Thruster Tube for Lewmar 140TT

[Icy]

I am having fits trying to find a 5000 series tube so I can install a bow thruster on my boat.

Lewmar specs call for a tube that is 5.5" ID (140mm) with a wall thickness of 3/16" (5mm).

I have called all over the place and just can't find a source.

nyone have any ideas?

Thanks!!

[Tfitz]

Cut a small section out of a 6" pipe, pinch it closed and weld it up

[kmorin]

Icy, I think a big issue might be the alloy for the extusion? Almost none of the large diameter (>3") pipe extrusions are 50xy series alloys, at least that I've ever heard or seen here in AK, watching and buying form the Puget Sound metal suppliers. Most would be 6061-T6 but a sched. 40 5" pipe, listed in most PNW suppliers' catalogs is 5.047" ID so a little small? However, when you move up to 6" (nominal pipe) the ID is 6.065" ( extrusion target size) so that's a jump where 'pipe' doesn't seem to fit?

Tube products in 6061-T6 at least have a (standards table) listing for an 0.188" (3/16") wall 6" tubing with an ID of 5.62" that may work? But I have no idea how common that tube dimension is in actual manufacture? http://www.teamtube.com/ Team Tube have branches all over the place, I've used them before to buy 'cut pieces' of odd sized tube materials you may try them?

Just a note that pipe sizes smaller than 12" (10? don't recall) are nominal size names and have varying walls, ID, and OD but tube size conventions, arriving a hundred years later on the market (rough timeline) are named and denominated by the OD as an accurate dimension. 5" Pipe is made (about) 5.563" OD but 5" Tube is always 5.00" OD as an example of the differences between these to "O-Beam" metal products.

Last idea, Icy, depending on your local service vendors' capabilities in forming equipment you may find a shop to roll some 50series alloy plate into a cylinder that will serve your needs? Smaller capacity rolls may not be able to handle 0.187" (3/16") 5086 to that diameter, and the larger rolls that may take the bending stress may have too large a diameter min. size finished roll? Purely speculating on the possibility of getting sheet rolled to this dimension.

Seems like the vendor of the thruster hardware would have this material or have it sourced?

Tfitz, the reason I can see to be cautious about slicing 6" to pull in the ID is the final shape might be egged or oval slightly? That means that if you cut a section out lengthwise to reduce the 6" down to 5.5" ID even though a narrow strip of the overall circumference of the original pipe- there's good chance the final re-welded pipe won't be round. I guess it depends on the prop tip clearance as to this being a problem - if it even happened to come out oval?

Cheers,
Kevin Morin
Kenai, AK

[Tfitz]

I would Call Lewmar they must have or know where to get what you need. But I bet my cut, pinch and weld method would work with a hammer little persuasion. But I may have more caveman in me than most

[kmorin]

Tfitz,

for that matter if Icy were using 6" pipe; I'd just go with sched 80 and its 5.76" ID and skip the resizing; that heavier wall (0.432" or 7/16" ) and bigger ID may have a bit too much tip clearance? ( don't know that figure of allowable tip clearance dimension?) but hammering on 6" pipe is "not-really-tradecraft-practice" of shaping 6061 alloy pipes!

Cheers,
Kevin Morin
Kenai, AK

[Chtucker]

Lewmar, Imtra, and Vetus all list aluminum bow thruster tubes on their websites, Imtra I believe lists them as 5000 series.