]

That's nine people -- a high, but not unreasonable load on a fly bridge.

Would not be a problem if you would spread them out over a large area, but this is an area 3 by 5 feet, that is not so big and chances are you will be putting all that weight on 1 or maximum 2 cross beams.

I would take your bags and fill them slowly, keeping a close eye on deflection -- how much the center of the area goes down. If it seems unreasonable, I might fab a 4x4 from under the deck to the next level down which you would insert only when the bags were filling. You might also think about putting them on the side decks, where the supports are closer on both sides.


Jim

Indeed, spreading out the weight over a larger area might be a good solution, so instead of 1 bag, spread it out over 4 bags and place those bags in different positions. Must be possible to collect the water and then divert it into a different bag.

Last winter I had electricians working on my boat, they placed my anchor chain (without my knowledge) on the bow deck. That was 140 mtr of 13 mm chain, which is 4 kg per meter, so that was 560 kg (about 1230 lbs) on roughly the same area as where OP now wants to put about 600 lbs more.
The deck plates on my bow have been dented a bit, so not sure I would want to try those 600 lbs extra on my bow, let alone on the fly bridge.

 

[ERTF]

There's a few reasons why the single 200gal bag is optimal in most every way besides weight distribution. With the single bag i can set the rain hoses to divert and let it fill up for awhile -- potentially even over night. The big bag is taller, so less deck space covered = less in the way. Lastly, one 200 gallon bag is half the price of four 50 gal bags. There's also a few other specific reasons that would require more explaining.

If four 50gal bladders was my only option. I would be tempted to also consider nesting storage totes (27, 40, or 50g) as an alternative. I know there are no shoddy chinese seams to fail on the totes ?. Basically the big bag allowed me to skip that part of the debate.

I'll ponder it for a little while. I just happened to see these cheap bladders and got an idea. I enjoy buying inexpensive handy boat "toys". The way the pricing graduates, i might as well just buy the 264g (sounds like closer to 200g in reality) and only fill it up half way if more than that feels sketchy.

 

[CaptTom]

That much weight up that high is going to significantly impact roll. Something I'd try to avoid on that hull.

 

[ERTF]

Out of curiousity, I looked above the headliner. Not sure the correct term, but my sundeck has what seems to be foam cored fiberglass "stringers" running crossways every 17". They're about 4" deep by maybe 1" wide. And there's 1/2" of teak on top of the deck (for whatever that's worth).

 

[kchace]

I definitely think that is too much weight on that deck.

Ken