The Materials for the stern extension


Abgehalftertes Segelschiff goes to Lieblingsdaycruiser

Abgehalftertes Segelschiff goes to Lieblingsdaycruiser

Mein Blog zum Leisure 22 bzw. Leisure 23 Refit und Instandsetzung


- HDF plate (hardboard) , one-side white laminated

- 3D CORE Hexagon Plate 1015 x 405 x 10 mm

- Epoxy Harz + Härter| HP-E111L

- 450 g/m² Glasfasergelege Bidiagonal | HP-B450E

- 350 g/m² Glasfasergelege Bidiagonal | HP-B350E

Inspiration …


stern extension

Rumpf und Deck


- Mold release agent based on wax | HP-BM 17

- PVB- Release lacquer

Although I had the idea to give my L22 an extended stern very early on, at first I had no idea whether and how I could implement it for my boat. I found inspiration and a great guide for the rear extension on the website of Guido Wiesel: ... on which documents the complex and technically clean refit and conversion of his MARE, a Neptune 22, Bj. 73 becomes. I will do it to Guido right away, because on the one hand I don't want to reinvent the wheel and on the other hand he has wonderfully succeeded in his new rear end.

Die HDF-Platte muss mit Holzlatten unterfüttert werden, damit die Platte in Form kommt und stabil bleibt. Die Latten habe ich mit langen Schrauben direkt in den Rumpf gebohrt. Die Löcher werden später überlaminiert werden.

2.   Apply release lacquer


Before the mold release agent can be applied to the formwork, the area on the mirror to which the laminate will later be applied, must be taped off, i.e. on the previously sanded area!


At first I applyed the wax-based mold release agent 4x with a brush. The waiting time between the coats is 30 to 40 minutes.


Then I wiped / polished the surface with a cotton cloth.


When the 4th layer has dried properly, the blue PVA release coating can be applied. I put on a shift. I let this layer dry for several hours at 16 degrees C.



Leave a generous margin. Cutting off is always possible!


Be sure to try the first cut on the formwork.

4.   Lamination work


Now to the procedure… In the first two layers I used 450 full-size bidiagonal fiberlass (cut out according to an template). Then I glued approx. 20 cm wide strips from the 450 bi-fiberglass from the mirror to the rear, with a slight overlap to the neighboring strip. The fiberglass strips I laminated about 5 cm at the mirror. Then, as the 4th layer, there was a full-size 450 bi-fiberglass. Then in the 5th layer I applied the 20cm wide strips again, just like in the 3rd layer, but this time I already laminated 10 cm on the mirror. Now there comes another layer of full-size 450 bi-fiberglass ... etc. ... I had to stop in the 5th layer because my epoxy was used up. ... Then I put on a peel ply to prevent amine blushing and glued it in place. Against the nocturnal, high humidity, I covered the rear with a tarpaulin in the evening. … I will continue to laminate for the coming days.

Today I finally applied the laminate to the formwork at 20 deg C.

In the first layer my mixing ratio was wrong, which I noticed in time before I mixed the epoxy for the second layer. The glass fiber mats that had already been cut out were also too small, although I had cut them out the day before with the addition of a template. Then I had to do some tricks. The sun also bothered me, because in the sun the epoxy gels and attracts much faster. Fortunately, my epoxy had a pot life of 110 minutes. ;-)



Don't work in the blazing sun!


Work in pairs.


Uses epoxy resin with a very long pot life.


Buy enough epoxy! Ask if you can return unopened canisters.


Incorrect mixing ratio requires a total new beginning with epoxy, as it remains soft !!!!!

1.   Mold making and stencil making

7. - 11.4.2020

An HDF board with a one-sided coating becomes the shape for your own stern extension.


On the brown side, the plate is sufficiently to wet with water that is to disperse with a scrubbing brush for approx. 1 hour, so that it becomes flexible.


Then the plate is bent around the stern with a lashing strap. If you sanding the edges of the stern  (stripes of 20 cm width) into the GRP is sanded, you do not need to remove the HDF board.

When sanding, you should remove 3-4 mm.


With the help of a line laser, then I drewed the cut edge on the outside of the HDF board s and drilled many small holes along the line with a small drill, so that I then included my template in the inside of the board around it from the port stern to be applied to the starboard stern. I adapted the template from many A4 cardboards. It took me two days to be satisfied with the result.

After the template was made, I was able to mark the HDF board on both sides and saw off the excess of the board. So you can see a little bit the later shape of the rear.


Before the formwork is attached again, I sand the edges of the rear about 15 cm so that the laminate can be glued there. I'm grinding down about 3mm.


Then I put the formwork back on.

3.   Glasgelege vorbereiten


I already cut out the bi-diagonal glass fabric and used the created rear template for that. When cutting out with the sharp scissor, I leave about 8mm on the edge.


I also marked the 3D core sandwich material with the template and cut it out with the cutter knife. This is very easy with the 10mm thick material.


In 10mm thickness, the plates can be pressed very well into the shell without breaking. The 3D core is very hard, similar like duroplast, but due to the hexagon structure it can be bent and twisted slightly. The epoxy resin can flow between the hexagons and form additional bridges.

4.   Strip the formwork



After 48 hours of drying, I take off the formwork.


Before I could take off the formwork, I first removed the peel ply, then I cut off the excess edge of the laminate with a flex.


The formwork was very easy to remove and only approx. 10% of the thin, white hard fiber surface stuck relatively loosely to the rear floor.


I am very satisfied with the result ...


... Tomorrow, two more layers of fiberglass and the Core 3D sandwich-material will come in.

After I glued two more layers of the fiberglass into the stern extension, then I have the first layer of the

Sandwich material applied at the same time.


The 3D core material is ideal for sandwich work with bends. Furthermore, the liquid epoxy can flow into the gaps between the hexagons and make the already hard material even firmer.

Before applying, the underside and the surface on which the 3d core is placed are soaked with epoxy resin. If you do not apply the plates using the vacuum method, you weight the plates with stones, bricks or other suitable weights.

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