Hull Flip

The day of the hull flip is getting closer. There was no time to be nervous or have a ceremony because I was short in time. Don`t wonder about the uneven surfaces on the hull and the dark blue stripes. It’s just an epoxy layer with blue color pigments to temporarily seal the filler during the winter stay in the shed. I still have to do the final finish next spring with another layer of filler.

A few days before the hull flip i made contact to the road construction workers in front of my workshop. I asked them for helping me with the excavator when putting my boat on the trailer. They agreed and we made an appointment for the day after tomorrow. So I had 2 days to prepare for the hull flip. I still had to install a pull point on the steel beams of the ceiling, build a wooden rack to place the hull on top and some trailer adjustments. I bought the trailer from a clubmate six months ago and parked it in a shed. With 2.5 tons maximun weight it’s a bit oversized but it will give me driving stability at all times.

I thought a lot in the past year what method is the best to flip the hull. I studied many ClassGlobe builder`s blogs and check the facebook group to see what techniques are recommended. Many ClassGlobe colleagues have already developed good concepts and each one works very well under the given conditions.

In two days I couldn’t gather people together. As a solo sailor I am always forced to find a solution on my own. I had to think about a save and simple method to flip the hull. First I planned to lay mattresses on the floor and roll over the hull to the side (Like the method other builders has used with tyres laying out at the floor). I built an edge guard and a protector for the skeg. Then I got respect because i had no chance of slowing the hull when it fell over to the side since i was alone. The night before the big day I came up with a construction of pivot points. At the stern I attached the wooden slats for the pivot point to the bolt holes of the daggerboards that were already there and to the jig. On the bow I attached the wooden slats to the holes for the towing eye or where the bobstay is attached and again to the jig. The stern pivot point is 28cm above the top edge of the transom. The pivot point at the bow is 50cm from the top edge of the stem cap.

Pivot point at the bow.

Wooden slats and skeg protector for the stern pivot point.

The skeg protector from the side.

Stern pivot point, red marked are the bolts to the daggerboard support fixing points.

Everything was prepared for the hull flip. Early in the morning I began to raise the hull with a chain hoist at the stern and ratchet straps at the bow. I had to keep adjusting the ratchet strap at the bow. To do this I supported the hull in the bow area with pallets and lifted it with a car jack.

I kept lifting from bow to stern and stern to bow. When the hull was hanging in the air, I pulled on one side of the transom using the chain hoist to rotate.

Stern pivot point and chain hoist fixed to the skeg after uprighting the hull.

After 20 minutes the hull was easily and safely turned. Sadly I don’t have a scale. I would be very interested to know how much the boat weighs with the jig.

I then lowered the hull onto his rack.

I attached 4 heavy-duty trolleys to push the hull with the rack out of the workshop. Now it was 11 a.m. and the excavator i have ordered arrived. We built a platform with pallets in front of the ramp. With two towing straps around the rack, the hull was pulled further out of the workshop onto the platform with the excavator.

Once the hull was hanging in the air we removed the platform and pulled the trailer underneath.

They did a great job and after 20 minutes the hull was hanging in the air and then was placed to the trailer.

My boat hits water for the first time. Unfortunately not swimming because the water comes from above. It was raining non-stop.

Knowing the weather forecast, I bought a heavy duty waterproof tarp. I placed it immediately over and started drying the boat inside.

Luckily it stopped raining in the afternoon so I was able to drive the trailer back to the winter storage in the shed 40 km away from my ex-workshop-

After this I had to clear out and clean the workshop in no time.

Some very productive and exciting month in which I made good progress with the build are gone. Unfortunately i have to deal now with interruptions. I have to find a new workshop and must earn money so that I`m able to proceed.

Keel try on and drilling the keel bolts

Now things had to happen quickly. Before I flip the hull and take it out of the workshop, I wanted to try on the keel and drill the holes for the keel bolts. I thought it would be easier to do this as long as the boat is upside down and here in the workshop I have sturdy iron supports on the ceiling for the manual chain host.

