I want to cantilever a dock out over my pond. Have tried to search the internet for the way I want to do it and found nothing. Basically I want to install a concrete base in the ground on the shore with 2 3/4" masonry threaded rods 4' apart sticking up about 6". Take 2 3" or 4" black iron pipe 20' long and drill a hole about a foot from the end of the pipe slip it over the rod and fasten with washer and nut. Put my deck on top. The pipe might end up being 15' out over the water.
You didn't state what size dock you have in mind, but even a small one might act like more of a diving board rather than a stable platform, given the construction details you've listed here. I'm thinking the supports for such a platform would need to be massive, if any hope of rigidity is to be realized.
Unless you're going to add posts or piers to support the free end?
"Forget pounds and ounces, I'm figuring displacement!"
If we accept that: MBG(+)FGSF(=)HBG(F1) And we surmise that: BG(>)HBG(F1) while GSF(<)HBG(F1) Would it hold true that: HBG(F1)(+)AM500(x)q.d.(=)1.5lbGRWT? PB answer: It depends.
It's going to be 5' wide by 15' long. The 4" black steel pipe is quite ridged and it would be 2 of them. How much flex is what I don't know. I'm not as worried about the concrete bolt anchoring system as I will make it beefy with re-bar and all that with a concrete tail in the footer. No posts. I have 4 28' steel light poles that go from 2.5"at the top to 6" at the base. One I used as a 25' commercial flag pole. Very ridged at that length. For this I was going to use 21' black steel pipe from the plumbing trades.
I wonder if a system of smaller dia. pipe, welded in a truss fashion, might be more rigid than a single, larger dia. pipe?
I noticed that one of the manufacturers Zep linked to uses a cable system to support the outboard end.
"Forget pounds and ounces, I'm figuring displacement!"
If we accept that: MBG(+)FGSF(=)HBG(F1) And we surmise that: BG(>)HBG(F1) while GSF(<)HBG(F1) Would it hold true that: HBG(F1)(+)AM500(x)q.d.(=)1.5lbGRWT? PB answer: It depends.
Yes the cable system would give the support needed with smaller lateral runs. I was looking for the simplest with minimal work. I got barrels for a floating dock that I was going to do at the beginning of the year, their still in my barn. I built a fish trap turned out beautiful and works, guys on the forums said they did it in a few hours after work, I took 2 days.
Wow equations! That's the only real way to know. Wish I was smart enough to figure it out. Do you think the weak link is the rod. That can be worked around. I can find out the thickness and grade of the pipe. The rod was going to be hot dipped made for exterior application.
I wouldn't use threaded rod for anchor bolts. At least make them out of 4140, and only thread the necessary part.
Yeah, there is a bit of math involved for cantilever designs. Really cool, but probably not the best option in a DIY situation if safety is a concern. You'll need a robust anchoring system, which will probably require a lot of concrete. You live in NY, so you have to consider heavy wet snow loads, so yeah, there is a bunch to deal with.
For reference, I just shot off an RFQ for (2) 12@31.8 x 40' American Standard I beams to one of our steel suppliers. This will be the highest priced supplier. I'll let you know what they say tomorrow.
Back in the 70's I had a lake friend that had a suspension dock that looked somewhat like 1/2 of the Golden Gate bridge that seemed to work well. The advantage of his dock not being in the water was that the winter spring ice would break up in large chunks and destroy docks that had been left in the water through the winter.
JCN I don’t think 3" or 4" black iron pipe is going to cut it if your wanting a 15' cantilever. Even with 6" your still going to feel some spring, JMO.
Some of the long time PB members might remember this project I built 6 or 7 years ago. I had a vision of what I wanted and started with 2-80' long I beams and ran with it.
I wouldn't use threaded rod for anchor bolts. At least make them out of 4140, and only thread the necessary part.
Yeah, there is a bit of math involved for cantilever designs. Really cool, but probably not the best option in a DIY situation if safety is a concern. You'll need a robust anchoring system, which will probably require a lot of concrete. You live in NY, so you have to consider heavy wet snow loads, so yeah, there is a bunch to deal with.
For reference, I just shot off an RFQ for (2) 12@31.8 x 40' American Standard I beams to one of our steel suppliers. This will be the highest priced supplier. I'll let you know what they say tomorrow.
JCN I don’t think 3" or 4" black iron pipe is going to cut it if your wanting a 15' cantilever. Even with 6" your still going to feel some spring, JMO.
Some of the long time PB members might remember this project I built 6 or 7 years ago. I had a vision of what I wanted and started with 2-80' long I beams and ran with it.
If I remember the next time I'm at the lake house I'll take some measurements for ya. We cantilevered I-beams out of the house for a porch and ended up putting in support columns because of the deflection.
Nice. I personally have always liked working with steel over wood.
My dock It is made of 8" light I-Beam (don't remember the proper term for it, but it is lighter than standard I-beam). It has 4' of cantilever off the end with an 8'hinged connection to a 12x16 floating dock.
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