Though I started at the beginning of February, progress is pretty slow. Only two days ago I joined the hull together. The biggest concern is seams, and it's a pain sanding them smooth. (Are all Trumpeter kits like this?)

The torpedo tubes have been relocated 3/8" higher up on the hull, since the uppermost door on each side is just above the midline. I've reshaped the sail top, added a beacon to the dorsal rudder, and the new pumpjet shroud is nearly finished (fashioned from a segment of model rocket nose cone).

http://jtrun.mine.nu/cc/fox/Seawolf04.jpg
http://jtrun.mine.nu/cc/fox/Seawolf05.jpg
http://jtrun.mine.nu/cc/fox/Seawolf06.jpg
http://jtrun.mine.nu/cc/fox/Seawolf07.jpg

The ventral diagonally-placed "shark fins" are also repositioned higher up, as per photos of the real thing and other models. The bow shape is still inaccurate, but not enough to really bug me. Also visible are the new escape trunk hatches, which exist as blisters on the weather deck. The wide aperture arrays are also reshaped.

I'm still trying to decide on paint job: black with red lower hull (all-black sonar dome) or all-black. Opinions?

I like your modifications. How long is that model? It looks to be a a decent size. Also What version od the Titanic is in the background? I don't reconize the lifeboat/davis design.

Jake

Thanks. The Titanic is the sinking toy/model that came with an educational booklet. It's designed to fill with water and split in half when it reaches a critical point in sinking.

Right now, the biggest problem I see with the Seawolf kit (aside from the inaccuracies) is the poor joints, especially between hull halves. While smoothing them out, the joints are flexing as I'm applying pressure to the hull, and I ended up with an 8-inch split along the seam. I've spread some glue on the affected area, and I'm hoping that will help solve the problem. I probably won't eliminate the seam completely, as it'll be needed as a guide for painting the red lower hull.

While smoothing them out, the joints are flexing as I'm applying pressure to the hull, and I ended up with an 8-inch split along the seam.

I reinforce the seams on virtually every plastic model that I build. Even the small models get reinforced.

I have a package of Evergreen styrene strips. They are .015"X.188". On some models (like most WWII airplanes), you can reinforce a fuselage joint after initial assembly. There's generally a gaping hole in the bottom of the fuselage where the wing sits so you can assemble the fuselage and then glue styrene strips along the joint through that big hole.

If I can't access a joint after assembly, I will glue a styrene stip along ONE side of the joint with half of the plastic glued in place and the other half exposed. This creates a lip on one side of the hull that will form a lap joint when the hull is assembled. Smear some glue on the lip formed by the plastic strip and assemble the hull halves. The edges of the hull joint butt up against each other as in normal assembly. The plastic strip laps over both sides making for a much stronger joint.

I didn't discover the seriousness of the problem until after the hull halves were assembled (the bow and stern subassemblies, as well). I think I've solved the problem by squeezing the seam open and filling it in with glue, followed with a thin veneer of putty, that I sanded smooth.

The seam seems to have been taken care of, and now I've moved forward and aft to take care of the bow/stern attachment seams. I still haven't decided if I'm going to eliminate the scribed line along the freeboard waterline, however.

Thanks for the tip.

Leet, great modification.
I think the scribed line on the waterline will be needed for painting?

Looks COOL Leet! :thumbsup: can't wait to see it compleated!

I'm not far from painting. All that's left is to smooth out the shroud and finish smoothing out the hull. Here's some progress pics:

http://jtrun.mine.nu/cc/fox/Seawolf08.jpg

Overall view. Note the escape trunk blisters.

http://jtrun.mine.nu/cc/fox/Seawolf09.jpg

Sail with new top, cut out lookout position, and slightly lengthened forward ramp.

http://jtrun.mine.nu/cc/fox/Seawolf10.jpg

Stern showing repositioned shark fins, tail lamp, and new forward pumpjet struts. No impeller, since I don't know its design (nor does anyone but the builders, I imagine).

