LORRAINE by a butcher

[Andy CParticipant @andyc56856]

Been having a look around the web, People Scale are a US sight but say the deliver to the UK. How th at would be I do not know. there website is here

Lots of different figures, not just the usual Armed Forces, searchable by height.

Andy

[lnvisiblemanParticipant @lnvisibleman]

Thanks Andy, I found that one earlier but didn't really want my crew in business suits and that is all they have in the required scale.

Just an observation but why is it that that there are so many model boat and accessory manufacturers yet so few do any figures to go with the models?

Those that do seem to cast them in gold judging by the price they want .

Ignore me, just an OAP having a moan.

[Dave MilbournParticipant @davemilbourn48782]

From the box containing one of his figures:

Adrian's Marine Figures
The Well House
27 Smith Street
Spratton
Northampton NN6 8HW
Tel: 01604 846461
E-Mail [email protected]

There doesn't seem to be a website at the moment but I'm sure he will have a catalogue of some description.

Dave M

[lnvisiblemanParticipant @lnvisibleman]

Thanks Dave

**LINK**

I found this link and it seems that Adrian only does lifeboat figure or trawler crew at the scale I need.

I tried the phone number but after ringing for ages, it goes to a fax machine !

**LINK**

I have also sent email to the address given here but it is sent back as undeliverable or delayed !

Mike

[Amy jane SeptemberParticipant @amyjaneseptember49770]

….looks like you'll just have make them yourself…….Ashley will explain how to make them from a tree branch….

[lnvisiblemanParticipant @lnvisibleman]

Spent ages whittling out a few more bits for the cabin and made some progress on assembly.

It has been a bit of s struggle getting a good fit around the superstructure but I think that the current situation is acceptable, unless you awl thinks different !!

Would it be silly to print pictures of the cabin interior and fix them inside the frames to give the illusion of looking inside?

It would get round the problem of a crew but I would still need the obligatory bikini clad babe on deck somewhere.

Any volunteers Amy ?

[lnvisiblemanParticipant @lnvisibleman]

Changing the subject for a bit, I am starting to look at power plants for this little lady.

As the object is to save as much dosh as poss and get her running for as little pain as pos, I intend to use one of the mobility scooter motors that I have been given. They are mostlyl 24v but vary a lot in power output.

1/ unloaded speed 4,500 rpm 170 watts

2/ 6,000 rpm 275 watt

3/ 2,500 rpm 350 watts

4/ 12 volt 4,000 rpm 200 watts

Any suggestions as to which to use and what prop to hammer onto it would be much appreciated. The overall weight of the boat should be in the region of 40 lb or 18 kg.

BTW I am looking for something like a scale speed of 30 knots if possible , or MORE if I can

Edited By lnvisibleman on 25/04/2014 12:02:37

[Amy jane SeptemberParticipant @amyjaneseptember49770]

Good evening.

I think you would be struggling to get that sort of performance from any of those motors. For a comparison, my "birthday boat" weighs in at 30+ lbs, has a scale speed of 20 -25 knots on a 2 hp (1700 watts) engine. Granted my engine is not a particularly 'hot' unit, but would still be useing at least 1000-1200 watts at around 4,000 rpm. The prop is a 4 x 7 inch

Looking at your boat, I think she would be somewhat easier driven than mine though.

(I shall go and change into my bikini, jump into the scanner, email the logarithims, and you can pop me out of your 3d printer)

[lnvisiblemanParticipant @lnvisibleman]

Morning Amy !

I think your monster is a somewhat larger scale than mine. At 1/16 scale, I think 30 knots equates to only just over 3 ft per sec. so I didn't think it would be a problem. Maybe on of the more technically brilliant members will be able to help out with the calculations.

Looking forward to the email with baited breaths !

[Amy jane SeptemberParticipant @amyjaneseptember49770]

Hi there.

Just thinking aloud here, so please bear with me. I may well be wrong, and hopefully some one will tell me if I am!

Any way, here goes.

Scale speed of a model is determined by the wave pattern that the hull makes as it moves through the water, rather than the scale the model is built to. I haven't decided the scale I will build my boat to yet. at 2"=1' it will be a 30 odd footer, and at 4"=1' it will be 15 odd feet. At either scale the wave pattern will be the same, and at either scale she will be travelling at the same speed, and will look as if she is doing 25 knots.

I'm guessing here, but I would pick that the full sized version of your model would be 50 odd feet? At 30 knots a 50 footer would be fully planning, so the model would also have to be. 3 feet/sec = 180 feet/min x60 = 10,800 feet/hr , / 6040 feet ( a nautical mile?) =1.7 knts. (Gee I hope I've got this right) I don't think Your model will be fully planning at 1.7 knots. What ever the case, you are going to need enough power to get a 40 lb model fully planning, which may well take more than 1/3hp.

