Mississippi 1870 Build

[Eddy Matthews]

Yep, it looks magnificent Richard! You've certainly done a superb job, and I hope your happy with the results?

[Khephre]

With a bit of care you can tune a model to the conditions by distributing ballast around the hull in different ways.


You can minimize pitching by putting your ballast at bow and stern. This helps keep the hull stable and helps to cut through waves instead of riding them.

If your model is relatively top heavy or has a lot of weight high up and outboard (e.g. a side paddler or a shallow draft stern wheeler) , then you can achieve the strongest righting effort by concentrating the ballast along the centre line.

However if your model is relatively light in the superstructure, then you might be able to spread the ballast across the beam to give an easier roll and more realistic handling.

cheers
Tony

[bundyrap]

Hi All

Not a good day on the pond.

After securing 2kg of lead down low along the centerline of the hull ( thanks for input guys) I thought I would be in business but it was not the case. With a bit more of the rigging and assorted poles added I found that this 2kg was not enough to hold her up in anything above dead calm conditions. No more ballast could be added with water lapping the decks with 2kg of lead in the bottom.

Drastic action was needed. Out came the ballast and a .5m long, 1.5kg  keel was slung 200mm below the hull! This gave me a little more free board and certainly stiffened her up but very unscale. Out onto the open lake and moderate conditions of 5 - 10 knotts and the first gust tipped her over!

Doing the sums, at this size the Mississippi displaces about 5-6kg. If I made her half as big again giving her a length of about 1.4 metres she would displace nearly 20kg.

My thinking is that a boat of this style, amount of superstructure and detail built to a scale giving a sub metre length is not a practical model in anything other then dead calm conditions - great for the shelf though.

So this is where my Mississippi project ends for now. It has been great fun, I've learnt so much but I haven't ended up with very sailable model which was my main aim. Time to move onto a lower, bigger boat with new challenges.

Thanks for everyone's input over this build and look forward to the new one.

Richard

[derekwarner_decoy]

Hi PD's  & as 'bundyrap' says....

Doing the sums, at this size the Mississippi displaces about 5-6kg. If I made her half as big again giving her a length of about 1.4 metres she would displace nearly 20kg.

Michael...if I may suggest

1) you have completed a superb looking scale model & with the   accolades of many PD members
2) we cannot scale mother nature, so the cube root of wind = any model vessel with high potential will suffer from WINDAGE
3) last week we had Brett S Hallet repost after two years in the desert.......if you go back to the old PD postings you will find many communications from Brett & others on what not to build... like our PS GEM or PS Captain Stuart...... all due to the   above water superstructure WINDAGE issue etc

Have   & then GOOGLE  'Float a Boat Plans' & :news  you will be happy

regards Derek

[derekwarner_decoy]

OK   ...& appologies....the communication was to Richard.....who the the bloody hell is Michael  :rant anyway :?:  :?:  :?:  :?:  Derek    

[derekwarner_decoy]

OK, the fog has lifted......Bundyrap...   again.. have you considered increasing the actual draft of your Missi....

1) go to the fruit market, get an empty polystyrene brocilli box [580 x290 = 168200 sq mm]
2) fill the bath with water, get the kitchen scales & trial the required force [mass = extra displacement] to get the box to draw say 25mm
3) go the a surfboard manufacturer & get a 60 mm thick off cut of board foam
4) epoxy resin the board foam to the hull of Missi.... & then blend it in
5) after the desired displacement increase has been trialed [2 to 4 kg?] it's a simple matter sanding, blending & filling then glass matting & epoxy resin

A simple alternative to the Missi.... just collecting dust & the vessel will not look out of keeping.....
Some time back our cousin, Tony [M]  from NZ suggested  :computer  using granulated lead shot [available from gun shops] as ballast - insert  a few layers of cling wrap into the hull cavities, pour   the pre calculated amounts of lead & then flood with epoxy resin....  then this provided ballast blocks that would not move and are removable   etc....

