Build the plug

The process is best explained by Brad Gibson, in his video  

Build the hull plug   but there are some nuances which I cover below:

Click on any picture to expand the image.



Build the styrofoam hull

What you need

A  measured 1.1m flat board to lay the styrofoam frames onto. 

2 off 600x600x100mm sheets of styrofoam.  Ebay shop 

UHU POR glue to stick paper onto styrofoam.  Amazon

Hot wire cutter.  Amazon

Balsa wood planks for sanding the styrofoam  300*50*3mm and 400*20*5.   EBay shop

Stencil knife

Builders square

600mm rule

5 minute epoxy to stick foam frames together.  East Coast Fibreglass

Sandpaper - Dry, various grades, course to fine, wet and dry 150 down to 2500 

Epoxy resin - slow cure gives about 30mins of work time

Glass to cover foam - 2 layers of 135 E cloth and 1 layer of 125 S cloth as the outer skin.  East Coast Fibreglass

Epoxy micro balloons for filling and for use later on. East Coast Fibreglass 

2 pack high build epoxy primer.  SML Paints

The process

The Foam Plug

  1. Mark up the board with a centreline and 100mm frame positions and a 50mm and 38mm mm frame positions according to the plan.  Mark as accurately as possible and use the builders square to mark the frame lines.  Image 2

  2. Print all the frames onto coloured card and cut out each frame, red or black provides good contrast to blue Styrofoam.  The colour becomes relevant later

  3. Cut out the frames with a stencil knife and stick to the styrofoam with UHU Por.  Only glue round the edges of the card and avoid putting any glue in the deck area.  Bear in mind when cutting out your frame, frame 5 is the largest.  When cutting the stern frame, mark an outline for frame 2 and cut that out.  Do the same for all the foam cutout unto frame 5 and then do the same form the bow back to frame 5. Do this otherwise you will end up with steps rather than a fair hull. Expand image 5 and 8 picture so you can see the detail of the cut

  4. Cut out the frames using a wire cutter.  As mentioned above, mark out the next size frame and cut out.  

  5. I wedged my wire cutter into a wooden board so I could get a vertical cut all the time.  Practice with some samples first to judge how fast you can cut.  It is a smelly process so cut the foam out doors.  See image 5.

  6. Carefully cut out the centre of the red card hull frame and a narrow slot on the deck line to help when finding the deck during sanding.  See image 7

  7. To cut the 50mm and 38mm slices I marked a line on my board, held a straight piece of wood on the board and used that as a guide to get the right thickness of frame.  Image 6.

  8. When you add all the frames together they should give you a length of 988mm.  However, because you have added glue and card to the foam frame the width of the frame will be slightly more so sand down the back of each frame by about a mm until the width is correct.  I only found out about this after I had glued all the frames together and ended up with a 1m boat before the bow bumper was fitted.

  9. Starting at frame 5 in the middle glue the frames to the board and themselves, 1 at a time using 5 min epoxy.   Remove excess styrofoam with the hot wire and sand coarsely into shape as you go along.  Only stick the styrofoam with the epoxy.  See image 7 and 8.

  10. Only sand with a sanding board and always down the length of the hull to start the fairing process.  Once all the frames are in place, bring the surface down until you start to see evidence of the red card.  At this point move to the lighter sandpaper and carefully sand until all the red card is exposed.  If you have been patient the hull should be perfectly fair and true.  I was amazed at the end result.  See image 3 and 10 - 12

  11. Use a saw and remove the hull from the build board.  Start at the stern and keep the cut well clear of the rising deck.  Be careful with the plug as the foam will damage easily.  Once removed I supported the hull with bubble wrap.

  12. Sand down the deck in the same way as the hull.  Sand the radius edges on the corner of the deck as per the plan.  Image 14


The Foredeck

  1. Prepare the foredeck frames as before.  Image 15

  2. Glue the frames together on the deck and chamfer the edges slightly to get a tight fit.  Protect the hull with cling film so as not to glue the foredeck to the hull at this stage.  Frame 16.

  3. Glue onto the hull and sand to final finish.  Fill any gaps with 5 min epoxy and micro balloon filler.  Sand very carefully to finish. Image 17 and 18

  4. Add a post for handling the plug and keep it a max of 50mm from the foredeck.


Epoxy and glass the hull

  1. Rough cut 3 layers of 4-5oz glass e cloth to wrap completely around the plug. Draw a line along along the keel line on the foam plug and the cloth so you can align the cloth exactly.  Image 19

  2. Support hull post in work bench and apply 3 layers of to 4 -5 oz glass and epoxy resin to hull and decks.  Use peel ply as a final layer.  Take care with corners and ends to make sure there are no air bubbles.  For each layer I apply the glass and epoxy to the hull and then turned the plug over and did the deck.  I applied 1 layer after the other until all three are complete.

  3. Paint the plug in epoxy and add the first layer.  Use a roller to remove air bubbles and saturate the cloth.  Once the first layer is on, carefully paint on more epoxy and add the second layer.  Repeat for the third layer.  Once you are happy with the result, wrap the hull tightly in peel ply, which will absorb any excess epoxy and prevent an amine finish.  Images 19-21.

  4. When working with epoxy, make sure you are in a well ventilated area, you are wearing nitril glove and  preferably glasses or safety glasses in the event of flicking epoxy in your eyes.

  5. Epoxy will start to go stringy after half an hour or so.  When it does, throw away what's left, clean tools and gloves with acetone, reload with fresh epoxy and continue the layup.

  6. The temperature during layup must be 10 degrees or higher and ideally cure at room temperature or higher.

  7. Remove the peel ply and immediately add 2 coats of high build epoxy primer.  This will look really ugly but once sanded with wet and dry and polished with  t-cut, you will have a beautiful plug on which to mould your hull.

  8. Finally apply at least 6 coats of release wax before laying up the hull.  Finished product in image 22



Sanding boards.jpg


Hot wire kit.jpg


Hot wiring the shadows.jpg
Cutting the forward frames 38mm and 50mm
Gluing frames forward.jpg
Gluing frames aft.jpg
The plug from the bow.png
Stern view.jpg
Guing foredeck.jpg
Deck view.jpg