I built a small cart to transport the keel. With a laser and a string I marked the center of the hull. I fitted the jig with 4 heavy-duty rollers so that I could move it around in the workshop. With the chain hoist i lifted and aligned the keel fin to the laser and string line.

Then I first drilled with an 8mm drill and after this from the inside of the hull and from the outside with the 12mm drill.

On frame D` I had to drill from the inside with the angle drill due to the lack of space.

The keel plate adapted quite well to the hull, although not perfectly. That’s why I decided to remove the filler in the area of the keel plate. Later when it`s time to fix the keel i will apply an additional layer of epoxy resin compound to fill the gap and will have this connetion as sturdy as possible.

Fairing

I had to get to work on the job I really didn’t like: filling and sanding. But after hours of work and when you get closer to your goal, it can be fun.

I applied the first layer of epoxy filler very thinly. I mixed 11 portions of epoxy filler  (each 500g resin + 150g GL-2 R&G hardener) and mixed in total 12 liters of micro balloons for this 1st fairing.

First layer epoxy filler.

After a few days of curing I was able to start sanding with the sanding board.

Then i applied a second, thicker layer of epoxy filler. Again it took a few days for final curing and more than 1 day of hard sanding work to smooth it out.

After these two runs of filling I had to clear the workshop because my time was running out here. So I applied a protective epoxy layer with blue color pigment. Next spring when I apply the 3rd layer of filler i have a good contrast and can better identify the areas where to put more filler.

Keel welding and drilling the keel bulbs

There is a detailed plan from B&B Yachtdesign of the keel construction. When i purchased the ClassGlobe plans, i also get the CNC-files for the keel fabrication.

The keel is a safety-critical component of any sailboat. Therefore, it is better not to make compromises. Profiling the keel fin is a sweaty job that can hardly be done with amateur tools and anyway the welding must be done by a certified welder. I had the keel fin cut according to the CNC-file a year ago. My boat building colleague Christian (CG #103) rented his workshop from a metal construction company. The staff helped us in questions of keel fabrication and welding. Before welding, we had the keel fin profiled from a professional CNC-cutting company.

Weld 15mm

Signing the ClassGlobe welding certificate.

Keel welding certificate.

To make the drill holes in the bulbs, Christian and I first built a wooden plate as a drilling jig using a keel fin template.

You can find more information how i build and cast the keel bulb here:  (see my blog: https://minisailer.ch/?m=202208)

With this jig we were able to transfer the drilling position and fix the bulbs in the drill machine.

First we drilled the recesses with a 30mm Forstner bit and then drilled through the keel bulbs with a 13mm drill.

Once again, the construction of the ClassGlobe proves to be very compatible with the standard Euro pallet format and loading space of my VW transporter. With a little balancing you can heave the 105 kg keel fin onto the loading area.

The skeg

I prefabricated the skeg a year ago when I was doing the small parts in my basement workshop.

The skeg plan

First I made a positive mold which was covered with fiberglass. There is even a 3D model of the skeg that you can use to have the shape milled. Since I don’t have access to 3D milling. I glued two 20mm Styrodur plates together. With my orbital sander i reduced them to 38mm thickness. With 2x 1mm glass fiber laminate I get the necessary width of 40mm.

This positive skeg model had to be insulated with adhesive tape. Then i applied some layers of 300g/m2 fiberglass fabric.

Removing the Styrodur material from the skeg mold was a bit tiring.

The skeg is bolted to the hull. I bought 6 M10x120mm V4A screws and V4A rods. I clamped the screws into a jig. The welding of the skegbolts was done by a professional welder.

The welding jig

The skeg bolts must be casted in the skeg mold and the mold has to be filled up with epoxy resin. This must be done step by step because of the generated heat when the resin is curing. The M10 skeg bolts must not protrude more than 5.5 cm above the edge of the skeg mold.

5,5 cm is the optimum bolt lengths.

I added microballoons to the last layer so that I can sand it easily and adapt it to the hull.

After the hull was planked and laminated, I marked the centerline of the boat with the laser level and drilled the holes for the 6 skeg bolts. From the inside I attached a 10mm thick plywood panel as per plan. I glued the skeg to the hull with a mixture of epoxy and cotton fibers and fixed it with the bolts to the hull. I also laminated the transition from the skeg to the hull with fiberglass tape.

Skeg glued and laminated to the hull.

You have to be careful that the rear bolt is not too far aft, otherwise you will have problems screwing it on to the transom frame wood.

Rear skeg bolt very narrow to the transom frame. This is maybe the problem because i added a plywood doubler to the bottom of the transom.

The skeg bolts, nuts and washers in stainless steel V4A quality from the inside of the hull with a plywood doubler as per plan.

Hull lamination

Before laminating the hull it is necessary to round off the corners because the fiberglass fabric cannot bend around sharp edges. I also sanded the plywood to make it clean and smooth prior lamination.

Choosing a transducer modell for the echo sounder gave me some headaches. The ClassGlobe 5.80 class rules allowing a simple depth gauge. A log / speedometer or other multi-sensors are not permitted. I decided to assemble an Airmar P79 in hull transducer. It can`t be placed on the wooden hull structure and must be cast in a layer of epoxy directly to the glasfiber hull construction. So I had to drill the hole for this transducer before laminating the hull. To do this, I drilled a 10cm hole with the circle cutter in the floor plank directly in front of frame D. I closed this hole again with 20mm thick foam and secured it from below with a plate and a support.

Installation scheme for the Airmar P79 in hull transducer.

Transducer hole with foam block from the inside of the hull.

Support of the foam block while laminating the hull.

I have done the lamination in 2 steps:

  1. Laminating the edges and plank connections
  2. Hull lamination

Step 1: Laminating the edges and plank connections

I laminated the edges with 600g/m² roving glasfiber according to the plan. I covered the area of the bottom plank, the stem and transom with 2 layers of 600g/m² (first layer 10cm and on top of that a second layer 15cm width).

I covered the plank connections with 15cm 600g/m² roving glasfibermat. I also attached 2x 600g/m² roving fabric in the area of the dagger board holders. Finally I applied peel ply for surface conditioning.

After some days of curing, I sanded and filled the transitions to avoid possibly air bubbles when laminating the glassfiber fabric.

Step 2: Hull lamination

According to the building regulations, the hull must be covered with 1000g/m² fiberglass fabric. Due to the easier handling, I decided to make the fiberglass structure in 3 layers and used woven glassfiber fabric 345g/m² and 1 meter width. I laminated wet-on-wet in one pass with overlappings of 5-10 cm. After applying the first layer I added reinforcements with 600g/m² roving fabric in the area of the skeg, the keel plate and a band round the hull to strenghen the hull in the position of the shroud chainplates. I used epoxy from the brand R&G which I knew from my previous boat building so far. Namely it was the resin L and the slow-setting hardener GL 2. This epoxy resin is thin flowing and slowly curing. It soaks the fiberglass fabric very well.

I built a rolling scaffolding that was moveable along the hull from the transom to the bow. I pre cut the fiberglass mats a day before. The order of applying the fiberglass fabric was starting at the transom as follows:

  1. layer fiberglas fabric.

2. layer fiberglas fabric

3. layer fiberglas fabric

4. layer fiberglas fabric

5- layer fiberglas fabric

5. layer fiberglas fabric overlapping the transom

6. layer fiberglas fabric

7. layer fiberglas fabric

8. layer covering the transom with peel ply

9. layer fiberglas fabric

10. layer fiberglas fabric

11. layer fiberglas fabric

12. layer fiberglas fabric

After applying these 12 coats, I planned to take a break to eat and drink. Then i was able to proceed with this 3-layer system to the bow.

The advantage with this method is that I can stop the laminating process at any time and simply cover the laminate with peel ply and continue the next day or after a few days. For example, if you are a small team and you have to take a break or there are problems with the resin etc. you`re able to stop and continue later.

Time for the big day.

Christian (CG #103) and Thomas, a friend of mine from sailing club, came on a saturday to my workshop. We worked great as a team. I mixed the epoxy, added the pre cut fiberglass mats from above, applied the epoxy and vented while lying on the scaffolding.

Christian laminated the starboard side while Thomas took care for the port side. I mixed each 1 kg of resin and 300 grams of hardener in a 3 liter bucket. I took control samples of each mixture. This way i was able to check the curing later.

Sample cups to control the epoxy curing.

In total we used 26 kg of epoxy resin. Laminating 4 layers (3x fiberglass + 1 layer of peel ply) takes time. Time was flying so fast. With a short break, the three of us took 12 hours and bravely held out until early morning. Very good job guys. The result is excellent.

General tips for laminating:

A few days before the laminating day it is time to check and control the material. Then there is still enough time to order missing things. Calculate is there enough resin / hardener? Are there enough tools (brushes, rollers, mixing sticks and containers, venting rollers, a second scale to be on the safe side if the usual scale is defect, protective material such as gloves, suits, respiratory protection, etc.).

Maybe it gives you confidence when you mix the epoxy and check if it is curing and that all materials are compatible. There’s nothing worse than finding out that the resin doesn’t work!

I laminated the raw Okoume plywood planks. They where not prepainted with some epoxy layers. Keep in mind that the wood sucks out the resin of the fiberglass fabric. You have to apply a liquid epoxy layer to the wood about half an hour before. Immediately before placing the fiberglass mats, apply another good layer of epoxy. Always make sure that each layer of glassfiber fabric is well soaked with resin before applying the next layer. If the fiberglas becomes translucent then you can be sure that it is well soaked with epoxy resin.

When putting on the peel ply, don’t apply too much epoxy resin. Otherwise waves could form. It’s not a big problem to sand them down later, but it’s better to avoid this.

Epoxy overload.

After the lamination is done and the peel ply is on it is best to continue working with the ventilation rollers for about half an hour to hold and fix it down while it becomes more and more sticky.

I personally got some tips from Joachim (CG# 165) who also wrote a very good blog about laminating the hull. Thank you Joachim!

Some more impressions from laminating the hull ClassGlobe #66:

Trolley with fiberglass and peel ply rolls.

Epoxy mixing bar.

My co-wokers Christian and Thomas.

Thank you so much guys for your great effort and the unforgettable moments when laminating hull ClassGlobe #66.

Hull planking

Before planking the hull i had to trim the stringers into shape. This step must be done very precisely to avoid any bumps in the planking that gives you significant amount of work when filling. I started to trim the stringers with the electric planer. The finishing was done with the hand plane. Finally, I used my sanding board to shape the stringers. I use a measuring stick to check whether the smoothing is sufficient.

Handplaner with guide rail

Sanding board

Measuring stick

Stringers shaped and ready for planking

Be careful with the 30mm stringer at the flat hull side (not the 30mm chine stringer) between frame B and frame C. Due to the bend, it can protrude slightly outwards. If you now try to trim back these protruding part of the 30mm stringer, they will be thinned out and therefore bend even further outwards.

The hull is covered with 10 mm Okoume plywood. The bottom is planked with 20mm (2x 10 mm).

I have done the planking in 4 steps:

  1. First bottom planking
  2. Side panel planking
  3. Chine panel planking
  4. Second bottom planking

This order may only be possible if you build by plan. The CNC kit planks are short cut and therefore a different order of planking must be chosen (1. side planking, 2. chine planking, 3. 2x bottom planking).

I cut the planking to size by placing the large 1.22 x 2.50 m panels on the hull, marking and cutting them out. I left about 2 cm overhang on each side. I dryfitted the planks and fixed them with clamps on the stringers. I climbed under the hull and marked the position of the frames and stringers from the inside. Then i took of the planks again and drilled the holes for the screws.

