LakeErieMonster

Does anyone other than MarsKeel make split torpedo bulbs to add on a keel?

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Just curious: what sort of additional structure are you planning to handle the RM loads? Or are you cutting down the existing keel and adding bulbs up higher, maintaining the approximate lever arm?

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11 hours ago, Diarmuid said:

Just curious: what sort of additional structure are you planning to handle the RM loads? Or are you cutting down the existing keel and adding bulbs up higher, maintaining the approximate lever arm?

Planning on adding a bulb (approximately 300 lbs) to the bottom of an existing fin keel.  Will need to reinforce the keel sump and surrounding areas.  Will also make some enhancements to the chain plates and supporting structure to account for the extra load on the rig.

 

Thanks for the link, sailorman44.

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5 hours ago, LakeErieMonster said:

Planning on adding a bulb (approximately 300 lbs) to the bottom of an existing fin keel.  Will need to reinforce the keel sump and surrounding areas.  Will also make some enhancements to the chain plates and supporting structure to account for the extra load on the rig.

 

Thanks for the link, sailorman44.

While reinforcing the sump won't hurt,  for most boats all adding a 300 lb bulb will do is slightly reduce the SF - provided you aren't talking about a 2,000 lb boat.

Rig wise, a 300 lb bulb is like putting another couple of bodies on the rail - at best at normal heeling angles.  So again, while bolstering the chain plates won't hurt, I don't think it is necessary.

Performance wise, those Mars add on bulbs do not have a low drag shape.  You really want a pointy laminar bulb for low drag - if you are doing this for performance reasons.  I know a couple of boats who have added these and they make the boat stand up better, but overall it was considered to be a detriment to performance.  Mind you, this was in the lighter winds of PNW, so YMMV.

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How about adding balast tanks.  I've seen one of Soverel had a bulb, which was manufactured in Canada.

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6 hours ago, 12 metre said:

While reinforcing the sump won't hurt,  for most boats all adding a 300 lb bulb will do is slightly reduce the SF - provided you aren't talking about a 2,000 lb boat.

Rig wise, a 300 lb bulb is like putting another couple of bodies on the rail - at best at normal heeling angles.  So again, while bolstering the chain plates won't hurt, I don't think it is necessary.

Performance wise, those Mars add on bulbs do not have a low drag shape.  You really want a pointy laminar bulb for low drag - if you are doing this for performance reasons.  I know a couple of boats who have added these and they make the boat stand up better, but overall it was considered to be a detriment to performance.  Mind you, this was in the lighter winds of PNW, so YMMV.

Is there a company that makes "pointy laminar bulbs" like you describe?

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7 hours ago, 12 metre said:

While reinforcing the sump won't hurt,  for most boats all adding a 300 lb bulb will do is slightly reduce the SF - provided you aren't talking about a 2,000 lb boat.

Rig wise, a 300 lb bulb is like putting another couple of bodies on the rail - at best at normal heeling angles.  So again, while bolstering the chain plates won't hurt, I don't think it is necessary.

Performance wise, those Mars add on bulbs do not have a low drag shape.  You really want a pointy laminar bulb for low drag - if you are doing this for performance reasons.  I know a couple of boats who have added these and they make the boat stand up better, but overall it was considered to be a detriment to performance.  Mind you, this was in the lighter winds of PNW, so YMMV.

Original post did not specify bulb weight; thought maybe it was 700-1000 lbs, or something. Since the Soverel 33 is already running a ballast/D ratio of around 48%, likely the keel attachment is pretty stout & can handle an extra 12%. Tho dynamic loading is a tricky business....

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57 minutes ago, LakeErieMonster said:

Is there a company that makes "pointy laminar bulbs" like you describe?

Not that I am aware of.  They would have to have a vast array of molds to cover varying lengths and widths, bulb volume, etc. 

Probably have to be custom made.  To be honest I haven't seen too many early day bulbs that don't have a pretty crappy shape.  Usually way too full forward because they were using shapes derived from 2D foils (aircraft wings).  Tom Speers I believe is the guy who took 3D flow around a bulb into account and he suggested taking the y ordinates of a wing section and raising them to the 1.5 power which generates a much pointier shape than a standard wing section.

But first you want to start with a 2D laminar section like a NACA 66xx.  A four digit NACA as a starting point would be a poor choice for a bulb

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5 minutes ago, Diarmuid said:

Original post did not specify bulb weight; thought maybe it was 700-1000 lbs, or something. Since the Soverel 33 is already running a ballast/D ratio of around 48%, likely the keel attachment is pretty stout & can handle an extra 12%. Tho dynamic loading is a tricky business....

No, but he did in the third or fourth post.  300 lbs per below

13 hours ago, LakeErieMonster said:

Planning on adding a bulb (approximately 300 lbs) to the bottom of an existing fin keel.  Will need to reinforce the keel sump and surrounding areas.  Will also make some enhancements to the chain plates and supporting structure to account for the extra load on the rig.

 

Thanks for the link, sailorman44.

 

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OP gave the weight in response to my question. So it's not like I missed it.:rolleyes:

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