Building my own davits

[paulg222]

Originally Posted by billknny

If you do not understand the purpose of "all those extras bars" in the picture you showed you probably don't have the technical expertise to design davits.

Can you calculate the static load on the deck when you hang 150lbs of dinghy at the end of a 5 foot lever arm? Can you estimate the dynamic load in a seaway? If not, then that expertise is what you are paying for when you buy davits. That and the technical skill of welding.

If you think that is nothing, then go ahead and build a set...

I was sort of joking about the extra bars because the picture is not that clear and it is an a-typical setup.

Yes I know how to calculate the loads (mostly), judging from existing designs, there is nothing that startling here. Get some stiff tubes and support in at least 2 places. The upper support generally reduces/eliminates the moment/torque that would be felt if these were only supported at the bottom. Using single tube design for each side does present some strength challenges.

One thing I do worry about is the horizontal force on my pushpit/stern-rail if I use that as the upper connections. But this seems very common in store bought davits.

=> If not, then that expertise is what you are paying for when you buy davits.
No you are paying that much because a lot of boaters don't mind spending $$$ on what they love. The expertise was bought and paid for a long time ago.

[Disailor]

Check out youtube for bending tubing. My dodger is made from steel conduit & 90^sweeps. 3/4" galv pipe close nipples were used in the joints. I welded mine but they could be tapped & screwed together with Permatex #1 liberally used inside the joints. 3 coats of a 50/50 mix of linseed oil/turpentine (dry 1day between coats) & rustoleum enamel brushed on = 3 yrs no rust. I also put several ounces of the 50/50 mix inside the tubes.
If you cant KEEP the water out you have to LET THE AIR IN. Oh & occasional heavy sprays of WD40down the tubes.

[Hudson Force]

I had a moonlighting pipe fitter whip up a pair of stainless steel davits out of 2" pipe in his garage. I had existing mounting pads on my aft deck; smaller SS pipe braces triangulated across the bend in the pipe. They might show up in my avatar. I've never seen any stronger on a boat my size and the price was right. A skilled pipe fitter from a local industry might be interested in such a project.

You may also see, in my avatar photo, that I have adjustable shrouds leading from the distal end of my davits to the top of my mizzen and a solar panel spanning the top the davits. (..I should say "had" as I sold this boat)

[joehixon]

I had he same reluctance to spend more than a boat unit on davits for my 33 foot sloop. Then I discovered Dinghy Rings. This rig hangs from your stern with two rings that fit the rear points of your dinghy. Back the dinghy into the rings and raise the dinghy like a draw-bridge. With shipping it was about $6oo USD.
https://www.facebook.com/dinghyrings/

[stainless guy]

When clients contact me asking for pricing on items that are readily available, i direct them to purchase the item. If they say they cant afford to buy said mass produced item then they definitely cannot afford to have it made custom.

[KP44]

I had an arch built with davits. (I also have solar on the arch.)
Higher is better.
Higher davits keep the dingy well-above following seas in protected waters where you will use davits.
And higher davits discourage thieves. (A visible chain on the dingy or the outboard is even better.)
But many thieves ghost in after dark with a larger open boat, reach up and cut the davit lines, and drift away or speed away after the dingy drops into their speedboat. If the davit lines are too high, they will look for an easier victim.

[VChild]

You’ll need a real tubing bender for a job like this.
Example: JD Squared Model 3 Tube Bender or better.

https://www.jd2.com/model-3-bender


Otherwise the tube will kink.
Also a tubing notcher would be helpful for joining tubes at various angles.
Usually the type of tubing you’re looking for is sold only in 20 foot lengths.
Then you’ll need someone to actually weld it all up, as the learning curve for this type of TIG welding is very steep.
I doubt you would save any money doing it yourself especially if you don’t weld.
Honestly, it’s not that difficult to polish out a used stainless steel structure to a beautiful “as new” finish with the right polishing wheels and compounds. Just make sure used davits are structurally sound without any stress cracks. Of course stress cracks can be repaired with TIG welding as well.

[joelhemington]

Originally Posted by paulg222

Yeah I was going to mention that. Now I've seen some inexpensive hydraulic pipe bending machines that are sub $200. Here is one:

https://www.amazon.com/XtremepowerUS...a-806751751675 And don't forget that davits add to the total overall length of your boat which may not bother you until your marina starts charging extra each month for that length.

Now some reviews I've read on these cheap benders are not so good, but then again I only need it to work 2 times . Also I guess there are different kinds of benders for tubes that are less likely to kink or damage them (also tube is measured by OD and pipe by ID). Anyone have experience with bending?

Yes, I have experience bending electrical conduit which far thinner than anything you'd be looking at. This is not a job for an amateur. The cheapest and easiest thing you could is rig a harness for your dingy to a halyard ahead of the mast and do it the way real cruisers do. A 4'x8' sheet of marine ply cut into two cradles and a couple coats of high gloss white paint and you're set. You could even leave the motor on the dingy and just tie the whole thing to the stern when you're on the hook for any amount time.

