Beginners_Boat_Building_Part1_R1.pdf

Edinburgh Model Boat Club

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Beginners Boat Building

Part 1 - Balsa Sheet Construction and

Stand-off Scale

Basic advice and guidance for the absolute beginner who wants to build a boat but

doesnÓt know where to start or how to do it.

More advanced hints and tips can be obtained from various model building articles

in Model Boats Magazine and in Marine Modelling magazine although these are

usually directed at construction of specific models.

Sample plans are available (view only) at the tutorial and information on purchase

etc. is provided.

There will be more Tutorials in the Beginners series :

Plank on Frame Hulls;

Making your own Boat Fittings;

Beginners Box Kit Building;

Beginners Yacht Building

Watch the Club Notice Board, the Web Site or read your Club

Newsletters for more information.

A copy of all Tutorial Notes are available for reference in the EM-

BC Boat Compendium kept in the Club House.

Iain Moffatt - Beginners Boat Building Tutorial

Edinburgh Model Boat Club

Page 1

And in the Beginning ..............

Like most things in life, the IDEA is all powerful !!

Unfortunately, for most people, the idea is an image of the finished object be it a boat, plane or whatever. This inevitably

leads to initial disappointment when you find out how many decisions must be made and how much work must be done

to realise the idea.

Many people have houses and garages full of unfinished projects (mine is not quite full yet!!) largely as a result of waning

interest when a problem appears that cannot readily be solved.

So my message to you all is ...........

PLAN AHEAD

In model boat terms this means that a number of key decisions must be made BEFORE anything is bought.

1 What kind of boat do you want ?

2 What are your manual skills like ........ good, excellent, non-existent, donÓt know yet?

3 How long are you prepared to spend building it ?

4 How much money are you prepared to spend on it ?

Remember ... motors, props, batteries, speed controllers, radio control all adds to the cost of basic materials.

5 Are you elderly or disabled?

If so you should consider the size and weight of the model you want to build. Remember, it has to be launched and

recovered (and carried in a car).

6 The next thing to be considered is the issue of detail.

Are your manual skills, eyesight and patience up to dealing with fine detail?

If so ...... good for you ! If not ....... consider a Òstand-offÓ scale boat that stands up without too much detail but which

can be enhanced if you feel up to it.

Remember also that detail costs money - even more if you have to buy it. Fittings kits are very often more than 3 times

the cost of the hull & plans. Making fittings yourself is very cost effective but .......

7 Where are you going to build it ?

If you have a workshop or garage in which to do the construction, then construction methods can be less of an issue.

If however you have to work in the house and move (or tidy away) before meals etc. you donÓt want anything that has a

multitude of parts and that needs a complex build strategy ......... keeping it all safe and sound during many moves is

not so easy!!

Some advice on hull construction to help with the decisions:

1 Stand off scale boats, depending on the size, can be built from balsa sheet wood that is relatively cheap to buy and

easy to work with. Also produces a ÒlightÓ boat and, if constructed correctly, one that is strong and long lasting. Witness

a balsa Leander class frigate built in 1975 that is still looking good and sailing to-day. Generally strength considerations

limit these to a maximum of about 36Ñ LOA.

Light plywood + balsa can easily go up to around 60Ñ LOA with correct construction.

2 Plastic Sheet (Slaters Plasticard for example) is great stuff to work with but the size of sheet produced (12Ñ x 12Ñ)

tends to cramp the style where larger hulls are concerned and, although capable of giving an excellent finish, can be

very expensive. Always use solvent weld techniques for gluing. Always provide adequate stiffening - sheet is not stiff

in its own right.

Plasticard is ideally suited to the construction of boat superstructures and detail.

3 ABS (moulded plastic) hulls are relatively cheap but require a fair degree of internal stiffening (bulkheads etc) and can

be difficult to ÒstickÓ to.

4 GRP (glass reinforced plastic) hulls are more expensive but much stronger. Working with the hulls can be messy (lots

of glass fibre dust if you have any sanding or cutting to do). You must be very careful not to inhale such dust - wear a

mask .. cost pennies. Always use Araldite (epoxy) type adhesives. Car body fillers and repair tape can be used.

5 Plank & Frame or Sheet & Frame hulls can be immensely strong if well built and there is no practical limit to their size.

Building requires great attention to the alignment of the hull framing components and sequential application of planks

or sheet plates to prevent warping of the whole structure. The resulting hull is very light but very strong. Waterproof

adhesives MUST be used throughout.

Plank on Frame can produce a wonderful result but takes a LOT of care and patience even though its basically a simple

technique. It can also deal with compound curves (round the stern section below the waterline for example).

