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Author Topic: Miss Britain 3  (Read 8494 times)

dadandlad

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Miss Britain 3
« on: February 01, 2011, 11:45:09 PM »

Hi and welcome to the start of my build of Miss Britain 3 please feel free to jump in with any comments and advice
THE MODEL
My aim is to build a double size Miss Britain 3 from the free plans in Jan 2000 MMI powered by a 26cc converted Strimmer engine which will give a 1/6th scale mode with a OAL of 49 inch or 1220 mm

THE HULL
The hull will be constructed from marine grade ply,1/4inch for the bulkheads,1/2 inch laminated keel and skinned with a thin 1.2mm birch ply. In addition i will be adding 1/4 inch stringers which do not seem to be shown on the drawing

THE ENGINE
The engine will be a converted 23cc 2 stroke strimmer engine which will have the following work carried out to it,Water cooled head and exhaust flange and a Gas/Glow conversion.

Now here is where i need your help
Where in West Yorkshire is the best place to obtain the plywood and does anyone have a old strimmer they would like to sell prefrebly again in West Yorkshire
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phillnjack

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Re: Miss Britain 3
« Reply #1 on: February 02, 2011, 12:04:25 AM »

why bother using marine ply ?
your not going to be leaving the boat in the water like a full size boat, and if you seal the wood then no need for
the extra expense of marine ply.
especially if you are going to cover it with birch ply.

I would just go to local wood yard and seek out a nice piece of ply with decent grain, then seal it.

Now for the engine, have you seen the nice little ryobi 30cc strimmers with built in 12 volt electric start ?
Not only a starter but also 12 charging system as well, so could run other things as well.
They are real nice little motors and cost around 100 brand new.
Might be worth looking at if your buying a new motor.



phill

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dadandlad

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Re: Miss Britain 3
« Reply #2 on: February 02, 2011, 07:02:33 AM »

Cheers Phill
Point taken with the ply,i shall have a look for some decent quality at the local wood merchants.Have i got the name right for the really thin ply used for skinning?

Yes i have seen the Ryobi strimmers with on board starter and as you say they are a nice bit of kit.
I don't really fancy pulling a brand new machine apart and would prefer to have a go at something a little cheaper in case i get it wrong
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Circlip

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Re: Miss Britain 3
« Reply #3 on: February 02, 2011, 12:56:37 PM »

Beware D&L, there's a reason that marine grades of ply are more expensive, structural integrity being the most important. Not only the final use but also the basic materials the ply is constructed from. Something to be considered when making a potential missile. West Yorkshire has a bad enough name for other things without adding to it. {-)

   Regards  Ian.
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phillnjack

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Re: Miss Britain 3
« Reply #4 on: February 02, 2011, 03:53:46 PM »

The only difference between marine ply and normal ply is the glue used on the lamination of the plys.

Most ply laminations nowdays are using glues that are almost identical,in sonme instances they are the very same.
If you get ply for shutting you will be getting the very worst, but getting normal exterior ply should be fine.

Now being as the boat is not full sized and will NOT be kept in water, you probably will never know the difference.
Also marine ply is often used with inferior grades of ply as it will often be covered by paint or something similar.
This is one of many reasons the grain is sometimes good on one side and very poor on the other.
If the wood is sealed good you wont ever notice a difference especially on a model boat.

Shakespeare powerboats used marine ply for their 27 foot powerboats during the 60's and early 1970's.
But not on their speedboats, the speedboats that were made by this company are often still seen around to day.
Bristol wooden powerbioats didnt use marine ply neither, this could of been to do with weight i dont know.
When full size boats need to have ply replaced they do use marine ply, this is because water has already attacked the
beams and insides of the boat etc and marine ply gives that little extra help.
But even with marine ply, you still need to seal the wood, this can be done with eithera 50% varnish and 50% white spirit mix
or with a epoxy coating, the choice is yours.

Riva speedboats seal their boats using the 50-50 varnish and white spirit mix, and if its goiod enough for Riva, then its definitely
good enough for model use.
Other companies who have used this method to seal wood in the past has been c.j broom norfolk,peter freebody hurley,
w bates and son chertsey,hucks boatyard hampton,turks boatyard teddington to name just a few top notch boat builders.

