Masterclasses > VOSPER MOTOR TORPEDO BOAT BUILD

An in-depth build of a GLYNN GUEST plan, for the beginner

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John W E:
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John W E:
Skinning the hull                  
The sides of the hull are the first to be skinned with 4mm balsawood Commence at the stern of the boat first gluing and pinning the sections into place alternating from side to side.  You will find that this will stop distorting the hull (also take note in which way the grain runs on the skin - it should run top to bottom or from the deck to chine) (fig. 23).  When the side skins have been completed and the glue has dried - sand the bottom so that the edge which is glued to the chine is flush with the chine and also has the same angle as the hull bottom, (tip mark the centre line along the length of the keel - this is a visual aid so that not too much materials are removed when sanding the keel) - use a long wide sanding board (fig. 24).
Skinning the bottom of the hull
The bottom skin joints are offset to the side joints by half the width of a plank.  This is to improve the hull strength, we start at the stern of the hull and glue the first plank half its width forward of the stern and again alternate from side to side (see the arrows in fig. 25) When planking towards the bow, we may find it easier to reduce the width of the planks to help with the bow angle.  If the prop shaft has been removed for ease of skinning, it helps to put a reference mark on the skin at the point where the prop shaft hole is.    
Sanding and filling the hull skin  
For filling small gaps in the hull it was found the soft fillers such as polycel or plastic wood worked well but I found that a plastic filler called white putty did the job just as good as the rest and sanded very easily. When sanding the hull skin use the largest sanding block you can to prevent sanding hollows either side of the glue joints as the glue hardens the area surrounding the joint.
Big hint: when sanding the hull work on a clean bench free from all off cuts and mess as when I had finished sanding and turned the hull over there was a big score mark in the deck from a screw that had been left on the bench after I had removed the motor HUUUUUMMMM   

John W E:
Smelly Sticky stuff and tissue  
Sealing the hull
As in all walks of life there are many ways of doing things and it is the same for sealing the hull, my first idea was to use a two part finishing epoxy such as Z-POXY but after a long think and a good supply of caffeine the down side of this method for the beginner became apparent (it’s sometimes difficult to achieve a good even finish and you must have the resin mix perfect - if it all goes wrong you may end up destroying the hull to remove the epoxy)  so we will put that idea on hold for a new day.
So let us stay with the method used in the model boats magazine article.
First off we apply three coats of sand and sealer rubbed down between coats.  
The tissue used is of a medium grade - it was found best to cut it into 4 panels one for each side and the other two for the hull underside, start on one side by applying dope to the hull side.  Attach one short edge of the tissue with a small amount of dope to ‘tack’ it down at the stern (just at one point here, allowing the dope and the small area of tissue to dry).  When the dope is dry - stretch the remaining tissue panel towards the bow remembering to smooth out any wrinkles working towards the bow we apply ‘neat’ dope with a brush. Keep doing this until the whole of the side area you are working on has been treated. This was done on the two sides first and when the tissue and dope had dried, the top deck edge of tissue was trimmed level with the deck.   The small overlap at the chine was trimmed evenly.
The bottom panels were applied using the same method beginning at the stern and working towards the bow.  When the dope had all dried out 3 other coats of dope were applied on the top and a very light sanding between each coat of dope to help produce a smooth finish. The sealing of the deck is done using the same method    I did try spreading the dope with an old plastic credit card - but speed is of the essence here – before the dope dries out.   I would advise strongly a lot of practice being put in, before attempting this method of applying the dope with the credit card spreader.   See fig 26 and 27. The next important thing to do is make a stand for the boat to sit on and hold it steady when we do the rest of the work .the stand was made from 12mm plywood the bottom hull profile is marked onto cardboard and when the correct shape is achieved through trial and error this is then transferred to the plywood then we fit some soft foam for the hull to sit on
At this stage the access hatch was market out on the deck, and using a new sharp blade in the knife and a steel strait edge the hatch was cut out it is best to cut the short section across the grain of the deck first the cut the long sections last using the steel strait edge to stop the blade running off (fig.28)

John W E:
Fitting of the prop tube
If you have remembered to mark the position on the hull for the prop tube it is a simple task of opening the hole up gradually with a small set of drills then files (fig 29-30) test fit the tube into the hull and when happy with the fit and position mark on the prop tube with a pencil where it exits the hull so that when we replace the tube with glue on it, the tube will be refitted to the same correct position, then we abrade with sandpaper  the section of tube which is going to be bonded into the hull
Temporarily seal the end of the tube to prevent any glue entering inside and this is achieved by covering the end with cellotape (fig. 31) next we need to mix the epoxy glue, slow setting is best for this job as it gives us time to make any small adjustments which may be required when fitting the tube in place.  We apply the glue mix in to the hole in the hull with a small spatula or a tea /coffee stirrer from your local fast food take away, as we insert the tube into the hole rotate the tube 360° to spread the glue in the hole as the tube is fitted (fig. 32).  Just before the glue has set and it is rubbery, check the alignment of the tube then cut off any overspill  with a sharp knife (fig 33-34) then set the hull aside for the glue to fully dry.

John W E:
and more pics

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