Your model looks good on the water, I have a similar problem on my old aerokits 34.5 inch version due to the fact it was originally ic powered and the angle of the propshaft is too steep, this tends to lift the stern as it pushes.
Also I found that by increasing the size of rudder helped in the turns.
In the pictures of my Norstar 34.5 inch version I have lowered the thrust angle, the prop is a 40mm 3 blade brass, and the rudder is 50mm deep, set with a 25 mm spacing to allow for the water pick up and easy prop change.
I am also thinking of fitting the rudder with a horizontal fin on the bottom to help stabilise the thrust .
Cheers Colin.

Hi Schmango

I have my two 3S 4000mah Lipos mounted each side of the rudder.
That's the only way I got mine to turn better.
The boat is not great on the turns at the best.

Props, try Float a boat in Melbourne.
Canabus

Hi all - finally got to sea trial this today . The most notable issue is shaft alignment which is why it sounds like a two stroke engine . The 5mm shafts are very old and have some pitting in the metal which is strange. There is a small amount of play with them which I’m guessing is causing the noise . The motors are cheap 700 size drill motors from eBay which do the job I think. Props are 45mm but I couldn’t find counter rotation in 5mm props so they are the same which isn’t a big issue.

Turning circle is terrible and it wants to nose dive even though the lead acid battery is towards the aft. Looking at other models of this boat it seems to be common though ? Is it normal to have the props and rudders a fair way apart as per the pictures?
I restored this model so I don’t know it’s history or age - it has definitely been built by an amateur and was possibly petrol powered once. I’m guessing it’s from the 1970 era .

Overall it’s a great boat and I’m happy with it .



Cheers

The 4.8s are as good as 5s and would only require a bit of clearing out. I would run a 5mm drill in reverse through them which should make them a good firm fit or just give them a touch with a needle file. See if you can make a jig with close fitting dowels to stop them spinning and use a blunt drill to stop it biting, (you can take the edge off by gently drilling a concrete block for 1 sec) - start off with say a 4.2mm drill, then 4.5 etc and work your way up to just undersize, then use a 4mm reamer to finish it off. less chance of getting a bit off square. Bit harder without a drill press but it can be done. I'd go for a 4.8 if you can find the right diam. Use leather gloves to hold the prop, not your fingers, (you'll see why if you don't.)😮😭 The 4.8 is so it fits on the thread of the shaft,- you might find that you can just line up the shaft and screw it into the 4.8, fit a nut and that's it, - may have to only drill a small depth at the front of the prop to clear the shaft to show enough thread for the nut.

JB

Be aware some motors available chow power at an alarming rate

Thanks for this info but I couldn’t find any 5mm - they are 4.8mm surely they are not the same ? Anyway I will have a look at drilling out a 4mm and using a lock nut . My concern drilling is getting it out of centre as I don’t have a drill press.

Hi Murray, as previously mentioned, there are a lot of 5mm props on Ali Express in left and right hand. You can drill a 4mm prop out to 5mm without any problems also (there are tons of 4mm props on the site as well) Not sure why you would want to change the shaft. The store shown has a good selection of props. Just bore a 4mm prop out and use Nyloc nuts and a drive dog (you can cut notches in the front of the hub) with a Teflon washer behind the prop. LocTite the nuts on if you are worried.

JB

Hi Murry,
Your idea of the prop end conversion is very unusual and i have not heard of this being done before.
However i still think that you could end up with wobbly props.

As for having a pair of the same handed props i would imagine that a bit of rudder offset will be required.

I am by no means an expert and would also like to hear other members thoughts on this.

Martin555.

Hi - I have the motor that’s in the pictures I posted - it has similar specs to a graupner 700 but is out of a leaf blower 🤣.
I found an m5 45mm prop but not a counter rotation option so I will ha e to see how it goes with two right hand rotations . Anyone noticed much prop walk/ torque issues here ?
As a back up I have also purchased two 5mm to 4mm shaft couplings which are designed for motor to shaft applications but I might try and adapt them to the prop end by cutting an m4 screw for the prop end and attaching the prop that way if the props I have ordered don’t work.

Thanks for your help - it’s greatly appreciated
Cheers
Murray

It work hardens like a devil even 316. I know being a Mining Engineer😀😀

As a person who did an apprenticeship as a fitter and turner ,😠stainless steel and stainless iron( used to make caps for nuclear fuel rods) it is a real pig of a material to work especially if you had to work to fine limits

Hi Doug
Last time I tried it I buggered it up Best to buy a shaft already made. The die nut needed is expensive as it's HSS.
Not unless you got a thread cutting Myford but at that diameter no matter how accurate your tool height is it tends to climb the tool even with a rear toolpost☹️☹️

Hi Ian,
I tried rethreading on my Proxxon lathe, the die just didn't want to know!
😎

I have tried it in the Myford but you have to have a High Speed Steel Split Die and a very slow feed with lots of oil as the 5mm thread bottom is as close to M4 that you can get. Not for the faint hearted.

Hi Schmango (🙄),
Re-bushing is not so difficult as it may sound😉
You can use the old shaft as a drift to tap the old bushes out.
Tapping the new ones in is also not so hard.
(Even easier if you freeze the bush and warm the end of the tube 😉)
I use the new shaft as an alignment tool to make sure the new bushes are sitting right and everything is in line. A short chunk of suitable tube as a drift between hammer (tack hammer) and new bush.
Good luck🤞 Let us know how you get on👍
Cheers, Doug😎
PS You may be right about 60mm props on the 700s, although there seems to be many variants; with can diameters from ca 44mm to 67mm! The 67s can probably cope with 60mm but the smaller ones might labour a bit and draw more current to no good effect.
Which model 700 do you have? Can diameter? 5 pole?

Thanks Doug - I am running raboesch on my other model amd they are the best but this boat swinging 60mm props are going to be too big for 700 size motors I think.... ?
How do you go about re-bushing the shaft ? That might be a good option .
Appreciate your advice -very helpful
Cheers

The big problem here is that Stainless steel work hardens so once it has been threaded you cant recut the thread even in a lathe I have tried.
Suggest as what Doug said use Raebosch Props they have M5 Props

Schmango,
My favourite well made and nicely balanced brass props are from Raboesch, a Dutch company specialising in precision parts for model boats. They do some 5mm thread props in various 3 blade formats.
Can't find a distributor/dealer in Oz so you may have to go to a UK / EU supplier.
I get mine from Krick here in Germany.
You may find that you may need to go to a 50 or 60mm prop to get a 5mm threaded version!
If you want to stick with your 45mm / 4mm props Maybe no space for larger ones) I would re-bush the shaft tube with 4mm sintered phosphor-bronze bushes and fit a new 4mm shaft.
Raboesch catalogue attached so you can see what I mean.
Cheers, Doug 😎

"Trying to to run an M4 die down an already M5 threaded shaft is unlikely to end up running true."
I heartily agree Mike👍
Tried that once going from 4 to 3mm. Never again!
The naked eye could tell it was off, and the prop wobble proved it.☹️
Sooo; new 3mm ID bushes in the toob and a new 3mm shaft!
Cheers, Doug😎

cornwall advertise 5m props

Trying to run an M4 die down an already M5 threaded shaft is unlikely to end up running true.
Try Wheelspin UK

Hi Schmango,
It is possible to re-tap the threaded end of the propshaft to 4mm if you go carefully.

Martin555.

Ali Express has many different types of 5mm props, plastic and metal.

JB