Hooray :) - I've receive my Seawolf 1/144 yesterday, and have examine the hull, and other parts which consider necessary to be modified.

the bow, eventhough not favourable but I think won't be modified (too much effort, and I'm too anxious to build one).

for torpedo bay, Leet's model are tempting me to do the modification. I will consider doing the same with mine.

For the top of the sail, I'm thinking to build the mast to be retract/extractable.

and for the impeller, I dunno how to build this one. Should I replace the schimitar blade with maybe (papermade) fan like shape?

and for the impeller, I dunno how to build this one. Should I replace the schimitar blade with maybe (papermade) fan like shape?

I would suggest looking at turbofan construction for clues about this. Check out the fan on this Trent 900:

http://www.azom.com/news.asp?newsID=2445

One of my first jobs was as a turbine compressor case inspector. Part of that job involved insuring the minimum possible clearance between the blade tips and the interior of the compressor case.

A tight seal is necessary to prevent "tip loss" where pressure bleeds away at the end of the blade tips.

The use of a scimitar shape inside a shroud makes very little sense. Because scimitars come to relatively small point at the outer end, you can't effectively seal pressure at the tip. If you can't seal pressure at the tip, there seems to be no point in using a shroud. I would also point to aircraft piston powered ducted fans as an example. When the propellor is shrouded, the tips are usually broad and flat.

Brent, thanks for the tips and reference. I think I'll use the blade close to Trent 900 for my Seawolf impeller (accuracy is not guarantee though) :).

Sorry if this is going off topic, but still related to the ducted propeller. I've seen a Typhoon (Russian SSBN) using shroud and the prop blade is not schimitar, it's more to the props with broad-plane.

Can it be said in simple way that, shrouded propeller will be more effective to have a broader props, instead of the schimitar like?

This is where aviation continues to provide the best and most visible analogies.

Note the wings on the world's most efficient aircraft. Check out that jet that Steve Fosset just flew around the world and the plane Rutan and Yeager flew around the world non-stop a few years back...and gliders. Those all have extremely high aspect wings. In other words: enormous wing spans compared to wing chord.

A wing and a propellor both create high pressure on one side and low pressure on the other. In both cases, that pressure will bleed around the tip and make the other wing or prop less efficient. That's why aircraft generate wing-tip voticies. The wing-tip vortex is caused by high pressure air bleeding out sideways and swirling into the low pressure on top of the wing. That causes inefficient lift production at the wing tip.

By creating a long wing, that area of inefficiency is made to be a small part of the total wing. That inefficient area still exists...but it may account for only 10% of the wing instead of 20%.

Have you noticed most modern jets have turned-up "winglets" or tip sails at the tips? This has the effect of blocking the bleeding air from swirling into the low pressure area on top of the wing. It makes the wing more efficient by "sealing" the low pressure top wing from the high pressure air under the wing. A 10' tall tip sail is said to be the equivalent of an extra 30' of wing span for increasing efficiency!

Propellors work EXACTLY the same way. If a prop is not shrouded, a long scimitar shape is most effective. It acts as a high aspect ratio foil which provides a lot of area with minimum efficiency loss at the tip.

If the prop is SHROUDED, it is not necessary for the blades to be long and thin. The shroud itself will seal the pressure at the tips. The shroud becomes like the tip of an infinitely long wing...like a continous tip sail. Therefore, you can use a much broader prop to creat more lift or "drive" generating area.*


*Obviously, I don't design submarine propulsion systems! But this is still fluid dynamics (just water instead of air) and I've spent a lot of time with turbine compressors. I have a compressor rotor in this room from an Allison 250 helicopter engine (a souvenir from my old job :)) and it looks and awful lot like a submarine pump jet.

Brent, thanks for the in-depth illustration. As an amateur on this matter I agree with your statement. Especially the 'continuous tip sail', now it make sense.

One more question, for shrouded prop, does a let say 10 wide blade prop will give a greater speed then the 7 wide blade prop? Or still have to consider the number of blade against the pressure or maybe drag?