If you dont seal the wood then paint or varnish can come off leaving exposed wood that will soak up water and eventualy it will
come through and damage the interior of the ply.
Also by sealing the wood you will not see as much movement in the wood due to temperature and moisture.
By the process of the sealing, the fibres of wood change, so whatever wood you choose ,do make sure you seal it.

why not just use birch ply for the whole outside of the boat anyway ?
youl find it gives a much smoother base to start with.

if you were going to leave the boat in the water all the time, then circlip would be right



phill
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Roadrunner

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Re: Miss Britain 3
« Reply #5 on: February 02, 2011, 04:21:06 PM »

Dude, im gonna give you the best bit of advice ever.

Do it the way you want  :-))

Use the materials you want to use. spend what you want to spend.

If you want to use marine grade ply, use it, it certainly won't do any harm in the long run even 'sealed' normaly ply will not last long once the paints or varnishes get chipped off and you have a few dents on the hull. O0

All my wooden boat builds have been with marine ply, when using sheet material, the cost is somewhat more expensive but really a 8x4 sheet of  normal ply =20 here mariner grade 28... (thats 3mm) hmmm i rather spend a further 8 on marine grade just to know that my boats gonna live longer then 5 years before i start spotting mould, or rott appearing.

All that aside my other motive for using marine graded ply is that i run on salt water not clear pond.
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dadandlad

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Re: Miss Britain 3
« Reply #6 on: February 02, 2011, 10:01:45 PM »

Cheers boys lots of advice for me to think about there
Roadrunner thank you for that first piece of advice,i have fallen into the trap of building for others i:e just as one build is completed people are asking what you are building next and before you realise it you are building another model and missing out on the pleasure of what you have just completed and it becomes a chore not a hobby

Had a Mcculloch chainsaw given today which had seized,turned out a fuel tank bolt had come loose and jammed in the flywheel so i now have a engine
Quite a nice compact unit which will fit under the superstructure and the bonus of being 39cc
The engine has a two bearing 4 bolt mains crank and needle roller small and big end so should be plenty strong enough
With it coming from a chainsaw it has a output shaft at either end of the engine one for the magneto and one for the clutch
The clutch is going to take a little thinking about to set up as the clutch bell is the opposite way to what you would expect i:e it drives at the rear of the clutch bell rarther than out the front as you would expect if you get what i mean (may have to post a pic or two)

I have a question for you,viewed from the rear of the boat which way does the prop turn
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Arrow5

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Re: Miss Britain 3
« Reply #7 on: February 02, 2011, 10:18:21 PM »

Props can turn any way you like, custom made props are available . Are you going to do a bit of tin bashing for cowlings etc?   Oh I do think pictures are in order , yes.  Even engine butchery pics. Check your email, Duncan.
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martno1fan

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Re: Miss Britain 3
« Reply #8 on: February 02, 2011, 10:21:46 PM »

I have to agree with Phill Marine ply is a waste of money on a model boat,just seal it well using slow setting epoxy and an old credit card spreading thin layers and scraping off the exess and your good to go.Brush it on the inside and its never going to rot,these are toy boats not real boats lol.As for engines try ebay you can pick up soveriegn 28 cc strimmer engines very cheap and theyre great little engines,way better than mcculoch.Also check your chainsaw motor they usually rotate the wrong way ie clockwise instead of anti.
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Arrow5

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Re: Miss Britain 3
« Reply #9 on: February 02, 2011, 10:26:44 PM »

Why is it the wrong way Martin, its not a circuit boat ?
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martno1fan

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Re: Miss Britain 3
« Reply #10 on: February 02, 2011, 10:43:33 PM »

Wrong way because he will struggle to find the right props in rh rotation,theres limited props for these size engines in rh rotation so its easier to go with a motor that spins the right way  ;).These motors need large props to perform well.
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phillnjack

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Re: Miss Britain 3
« Reply #11 on: February 02, 2011, 11:13:45 PM »

when looking at the boat from the stern (back end) the prop turns anti clockwise.

youl probably find you cant use the clutch end if it spins clockwise, unless you plan on
getting either special props or a gearbox.  (expensive )

This is why not many people use chainsaws, the power is there but the wrong way round.