Designing a customer davit system only makes sense if you have a peculiar need which a manufactured davit system can't solve and it doesn't sound like this is your issue. If you're anywhere near a salvage yard you'll most likely find a cheap pair of davits that will suit your need. Of course you'll need to clean them up a bit and mount them but this won't require welding or a bender.

[joelhemington]

Originally Posted by joelhemington

Yes, I have experience bending electrical conduit which far thinner than anything you'd be looking at. This is not a job for an amateur. The cheapest and easiest thing you could is rig a harness for your dingy to a halyard ahead of the mast and do it the way real cruisers do. A 4'x8' sheet of marine ply cut into two cradles and a couple coats of high gloss white paint and you're set. You could even leave the motor on the dingy and just tie the whole thing to the stern when you're on the hook for any amount time.

Designing a customer davit system only makes sense if you have a peculiar need which a manufactured davit system can't solve and it doesn't sound like this is your issue. If you're anywhere near a salvage yard you'll most likely find a cheap pair of davits that will suit your need. Of course you'll need to clean them up a bit and mount them but this won't require welding or a bender.

And don't overlook the fact that if you're in a marina they'll charge extra each month for the additional length to your boat. After awhile those cheap davits can get quite expensive.

[paulg222]

Originally Posted by joelhemington

And don't overlook the fact that if you're in a marina they'll charge extra each month for the additional length to your boat. After awhile those cheap davits can get quite expensive.

Damn, I did not consider that. Oh well. Would be neat to have foldable davits, and then marina may not charge for them if they are down while in slip and only up while using.

Has anyone ever seen foldable davits where the arms fold down?

[Pelagic]

Originally Posted by paulg222

Yeah I was going to mention that. Now I've seen some inexpensive hydraulic pipe bending machines that are sub $200. Here is one:

https://www.amazon.com/XtremepowerUS...a-806751751675

Now some reviews I've read on these cheap benders are not so good, but then again I only need it to work 2 times . Also I guess there are different kinds of benders for tubes that are less likely to kink or damage them (also tube is measured by OD and pipe by ID). Anyone have experience with bending?

You don't need to bend if you design otherwise like what I have on mine with straight cantilevered sections of stainless pipe

Super strong and rigid that also can double as a stern Gangway, I have since added a solar support above the tender davits to compliment my Bimini panels and provide shade for tender.

[valhalla360]

Originally Posted by joelhemington

And don't overlook the fact that if you're in a marina they'll charge extra each month for the additional length to your boat. After awhile those cheap davits can get quite expensive.

Never once had a marina try to charge for the extra 3ft the dingy took up. I'm sure someone will come up with an exception but 99% of marinas take the model length and run with that even if they say it's the overall length. Now if you have old style with a 20ft bow sprit, they might consider it differently but 3-4ft off the stern, it will be the rare marina that takes issue with it.

We made up davits with 1" stainless. Had some scrap that came with the boat and bought the rest on ebay. Found a local welder could could do the 4 bends and knew stainless welding (standard steel welding will rust out quickly).

As mentioned, you need to understand how to calculate the loads.

I think all in, it was about $300. They were fine when we sold the boat 9yr later.

[GILow]

Originally Posted by joelhemington

And don't overlook the fact that if you're in a marina they'll charge extra each month for the additional length to your boat. After awhile those cheap davits can get quite expensive.

I’ve heard of this, but I’ve dodged it so far by very clearly stating my official LOA as recorded in the shipping register. A bit of dissembling, but it works.

[44'cruisingcat]

How about composites? Some uni glass and resin, no special tools or welders required.

Here's my home built targa. Each of the four legs could independently support my weight (115 kg) bouncing on them. The top span only increased the strength. I once broke a 750kg rated snatch block mounted on the targa, trying to unstick a stern anchor.

There's 300W of solar panels mounted on it now too.

100 6643 - Cruisers & Sailing Photo Gallery

[Andynonymous]

I had a local metal working shop build me custom 40mm stainless davit arms, with mounting points for solar panels, eyes at the end of each arm, two collars on the uprights to connect to the stern railing for more rigidity and a couple of cleats.
I later added the two straight sections of stainless tube that support the horizontal arm of the davits, and they meet the stern either side of the swim ladder on a couple of teak blocks with backing plates. Before that the arms 'bounced' a bit too much for my liking, but now are very sturdy.

I mainly use the davits as a solar arch, and a means to raise and lower the outboard and dinghy out of the water. I have a small 2m inflatable, so I use the davits to pull it into the cockpit and deflate before stowing for passage making, or it gets towed for short distances.

All in, the custom davits were about £1200