Iain Moffatt - Beginners Boat Building Tutorial

Edinburgh Model Boat Club

Page 2

Sheet on Frame will NOT do compound curves easily but works well for the straight sections in the centre half of a hull

for example.

6 Bread & Butter Hull construction.

Now a days this type of construction is very costly, given the price of reasonably stable, straight and knot free timber.

However if you have a ready source of off cuts of old oak or pine floor boards (the thick variety!) .......

Hulls are built of many horizontal layers of pre-cut wood glued together (bit like a sliced loaf on end!). The outer and

inner surfaces are hand or power dressed to give the finished hull profile.

Hulls are generally heavy. Finish is entirely down to hard work and elbow grease plus lots of filling and preparation.

Some beautiful results have been produced however, witness most of the ship models in museums.

Summary of Bread & Butter Construction

Iain Moffatt - Beginners Boat Building Tutorial

Edinburgh Model Boat Club

Page 3

Illustration is for a small yacht hull built from

balsa sheet.

However the principle is identical no matter

what the hull form or what wood is used.

It is essential that a completely waterproof

glue be used.

Furthermore effective sealing of both the in-

side and outside surfaces of the hull is es-

sential after carving has been completed.

Iain Moffatt - Beginners Boat Building Tutorial

Edinburgh Model Boat Club

Page 4

About Balsawood

The most remarkable thing about balsa is its light weight - less than 1/3rd of the weight of other woods. It is also re-

markably strong for its weight. It is soft, with a marked grain that is not very visible. The strength of balsa is directly

proportional to its density. For example 18 lb balsa would be 3 times as strong as 6 lb balsa. It would also be 3 times

as hard to cut. The stiffness of balsa is governed by the ÒcutÓ. Quarter grain sheet with a speckled appearance is stiff

and rigid and cannot be bent either end to end or edge to edge without danger of splitting. Normal sheet with a plain

grain appearance may have varying degrees of ÒbendabilityÓ.

Basic Grading

Density (lb/cu ft)

Fine Grading

Where balsa has to be as strong as

possible, a hard grade should be

chosen - for example flat hull

sheeting.

For curved hull sections use a

Medium grade.

4 - 6

ultralight

6 - 8

light

Soft

8 - 10

light to medium

Medium

10 - 12

medium

12 - 14

medium hard to hard

hard

14 - 16

hard to extra hard

Where to Start ?

Assuming that you have decided on the boat you want to build, the first step must always be to get a set of plans. The

plans will normally be drawn taking account of a particular construction technique (sheet, plank on frame etc.).

For a beginner it is therefore important to select a plan set to match your planned construction method.

It is relatively easy to convert a set of lines plans to sheet construction, but, for an absolute beginner, this may be a bit

too much to undertake for a first build.

Bow

Transome

Waterline

Forefoot

Drawings for simple sheet type hulls will normally contain hull outlines both plan and cross sectional views together with

outlines of transverse bulkheads at positions along the hull length. These positions are called ÒframeÓ positions. There

will normally be at least 2 positions and therefore 2 bulkhead outlines plus the transom.

Material sizes (including thicknesses) are also normally shown.

For example, a ÒstandardÓ length of balsa would be 36Ñ x 4Ñ.

For the bottom it would have to be 1/2Ñ thick. The transom would normally also be 1/2Ñ thick.

The deck may be of 1/4Ñ thickness and would require the use of longitudinal stringers to add rigidity. The

stringers would normally be strip hard wood.

If the deck is also 1/2Ñ thick, stringers can be dispensed with.

Hull side sheeting will usually be 1/8Ñ (3mm) and when you cut, remember the grain MUST run vertically.

Balsa Sheet is normally available in the following widths :- 3Ñ; 4Ñ; 6Ñ and in either 36Ñ or 48Ñ lengths.

Thicknesses range from 1/16Ñ up to 1/2Ñ in 1/16Ñ increments.

Block balsa can be obtained in sizes up to 4Ñ x 4Ñ.

Balsa is naturally porous (likee sponge) so it MUST be well sealed (inside and outside) before painting.

NEVER seal an area that has to be glued later!! Glues do not take kindly to sealers.

The best sealer is Sanding Sealer although Fuel Proofer coatings can be used (a high tech balsa sealer resistant to IC

fuels). Several coats of sealer are generally required with light rubbing down between coats. The sealer tends to raise

ÒnibsÓ in the wood and if these are not sanded off, a very poor finish will result.

Iain Moffatt - Beginners Boat Building Tutorial

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