I done it years ago with a chainsaw ,and got a AMPS outdrive unit and turned the gears around to give me the right direction, but it
was total disaster for finding right size prop.
Ended up going back to glow  and strimmer engines.


phill :-)
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Arrow5

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Re: Miss Britain 3
« Reply #12 on: February 02, 2011, 11:26:52 PM »

Thanks  Martin , and Phil,  good for future ref, well I can dream cant I. {:-{
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Bill D203

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Re: Miss Britain 3
« Reply #13 on: February 02, 2011, 11:28:31 PM »

Cheers boys lots of advice for me to think about there
Roadrunner thank you for that first piece of advice,i have fallen into the trap of building for others i:e just as one build is completed people are asking what you are building next and before you realise it you are building another model and missing out on the pleasure of what you have just completed and it becomes a chore not a hobby

Had a Mcculloch chainsaw given today which had seized,turned out a fuel tank bolt had come loose and jammed in the flywheel so i now have a engine
Quite a nice compact unit which will fit under the superstructure and the bonus of being 39cc
The engine has a two bearing 4 bolt mains crank and needle roller small and big end so should be plenty strong enough
With it coming from a chainsaw it has a output shaft at either end of the engine one for the magneto and one for the clutch
The clutch is going to take a little thinking about to set up as the clutch bell is the opposite way to what you would expect i:e it drives at the rear of the clutch bell rarther than out the front as you would expect if you get what i mean (may have to post a pic or two)

I have a question for you,viewed from the rear of the boat which way does the prop turn


If you look direct onto the prop from the reear of the boat the prop gose anti clock
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dadandlad

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Re: Miss Britain 3
« Reply #14 on: February 03, 2011, 12:13:49 AM »

Cheers boy
Luckily with this build the engine will be running the right way  due to the hull not being very deep and the long shallow angle the propshaft comes through the hull at i will have to have a gearbox at the front of the boat.
I already have plans to build my own gearbox from a small hydraulic gear pump  :-)) which basically involves milling a old pump body down and making a couple of covers,when i have obtained the pump i will show you with pictures how it is done( yes i have made one before) these gearboxes have a 1-1 ratio

Now i dont want to start world war 3 but what size prop would be a good starting point
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Roadrunner

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Re: Miss Britain 3
« Reply #15 on: February 03, 2011, 08:47:29 AM »

Between 40mm and 50mm is a good starting point, i would suggest a 3 bladed prop personally but you can use a two blade with no problem , best solution is to buy plastic props first and test the boat,(so 40, 45&50mm in 2 or 3 blades or both)  once your happy with the right prop you can look at upgrading to Brass.
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martno1fan

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Re: Miss Britain 3
« Reply #16 on: February 03, 2011, 11:50:31 AM »

Not wanting to cause any confusion but why not go with leccy power ? the new brushless motors are cheap nowadays and i reckong with a low kv 880 motor you will get reasonable speed also.The turnigy t 600 880kv motors seem popular and at $35 theyre cheap,run it on 6s lipo and it should move quite well.
Heres a 40" cat running one with 1100 kv on two 6s lipos.If you want to go petrol id go with a strimmer engine rather than the chainsaw one just for simplicity.Incidently a friend has started a build of a 58" apache with two of these motors,together they can put out arround 6+ hp lol.Checkout offshore electrics forum and ask for some info there might be better options but for the price these motors seem pretty good value.
Mart
http://www.youtube.com/watch?v=9kgn5vhOdZQ
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Roadrunner

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Re: Miss Britain 3
« Reply #17 on: February 03, 2011, 12:23:17 PM »

Problem with electric is run time and cost of lipo's if your suggesting brushless electric setup. ( don't say get cheap imports as an answer to this comment, if your going to use lipos use decent quality ones, its just not worth the cost when they go bang!)