Leet, maybe this discussion can give us a rough idea about the impeller for our Seawolf?

Leet, regarding the shroud for 1/144 Seawolf model.
I found this pic:
http://subase-inet.tripod.com/images/seawolf_con1.jpg

and after a rough calculation, I found that the shroud provided by Trumpeter is more and less have a same dimension to the picture. So, it seems that the shroud for the model won't have to be bigger as per Thor designed?

Using the aircraft engine analogy (with which I am most familiar) there are several factors involved in the size of the blades.

When you have a powerful engine, delivering that power becomes complicated. I have recently posted pics here of a model Sea Fury and a Corsair. Both were very powerful piston engined fighters. The Corsair produced around 2300hp and had an enormous prop...13' in diameter as I recall. The Sea Fury was even more powerful at almost 2600hp. This created a problem because, as a prop gets larger, the tips near supersonic speed and become very inefficient. Rather than go to a larger diameter, an extra blade was added. You will note if you look at the photos in my Sea Fury thread, it has a 5 bladed prop.

You can also make the blades wider. The width of the blade is refered to as the "chord". The same term describes the width of a wing frm leading edge to trailing edge.

Yes a 10 wide prop blade can deliver more power** than a 7 wide prop blade. However as the chord increases (be for a wing or prop/fan blade, a phenomenon called "induced drag" also increases. Induced drag is the byproduct of fluid passing over a surface. For this reason, you don't want to make a driving blade any wider than necessary.

So think of fan or propulsor design along these lines:

1)How fast is it turning? The faster it turns, the smaller it must be (example from my own experience...a big T-56 turbine engine from a Hercules which is a couple of feet in diamter turns at 15,000rpm but a little Allsion T-63 turbine at 6" in diameter turns over 50,000RPM)

2)How thick (chord-wise)can the blades be before the induced drag is too great?

3)If the blades can only be a certain length because of the speed...and they can only be a certain chord because of the induced drag...then you can calculate the number of blades you will need to optimize performance.

It's a balancing act.

**I use the term "power" instead of speed. In the airplane world, there is a expression that power doesn't buy speed. You can take a small plane that does maybe 150mph on 150hp then DOUBLE the horsepower with a 300hp engine...but maybe only gain 20mph! Speed is most commonly determined by the efficiency of the airframe or, in the case of a ship/sub, the hull.

However, even if you don't get a speed advantage, the extra power does give several other advantages. You get substantailly increased acceleration, rate of climb and load carrying ability. Another way to look at it: my 455 engined Trans Am isn't much faster than my mother's 4 cylinder Corsica...but it get's up to maximum speed a WHOLE lot quicker and it could do it towing a trailer :).

As a little addenda to all this, for those who don't know, I actually have a 1/48 scale radio controlled LOS ANGELES class sub model.

It has a very unusual drive train.

Because it has a prop that's almost 6" in diameter, it has to be geared to an almost unheard of low speed.

Most model boat electric engines run from about 15,000RPM for smaller ones to 5,000RPM for larger motors. Geared motors tend to be in the 3,000RPM range.

My submarine model is geared down to 320RPM! Not 3200...but 320RPM. It has so much prop that turning it any faster would not only be unrealistic, it would probably snap the unuiversal joints.

I don't have a picture of this sub on my site but it can be seen on the Deboer website.

Brent,
for discussion, let say Seawolf do have 10 wide prop blade (refering to more blade, maybe she can have 11 or 12, we don't know eh :) ). She has more power, can the drag be compensated by the shroud?

if the drag can be compensated, maybe the speed of 10 prop shrouded can be said is faster then the 7 prop shrouded?

The roundabout way to answer that is to say you can always compensate for drag if you have enough power. If you are trying to harness a lot of power, you may have no choice but to make very wide blades.

