Joining 25mm tube to 50mm

[Kelpie]

My davits are made from 50mm tubing and the way they are designed, are free to rotate in their mounting sockets.
I'd like to fit a bracing strut to triangulate it to the pushpit, but I'll need to think of a way to join the 25mm strut to the 50mm tube. The attachment will have to be able to pivot in order to get the right angle.
Best I can come up with is to fit an eye end cap on the strut, and thenuse one of these:
STAINLESS TUBE FORK MOUNTING. FOR END EYES.
and carefully grind it to be a better fit on the 50mm tube. Will be a bit fiddly to fit though.
Can anybody think of a better way?

 

[rogerthebodger]

This is my engine hoist that can swivel on a bearing at top and bottom

You will need a beating supporting the top of the tube to allow it to swivel

https://flic.kr/p/231Pjhm

If you an post a pic of how your davits swivel we may be able to make a better design

 

[Poignard]

 

[rogerthebodger]

I make similar clamps when I am making a rigid connection to static tube but my understanding the OP wishes the davits to still pivot

You can see one of my clamps on th 50mm dia tube attaching mt enfinr lift to my taga

If you wish to use a clamp get a split bush and clamp around the bush around the davits to allow pivot

 

[Martin_J]

Shame I don't have a clearer photo but are you looking for something like I have on the wind generator pole fastening it to the pulpit..?

It's basically a flat square of metal about 75mm x 75mm with two 25 mm u-bolts through it vertically and two 50mm u-bolts through it horizontally on the other side..

(So just 8 small holes to drill in the square plate if you make it yourself, although I do recall a chandlery somewhere selling them in the past).

 

[Martin_J]

Oh and I put a bit of clear tube around those nearer u-bolts just to reduce vibration.

 

[Martin_J]

I was trying to describe what is easier seen in the picture below - Wish I could recall which chandlery sold them ready made up..


Once the u-bolt heads are ground flat with the nuts, you don't notice they're there.

TBH - I think I made mine from a spare keel stud washer about ten years ago. I intended at the time to replace with a stainless plate but it's worked fine ever since.

 

[rogerthebodger]

Oh and I put a bit of clear tube around those nearer u-bolts just to reduce vibration.

Can your wind generator pole rotate / pivot as the OP wishes

 

[Martin_J]

I read it as he needed it to rotate and then clamp in position..

 

[Martin_J]

I guess if it's permanent rotation that's needed, then that is exactly what the clamp for the Force 4 'engine lifting davit' does..

 

[Poignard]

I read it as he needed it to rotate and then clamp in position..

That's what I thought

 

[rogerthebodger]

I read it as he needed it to rotate and then clamp in position..

Mine is exactly like that with the back plastic handle designed to lock my engine hoist in the desired angular position

 

[Kelpie]

Thanks all.
Apologies if I want clear enough- quite hard to explain without doing a drawing.
I do NOT want the davits to pivot. It's the rotation that I am trying to prevent.
They originally had simply a bolt going through them to keep them in the right position, but that very soon began to wear and now there's enough slop to let the dinghy build up a fair bit of momentum.

The strut will meet the davit arm at an angle of around 20⁰, but it won't actually cross it.

The baseline marine clamp looks like it might work- just need to check that they do it in 50mm.

 

[Kelpie]

All I really need is a bigger version of these:
All Stainless Clamps | Baseline Marine Products Ltd

The very nice two-part ones from Baseline will work, but they're a bit expensive. If nothing else turns up they will do the job though.

 

[Mister E]

If it is just to stop retation how about glueing them in the sockets with some sealant adhesive.

 

[Kelpie]

If it is just to stop retation how about glueing them in the sockets with some sealant adhesive.

There's just too much force involved. There's a dinghy with o/b hanging off the end of the davit arm, and in a rolly sea it gets thrown around.
I wondered about getting somebody to add some weld- the davit arms are tubular, but the sockets are square. With a bit of careful grinding I could probably get a nice tight fit. But it would be a be tedious job. A strut would be a better option, I think.

 

[rogerthebodger]

If you dont need it to turn there are all tyoes of pipe clamps that ca be used

50mm pipe clamps - Google Suche

I used one of these to support my SSB Antenna

Its also way to make if you have a bench drill and 50mm hole saw

 

[Martin_J]

Ahhhhh. So it's the bracing that you need rather than the connection to the pulpit..

The upper part of the my 50mm wind generator pole is braced with 25mm braces, but that type of connection would not prevent a dinghy turning the davit.

 

[Martin_J]

How about putting a cross brace like I added in red to the photo (from the internet) below..

The triangulation would prevent side to side movement of the ends..



Without a photo, it's hard to see how much room you have or how permanently fixed you need the bracing to be.

 

[Kelpie]

How about putting a cross brace like I added in red to the photo (from the internet) below..

The triangulation would prevent side to side movement of the ends..

View attachment 160297

Without a photo, it's hard to see how much room you have or how permanently fixed you need the bracing to be.

I thought about that, and it would stop the rotation, but it doesn't solve the issue of connecting 25mm to 50mm.
It would also get in the way climbing up the transom ladder.

A thought just crossed my mind, I could get somebody to weld on a little lug and then drill a hole in it. Might work out easier, cheaper, and stronger.