From memory some of the plans for OZ paddlers from Float a Boat  are listed as having the draft incresed for scale stability... I did the same in Y2000 when I drew the lines for my PS Decoy, but  :ohno as I need extra ballast - [Decoy I mean] - Derek  :music

[bundyrap]

Hi Derek

Interesting idea that - love the way you think.

So I strapped a 500 x 150 x 70 chunk of foam on the bottom with 2.5 kg of lead imbedded in it. This brings the water line up to where it should be but the C of G is still too high.

My problem is the top decks weigh all of 1.8kg and sits nearly 300mm above the water line and this is with only 2 of the 4 funnels fitted. I need way more than 2.5kg of lead and much deeper than 70mm to counter this in a static sense let alone to counter windage out on the water.

I'm very happy though with it. I've learnt heaps, had great fun building her and the design intrigues me enough to have another go in the future at a multideck, rearwheeled Mississippi style boat.

For now I'm looking at the PS Adelaide or the Zulu. My thinking is they are lower and bigger with more displacement. Would either of these be a reasonable choice?

Richard

[Eddy Matthews]

I can't comment on the Adelaide Richard, but certainly the Zulu makes a superb working model....

One othe rsolution to your stability problem is to use Dereks idea of adding to the bottom of the hull to give more bouyancy, but then add a removeable drop keel (a smaller version of a yacht keel) to get the COG even lower - Lots of models have been built using this method, and if you have it as a bolt on attachment it can be removed for static display...

[thewharfonline]

Adelaide would have very little deck housin which means (depending on materials used) it wouldn't really be too heavy on the top.

She has her wheel house and a small cabin on top, the sunken cabin in the stern, the two sponson boxes and that is all, well apart fromt he incredibly large engine and boiler!

If you want any photos feel free to ask...I just seperated all my adelaide potos into a seperate folder.

[Peter Webster]

I have so far built the Pevensey, Adelaide and Captain Sturt and am currently building a larger Pevensey, the first on was only 1/32 scale and this one is from the Float A Boat plan at 1/24 scale, and the other boat is a bit of fun and is a Blockade Runner based on Glynn Guest's boat and is scaled up 1 1/2 times with a different bow and stern and some aother mods and additions but all of these models have been or are being built of mainly balsa hulls and superstructure and doped with usually 4 coats of progressively thinned dope. No problems so far and that is after about 2-3 years of heavy use. The only problem I have encountered is windage with the Captain Sturt so that is relegated to calmer days, so try using balsa andif you choose the Adelaide just keep the weight low.
Peter Webster

[bundyrap]

Hi All

I think I will build both the Zulu and Adelaide. I'm spoilt with two big work benches from plane building days and I tend to 'bog down' just building one thing for months so two it is.

The Zulu's engineering is captivating and it is proven design. The problem is getting a plan. I've had one on order from Taubmans since October but the last email from Don says he should have it on the way to me this week so we will see. Meanwhile I'll start finding out about a lathe and how to hook it up to the CNC software.

The history and local flavour of the Adelaide make it a must build. Again as Peter has found it seems a good design to model with relatively low superstructure and if I scale up the Float-a- Boat plan one and a half times to 1.5 metres there should be plenty of displacemnet to play with. Did you increase the hull depth Peter with any of your Murray River models?

Pictures of the PS Adelaide would FANTASTIC and the more the merrier! Would it be alright to post them in here or should I start another thread on the building of the PS Adelaide? I'm guessing pictures of the Adelaide would be as it is today with the round paddle guards and lowered rear cabin. My current thinking would be to build it in this form as it was originally built and not the modified square box version.

Lots of reading and sums to do.

Richard

[thewharfonline]

Wherever you want me to place them I will. Square box Adelaide definately isn't as exciting as the 'original' round box version.

The Float-A-Boat plans are for the square box aren't they?

