Vic Smeed’s Silver Mist

[Ray Wood 3Participant @raywood3]

Hi Bob

I think Vic may have designed SM as a relatively light displacement hull, I will weight her on the scales and let you know the all up weight. The wheelhouse is removable as a unit and the deck & cockpit well lifts out, the rear deck with the dinghy is also removable, with a small hatch/companionway over the tiller/steering for adjustment. With a 600 size motor + 2 battery packs in the bilges either side in the centre of the hull only weight needed at the bow. the construction of balsa planking,frames and 1/4 ply keel she is very light.

Regards Ray

[Paul TParticipant @pault84577]

Sir Bob

If you are doing a free flooding hull the question of ballast becomes far less critical but if you want to build a traditional non flooding hull simply redo your calculations based upon the correct measurements.

At a rough guess I would estimate the dimensions of a 4ft Silver Mist as being:

Length = 1200mm Beam = 270mm Draft = 130mm

[1200 x 270 x 130] = 42.12

42.12 x 0.6 = 25.27kg (55.71lbs)

Caveat: this is very much a simple 'rule of thumb' method of estimating a hulls displacement, far more accurate figures can be produced if you take the time to make exact measurements of the 'wetted area'.

Paul

[Colin BishopModerator @colinbishop34627]

In view of the discussions about the effect of changing scales etc. I have put up Glynn Guest's article on Modelling Mathematics published back in 2014 which you might find useful.

**LINK**

Colin

[Bob Abell 2Participant @bobabell2]

Thank you, Ray

Nice to see your build…….Were the balsa blocks essential during the build?

I'm hoping to plank the complete hull, as l like to see the plank lines showing through the paint finish

Your posts are very welcome

Bob

[Bob Abell 2Participant @bobabell2]

Thank you Paul and Colin for the calcs etc

At the moment, I'm stuck between the Devil and the deep blue sea!………..Nice old saying?

We've got some very confusing ballast figures to think about now

I will go for the flooded hull idea now, as I feel sure the 4 foot hull is bound to be quite heavy, but may build the hull as drawn and do a floatation test, before I jump in with both feet!

Should be quite interesting

Bob

[Paul TParticipant @pault84577]

Bob

Why are the ballast figures confusing?

If you don't understand the process then Kevin has no chance and his opportunity to learn about free flooding is lost so lets go back to basics and work out what it is that you find confusing.

Paul

[Bob Abell 2Participant @bobabell2]

Hello Paul

You have calculated a ballast of about 40 lbs, this is too heavy for me to handle, so I decided that we must go the water ballast route and hopefully, we won't need any ballast?

Then along comes Ray, with a 30" hull and he only uses 1/2 lb of lead!……Plus all the gear

This made me stop and think

The plan now is to build the hull as drawn and see how much ballast is actually required

Then decide on the ballast method

Kevin……Please note that this model is an old design by Vic Smeed and Paul is only getting involved out of pure interest. Pauls comments are always welcome

Have laid out the keel now for a four foot model and it is looking quite large!………Crumbs!……Here we go again?

Bob

[Ray Wood 3Participant @raywood3]

Hi Bob

I have weighed SM @ 30" ready for the water 5lbs 12oz

As Vic says in the original article she was drawn from a couple of photos so I doubt if the hull lines are correct, but he designed for the weight of Mabuchi or Kako motors and torch batteries in those days, I built the 21" version when I was 12 at school. I doubt these days If they would be let kids near a Stanley knife !

The blocks for the bows are not required, planking will be fine but the cruiser stern vertical sheeting and blocks under are a good solution, I'd double the number of frames to support your planks, I'm tempted to have a go a 1/12th version of Silver Vanity at 54" long

Regards Ray

[Bob Abell 2Participant @bobabell2]

Many thanks Ray

Your model appears to be extremely light?………Have you used Balsa Wood?

I do like your colour scheme…….She looks very smart

Can you show us your motor installation, please?

A 54" Silver Mist would look very nice and would look grand on the water

Big boats are a treat to work on…….Have you seen my Vintage Gentleman`s Cruiser, I built over the last years?

Designed by my good friend Paul Thomason?……..We had great fun

We showed it at a few shows too………If interested, have a look at our marathon story on this forum

All the best………Bob

[BRYAN ASTONParticipant @bryanaston57723]

Greetings all

After reading on the forum about using a free flooding hull as ballast could somebody explain to me how this would work, is the complete bottom of the hull open to the water, I know there would be another deck above but surely this would be a heavy drag on the speed of the boat, or have I got it completely wrong.

Regards , a relative newcomer to this game

[Ray Wood 3Participant @raywood3]

Hi Bob

Yes I've followed your gentleman's cruiser progress. I was impressed with all those motors & belts.

The bulkheads and planking and blocks used are all balsa, 1/4" ply keel & doublers, 50 years of Aeromodelling I still use balsa cement for planking and it sands well.

Currently building 30" MTB 71 from the Vosper drawings for my grandson because he wanted something fast but my next big project is HMS Belfast @ 1/96 scale which come out at 6' 4" could be a 5 year job as I still have to earn a living inbetween model making.

Regards Ray

[Bob Abell 2Participant @bobabell2]

Hello Bryan

We don't really know how the idea will work out, but we've got nothing to lose, as it can be put back as designed!

I used to say, years ago, that we could build a model on a plank and no hull……But we didn't persue that idea

But the latest idea is still a plank, as this is what the superstructure sits on

The hull is still a complete hull, except that it has a few small holes to let the water in

To avoid a trapped pocket of air, Paul has devised a screw down valve on deck somewhere

Because the model is wide, we may get away with it

Fingers crossed….eh?

