Kort Nozzles

[des]

Does anyone know where I can get a pair of Kort nozzles to suit Prop Shop 48 mm props?

Some months ago I emailed a supplier / manufacturer in the UK to find out if their Korts are true diameter, or nominal - ie, will a 50 mm prop swing inside one of their 50 mm nozzles?  The reply was no, their 50 mm nozzles are true ID, and they recommended using a pair of Simon Higgins' props which are made slightly smaller to suit the nozzles;  plus they also provided a lengthy discourse how not all nozzles are equal, and how theirs are designed to the correct dimensions.

More recently I emailed the manufacturer again to obtain dimensions of their nozzle and rudder kits, to ensure that it would fit under my hull.  No response at all.  But I thought that since the nozzle dimensions are all fixed in relation to prop size, then a "50 mm nozzle" will be of true shape regardless of the scale being modelled, so I ordered a pair.  Wrong.  When I received them my first response was that these are massive.

At the same time I also ordered a pair of props from Simon - and they are a nice looking pair of props.

So now I have a pair of oversized nozzles - the only correct dimension is the ID (which is 51 mm, not the "true" 50 mm as stated), but all other dimensions are 50% oversize.  And the cost of shipping them back to the UK for a refund is just not worth the effort.

There is another supplier of 50 mm (nominal) nozzles, but they will be too large for my 48 mm props.  It's bad enough having to buy new nozzles without having to also buy new props.

Any ideas anyone?

(I have looked on Shapeways, but they only show overall external dimensions.)

Des.

[Capt.Towline]

I’ll have a dig around on some of the sites I’ve got bookmarked and let you know if I find anything Des

CT

[deep diver]

Hi Des

Have a look at this site https://www.mobilemarinemodels.com

Fred

[des]

Thanks Fred.  Shall we just say that I probably won't be buying Korts from MMM.

Des.

[sea monkey]

48mm props in a nozzle with 50mm ID should be fine - that’s only 1mm on each side.
I have had some Kort nozzles printed at Shapeways and
they are quite accurate in the finished product dimensions.
The finish on the surface is not as smooth as I would like but after a few coats of paint it’s OK.
Send me the dimensions you need (HxLxW, ID, OD, angle of cone, fixed/steerable?) and I’ll see if any on mine will do.
You can the drawing at:
http://modeltugforum.com/index.php?topic=6101.15
To mark the dimensions you need.

[des]

Thanks again Steve.  I'll pass on Shapeways for  little while;  I think I can get them turned up on a lathe, using some PVC pipe.

One advantage of using Shapeways is that I can get the mounting seat and the rudder skeg both printed integrally instead of having to fabricate them separately then mount them to the nozzle.

Can Shapeways work from 2D drawings?  If so I can provide 2D dwg drawing files for them to import and create a 3D model file for printing.  Might cost a bit more first time up, but I can use them again in order to spread the cost over several models.

Des.

[olscuzbut]

Any thought of building your own kort?  Can explain how if you are interested.

[des]

Yes - I am considering just that.  I have a copy of the dimensions for a 19A nozzle.  I've identified a pvc pipe fitting with dimensions close to what I need;  all I need then is access to a lathe.  It will just be a bit fiddly fixing a mounting seat to the nozzle, and a bit more so fitting the skeg directly opposite.  But, do-able.

Des.

[des]

Yesterday I took another look at those Korts.  I had decided that they were not as I wanted (nor even as described by the manufacturer), and I had prepared myself to either buying or making another pair.  So I had nothing to lose if I tried to modify them but stuffed them up.

I decided that the major issue was the nozzle length (50% too long) and wall thickness of the nozzle (50% too thick).  I couldn't easily do anything about the thickness, so I decided to cut off the excess length and see what it looked like.  The thicker (inlet) end seemed the logical choice here, so I cut 13 mm (1/2 inch) off from the thick end.

If anyone else has any similar ideas, be prepared.  The dust from cutting, filing, sanding, or drilling this stuff (HardyCast) is not good.  Wear  PPE - dust mask (a good one), eye protection(goggles rather than glasses), surgical gloves, etc.  Disposable overalls if you have them, or be prepared to throw your clothes into the laundry immediately after you've finished cutting - and jump into the shower yourself.  Definitely use a dust extractor if you have one;  and use a wet cutting system if you can.

I don't know how the manufacturer can ship this stuff without an accompanying MSDS.

Anyway, after cutting the nozzles to a more acceptable length I was left with a "square" edge to the inlet - so I sanded it until the inlet was fully rounded.  The final result, although still too thick at the inlet, looked a lot better than the original, so I decided to keep these, and use them on my project - at least now they will fit under my hull.  But I probably won't buy any more from this supplier.

The material itself I found to be easy to cut and sand using a Dremel diamond cutting wheel and sanding drum.  It didn't respond well to a small file, but did sand well with wet-and-dry paper for finishing.