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Author Topic: twin prop installation  (Read 1539 times)

roger

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twin prop installation
« on: October 12, 2010, 08:01:56 AM »

I have looked - for the last hour! It's all really interesting, but you are all so prolific that I could be looking for days :o , so I apologise if my question has already been answered somewhere here.

I haven't made a twin prop model before. Do I install the propshafts parallel or toe them out like you see in aircraft twins?

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derekwarner

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Re: twin prop installation
« Reply #1 on: October 12, 2010, 09:05:25 AM »

Welcome Roger...... {-) ...it is not a silly question...but could I ask do you have a plan for the original full sized vessel?

If so scaling the dimensions/angles could be a good starting point.......................... :-)) Derek
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Derek Warner

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BarryM

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Re: twin prop installation
« Reply #2 on: October 12, 2010, 10:15:24 AM »

Roger,

Parallel.

Barry M
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roger

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Re: twin prop installation
« Reply #3 on: October 12, 2010, 04:25:06 PM »

Not an issue Roger but could you please leave Blue text for the moderating team.  It helps it to stand out and everyone knows it's a comment from the Mods.

Thanks

BB



Thanks for the prompt replies guys.
Hey, Derek, it never occurred to me that it was a silly question! %)  This oneís a 1:32 Stantug 1906 using a MMM hull (not yet started Ö itís my winter project). The Damen drawings of the original (that I have scaled up ready for the workshop) are rather basic, but it seems to show parallel propshaft lines (as Barry says) as far as I can tell. The MMM drawing is even worse and doesnít show propshaft locations at all.

I read somewhere that toe-out on model aircraft twins makes no noticeable difference if the engines are close together. However, as I recall (from several years ago), the full-size Grumman Goose (I think it was) has a most noticeable toe-out.

Old No7 on rcgroups.com (http://www.rcgroups.com/forums/showpost.php?p=12902938&postcount=10) does suggest toeing in the rudders slightly so the inboard rudder turns a tighter circle than the outboard rudder. I havenít been able to find any more info yet.

I guess I could build in offset for same-handed props, but the props will actually be opposite handed.

Anyway, itís a tug not a speedboat so I donít think it really matters. Iím just being fussy as usual Ö which is why Iíve stuck to bash-around toys so far! :-)

Iíll post some build details when the winter weather drives me indoors Ö and every year thereafter Ďtill itís finished! :}

Regards,
Jolly Roger
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roger

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Re: twin prop installation
« Reply #4 on: October 12, 2010, 05:23:22 PM »

Thanks for the headsup BB. I didn't know that.
JR
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nemesis

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Re: twin prop installation
« Reply #5 on: October 12, 2010, 08:00:01 PM »

Hello, You often find that the rudders are not directly behind the props centre line, they are offset, either inboard or outboard depending on the craft. It is to fascilitate the removal of the drive shafts without disturbing the rudder gear.  Nemesis
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roger

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Re: twin prop installation
« Reply #6 on: October 12, 2010, 10:59:24 PM »

Quote
...often find that the rudders are not directly behind the props centre line...

Thanks Bill, I hadn't thought of that. In this case, though, the props will be in fixed Kort nozzles and the rudders will need to be (easily?) removable just to get the props off.

@@@@@@@@@@@@@@

As I said, I'm nowhere near ready to start construction yet. In fact it may be two or three months away as I have a few other projects on the go. (One of which is actually modifying one of those plastic Seaport Workboats to the style of a Stantug 1906 (albeit single prop), so I'm aiming to make all my mistakes on that first!)
I'm presently just doing some planning here and there and collecting materials and goodies as the pocket money allows. :((  And, of course, I'll be seeing what ideas and tips I can steal learn from here. :-)

I'm sure I will have many more questions later but I'll collect them up and see what I can solve myself first. It's all part of the learning process.

JR
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