Bob and Paul

[Bob Abell 2Participant @bobabell2]

Many thanks Ray

You are obviously still an Aeromodeller, at heart?

I used to enjoy flying, but we lost our field a few years ago and that was that!

I used to fly a quarter scale PiperCub with Saito 120 and it was very forgiving and lovely to fly

And I managed to worm my way into The Brit Aero space club and airfield at Woodford Cheshire

Alas……That has gone too!

Bob

[Ray Wood 3Participant @raywood3]

Hi Bob

Yes I still build and fly RC aeroplanes, but in the past every Sunday morning for 25 years I used to drive 20 miles each way to my old flying club at a farm on the Isle of Grain in Kent to make a noise with ic powered models. But as brushless electric's are so good now & make little or no noise I now fly from a field 5mins walk from our house, not needing to be a member of a club now I keep up my BMFA membership for insurance. I manage to get to Chantry Model Boat Club at Bluewater Shopping Centre most weekends to sail & motor my boats

Regards Ray

[Bob Abell 2Participant @bobabell2]

Some forum readers are asking about work in progress already!

There`s not much to see at the moment, chaps

I`ve scaled up the Keel and Hull formers by 1 : 2.25 to achieve a 48" hull and cut a few out

The formers are not down to the finished size yet, as there may be some adjustment necessary, due to my sloppy marking out!

Just wondering……How do I make intermediary bulkheads that are right first time?

This is quite a tricky job?

Bob

[Colin BishopModerator @colinbishop34627]

Bob,

Basically you need to use the formers you have got to develop a set of waterlines (like bread and butter hull,planks). A flexible curve can be handy for doing this so you get a nice smooth curve from bow to stern at each waterline level. Then you can take off bulkheads wherever it suits you at intervals along the keel. The closer you make the waterlines the smoother the overall result will be. If you are using the original plan as a pattern to do this initially then maybe 3/8 inch or 1cm vertical intervals will probably do the job.

Colin

[Bob Abell 2Participant @bobabell2]

Thank you, Colin

That's easier said than done!

I've got more chance of making the new bulkheads by trial and error, than geometrically constructing them!

Those funny wavy lines have always puzzled me in the past

I'll have a look on the net

Bob

[Colin BishopModerator @colinbishop34627]

Bob, a rough and ready short cut would be to mount the bulkheads that you do have and then temporarily pin a thin flexible piece of stripwood at different levels along the hull. Make sure that it follows a smooth curve and doesn't 'flatten' between bulkheads (i.e. don't pull it too tight). Then you can measure off the horizontal distance to the keel at each level in the position you want your new bulkheads to be and mark them out accordingly.

Colin

[Bob Abell 2Participant @bobabell2]

Hello Colin

I think that if I used slightly thicker planks of 10mm x 4mm section, intermediary formers may not be required?

Having just bridged the gaps, with the intention of measuring up for the extra formers………They look quite reasonable?

Will look into it tomorrow…….With a fresh outlook on the problem

G`night

Bob

[Colin BishopModerator @colinbishop34627]

You might get away with that Bob although it may then be prudent to reinforce the inside of the hull with GRP or internal ribs to keep it nice and rigid as you would be constructing a partial shell. You don't want to risk springing the planking in the event of a collision.

Colin

[Bob Abell 2Participant @bobabell2]

Planks of 10mm x 4mm section seem to have bridged the gap satisfactorily and further bulkheads may not be required now

At the moment, I`m trying to decide on the various heights of the bulkhead tops and the actual construction of the keel top edge. Since there is no cross section available, I`m having to crib off Ray and Ian`s examples

Bob

[Bob Abell 2Participant @bobabell2]

For the benefit of future builders……

As drawn, the bulkheads rest on the top edge of the keel

I have since, notched out the keel where the the bulkheads are positioned…….For a positive repeatable position, so we can't use this for setting the bulkheads to the correct vertical height

Taking a flexible strip, the strip rests on each end of the keel……As shown and the the bulkhead notches can be cut out to produce the precise and correct fore and aft shear, using the top edge of each bulkhead

The maximum hollow dimension is 18mm

To the casual bystander, this may seem complex and irrelevant, but to an actual builder, this info is essential

We can now proceed with confidence

Ian and Ray……How did you find this facet of the build?

Bob

[Bob Abell 2Participant @bobabell2]

This is what all the fuss was all about!

The flexible strip is touching all the bulkhead tops……….As Vic designed

The shear has 18mm hollow……Shown in red

Now to adjust the bulkhead widths and final profiles

Next big job is to set the waterline and cut out the bulkhead lightening holes

To avoid the nasty job of drilling the keel for a single propshaft, I`m thinking of going for a twin prop jobby, single motor and twin timing belts for engineering interest

Bob

[Colin BishopModerator @colinbishop34627]

Looking promising Bob. Yes, no reason not to have twin props but if you are having just the one motor then keep them reasonably close to the keel where the rudder can catch the waterflow. Also keep them as low as possible so that the propwash doesn't break the surface. All this would suggest that relatively small fast running props will give the best result.

Colin (teaching Grandad to suck eggs…..)

[Bob Abell 2Participant @bobabell2]

Hey Paul

Need your expert opinion!

Suppose we let the water into the hull at the designed waterline……..The weight of the hull, motor, battery and gear will cause the hull to sink even lower!

This is a surprise!………..Does it mean the false floor will need to be about 1" lower to compensate?

Think we need to test float a plank on Coniston Pool………Before we get the eggs out!

Bob

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