You can get plans for all three of the Port of Echuca's boats from their gift shop and I assume this is round box Adelaide.

[Peter Webster]

Richard,
             No , I didn't increase the hull depth but did use the foam method as outlined by
Derek as an increase in buoyancy and a safeguard against sinking , if needed, but
thankfully this has not been required as yet.
Peter W
( In smokey Melbourne)

 Hi All
 
 I think I will build both the Zulu and Adelaide. I'm spoilt with two big work benches from plane
 building days and I tend to 'bog down' just building one thing for months so two it is.
 
 The Zulu's engineering is captivating and it is proven design. The problem is getting a plan. I've
 had one on order from Taubmans since October but the last email from Don says he should have
 it on the way to me this week so we will see. Meanwhile I'll start finding out about a lathe and how
 to hook it up to the CNC software.
 
 The history and local flavour of the Adelaide make it a must build. Again as Peter has found it
 seems a good design to model with relatively low superstructure and if I scale up the Float-a- Boat
 plan one and a half times to 1.5 metres there should be plenty of displacemnet to play with. Did
 you increase the hull depth Peter with any of your Murray River models?
 
 Pictures of the PS Adelaide would FANTASTIC and the more the merrier! Would it be alright to
 post them in here or should I start another thread on the building of the PS Adelaide? I'm
 guessing pictures of the Adelaide would be as it is today with the round paddle guards and
 lowered rear cabin. My current thinking would be to build it in this form as it was originally built and
 not the modified square box version.
 
 Lots of reading and sums to do.
 
 Richard
 
 

[Bierjunge]

 > If your model is relatively top heavy or has a lot of weight
> high up and outboard (e.g. a side paddler or a shallow draft
> stern wheeler) , then you can achieve the strongest righting
> effort by concentrating the ballast along the centre line.
>
> However if your model is relatively light in the superstructure,
> then you might be able to spread the ballast across the beam
> to give an easier roll and more realistic handling.
 
This statement and the pictures are somehow misleading, so let me  
please try to put it right:  
 
If you take the same amount of lead ballast (i.e. to achieve the correct  
draft) and either concentrate on the centerline, concentrate it at the  
chines, or distribute it evenly over the beam:  
The righting torque and the stability will be always exactly the same  
(as long as you don't change the height of the ballast).  
If you list the ship with a given angle under static conditions,  
it will malke absolutely difference in righting lever and -torque.  
 
What however changes is the moment of inertia, which doesn't  
affect the static stability at all, but the dynamic properties:  
If you concentrate the ballast right under the center, you get the  
smallest inertia; if you spread it wide, the biggest.  
Large inertia and same righting torque result in a slow frequency  
of the rolling motion; small inertia in a high frequency.  
 
The same applies for the pitching motion if you distribute the ballast  
to bow and stern: The pitching gets slower, and you get the impression  
that the vessel cuts through the waves. Concentrated ballast results  
in a smaller inertia and thus faster pitching, allowing the ship to  
follow or ride the waves better.  
 
But again: Concentrated ballast does NOT result in a stronger  
righting lever. Static listing angle and capsizing tendency stay the same.  
Only thing you get is a faster rolling motion under dynamic conditions.

[Khephre]

...The righting torque and the stability will be always exactly the same (as long as you don't change the height of the ballast).
If you list the ship with a given angle under static conditions,
it will malke absolutely difference in righting lever and -torque.

What however changes is the moment of inertia, which doesn't
affect the static stability at all, but the dynamic properties ...

:shock:


Many thanks for your corrections Gretzschel, although I think that Richard's problem is all about dynamic effects of wind and wave action and I wonder about the relevance of static stability?  After all the model (great looking model, Richard) floats upright and any tendency to list can be trimmed....

My lack of grasp of physics and my misuse of the words used to describe righting effort, moments of inertia, centroids and concentration/dispersion of mass is why I'll stick to building and sailing models and avoid designing them in future!!!!  :idea: