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Author Topic: how to make my pt faster  (Read 5360 times)

edible_engine

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how to make my pt faster
« on: January 10, 2007, 11:57:15 pm »

hi i have made a pt boat in the summer it is fas but i want it to go faster its from plans in an old model boats mag.
Its running a mfa 850 with a 50mm brass 4bl prop would a racing prop make it faster?

sorry i havent got any better pics i took a load then i drop my cam in the drink end of that lol :(
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BobF

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Re: how to make my pt faster
« Reply #1 on: January 11, 2007, 11:54:44 am »

Hi E E

A two blade prop is the way to go for speed. Three and four blade are for torque.  There are exceptions to this, but this is the norm.

My friend had a three blade fitted to his PT boat and although quite happy with the speed, thought it could be a bit faster. I lent him a 40mm two blade, and it was so much faster, that he has now fitted a smaller motor but still with the 40mm prop.

Bob
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White Ensign

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Re: how to make my pt faster
« Reply #2 on: January 11, 2007, 01:13:48 pm »

There are a view parameters which could lead to a problem. First of all, take the amps which the motors will draw with the actual props. Do they become warm or hot with the actual configuration? If yes- making up the speed will be a problem. If no- change to a 2-blade prop and have a try by amps they draw now. If it is nearly the same or lower, have a try at the pond.
Also you can go up by voltage, but this will change the draw in Amps as well.
There is no basic rule, it all depends on the weight of the model, the technical equipment and the voltage. All together (or even changing a single parameter) can make your boat faster (or slower). Though it`s lots of guess and try.

Jörg
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Shipmate60

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Re: how to make my pt faster
« Reply #3 on: January 11, 2007, 01:32:37 pm »

MFA do produce a plastic 2 blade prop for this motor and its only cheap too.

Bob
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edible_engine

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Re: how to make my pt faster
« Reply #4 on: January 11, 2007, 04:35:05 pm »

yeh think Ive seen them on the net they come with the set its a Little red one doz any one no what size the one MFA is i,m might and How many volts can this motor take  the motor gets to hot to touch after about 25Min's flat out
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Stavros

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Re: how to make my pt faster
« Reply #5 on: January 11, 2007, 11:22:13 pm »

Right EE the answer is simple I have had this problem with a Sea Queen and is ever so simple to cure
1 Buy or make a cooling coil
2 Fit a water scoop and outlet to your hull
3 Buy a MFA water pump and connect into the the +and- of the motor this way the speedcontroller will control its speed
4 Fit a 2 blade 55mm std pitch prop go 5mm either side of this to determine which is quickest
5 try out on the lake and enjoy
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edible_engine

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Re: how to make my pt faster
« Reply #6 on: January 11, 2007, 11:29:15 pm »

thanks, i was just going to try sumthing like that can you tell me what a "std pitch prop" is
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Stavros

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Re: how to make my pt faster
« Reply #7 on: January 11, 2007, 11:38:03 pm »

yes simple go down to your local model shop and ask for a 55mm 2 blade prop by graupener or similar
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justboatonic

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Re: how to make my pt faster
« Reply #8 on: January 15, 2007, 08:02:21 pm »

The way toget greatest improvement in speed is by bigger voltage \ capacity batteries, better motor and prop. Other than that, reduce the drag the boat has on the water (super smooth hull!).
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edible_engine

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Re: how to make my pt faster
« Reply #9 on: January 16, 2007, 01:09:10 am »

ime going to try the prop first i tried the motor on 24 volt in the bath with the 50mm brass one and their was sparks coming from the motor not just a little blue arch on the brushes but a sparks coming out the can of the motor ime charging up the batters all ready
i Cant afford to go more than 12 volts because i would have to get a new controller the boat is about 1m long and is about 7kg 14pound in English i think the main problem is it is to heavy it is very strong tho all the sides and bottom apart from the very front are made from 1/8 ply.
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justboatonic