Maximum "efficiency" is not always the desired outcome. The wings on a sailplane are 10 times more efficient than the wings on an F-104 Starfighter. But try putting Schweizer glider wings on an F-104 and what happens? Believe it or not...that very idea exists (sort of): The U-2. The net result is a very efficient airplane that flies very high and very slow. That's great for a recon plane but useless for a fighting plane.

I would assume the makers of the Seawolf do the same balancing act that any fan maker does. Making very wide blades may be the only choice when faced with various options (adding more stages with more drag, making longer slow turning blades, etc.)

hmm, great. Now I'll try to model the blade of my Seawolf prop, refering to pic posted earlier by you and prob will have wide blade. Thanks Brent.

It's been a while. Here's where I'm at at the moment:

http://jtrun.mine.nu/cc/fox/Seawolf11.jpg

A bit blurry, but you can see the pumpjet shroud is in place, and the capstans are painted. Since that photo was taken, I've installed the masts and now I'm mulling over the gloss finish. I'd like to try Future, but I've never used it, so I'm afraid of ruining the paint job. Any tips?

Some clearer photos:

http://jtrun.mine.nu/cc/fox/Seawolf12.jpg
http://jtrun.mine.nu/cc/fox/Seawolf13.jpg
http://jtrun.mine.nu/cc/fox/Seawolf14.jpg
http://jtrun.mine.nu/cc/fox/Seawolf15.jpg

Leet, great paint job :)
Too bad I can't give any tips regarding 'Future' have heard it but never use it.
btw, just curious, why do you want to have a gloss finish? most of the modelling tips I've read is suggesting to at least semi-gloss it or using a clear doff to increase the real look of a model.

The gloss is the undercoat, for applying the dry transfers before I finish with a flat coat.

And I've gone with a Krylon gloss coat, speaking of which. My lack of an airbrush precludes using Future.

hi Leet, any pic of the finished model of the Seawolf :)
after the decal, etc.

None yet. I'm still waiting for the dry transfers to come in. I have no itention of using those.... decals.

Leet, just to let you know, if you are going for authenticity... the anti-fowling paint (what use to be red) is now black. My brother in law is on the Seawolf, so yes... this is a confirmed source. just thought i would let you know before you finished the model completely.
-Mike

I've known about the all-black scheme for some time, actually. :) Seawolf was apparently first fielded with a red lower hull, however, so that's what I decided to go with. Adds a bit more interest to the boat than painting it with subtle shades of black.

Of course, if I decide to kitbash one into SSN-23, I'll be required to paint it all-black.

There ya go, nothin wrong with switchin things up a bit right? ;) ya this is going to be my next model, i'll be using the acrylic water to make the wave break over the front of the ship (that will be interesting to make), then obviously the massive white caps next to the boat. Like you i'll be using the dry transfers, giving it a more realistic look. i'll be sure to post pics as i go along, showing minor modifications and such. most likely after the Seawolf, i'll be moving onto an SSBN. probably the Ohio. BIG BOAT! :tongue: ok well enjoy the rest of this build! good luck and post more pics once you're finished!

-Mike

SSN-21, thanks for the confirmation upon black anti-fouling for current Seawolf.
Still the red scheme of the boat give a more interesting color to the model LOL.

btw, does anyone have the photo of SSN-21 USS Seawolf photo showing the black anti fouling (dry dock pic)?

Here's the USS Texas (SSN-775) launched on April 9th:

http://www.navsource.org/archives/08/0877526.jpg (copy and paste to your browser)

She obviously has a grayish scheme running down from a few feet below the freeboard waterline to perhaps the midline. It might be a more purplish color. Someone on modelwarship.com's forum commented that a similar scheme was used on Seawolf when she was commissioned, but that it was only a temporary scheme.

Leet, thanks for the link - great pic.
using the graying scheme from waterline to midline, probably the remaining parts of the lower hull is painted red?

ok, here's my work.
still lack of the mast and bridge extension (I dunno what it called, the iron's crow nest in the top of sail).

some part of the sail is being modified based on real thing