SUBSIM Radio Room Forums - View Single Post - Deck Gun Removal Mod for GW [MOD RELEASE]

Observer · 04-26-06, 10:36 PM

Since you asked for feedback...

I'd like to first point out that I don't have any data to prove or disprove this mod, so on to my points and questions:

1. German U-boats (Type II, VII, and IX) were not generally optimized for underwater travel from a hydrodynamic point of view. The hull shape, very similar to that of conventional surface ships, was optimized instead for surface travel (obviously with an eye towards surfaced and submerged stability). It wasn't until later when submarine designers tried to optimize hulls for underwater travel (for example, but not limited to, albacore shaped hulls).

These optimized types of hulls do suffer from changes in flow across the hull that result in performance changes. A classic example is the 688 high speed turn behavior, or the loss in speed due to hull fouling (such as the "grass skirt" for those boats deployed to warm water areas such as the Med.). This type of fouling can have a significant impact on the boats performance. Also included in this optimization is the screw design.

2. How, exactly, does deck gun removal shorten the time it takes to submerge the boat? Do the ballast tanks flood faster? Does the change in buoyancy and center of gravity somehow cause the boat to submerge faster?

3. How, exactly, does the deck gun removal impact rudder efficiency and improve U-boat turn radius?

4. The increase in submerged speed you suggest is apparently due to the improvement in hull efficiency from the removal of the deck gun. While this may seem reasonable, it's probably not very likely for a number of reasons. First, U-boat hulls tend to have quite a few projections that will induce drag, items such as railings, flak guns, hand wheels on hatches, and so on. The loss of the deck gun and the subsequent improvement in hull efficiency is probably small when compared to all the other drag causing items attached to the hull. The most significant, and overlooked item is the sail. It has a much bigger impact on stability and drag than any other component. By the nature of its shape size and location, the U-boat sail is completely unoptimized from underwater travel (no smooth fairings, many projections and so on).

5. I suspect you can't find any information about the improvement in boat handling characteristics because it is negligible at best. Any improvement is speed is most likely too small to measure.

Just some thoughts with no U-boat data to substantiate...

04-26-06, 10:36 PM	#7
Observer Commander Join Date: May 2005 Posts: 477 Downloads: 6 Uploads: 0	Since you asked for feedback... I'd like to first point out that I don't have any data to prove or disprove this mod, so on to my points and questions: 1. German U-boats (Type II, VII, and IX) were not generally optimized for underwater travel from a hydrodynamic point of view. The hull shape, very similar to that of conventional surface ships, was optimized instead for surface travel (obviously with an eye towards surfaced and submerged stability). It wasn't until later when submarine designers tried to optimize hulls for underwater travel (for example, but not limited to, albacore shaped hulls). These optimized types of hulls do suffer from changes in flow across the hull that result in performance changes. A classic example is the 688 high speed turn behavior, or the loss in speed due to hull fouling (such as the "grass skirt" for those boats deployed to warm water areas such as the Med.). This type of fouling can have a significant impact on the boats performance. Also included in this optimization is the screw design. 2. How, exactly, does deck gun removal shorten the time it takes to submerge the boat? Do the ballast tanks flood faster? Does the change in buoyancy and center of gravity somehow cause the boat to submerge faster? 3. How, exactly, does the deck gun removal impact rudder efficiency and improve U-boat turn radius? 4. The increase in submerged speed you suggest is apparently due to the improvement in hull efficiency from the removal of the deck gun. While this may seem reasonable, it's probably not very likely for a number of reasons. First, U-boat hulls tend to have quite a few projections that will induce drag, items such as railings, flak guns, hand wheels on hatches, and so on. The loss of the deck gun and the subsequent improvement in hull efficiency is probably small when compared to all the other drag causing items attached to the hull. The most significant, and overlooked item is the sail. It has a much bigger impact on stability and drag than any other component. By the nature of its shape size and location, the U-boat sail is completely unoptimized from underwater travel (no smooth fairings, many projections and so on). 5. I suspect you can't find any information about the improvement in boat handling characteristics because it is negligible at best. Any improvement is speed is most likely too small to measure. Just some thoughts with no U-boat data to substantiate...