1/350 Kirov (Trumpeter Modified)

[cunumdrum61]

... The props also do not have the normal bullet shape spinner but have what I would describe as four flanges. ...

Simply amazing - I've looked at that picture a thousand times and never noticed the spinner flanges. Now that you point it out, I can see it clearly. Thank you very much! Of course, now I have to figure out how to build it...

By the way, do you consider the source of your plans (meaning the draftsman) to be accurate? I've seen several drawings and plans, some better and some worse, but all of them have at least some instantly obvious errors which, of course, makes the entire thing suspect. For instance, I have yet to see a plan that correctly shows the underwater hull tunnel around the props or a believable rendition of the stabilizer fins. Partly for that reason, I'm not using plans in this build. Instead, I'm trying to work strictly off of photos (they have their own set of problems).

Do you have access to photos that could be shared or posted?

Your project sounds fascinating. Please consider starting a build thread and showing us your progress. I'd be quite interested in the entire laser cutting process and how it turns out.

Thanks for your help!

Regards,
Bob

Hello Bob,
I am happy I could help you with the props.I am reviewing the plans for accuracy. I do not have photos at this stage but in May will be travelling back to Russia to visit the family and I will be visiting one of the ships for a photo tour. My Uncle has secured the general builders plans for all of these ships from the shipyard. I will collect them in May when I return. We had to pay for them one way or another, maybe you understand! I would really like to develope a kit in 1/200 scale for sale but I do not know if I have time for this. Is one reason I am cutting parts with laser and lexan for my build.I will only have to complete the difficult work once!

[carr]

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[Timmy C]

I assume you've seen all the Navsource pics, but in case not:

This one sort of looks promising:
http://www.navsource.narod.ru/photos/02 ... 165019.jpg

Also these:
http://www.navsource.narod.ru/photos/02 ... 165027.jpg
http://www.navsource.narod.ru/photos/02 ... 165028.jpg (looks like covered boats on the forward half of the deck?)
http://www.navsource.narod.ru/photos/02 ... 165034.jpg (not so much the deck, but does show strange lattice work in the mack recess)

http://www.navsource.narod.ru/photos/02 ... 165035.jpg
http://www.navsource.narod.ru/photos/02 ... 165037.jpg (sunlit, but annoyingly tarp-covered)
http://www.navsource.narod.ru/photos/02 ... 165038.jpg (well-lit and clear, but only the starboard half )


I'd go trawl through the Airbase forums, but they're down at the moment (and have been for the last few days), so I can't do that at this time.

[carr]

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[cunumdrum61]

Bob, on my plans for Peter The Great there are 4 hatches on this level with the three fuel cells.I can see if I can aquire a scanner to post it but is of the sister ship so they may not be the same.
Cunumdrum

[Admhawk]

Help! I need some photo interpretation assistance and/or propellor expertise. I'm working on the Kirov propellors and I can't decide what the curvature, if any, of the prop blades is. I understand that the blades have an angle relative to the axis of the shaft but I'm talking about an additional, compound curve. Here is the only decent photo I've come across. Ignore the tunnel comments. That was for something else.

Here are the three possible blade curvatures:
A - blades curve back towards the stern
B - blades are straight and have no curvature
C - blades curve forward towards the bow

I've argued myself in and out of all three possibilities and can't come to a definitive conclusion. There's a lot of optical illusion in the photo. Remember to look at both props before answering and, yes, I know the two sets are oppositie but, again, that's not what I'm struggling with. Can anyone help?

Thanks,
Bob

Bob, Most modern Naval props have a compound reversing curve, or whatever you'd like to call it. This photo is of a Canadian Frigate prop and the curve can be seen to go in both directions. A lot of countries use similar styles for military ships. It is a variable pitch prop and it is shown in the neutral position.

HTH's
Darren

[carr]

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[carr]

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[Neptune]

Sorry to lecture again, if it sounds so, but the compound curve only counts for variable pitch propellors.

When you put pitch 0, stopped, the shaft keeps turning, but the propellor pitch delivers 15% forward with one part of the blade and 15% thrust backward, this way you reach a total thrust of 0%, hence stopped. The engine however, is delivering 30% thrust. (this results in a total astern capacity which is a lot less than on a fixed pitch propellor going astern).
The circular base is indeed the pitch mechanism, the shaft is hollow, filled with high pressure hydraulic oil. This oil is pushing a ram towards the hub, on the circular base of the blades there is an excentric pin, which is engaged in that ram. By moving the ram aft or forward the blades turn. In the hub there is a spring, which pushes the blades aft towards the ram when you reduce the pitch. When hydraulic pressure falls away, the spring will also put the blades in neutral position 0%, so that you don't get into trouble (or less so ) when it happens.

