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Author Topic: XRAD'S YELLOW CAT 55"  (Read 1582 times)

xrad

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XRAD'S YELLOW CAT 55"
« on: July 25, 2017, 12:23:51 AM »

New build.   about 55" overall length stem to rudder.  Fairly well made fiberglass hull. Very light but with subjectively appropriate thickness. I ply reinforced the stinger/shaft mounts, machined the rudder mount and bushings, 3D printed the exhaust mounts, and milled/cut some 2mm carbon fiber for adjustable battery mounts.  Will make some carbon fiber ESC and servo mounts.  Most parts from offshore electrics.  Using Devcon plastiweld, slightly flexible and very strong bond to the Chinese fiberglass resin and all my mounts.

I bought the empty hull ~225$ (when first selling, more now) shipped to USA off ebay and chose my set-up.  You do have to make sure seller includes ALL the hatch covers and scoops.  Wire mesh vents are closed off inside the hull.
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martno1fan

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Re: XRAD'S YELLOW CAT 55"
« Reply #1 on: July 25, 2017, 08:16:44 AM »

Looks good mate just make sure the prop nuts are loctighted on as ive used those stingers and the nuts can come off,think theyre fastened using a grub screw? i filed a flat spot on the shaft as mine didnt have one . What motors are those they look like leopards but what size etc .
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xrad

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Re: XRAD'S YELLOW CAT 55"
« Reply #2 on: July 26, 2017, 01:32:18 PM »

Thanks. Yes, these are for initial setup/looks only. I only use locknuts when running.  The thrust washers are there between the nut and props 1) so that I don't lose them, and 2) so that when I measure and cut the flex cables, they are 1mm short allowing a little play on the cable clamp at motor, 3) easy to take on and off.

Have to keep motor size/kv/ props a secret until I get GPS some speed runs recorded.  Obviously 6s each side..... :-))
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martno1fan

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Re: XRAD'S YELLOW CAT 55"
« Reply #3 on: August 28, 2017, 12:58:27 PM »

Have to say ive used those stingers before and im not a big fan its a pain having to uninstall the shafts to grease things,i prefer a normal stinger where i can use the all in one flexshaft setups that i can release and slide right out to grease and back in in no time .Also those stingers are not very robust and i wouldnt trust them with big power setups on large boats theyre more suited in fact designed for the Genesis cats which are much smaller ,im also not a fan of 3/16 shafts on larger boats i use 1/4" stepped down to 3/16 so i can still use smaller props but not run the risk of the flexis snapping under the power.
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xrad

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Re: XRAD'S YELLOW CAT 55"
« Reply #4 on: August 31, 2017, 01:13:31 AM »

Thx for tips Martno.  These are one piece flex-solid shafts. Whole shaft slides right out once released at motor compression nut(yes, a risk of losing the flex-shaft...I am not adding the weight of a safety collar).  Yes, design looks weak, and that was an initial concern.  But these seem strong. I can lift the boat with them (subjective and not real life forces, I know). I do like that they are 'sealed' at hull mount.  I have another set with vertically located rear overhang mounts, but they were a PITA to measure up. 
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canabus

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Re: XRAD'S YELLOW CAT 55"
« Reply #5 on: August 31, 2017, 08:19:44 AM »

Hi xrad
If you use a piece of IC fuel tubing between the compression nut and the end of the outer drive tube(on the flex drive) this will save the prop etc dropping of into the water!!!

Canabus
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xrad

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Re: XRAD'S YELLOW CAT 55"
« Reply #6 on: August 31, 2017, 01:41:52 PM »

Great idea! will use it. Funny, I was using this same technique on my solid shaft boats!  Doh.....
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martno1fan

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Re: XRAD'S YELLOW CAT 55"
« Reply #7 on: August 31, 2017, 10:07:20 PM »

Thx for tips Martno.  These are one piece flex-solid shafts. Whole shaft slides right out once released at motor compression nut(yes, a risk of losing the flex-shaft...I am not adding the weight of a safety collar).  Yes, design looks weak, and that was an initial concern.  But these seem strong. I can lift the boat with them (subjective and not real life forces, I know). I do like that they are 'sealed' at hull mount.  I have another set with vertically located rear overhang mounts, but they were a PITA to measure up.