Step 1: The acces to the bottom of the hull was easy by climbing onto the stringers. I glued the planks with thickened epoxy (epoxy + cotton fibers) and fixed them with stainless steel screws. In the area where the planking rests on the frames I used 5×40 screws. To fix the planks to the stringers 5×25 screws was the maximun and I had to be careful that the screws didn’t come out on the underside of the stringers. Choosing the screw position is not easy because you cannot place the screw heads too close to the edges. These screws could bother you when sanding and rounding the edges later. As a solo builder, I used a support to help me hold the plate when gluing the bottom plank.

Step 2:  Side panel planking was a straight forward job. Before planking I cut off the butt blocks that will be placed on the inside of the joints.

Butt blocks astern (upper section is extended for reinforcement of the series drogue chainplate attachments).

Butt blocks in the cabin (plus extra 10mm plywood reinforcement for the shroud chainplates as per plan).

I used little helpers that I attached to the 70mm stringer to hold the plate when gluing. Again i fixed the planks with 5×40 stainless steel screws whre the planks meets the frames and 5×30 screws to fix them on the stringers.

Immediately afterwards I attached the butt blocks to the inside of the hull at the joints of the planking. With screws (3×16) and clamps i was able to press the butt blocks to the joints.

Butt blocks in the cabin fixed with clamps while gluing.

Gluing the side panel planks.

Then i had to trim the overlapping 2 cm of the bottom and side planks in the chines section and had to sand the stringers again.

Step 3: Fixing the chine planks where they meet the straight sections in the back of the hull was as easy as the bottom and side panel planking. The front chine planks in the bow section gave me some problems. With a lot of strength, straps and clamps, I managed to bend the 10mm Okoume plywood panels into shape.

Step 4: Finally, I glued the second bottom planks with a layer of thickened epoxy and fixed them with stainless steel screws (5x40mm screws to the frames through the first bottom planks and 3x16mm screws to the first bottom planking). I had to make sure the epoxy wasn’t thick. I started screwing in the middle of the boat and standing on the plank with my weight to let the epoxy flow out to the sides.

Finally, I sanded the planks where they are screwed onto the stringers and rounded the edges of the planking to easily apply the hull glass around the corners. This lowers also the risk of damaging the fiberglass when sanding the hull.

Next comes the lamination of the hull.

Gluing the stringers

Finally the stringers are glued. It was a tricky and sometimes physical job.

You can find information about cutting and preparing procedure of the stringers here:  (see my blog: https://minisailer.ch/?p=362)

Preparing:

First of all, it is very important to get a good knowledge of the ClassGlobe 5.80 contours. The stringers must installed according to the chines and shape of the hull. Therefore I studied the plans and many builder blogs. Then i was able to develop a feeling for the angulation and twist of the stringers.

Since i`m building from plan i had few information about the dimensions and position of the cut-outs for the stringers. The exact meassures are not included in the ClassGlobe 5.80 plan. One more time i have to take these details from the CNC-kit parts. Thanks i`m in touch with builder colleagues. Some stingers (mainly the one of 30mm dimension) are placed in the middle from the joints of most frames. But not in the bow area.

I split the stringers gluing in 3 steps. First i installed the 30mm stringers. This is the easiest part of this progress and you give the sensible frames construction stiffness that you`ll need when putting in the following stringers. The second step was to glue the 50mm chine stringers and last ones where the 70mm stringers at the deck level. It is important to glue the both corresponding stringers in one time so there will be no twisting of the hull.

Attention! The stringers are the foundation for the planking. Every mistake here will punish you with bumps in the planking that later give you a lot of work when filling and sanding. So be sure and check the position of the stringers with a level before gluing.

Tools:

With some helpful tools you can make the tough job of cutting out the frames, bending and shaping the stringers a little bit easier.

Some self-made tools are useful to get control wether the stringers are placed sufficiently, to bend them and hold in place (2 forks for the twist, templates and a gauge to measure the hight).

Jig modification and strenghening:

The jig needs to be strengthened as there is a lot of torsion in the bow area when installing the stringers. If frames D, E and the stem are not properly attached they could get warped.

I built scaffolding to the sides to make it easier working at height and to have better ergonomics.