I'll take some picture of our spare propellor on deck, perhaps the curve of a fixed pitch will be clearer this way. I'll also upload a pic of another fixed pitch prop. Later...

[carr]

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[Timmy C]

Mr. Foeth's member name is "EJFoeth": memberlist.php?mode=viewprofile&u=3582

[Neptune]

Yeah we have. A 4 bladed skew prop. She's a nearly 8m diameter and weighs a little over 27t. We have "a lot" (not so evident on gas carriers) of space here. Not so easy to take pics either, hence I didn't take it today, I need the intrincically safe camera for that.

Anyhow, here the other prop, from a previous ship. Fixed pitch hence the curve is going only in one direction.
The compound curve on the variable pitch prop (I was in a hurry this afternoon) is caused by the neutral position of the blades. As mentioned, in 0 position, the prop is pushing ahead (hence has an ahead pitch/angle of the blade compared to the hub) with one part of the prop and with the other part of the prop it's pushing astern. So practically the angle of these two parts has to be opposite, the two parts are the inner part and the outer part of the blades and hence the angle of the inner part of the blade has to be opposite to the other part of the blade. (hence the twisted look from the side) If the blades are in full ahead position the angles are turned so much that both of them push in the same angle, although of course the difference is still the same. In astern propulsion the shaft keeps turning the same direction, only the blade angle is changed so that the prop delivers astern power.

A fixed pitch prop is totally different. The angle is always ahead in one direction. To stop or switch to astern you stop your engine or you just reverse the turning direction of the prop.

[Admhawk]

I didn't mean to imply that all props had the same curve or that Kirov was a Variable pitch. I just wanted to show how much a prop blade can curve. Here is a pic of a USN Carrier prop, albeit in it's wrapping still. See how the leading edge is curved, the trailing edge is straight, the pitch is fwd, but the blade curves out and forward as well making it look odd. Not like the old style that looked like tulip petals or spoons.

[carr]

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[Admhawk]

The pitch angle looks right, but I think you have the leading edge and trailing edge reversed. If you look only at that blade, the top points almost straight up. The bottom, is pointing forward and is sort of pointed so that it digs into the water as the prop rotates. The Prop appears to rotate so that the top is turning out from the ship, which is also common on USN ships.

[Neptune]

Darren is right, leading and trailing edge are reversed, but the explanation of the base and angles is correct. You got it all right, the port prop on the Kirov is showing the same as what you can see in my first picture, taken from an angle towards the prop. You can see the blades look a lot different from a side or front view.

To go one step further, if I remember correctly that change in angle, from 40 to 70� or so, is caused by the fact that the tip rotates much faster than the base, to keep the pressures/forces on the prop balanced, they change the angle of attack of the parts of the blade, gradually of course. Outward turning props have a bigger wake, but are supposed to get a better manoeuvrability, no experience with it, so can't really say if it's true or not.

[Neptune]

Here is our spare one.




The ship is of the '90's just to give an idea that is an older prop. Leading edge is on top as this is a right turning propellor (means clockwise seen from aft).
The blades on the carrier prop and our props do seem to be somehow bent forward, but that could be optical illusion (although I doubt it). Mr. Foeth for sure knows more about it if you can contact him.

[carr]

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[EJFoeth]

The 'twist' you can see at the trailing edge is most likely a simple addition of curves of the propeller.

The pitch angle at the hub of the propeller is always the largest, but flattens out toward the tip (going to zero for a very large propeller). The side-view of Neptune's and Admhawk's picture shows this clearly. The outer area's sweep a much larger distance. So the pitch angle goes down, but the pitch remains comparable going from hub to tip.

The second curve is the skew; that's a line going from the hub to the tip halfway the chord length of the blade (chord is the distance from leading to trailing edge at a radius). This is a propeller with lots of skew:



This one doesn't have any



As you can see, this skew can drastically alter the appearance of the propeller! These two:



may have the same chord lengths at each radius, but appear slightly different due to the skew distribution.

The 'trouble' is that skew displaces the chord forward and aft: not purely in the aft view but along the pitch line which varies along the radius.



So, this combination of a varying pitch angle plus a varying chord length plus a varying skew angle can give that odd 'bent' trailing edge shape, but that is quite normal.

Nearly no propeller curves toward the bow when set in the normal setting (i.e., not in reverse), but nearly always curves aft.

[carr]

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