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[UserError]

Hello,
New to boats but exploring....
Just bought a GRM Scorpion Hydroplane in preference to a low-end RTR powerboat so I can learn & get a hopefully better boat at the end.  Just for fun rather than racing - may not be the most suitable of types but I'm not looking to realise its full potential as long as its better than something from Maplin.
Anyone got one of these - someone may well recognise this one?  I gather it's a good few years old, which suits me....

Vital stats are:
540 15 turn motor, 4mm shaft, length 600mm, gross weight ca 1250 grammes (inc 7cell subC pack)

I need a (threaded) prop for this - I've just been told by Prestwich Model Boats that "We do not have a 4mm prop small enough" which, in my ignorance, is puzzling me.

Can anyone advise on what sort of prop I need?
This is a "first step" so I'm after a basic prop for the time being.

I was going to go for a Huco UJ coupling as I need to keep costs down.  Is this OK?

I planned to use subC packs from my buggies (7.2v/8.4v) - these seem a bit heavy in such a light boat: is this OK?

Also, any gotchas I can be forewarned about?
Many thanks
Jonathan

[gwa84]

the shaft looks like it takes a dog drive prop not a screw on type to me and i would have thout a 540 would be to small ide thing more a 700 would be more sutable whats the width at its widest point ?

http://www.prestwich.ndirect.co.uk/octurapropellers.htm    the X435 is the only one on ther for 4mm

[GARY C]

visit Astec models,   WWW.ASTECMODELS.CO.UK

Contact Alan and he will be able to help, you only need to start with the Graupner props should be very easy to sort out for dog drive.

 good luck, Gary.

[UserError]

GWA84,
Just checked the shaft - the end is threaded with a plain nut on it.  Since reading your reply I have been trying to find a pic of a dog drive shaft but haven't managed it yet. I've seen the props & I think I understand how that works - is the dog driver screwed onto the shaft thread?

Boat is about 26cm wide.

I've got the 540 spare & was hoping to use that at least for the time being, partly to keep costs down & partly because I would hate to slam it into the side of the pond whilst getting to grips with it....(BTW, piece of paper whch came with the boat shows that it, at one time had a 16T double wind motor, but doesn't mention the type).  However the laws of physics are not to be contradicted & if it needs more grunt, then that is that. 

Will look at 700 motors (looking at the Graupner 700 speed race @17.5A, is that too close to the limit for a Mtroniks marine 20?)

GARYC
Thanks, will revisit Astec - I had come across their website but it seemed geared at the top end so had passed it by.
Thanks
Jonathan

[John Mk2]

Why not go brushless ? Much more efficient & not as expensive as you think For the type of boat you have ! Need to keep it light.

[gwa84]

the dog drive fits onto the smooth shaft behintd the prop the lokes in place with a grub screw in the side then the prp is loked against this with the nut on the threaded part

http://www.google.co.uk/imgres?imgurl=http://www.vac-u-boat.com/images/VacUCrackerPix/KitPropShaftPkg1.jpg&imgrefurl=http://www.vac-u-boat.com/KitsParts.htm&usg=__NQpYPcd8cbWEU4LKOwGT9FsfX7s=&h=293&w=997&sz=11&hl=en&start=0&zoom=1&tbnid=dG4F8Ip76DkS3M:&tbnh=81&tbnw=274&prev=/images%3Fq%3Ddog%2Bdrive%2Bprop%2Bset%2Bup%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-GB:official%26biw%3D1680%26bih%3D884%26gbv%3D2%26tbs%3Disch:1&itbs=1&iact=hc&vpx=630&vpy=123&dur=380&hovh=96&hovw=326&tx=215&ty=68&ei=DgIETZTSKYiBOqTumdUB&oei=DgIETZTSKYiBOqTumdUB&esq=1&page=1&ndsp=41&ved=1t:429,r:3,s:0


http://www.google.co.uk/imgres?imgurl=http://www.prestwich.ndirect.co.uk/w367pe2F.jpg&imgrefurl=http://www.prestwich.ndirect.co.uk/fastelectrics.htm&usg=__aEsP9hhKatnD_JCrlsAERti5a8w=&h=300&w=400&sz=8&hl=en&start=0&zoom=1&tbnid=XkVD9L27zSNsKM:&tbnh=136&tbnw=178&prev=/images%3Fq%3Ddog%2Bdrive%2Bprop%2Bset%2Bup%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-GB:official%26biw%3D1680%26bih%3D884%26gbv%3D2%26tbs%3Disch:1&itbs=1&iact=hc&vpx=129&vpy=382&dur=615&hovh=194&hovw=259&tx=156&ty=111&ei=DgIETZTSKYiBOqTumdUB&oei=DgIETZTSKYiBOqTumdUB&esq=1&page=1&ndsp=41&ved=1t:429,r:16,s:0


a chart of the groupner moters and amp draw

http://homepage.ntlworld.com/edward.matthews/ddmbc_files/motors/graupner.htm

and i would go with the Graupner Speed 600 7.2V at that voltege  or the Graupner Speed 700 Race 9.6V with an 8.4 buggy pack

and you could always go brushless but thats not my department still getting my teeth into that at the moment

[UserError]

Hi,
Due to shortness of time before Christmas, the need to sort the Severn out for my daughter ( & cash flow - redundancy looming) I've had to shelve this for the time being.

GWA84 - thanks for taking the time to post the links.  I now understand the prop side.  Your motor suggestions are more what I am looking for at present.  If Father Christmas leaves me some beer tokens I may well redirect them to this.

GARYC - contacted Astec -  He did take the trouble to reply but I was a bit disappointed as I set out my stall & he still advised to go LiPo & brushless - completely missed the mark as far as my requirements are concerned as his proposals would have cost £££. As I said, top-end stuff & I can't go there for the foreseeable future. 

What is probably more what I was looking for is the kit it would have had when it was new. I'm quite happy living in the past ;-)
Cheers
Jonathan