Cut-out`s in the frames:

The best way to cut out and grinding work on the recesses in the frames is to use a reciprocating saw, japanese saw, chisels and carpenter`s mallet, as well a small belt sander and wood rasps. For sure you need a lot of small clamps and lashing straps to hold the stringers.

I clamped the stringers in place and marked the position and angle of the cut out. With a mixture of drilling, sawing out with the Makita reciprocating saw and grinding with the belt sander and wood rasp, I got very precise cut-outs for the stringers.

Check again and again in between with the helper tools.

30mm stringer:

It is best to start with the 30mm stringers. As soon as these stringers have been glued, the construction is fixed and can no longer move. I was so glad when those stringers where glued. Finally, I no longer had to measure and check the distances and remeasure again and again. When doing the cut out in the stringers i checked theses recesses with this small 30mm try in block.

In the bow area there is a lot of twist and bending to the stringers. I was lucky to have these self-build forks to manage the twist of the stringers.

In the area of frames D` and D the stringer makes a strong kink. Here I have made an attachment to the jig post so that I can attach a strong clamp to press the stringer.

The chine stringers:

I made bending the stringers a little easier by already planing off the 50mm chine stringers. With this they lose some regidity and are easier to bend.

70mm deck level stringer:

This stringer isn`t lowered into the frames everywhere. At frames S, C and D` and D it is fully integrated. At transom, frame A, frame E and stem cap this stringer is only 45mm attached. 25mm are outside of deck level which will be planed later when the hull is turned and the deck is made.

When adjusting the stringer there is a lot of stress on frame S and it could get warped. Therefore i installed two bars while gluing the stringer.

Mission completed

Happy days are coming! The boat is taking shape. Heading forward now for planking.

Keel floors gluing

I prefabricated the keel floors from oak wood (see my blog:https://minisailer.ch/?p=258)

The keel beam No. 1 and No. 3 are already glued in with the corresponding frames D` and C. Now the keel beams No. 2, 4 and 5 have to be glued.

First i checked the correct position of the keel floors with the string line level.

When putting in the stringers there is a lot of tension in the bunksides / keel floors section. I attached teo slats lengthwise to prevent any movement during gluing the keel floors and stringers.

In order to make the connection as stiff as possible, I was very precise. First sand the adhesive surfaces of the bunksides and remove dust / degrease with acetone.

I did all the epoxy gluing steps in one operation. The keel floors and bunksides where precoated with a thin epoxy layer so that the glue can penetrate the wood. Then the joints where filled with a thickened epoxy (Mix epoxy and cotton fibers). I applied the filets directly while the epoxy had not yet hardened. This way I get a better adhesive connection and save myself grinding work.

To get a proper fit I weighed the keel floors down.

Gluing the bunksides

Since I don’t have a CNC kit, I have to cut the bunksides myself. Here it is a great work simplification if you have ordered a CNC kit. I got a cutout keel floors template from Christian (CG# 103). I also copied the shape of his bunksides from the CNC kit and then built another template out of 6mm simple plywood.

With the help of this template I cut the two bunksides for my boat from 8mm Okoume plywood with a copy routing technique.

Since the okoume plywood panels are unfortunately only 2.5 meters long, I had to lengthen them. To get a good finish, I sanded the panels with the orbital sander before adding two layers of epoxy. Finally, i sand everything down again with 120 grit sandpaper to prepare for later painting. That way I’ve already completed this work and don’t have to do it in a crooked position when the bunksides are glued into the hull.

Now I had to come up with a method of gluing the bunksides in place, taking into account the frame C that is inside the bunksides. Not easy when you`re a solo builder. It came up with an extension construction of the jig upwards.

In order to glue the bunksides in the exact position and to keep them straight, I supported them with four squared timbers when gluing.

With rectangular strips on the aft joints on Frame A and towards to the bow on Frame D`, I created a strong connection by gluing with epoxy and additional screws.

With this preparation I was able to glue the bunksides, Frame S, Frame B and Frame C in one operation in a one night shift. I used slow hardener and immediately applied the fillets in the corners as long as the epoxy hadn`t hardened.