Forgive me for rambling on, even If I'm talking through a hole in my head, it's food for thought, if nothing else!

I'm really enjoying your build, your models going to be a cracker! Thanks for sharing.

Amy jane

[lnvisiblemanParticipant @lnvisibleman]

" Scale speed of a model is determined by the wave pattern that the hull makes as it moves through the water, rather than the scale the model is built to. "

Oh dear !! I have shown my total lack of knowledge regarding "SCALE ". Can this be true ? Has size nothing to do with speed ? Someone please explain in words of one syllable coz at the moment this makes no sense to me . I wouldn't dream of arguing with a lady, or Amy Jane , but how can this be ???? Are we talking sci -fi principles here ?

[Dave MilbournParticipant @davemilbourn48782]

You will not get that hull planing – it's the wrong shape. This looks like the classic 30's gentleman's leisure cruiser and would be hard pushed to do much more than about 20 knots flat out. If you must use one of your motors then I'd suggest the one which does 6000RPM with no load, coupled to a three or four bladed prop of about 50mm diameter.
DM

[lnvisiblemanParticipant @lnvisibleman]

"You will not get that hull planing – it's the wrong shape. This looks like the classic 30's gentleman's leisure cruiser"

Morning DM

Can't say that planing was on my mind, just a decent turn of speed. I must have made the wrong model, I don't do " Gentleman " or "leisure cruising ". The reason for using one of my stock motors is simply to keep costs as low as possible. I am , after all, just a hard-up OAP having at bit of fun at the pond. My first venture was completed with a total cost of £48.76 including all rc equipment.

If all I can get is a steady plod then so be it, until my next lottery win comes around.

 

Edited By lnvisibleman on 26/04/2014 08:41:20

[Amy jane SeptemberParticipant @amyjaneseptember49770]

Morning.

Sorry if I've muddied the waters for you. I'll try to clarify things a little, (then I'll shut up!)

Basic principles:

(Please don't be offended, I am in no way trying to be rude)

A boat is a hole in the water, as it moves forward it has to dig the hole in front of it, and fill it in behind it. The size of the hole equals the weight of the boat, (displacement). At low speeds there is little movement of water. As speed increases, the boat has to dig the hole faster in front of it, and fill it in behind faster too. As the speed increases more, there will come a point where the boat simply can't dig the hole fast enough. It will have a big bow wave and the stern will squat low in the water. This is known as hull speed. On a boat like a tug boat it will happen at a bit more than the square root of the boats waterline speed. A boat with a 25' waterline length will reach hull speed at about 7 knots. In order to go faster there are two aproaches. 1. Design the hull so that it can climb up out of it's hole, and skim over the water surface ( planning) or 2. Make the boat very long and narrow, so that the water moves around it with the least possible resistance. Your boat is not narrow enough for option 2, so it will have to plane. As Dave points out, this may not be possible. (the hull shape is not too bad, but at 40 lbs it may not have enough bottom area to develop the lift required to climb up out of it's hole) I think, using one of the scooter motors you have a scale speed of 12 knots would be achievable and would be a very scale like and respectable result.

I hope this helps, if not ignore it!

looking forward to seeing her on the water.

(I'll shut up now)

Aj

[lnvisiblemanParticipant @lnvisibleman]

So am I right in saying that my next step should be to calculate the exact finished weight of the little lady ?

I am only stating a 40 lb point coz that is what Mr Smeed printed on the plans.

Maybe mine will be lighter as modern materials could be less dense and stronger.

But surely, no matter what the weight of the model, it will still have to be ballasted down to the correct waterline giving the same displacement regardless?

Excuse me for being an idiot, a good job I don't do "offended"

Mike

[ashley needhamParticipant @ashleyneedham69188]

Amy. Scale speed. Bang on. The speed at which a boat looks best on the water to your own eye. Mine usually go fairly fast (er than others might think of as scale)

Mike. What about having an off-centre motor mount and using belt/pulley drive?? this will enable easy motor swaps for trialing, and of course gearing would also be easy to do , to make best use of slower revving or higher torque motors?? will depend on getting some pully wheels of course. Could MAKE pully wheels for the propshaft, only needs drilled discs and a couple of nuts and washers…….or meccano ones if using 4mm shaft.

Printed interior. Unusual, easy, go for it. Light up the cabin interior to show the interior better. Make a card interior "film set" style. Fill it with big name celebrities… Colin, Paul T and so on..

