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Author Topic: what prop for a 50cm long trawler  (Read 5584 times)

MikeA

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what prop for a 50cm long trawler
« on: September 19, 2011, 11:40:46 am »

ok so ive got a practice hull but now im going to do one in WOOD!! i want to have all my running gear first though before i start so i want to know what size propeller i should use for a stern trawler plank on frame hull.

I plan to make the boat 50cm long roughly could be smaller depends on funding. i have a spare 380 motor which i feel maybe too fast i might build a gearbox for it.

all help is much appreciated so thankyou.

mike
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Tug-Kenny RIP

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Re: what prop for a 50cm long trawler
« Reply #1 on: September 19, 2011, 08:04:03 pm »


I would try a 35mm prop. If this warms the motor then you can drop it to 30mm.


ken

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MikeA

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Re: what prop for a 50cm long trawler
« Reply #2 on: September 19, 2011, 08:11:24 pm »

 i also have a 540 motor i purchased today. do you think this could work?
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Re: what prop for a 50cm long trawler
« Reply #3 on: September 19, 2011, 08:15:54 pm »


Even better. It's always nice to have power in reserve. With this motor you could increase the prop size and maybe get a 4 bladed one for low speed , more power, and better manoeuvrability on the like.

ken


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MikeA

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Re: what prop for a 50cm long trawler
« Reply #4 on: September 19, 2011, 08:26:23 pm »

ill use that then.

 i wasnt sure if it would be too fast though, my previous experience in fast boats has taught me that a 540 to 600 size motor doesnt want the prop to be any bigger than 34mm give or take.
this slow stuff seems to have different rules.

i have seen this. what do you think with a 540 motor direct drive coupling and not sure of voltage lol

http://www.ebay.co.uk/itm/Propeller-L-H-40mm-M4-/180714540169?pt=UK_ToysGames_RadioControlled_JN&hash=item2a136d0c89
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Re: what prop for a 50cm long trawler
« Reply #5 on: September 19, 2011, 08:31:58 pm »



Plastic props are a  NO NO.

Well worth the expense of brass ones.   :}


ken

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MikeA

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Re: what prop for a 50cm long trawler
« Reply #6 on: September 19, 2011, 08:40:56 pm »

aw why? im not building a scale replica or anything i dont have the funding or the skills. i use plastic graupners they do allright. This plastic 3 blade is a billings boat one.
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Re: what prop for a 50cm long trawler
« Reply #7 on: September 19, 2011, 08:54:45 pm »


I notice the Ebay one is 4.35 total !!!!  ( brass ones start a pound or two more)  Perhaps a member has one they could supply much cheaper than that.

The trouble with plastic props is that they bend and loose motor power in a wasteful way and you say you are going for a heavier wooden version.


ken

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MikeA

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Re: what prop for a 50cm long trawler
« Reply #8 on: September 19, 2011, 09:09:45 pm »

well tbh with you when you said bigger prop on 540 me being me jumped the gun as i allways do and went an bought it. well not that one actually a cheaper and nastier one:

http://www.ebay.co.uk/itm/200640649802?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2648

sorry ill bare in mind brass ones for the future.
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Re: what prop for a 50cm long trawler
« Reply #9 on: September 19, 2011, 09:12:43 pm »


Nothing wrong with that. It will do the job for you.

Let us know how you get on.


ken

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MikeA

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Re: what prop for a 50cm long trawler
« Reply #10 on: September 19, 2011, 09:25:51 pm »

well i like to have my hardware before i build. Ive managed to get:
new 540 motor £4
new prop for £3.45
new receiver £3
new servo £0.99

just need a propshaft, coupling and a speed controller although i have a mechanical one allready. I build to a steep budget I'm trying to keep the completion of the whole build under 50 quid.
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Re: what prop for a 50cm long trawler
« Reply #11 on: September 20, 2011, 09:36:50 am »

Might be a good idea to run it on a lot less voltage than what the motor is rated for.  It is supposed to be a trawler rather than a racer.  A look at  http://www.towboatjoe.com/towboat_info.htm under "shafts" will reveal his methods for economical shaft and prop production.
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MikeA

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Re: what prop for a 50cm long trawler
« Reply #12 on: September 20, 2011, 11:45:21 am »

i will have some overheating issues if i dont find someway of slowing down the prop. im considering using a gearbox, i have the parts allready.
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MikeA

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Re: what prop for a 50cm long trawler
« Reply #13 on: September 21, 2011, 02:07:13 pm »

made the gear box got a new prop shaft from mmb on the way. Only thing that has failed me so far is my local model shop running out of wood again. Wouldnt be so bad but he takes over a week to restock normally this time its going to be a fortnight.
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MikeA

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Re: what prop for a 50cm long trawler
« Reply #14 on: October 03, 2011, 10:12:05 am »

dont know if anyone is interested or not im posting some pictures of my build so far:

After practicing plank on frame with card board i had ago in wood. i dredged through pictures and build blogs on here to get the gist of how to do plank on frame and designed my own hull. I came across some hurdles and the results could have been prettier but worked. You can see the 540 motor and gearbox i made, propshaft and coupling from MMB.



