PT 109

Advert

New Replies

Report Bug

Help/FAQs

PT 109

This topic is empty.

Viewing 25 posts - 1 through 25 (of 30 total)

1 2 →

Author

Posts
19 May 2023 at 02:55 #7524
harry smith 1
Participant
@harrysmith1
Advert

19 May 2023 at 02:55 #104923
harry smith 1
Participant
@harrysmith1
Hello All

I bought this boat from a deceased estate with radio, charger and two 3300mah NIMH batteries.

No props which turned out one shaft totally seized.

Turns out the shaft is standard steel.

So I ordered new shaft kits and some nice bronze 37mm props.

Having removed the motors and ESC started cutting out the prop tube.

The plan is to replace both shafts and install new setups with Teflon lower bearing and roller bearing in the upper end of the shaft.

Replacing the 555 motors with 35mm 1250KV brushless motors and twin 80Amp ESCs.
19 May 2023 at 04:34 #104924
harry smith 1
Participant
@harrysmith1
Hi All

By changing to brushless motors and Lipo batteries will drop the weight by 585 grams !!!

This allows me to add more fiberglass to the very thin hull.

The boat has a dummy center prop shaft with no prop, but still has three very oversize rudders.

Harry
19 May 2023 at 06:38 #104925
gecon
Participant
@gecon
Very impressive Harry,

nobody could ever accuse you of polluting the South Pole! Your model revival and recycling efforts are second-to-none.

Strangely enough, I'm trying to source a PT109 crew at 1:35 scale (Italeri kit) to operate my Smit Ned'. Found kits all over the place….but not in Norway of course.

George
19 May 2023 at 08:52 #104926
harry smith 1
Participant
@harrysmith1
Hi Gecom

What about a Vosper crew kit from Italeri ???

Harry
19 May 2023 at 09:03 #104928
Richard Simpson
Participant
@richardsimpson88330
Lovely looking model from the outside, well worth getting operational again.

While we have someone who is familiar with brushless motors can I please throw in a question. I have been playing with a brushless set up for the first time in my life and I'm just getting my head around the fact that a Lipo cell is a much higher voltage than I'm used to and 5C is all about charging rates etc.. However when it comes to the motors what does 1250 KV mean? To my old fashioned eyes KV means 'kilovolts' so 1250 KV means 1.2 million volts. Reminds me of a certain parrot sketch!

So what does 1250KV mean and how does that relate to power or revs etc?
19 May 2023 at 09:36 #104929
Chris Fellows
Participant
@chrisfellows72943
Richard

The kv gives you the the revs per volt and is useful for sizing the battery to give the performance required and conversely deciding on the kv for a particular model. So for 1250kv on 11.1 volts would give 13875 rpm which is pretty much ideal for a cruiser like planing hull where you are looking for around 10k.rpm in the water. Obviously for a slower non-planing model you can use 2S/7.4 volts.

Generally speaking a lower kv provides more torque so for something like my Swordsman 33, which is quite big and heavy, I've gone for an 800 kv motor and so 10k. rpm ÷ by 800 = 12.5 which is the minimum voltage required. So for my Swordsman I will use a 4S or 14.8 volt battery.

For my other smaller lighter Faireys with planing hulls I'm using 1000 to 1200 kv motors on 3s/11.1 volts but anything up to around 1450 is fine. Higher kv can be used and the speed restricted by the throttle or battery. For full on race boats where the prop shaft and prop are designed for very high revs the kv can be substantially higher. Often inrunner motors are used which are less torquey but higher revving.

Chris

Edited By Chris Fellows on 19/05/2023 09:56:36
19 May 2023 at 09:53 #104930
harry smith 1
Participant
@harrysmith1
Hi Lads

Chris and Richard are spot on, but the length of the motor changes the power output.

The longer the motor the more power.

If converting from brush motors the RPM divided by voltage will give you a good starting point.

E.G. A 80 turn 540 rock crawler motor is 5,500 rpm (unloaded) on 7.2 volts.

So an 750kv brushless would work, on 3S (11.1 volts) 500kv.

IC motors you can general find it's specs on the internet.

Harry
19 May 2023 at 09:58 #104931
Chris Fellows
Participant
@chrisfellows72943
Morning Harry

Bit of a different project for you Harry, but as usual it will go well!

Chris
19 May 2023 at 10:13 #104932
Chris Fellows
Participant
@chrisfellows72943
As Harry says, the length of the motor casing has a bearing on the power output. For two motors of the same dia. and only a few mm difference in length the difference in power output /watts can be significant.

So for models where more power is required this needs to be considered as well. The Overlander Batteries web-site is worth looking at to give an idea of the power outputs etc. for similar sized and kv motors.

Chris

Edited By Chris Fellows on 19/05/2023 10:21:13
19 May 2023 at 10:44 #104933
harry smith 1
Participant
@harrysmith1
Good Evening Chris and Richard

Australia time.

I do have two Precedent Perkasa !!!

A Fairey Sea Raven which I must finish.

The C rating I think is the constant rate of discharge.