I might ballast to a minimum level that I was happy with if I were building this. Don`t want it too heavy, affects performance and your back.

Ashley.

[Gareth JonesParticipant @garethjones79649]

Mike,

Based on my collection of boat performance data I would go for the same suggestion as Dave Milbourn, use the 6000 rpm , no load motor with a 50 mm 3 or 4 blade prop as a starting point.

Just as a guide I have some data from a Graupner Speed 900 BB which has an unloaded speed of 6500 rpm.

With a direct drive 55 mm 4 blade prop it did 3150 rpm with an input power of 145 watts.

With a direct drive 65 mm 4 blade prop it did 2650 rpm with an input power of 170 watts.

Generally you should aim for a max rpm loaded which is around 70% of the unloaded speed so both the above props are too big. I think the other three motors might be too slow, unless you use a really big prop to absorb the potential power but then you are into tug boat territory rather than a cruiser.

Gareth

[lnvisiblemanParticipant @lnvisibleman]

Does the pitch of the prop have any bearing on this ?

[Gareth JonesParticipant @garethjones79649]

Yes, but I have not really looked at the effect of different types, just used general purpose ones rather than skewed blades or others suitable for high speed operation. I guess there will be an optimum pitch but your guess would be as good as mine as to what that is. I would get in the right ball park in terms of diameter first and then try different pitches if you want to optimise (and spend more money).

Gareth

[lnvisiblemanParticipant @lnvisibleman]

The reason I ask is that my old tug used to have a steam engine in it that ran at about 1400 rpm unloaded and that pushed it well. My son-in law then changed it  to an old car heater motor,(I'm not the only skinflint in the family ) and it was more like a speedboat afterwards.

That tug had a 70mm scale steam prop that is designed for low revs and very high torque. "Prop Shop " item No. V27541 with a pitch of 104mm ( 1:1.5 ratio). From what I can see, most general purpose props have a much lower pitch to cope with the high revs of most electric motors.

I'm probably barking up the wrong tree, but I thought that the heavier pitch would give me more POWER  ( thrust ) with these very high torque motors.

Mike

Edited By lnvisibleman on 26/04/2014 13:58:46

Edited By lnvisibleman on 26/04/2014 14:00:03

[Gareth JonesParticipant @garethjones79649]

Hi Mike,

You are right about the coarse pitch prop being more suited to a high torque low rpm motor. However there is a balance between the torque, rpm and power. You can absorb the same amount of power at a low motor rpm with a big diameter/coarse pitch propeller or a high motor rpm with a small diameter/fine pitch propeller. The first option is most suitable for a low speed application like a tug, the second is more suitable for a high speed application like a torpedo boat. The boat can't go any faster than the speed that the propeller pushes the water backwards.

I find its pretty difficult to accurately predict the best combination. With electric motors I usually measure the unloaded speed using a simple optical tachometer and then measure the loaded speed with the propeller in the water. If the ratio of loaded to unloaded is in the range 70-80% the propeller is about the right size. If its lower you really need a smaller propeller or a finer pitch, unless you are only going to use high power settings occasionally for short periods. If the ratio is higher, i.e. greater than 80% the propeller is too small for the motor or you need a coarser pitch.

Gareth

[ashley needhamParticipant @ashleyneedham69188]

Unless making a prop, I would advocate going for a simple two blade plastic one as they are really really cheap.

All this talk of different sizes and pitches is all well and good, and eventually will need to be considered BUT props in these ranges are moderately expensive , and considering the budgetery nature of this build this is an item I feel that could be left to last (if a shiny brass prop is desired). A bunch of forinstance 40/50/55 mm S and X pitch items will give a good range to play with but cost less than half a brass prop.

Gareth. An optical tacho has long been on my list of things to buy (especially considering the number of craft I have with air props..I dont think they are dear nowadays?? I should really get round to it!

Ashley

[lnvisiblemanParticipant @lnvisibleman]

Well Gareth, that makes things a bit clearer. As it happens, I am the owner of a digital laser tachometer that will do the job nicely. All I need is a paddling pool, or maybe the pond at the bottom of the garden, and I can check the readings against your figures.

Watch this space.

Mike

[lnvisiblemanParticipant @lnvisibleman]

Ashley, I have in my box of bit a couple of brass props, 1 x 50mm 1 x 40mm, so I will give them a try,

Hang on a moment !! When did I mention anything about "BUYING" anything ????

[ashley needhamParticipant @ashleyneedham69188]

Blast!! I forgot that! ignore me will you. Of course you have a few spares and are going to use them first..

Ashley

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