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Re: how to make my pt faster
« Reply #10 on: January 16, 2007, 08:18:24 pm »

ime going to try the prop first i tried the motor on 24 volt in the bath with the 50mm brass one and their was sparks coming from the motor not just a little blue arch on the brushes but a sparks coming out the can of the motor ime charging up the batters all ready
i Cant afford to go more than 12 volts because i would have to get a new controller the boat is about 1m long and is about 7kg 14pound in English i think the main problem is it is to heavy it is very strong tho all the sides and bottom apart from the very front are made from 1/8 ply.
12v should be good enough unless you're into serious electric racing. As regards the motor, you should really have the motor comm skimmed every 8 to 10 runs to get the maximum efficiency from it and, bin the motor after a max 3 skims! Yes its expensive but this is what the serious car racers do (in fact they probably skim the motor after every 4 or 5 runs!)
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Stavros

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Re: how to make my pt faster
« Reply #11 on: January 16, 2007, 11:11:17 pm »

24v on a MFA 850 sure way of blowing it up listen to what I have posted and you will not go wrong,my sea queen is of similar length and weight and goes like stink.Told you what prop to use,use the advice you get and listen and learn,we have all been there and had the T shirt,As I have allready read that you are only 14 and don't have the dosh to play around,but go the way you are going by trying silly ideas and it will cost you a lot of money,IE burnt out speed controller +motor =over 70squid comprend what I have said?????
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edible_engine

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Re: how to make my pt faster
« Reply #12 on: January 20, 2007, 11:55:48 pm »

i have tried it with a 45mm 2 blade prop and it gets fully on the plane
when i have the time i will go in town and get a 55mm
can you get 55mm ones with a m4 shaft ?
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edible_engine

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Re: how to make my pt faster
« Reply #13 on: January 22, 2007, 05:19:38 pm »

thanks pepole i got a prop today and it works well good the motor gets a bit hot but hey when i can be ass-ed i will sand the bottom of it but 4 now it will do this man up the lake said i should put trim tabs on it and it would plane better is this true
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Stavros

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Re: how to make my pt faster
« Reply #14 on: January 23, 2007, 04:56:00 pm »

try it to cool that motor you need a cooling coil
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edible_engine

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Re: how to make my pt faster
« Reply #15 on: February 08, 2007, 05:07:47 pm »

wher can i get long lenths of alumineum tube will small copper pipe work from a car
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Stavros

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Re: how to make my pt faster
« Reply #16 on: February 08, 2007, 05:40:02 pm »

wher can i get long lenths of alumineum tube will small copper pipe work from a car  can you explain in english what u want please
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chromedome

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Re: how to make my pt faster
« Reply #17 on: February 08, 2007, 07:22:15 pm »

 ;D
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dougal99

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Re: how to make my pt faster
« Reply #18 on: February 08, 2007, 07:42:27 pm »

wher can i get long lenths of alumineum tube will small copper pipe work from a car

You can get aluminum tube from most model shops.
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edible_engine

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Re: how to make my pt faster
« Reply #19 on: February 09, 2007, 08:46:14 pm »

yeah but there about a foot long and i get about 2 turns anybody now anywhere that sells long lengths
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Stavros

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Re: how to make my pt faster
« Reply #20 on: February 09, 2007, 10:58:58 pm »

right we now know what you want,go down to your local motor factor and ask for some COPPER brake pipe this is sold in a roll enough to do a car, I have used this to make my own cooling coils with good success,the size you need is 4.75mm.or5/16ths DO NOT get conned into buying a product called CUNIFER this pipe does the same job BUT it is not as soft as the copper and kinks far easier.Hope this is of use to you Stavros

PS price is around £10 for a roll
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HS93 (RIP)

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Re: how to make my pt faster
« Reply #21 on: February 09, 2007, 11:03:17 pm »

Also use a former SMALLER than the motor to wind it on ,that way you can spring it on for good heat transfer.  Peter
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edible_engine

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Re: how to make my pt faster
« Reply #22 on: February 10, 2007, 01:20:09 am »

thanks

i can get the pipe free from where I'm doing training  ;D
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