Charging rate is mah divide by 10 , eg 4000mah 4Amps, but charge at about half that 2 Amps.

Use a balance charger and safety bag, no problems.

Harry

Edited By harry smith 1 on 19/05/2023 10:51:10
19 May 2023 at 11:43 #104936
Chris Fellows
Participant
@chrisfellows72943
You've got that one covered already then Harry and have a large range of different models. Unlike me, who has a pretty limited range!

However, my next project will use a water-jet and is venturing into your world of high-performance motors! It will be using a 3660 2700kv inrunner with water-cooling to boot!

Chris
19 May 2023 at 12:32 #104938
harry smith 1
Participant
@harrysmith1
Hi Chris

What's it going in, a MFA Spearfish ???

Harry
19 May 2023 at 13:56 #104939
Chris Fellows
Participant
@chrisfellows72943
No, I sold the one I had, the hull would have been good for this project though. I shouldn't have sold it!!

It's going to be scratch built in timber and is based on the Stiletto/Rapier hull and at around 34" is sized somewhere in the middle. Bit more to do on the drawings and then I'll start a build blog.

Chris
19 May 2023 at 15:14 #104940
gecon
Participant
@gecon
Hi Harry,

thanks for the info, I ordered the PT109 crew earlier today. The Vosper crew look more the part so I have just ordered that too!

Many thanks,

George
19 May 2023 at 19:13 #104941
Richard Simpson
Participant
@richardsimpson88330
Many thanks for the input everyone. Gives me a much better idea of what is happening.
20 May 2023 at 07:18 #104945
harry smith 1
Participant
@harrysmith1
Hi All

I have dry set up the replacement drive line with the hole for the oiler drill out.

I have spare 1450kv motors(same size as the 1250kv on order) so waiting on solid couplings from my mate.

I may have one but I will have to check the spares boxes.

Harry
4 July 2023 at 13:05 #105312
harry smith 1
Participant
@harrysmith1
Hi All

Finally one shaft installed with the new 35mm 1250kv and solid coupling.

Soldered in an oiler plus adding some expoy glue around it as well.

Started filling around the shaft exit in the hull.

Next is remove the other shaft and install a new one as well.

Harry
5 July 2023 at 06:42 #105313
ashley needham
Participant
@ashleyneedham69188
Hi Harry. Do we take it that the new shafts fit nicely in the old shaft hole/channel? I would fit a pair of shafts at the same time normally in order to get them on the same line.

Ashley
5 July 2023 at 10:28 #105317
harry smith 1
Participant
@harrysmith1
Hi Ashley

No way, had to increase the hole size and grind out a lot of resin filler !!!

The new setup has a roller bearing top end and Teflon bearing on the lower end with an oiler near the top end.

Standard Harry setup for all boats, fast or slow boats.

AS the other shaft and brass bearings are OK, I will use them for a rudder setup for my next boat.

It's on the way !!!

My first totally new build !!!

I may build it faster than Ray builds a Boats !!!!!!!!!!!!!!

Yes, ewe can stir the pot, it's Winter down under.

Harry
13 July 2023 at 05:39 #105360
harry smith 1
Participant
@harrysmith1
Hi All

Lovely Winters day and 17C !!!!

Finally installed the both motors and drive line setups!!!

Also added 2 ounce fiberglass matting between the motor mounts and rudders.

The hull is thin fiberglass , also poured in some resin in the motor mount plywood frames.

I have block off all the water inlets and outlets, not required.

Next job is the rudder servo mount.

Only getting a few hours per day, too cold in the shed !!!

Harry
4 August 2023 at 08:46 #105504
harry smith 1
Participant
@harrysmith1
Hi All

A busy few days to get the boat ready for Saturday sailing, if weather is good ??

Have both motors rotating the right way and disconnected the RED from the second ESC.

Silcon greased the shafts.

Check the rudders turn the right way which are very over scale.

I will see on the trails what changes are required.

With the changes to brushes motors and Lipo batteries (2S ) drop over 500 grams .

Harry
5 August 2023 at 07:38 #105509
gecon
Participant
@gecon
Good morning (Norway) Harry,

We look forward to to seeing photos of her skimming the the surface and trailing a rooster tail. Like a out of .

George
5 August 2023 at 08:56 #105512
harry smith 1
Participant
@harrysmith1
Good Evening(Tasmania) Gecon

You Tube video of first run.

Only on 2S Lipo batteries!!!

Next week 3S Lipo's !!!

https://rctoystasmania.com/forums/topic/boating-the-canal-5th-august-2023/

Harry
12 August 2023 at 11:46 #105574
harry smith 1
Participant
@harrysmith1
Hi All

Second run today with 3S Lipo batteries.

I moved one forward of the motors to trim the boat.

Work well in a straight line, but turning with prop torque is a problem.

The same with my Perkasa boats.

I think the props are a bit over size, but look good.

I did get the lights working, but flashing port and starboard lights!!!

The bow light is light blue and the mast light is flashing white.

I have added video from todays run plus the other boats.

https://rctoystasmania.com/forums/topic/playing-with-boats-in-the-canal/

Harry
Author

Posts