Paddleducks

Paddler Modelling => Construction => Topic started by: mogogear on June 10, 2011, 01:38:34 AM

Title: Stability and the use of bilge keels
Post by: mogogear on June 10, 2011, 01:38:34 AM

I have seen much about the stability issues with paddlers. As I am working on design for a side-wheel ship- I thought I would ask about this . I have not seen any references to the use of bilge keels to assist with this.

I realize that they would not be able to be deployed on the hull at too great an angle due to the constraints of the wheels. This may be the geometry problem that I do not fully understand in hull design.

Would someone knowledgeable address if they( bilge keels) would be of service ?

Thanks

Title: Re: Stability and the use of bilge keels
Post by: andy on June 10, 2011, 05:13:14 AM

Maybe a keel like a head- like on some old spanisch galeons- maybe not so good for paddlers.
 ;D

Andy

Title: Re: Stability and the use of bilge keels
Post by: Mercury on June 10, 2011, 07:47:57 AM

Some real paddlers did have bilge keels but to be useful they would need to be over scale on a model. I have seen this method used to correct poor stability on a jeanie deans model and it can work well.

A more successful and less obtrusive method is to fit a removable fin keel with a bulb. This was recently retrofited to the Glen Rosa model shown in Model Boats a few years back and has dramatically improved stability.

Title: Re: Stability and the use of bilge keels
Post by: mogogear on June 10, 2011, 02:00:51 PM

Thank you for the replies...I understand the concept of removable keel.."bulb" I do not- I will see if I can find a google search to show me a picture for me to understand ( or if you know of a handy one...) ;)

Title: Re: Stability and the use of bilge keels
Post by: derekwarner_decoy on June 10, 2011, 03:25:18 PM

Hi PD's.......mogogear...conventional bilge keel plates could be best considered as used to minimise the PORT to STDB rocking motion caused by waves during motion

The stability issue noted with paddlers is more a metecentric point of balance issue together with the fine lines of some hulls AND high windage affected above deck structures

I do agree with Mercury that overscale bilge keel plates would be beneficial over scale bilge plates, just as overscale rudder surface area is helpful with model scale for improved steerage ...so technically model bilge keels must work in reducing side to side roll  :goodnews

Try GOOGLE for marine term "turn of bilge" & you will see a radius element between the lower hull horizontal plane & the hull vertical plane...if you considered installing a bilge keel plate at 45 degrees to both the horizontal & vertical planes you clearly see any limiting protrusion height

Another point to consider when looking at full sized vessels with bilge keel plates is that there is in most cases a series of longitudinal slots between the hull & the bilge keel plates which allow for a reduction in sea pressure acting on the actual keel plate..... :whistle

Having said this I added bilge keels to my Decoy hull build as below :hammer.......many years ago ....Derek

Title: Re: Stability and the use of bilge keels
Post by: mogogear on June 10, 2011, 10:54:43 PM

Thanks Gents- to you all !!! :trophy

Title: Re: Stability and the use of bilge keels
Post by: andy on June 11, 2011, 02:37:05 AM

And the roundabout stability of the running wheels?

Andy

Title: Re: Stability and the use of bilge keels
Post by: mogogear on June 11, 2011, 09:38:27 AM

Quote from: andy on June 11, 2011, 02:37:05 AM

And the roundabout stability of the running wheels?

Andy

I am lost with that Andy.....? :thinking......just call me thick

Title: Re: Stability and the use of bilge keels
Post by: derekwarner_decoy on June 11, 2011, 10:33:41 AM

Hi PD's........just guessing  :whistle ...but I think Andy is talking about the gyroscopic effect of the wheels rotating ......Derek

Title: Re: Stability and the use of bilge keels
Post by: mogogear on June 11, 2011, 11:26:22 AM

All good then...I will take all the stability I can muster- and if the paddles "gyro" action helps all the better


I am a live steamer so I will have a boiler / burner / fuel tank and an engine sitting pretty low in the hull and will be working on how to keep the superstructure light.

Thanks gain for helping me try to pt my arms around the new variables for me to consider

Title: Re: Stability and the use of bilge keels
Post by: the bombus on September 23, 2011, 06:03:40 PM

hello mogogear
i must have overlooked this one since i posted a question in the hulls forum
(on wich i already found an answer myself ;D)
i found a nice picture of something that could solve your problem i think
let me know if it was any good at all
oh yes , is there a reason why the sidewheelers are in the majority here  :P
greetings from bombus

Title: Re: Stability and the use of bilge keels
Post by: mjt60a on September 25, 2011, 12:00:28 PM

Quote from: mogogear on June 10, 2011, 02:00:51 PM

...I understand the concept of removable keel.."bulb" I do not- I will see if I can find a google search to show me a picture for me to understand ( or if you know of a handy one...) ;)

...as I understand it (not having built any sailing boats) a 'bulb' keel consists of a kind of torpedo made of lead suspended some distance below the hull, like this -
http://www.myhobbystore.co.uk/product/27873/mm1298-tricorn