A gargantuan leap of time later im at this stage today. so far build time has been a week for me this is the longest ever.


in this pick the esc installed, motors installed, steering hardware and ballasting. for ballast Ive used fish tank gravel in sandwhich bags  %% all covered with deck in place. i also painted theinside of the hull in a rainbow of colours that i had laying about to protect the wood from the elements. 


here is the prop and the rudder i made out of brass. Ive never soldered brass before and i had to do it with my soldering iron but its strong and it will hold.


i also used dope and tissue on the hull to seal the bottom


my scruffy interior. and my wooden gear box. quite chuffed with how that turned out  :-)


working on the deck now i think I'm going for a stern trawler it seems to be heading for that direction anyway.
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Re: what prop for a 50cm long trawler
« Reply #15 on: October 03, 2011, 10:16:16 am »


You're doing very well. It looks smashing. I expect you're proud.   :-))


ken

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MikeA

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Re: what prop for a 50cm long trawler
« Reply #16 on: October 03, 2011, 10:27:54 am »

thanks for the compliments. i mustm admit i am enjoying this build as its really trying me this time. My other speed boat builds were expensive and finished after a few days, This build has been cheap and its going to be another 2 weeks before im finished. I am kind of proud but its my first design and build of this type and i hope to build more, will no doubt in future work from scale plans of real vessels.
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Re: what prop for a 50cm long trawler
« Reply #17 on: October 03, 2011, 10:35:41 am »


I've never tried  tissue and dope. Is the effect smooth ? does it need any rubbing down ?

Ken

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MikeA

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Re: what prop for a 50cm long trawler
« Reply #18 on: October 03, 2011, 10:44:40 am »

the affect is smooth yes with work. very easy to use aswell. On this hull i first applied 3 coats on resin mixed with a bit of talc to the hull with sanding in between, then patched a tisse layer, then applied 3 more layers of neet resin on top of that with light sanding inbetween. I apply the coats lightly so they dry quickly, 30 to 45 mins and its sandable without clogging. it was finished in one afternoon.
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Re: what prop for a 50cm long trawler
« Reply #19 on: October 03, 2011, 10:57:09 am »


Ah,  I thought you applied the tissue direct to the planking.  My mistake as I see you've applied resin and rubbed down initially.   :embarrassed:

I had a smooth finish problem when I planked my 'Severn' so spent a lot of time with epoxy and sanding so thought the tisue might be a simpler solution.  (no substitute for hard work eh!)

Cheers

Ken

 
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MikeA

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Re: what prop for a 50cm long trawler
« Reply #20 on: October 23, 2011, 06:42:08 pm »

well ive just about finished my trawler now, ive got some lego tires to fit for fenders coming in the post though. in all honesty i dont know my **** from my elbow when it comes to trawlers and i cant follow plans to well so i worked from photographs off the rtr thunder tiger model and a billings model. Ive tried it at the lake today and atm it heaves and leans alarmingly so ill be working on that soon.



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pompebled

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Re: what prop for a 50cm long trawler
« Reply #21 on: October 23, 2011, 07:07:46 pm »

Hi Mike,

What a cute little trawler, congrats!

You didn't mention what material you made the superstructure of, if that's too heavy the sailing charactaristics may be alarming...

If you can add ballast as far down as possible, that would help too, if you're not on the waterline already.

Show us some pics of your boat on the water please.

Regards, Jan.
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MikeA

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Re: what prop for a 50cm long trawler
« Reply #22 on: October 23, 2011, 10:17:04 pm »

pretty much 98% of the boat is wood. i had a lot of scrap bits left over that i saved from previous builds and i didn't want to put any more money in to it than i had to so i basically manufactured everything. nothing is molded or shop bought except the running hardware. i wasn't sure where to get lead ballast from and in keeping to my budget i used fish tank gravel to ballast the boat.


20 mins after i left my last post i started work on adjusting the position of my batteries. Ive managed to put a chisel straight threw the hull  %% fortunately Ive manged ti fix it.
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malcolmfrary

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Re: what prop for a 50cm long trawler
« Reply #23 on: October 24, 2011, 10:47:42 am »

If the gravel doesn't do the job, try going to your local tyre fitter, asking nicely and looking plaintive.  If you just happen to have the boat with you, you will likely get enough dead balance weights to sink your next half dozen projects.
In the olden days, rocks were the normal ballast for sailing ships, so the gravel is in with a chance.
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MikeA

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Re: what prop for a 50cm long trawler
« Reply #24 on: October 25, 2011, 12:17:17 am »

well i installed the gravel ballast well early in the build. i sealed the hull then guestimated the weight of the superstructure and deck fittings because at that point i hadnt built them. i then weighed out in gravel that amount and plonked it in the middle. next i positioned small bags of gravel around the boat while the hull still afloat to get the desired water line, then removed the guestimated superstructure weight. all the ballast i have positioned it sat on the very bottom of the hull, but the 8.4v nimh battery and 540 motor ended up being inconveniently high, in fact actually on the water line above the fulcrum of the lean and heave, when i had built the boat and did the tank test the lean was only a slight wobble, it wasnt till i took it on the lake for the maiden run that i noticed that the slight wobble in a choppy water was quite a roll.

Any way what ive done is ive taken the 8.4v battery pack and dismantled it into 2 banks of 3 cells making 7.2v and now instead of bein over the prop shaft they are now straddling it and sat right on the bottom under the fulcrum.

 


please excuse me for the interior colour scheme its a mish mash of humbrol tins i had left over from older builds

i still got to try the tank test first see if it has worked
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