Lipo's are not for the faint hearted as it is and the charges become an expense many do not want to pay, your showing videos where a lot of money has been spent on decent lipo's and brushless setups, i have no doubt these guys know what there doing and have money to burn.

Even brushed motors running from LA may not be suitable due to weight.

Obviously using an engine may not sound the best solution given that many lakes/ponds now ban IC use and the hazards of running an engine powered boat cause a lot of other hazards unless fail safes are added.

But dudes decided he wants to go for an engine, and if he's got somewhere to run it then i say go for it, if it was a mistake then there's only one way to learn and that be the hard way!
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martno1fan

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Re: Miss Britain 3
« Reply #18 on: February 03, 2011, 01:25:21 PM »

The boat i linked has one $35 motor  ok2two batterys costing $100-150 an esc 120A about $60 with custom water cooling and usuall hardware,not that expensive and these setups seem to run very well.Runtimes on that setup is arround 12-15 mins im told,inexpensive setup i agree but proof is in the pudding as they say.
Not telling anyone how to do anything just giving other options,however the chainsaw idea is not worth the time and effort I.M.O. especially when strimmer engines are easy to get hold of but performance with one will be disapointing in this hull.Anyway whatever he decides to do is his choice ,good luck with it.
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dadandlad

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Re: Miss Britain 3
« Reply #19 on: February 03, 2011, 05:19:00 PM »

Why will the performance be disapointing with a strimmer/chainsaw engine in this hull ?
Wouldnt the same apply to electric
Past experience suggests to get a model boat going fast on electric tends to be quite expensive
Cost of engine so far 0.00
Well looks like the challenge has been set and maybe i will learn the hard way but at the moment Miss Britain 3 is going to be fitted with a unusable chainsaw engine :}
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Roadrunner

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Re: Miss Britain 3
« Reply #20 on: February 03, 2011, 09:24:22 PM »

i don't think there's really a difference between a chainsaw or a strimmer motor to be honest, either will work just as well  :-))

And yeah your right Brushless set-ups are expensive especially when using lipos!

keep with the engine sounds like a lot of fun, i only wish Ic wasn't banned here  >:-o
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phillnjack

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Re: Miss Britain 3
« Reply #21 on: February 04, 2011, 01:58:50 PM »

The difference between chainsaws and strimmers is the direction the motor turns
one turns one way, and the other turns in opposite direction.

so its easies t to get one that turns the right way.

if not you have trouble with props and shafts nuts etc.

both are very similar on power ofcourse, and if anything the chainsaw has a bit more grunt



phill
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dadandlad

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Re: Miss Britain 3
« Reply #22 on: February 04, 2011, 04:59:58 PM »

Phil
If you look at Miss Britain 3 the engine sits in the rear and there is a driveshaft that goes forwards to a gearbox which in turn drives through a long propshaft to the prop at the rear of the boat.
I propose to do exactly the same otherwise there is nowhere for the engine to fit,so the engine turning the wrong way into a gearbox with just 2 spur gears in changes the direction it turns to the right way for a good choice of props etc
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martno1fan

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Re: Miss Britain 3
« Reply #23 on: February 04, 2011, 05:28:41 PM »

Phil
If you look at Miss Britain 3 the engine sits in the rear and there is a driveshaft that goes forwards to a gearbox which in turn drives through a long propshaft to the prop at the rear of the boat.
I propose to do exactly the same otherwise there is nowhere for the engine to fit,so the engine turning the wrong way into a gearbox with just 2 spur gears in changes the direction it turns to the right way for a good choice of props etc
Why try to reinvent the wheel when there are ways to do it the KIS way (Keep It Simple).Strimmer engine and a flex cable is the way to go rather than chainsaw and gearbox,less things to go wrong etc etc.This is a model and for it to run well it needs to balance right so motor placement is crucial so sticking it at the back is a bad idea but what do i know.Anyway ive said what i think so ill just wish you well  :-)).
Mart
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Roadrunner

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Re: Miss Britain 3
« Reply #24 on: February 04, 2011, 05:34:10 PM »

A gear box may work just as well, especially if he wants to gear up or down the shaft output right?
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