PabloPicasso
Well-Known Member
Would adding a lead shoe to the bottom of a cast iron keel improve performance?
Lead
- Thread starter PabloPicasso
- Start date
penfold
Well-Known Member
How long is a piece of string? It will increase righting moment, wetted area, draft, strain on the keelbolts and the surrounding hull structure. Did the designer specify a shoe or lead keel?
Neeves
Well-Known Member
If you want to improve performance and are willing to stick your neck out:
Remove the cast keel, replace with a low profile deeper keel (machined from high tensile steel) but with a flange welded on with the same profile/area as the existing keel (so bolts straight on) and add a lead shoe to the fin.
The new keel will have lower surface area, could be designed with the same righting moment (so lighter) or better righting moment ..., strength of hull structure? It will obviously have more draft - you would need to alter your depth alarm
. You might need a bigger wallet.
Modifying keels is not uncommon. Machining the fin from HT steels is standard practice.
Jonathan
Remove the cast keel, replace with a low profile deeper keel (machined from high tensile steel) but with a flange welded on with the same profile/area as the existing keel (so bolts straight on) and add a lead shoe to the fin.
The new keel will have lower surface area, could be designed with the same righting moment (so lighter) or better righting moment ..., strength of hull structure? It will obviously have more draft - you would need to alter your depth alarm
. You might need a bigger wallet.Modifying keels is not uncommon. Machining the fin from HT steels is standard practice.
Jonathan
geem
Well-Known Member
Or if you are really keen on performance add a tungsten shoe. 1.7 times heavier than leadIf you want to improve performance and are willing to stick your neck out:
Remove the cast keel, replace with a low profile deeper keel (machined from high tensile steel) but with a flange welded on with the same profile/area as the existing keel (so bolts straight on) and add a lead shoe to the fin.
The new keel will have lower surface area, could be designed with the same righting moment (so lighter) or better righting moment ..., strength of hull structure? It will obviously have more draft - you would need to alter your depth alarm
Modifying keels is not uncommon. Machining the fin from HT steels is standard practice.
Jonathan
DanTribe
Well-Known Member
Yes it probably would, I've seen some competitve racing boats do this.
It isn't a 5 minute job though, and need careful planning if you aren't used to this type of work.
It isn't a 5 minute job though, and need careful planning if you aren't used to this type of work.
Lightwave395
Well-Known Member
I have a different keel (fin and lead bulb) to the original (the original design was an asymmetric fin, later with smallish added lead shoe), fine but get it done professionally. The floor and hull structure of my boat was strengthened quite extensively and there have been no problems since the job was done nearly 20 years ago
William_H
Well-Known Member
I agree. The weight on the tip of the keel increases righting moment but this only becomes significant at like 45 degrees or more of heel. A trigonometric function. Many boats at 45 degrees of heel will exhibit weather helm which must be counteracted by rudder so inducing drag. So for good performance you need to keep the heel a lot less.
So unless you have a concern regarding self righting ability extra lead may not help.
Regarding Neeve's idea of new keep deeper and I think he meant lower chord we have some boats here called BakwellWhite 7 with such a deep low chord keel with ballast bulb. The low chord means that the keel does not work very well to windward until you get some significant water speed. But once up to speed they go extremely fast.
ol'will