Hi mate thats good the ones i tried used a two piece shaft and flex setup.As Canabus said you can use silicone tubing ive also used small zipties as shaft savers ,dont forget to leave a gap between your drive dog and the drive to allow for cable shrinkage ok2 .Still think larger stingers with  1/4" shafts stepped down would be better but you might be ok for a few runs .
This type might work for you .
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canabus

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Re: XRAD'S YELLOW CAT 55"
« Reply #8 on: September 01, 2017, 06:25:39 AM »

Hi xrad

Same as me, but, I also use a piece top and bottom on my inboard rudders.
A boat without rudder in the middle of the pond is no fun.

Canabus
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xrad

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Re: XRAD'S YELLOW CAT 55"
« Reply #9 on: September 02, 2017, 11:33:18 PM »

Thx for tips!

I have a set of those stingers. Too lazy to measure and cut all the holes.  As far as the flex cable 'shrinking,' I am pretty sure that if you put it in correctly, the wind will actually cause it to lengthen.  I have opposite wound flex cables for pair of in-runners, you can see the starboard cable hanging out above, hard to see wind, but top of prop turns in, and cable 'tightens' getting a bit longer...


I have been busy finishing one of my steam builds. Which is 99% done.  And drawing up plans for a 55" New York steam tug....So this 55 cat has been on hold a bit....
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martno1fan

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Re: XRAD'S YELLOW CAT 55"
« Reply #10 on: September 06, 2017, 10:00:35 PM »

No all cables shrink under load as things tighten , if you put the wrong cable in spinning the wrong way then the winds can open up and ruin your cable and bind things up and destroy things pretty dam quick. L hand cables are for normal rotation r hand are for counter rotation do not swap them . You must have a gap at the stinger between dog and stinger like i said .
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xrad

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Re: XRAD'S YELLOW CAT 55"
« Reply #11 on: September 08, 2017, 04:22:06 PM »

 I see what you are saying but it does not make sense that a cable 'shortens' or 'shrinks'.  By 'tightens ' I mean the diameter decreases.  Overall length increases 'a bit'.  Due to geometry of coil winding, all coils with abutting winds (like our flex shafts) will have an overall length increase when 'wound' beyond their initial coiling. You may not be able to see it if coil is stiff, but if you can wind it, in general, the overall length will increase.

You would always want to run the coil in a 'winding' direction so that it maintains the same or narrower diameter in the tube. When run in a 'winding' direction, the cable lengthens.  Here is a diagram showing what I am describing.

If you 'wind' up the cable, it actually lengthens a bit. Therefore, I always make my thrust washer snug to tube bushing.  Never had an issue with washer wear, BB or plastic.  You can test this by winding a  wire around a tube diameter 'x', slide the tube out, and then twist the SAME length of wire around a smaller diameter tube than original 'x'.  The smaller wind diameter for given length of wire has an overall longer length of the coil. Same principle when 'tightening' the wind of our flex shafts.
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martno1fan

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Re: XRAD'S YELLOW CAT 55"
« Reply #12 on: September 09, 2017, 12:58:01 PM »

Nope your 100% WRONG i give up you clearly know better than everyone else who runs fast boats,every flex cable shrinks under load FACT OVER AND OUT .
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xrad

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Re: XRAD'S YELLOW CAT 55"
« Reply #13 on: September 09, 2017, 03:02:59 PM »

Got it, "100%"! :-)) %)

Since you obviously can't discuss anything rationally,  stay #@! far off my threads.

I still think this is a worthwhile discussion. Anyone else wishing to add insight welcome.

With 'forward motion' using the first image in pic above, the motor puts on a rotational 'load' (1) against the mass of the cable and prop and tube resistance, (2) and more rotational load as water resists prop blades/acceleration of mass of boat  (3) while prop adds axial force to thrust washer and torsional forces to the strut tube bearings.   Trying to assume what length the cable will 'shorten' under 'load' as you say would be pure guesswork.  Same as me trying to figure out how much a cable will lengthen.  Due to the inner cable wires, even with the winding effect, for the most part, the cable remain fairly stable in length or lengthen a bit. Therefore, snug prop /thrust washer /strut tube and importance of winding direction.  Also, if you guess at the length the cable will 'shorten' under load and leave a gap between thrust washer and strut tube, your motor bearings will be taking the hit.
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martno1fan

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Re: XRAD'S YELLOW CAT 55"
« Reply #14 on: September 09, 2017, 03:45:12 PM »

Outer wires go in one direction inner wires go opposite this creates stiffness as they  counter acts one another ,they have left hand cables and right hand cables for a reason,you use left for normal rotation and r for counter rotating props that is a fact .Your right the gap used is a bit of guess work but usually the shorter the cable the less gap is needed ,thats my last words on the subject .
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