Boat Building Project – Grainger MTB920 – Duracore Plank Plank Installation

In my previous post, I discussed the features and benefits of using DuraKore as a core, especially for hobby boat building, and why I chose to use this material on foam and western red cedar to build my Trimaran Grainger 9.2M.

In this article I will talk about how DuraKore is supplied and what work I had to do to make the slat planks for the project I was building.

DuraKore is supplied as planks, and for this project I ordered 13mm thick x 300mm wide x 2.4m long, which had to be spliced ​​to make the planks longer than the 9.2m hull length.

The scarves were made by machining a male cone into the 1.5mm thick hardwood veneer at the end of a DuraKore board, and a female cone into the board’s hardwood veneer to be glued and attached to the cone male.

A 1-in-12 cone provides a stronger joint than if there was no joint if produced correctly.

The test to demonstrate the finished joint is to scratch a sample from a 50mm wide strip board and clamp one end of the board to a bench with most of the board hanging over the edge of the bench. The joint of the scarf should also be a considerable distance from the edge of the bench. Add weights slowly to the end of the board until it breaks. If the joint is a good quality scarf joint, the break will have occurred elsewhere along the board.

A 1 in 12 cone means that the length of the cone will be 1.5mm x 12 = 18mm long.

The amount of balsa cut from the female edge will be at least 18mm deep, and the inside edge of the hardwood veneers will taper towards the 18mm deep balsa cut inside the female joint.

The male edge is simply machined with a taper that extends over 18mm on hardwood veneers.

The DuraKore supplier sells an accessory that fits a circular saw to do this easily. However, a template can be made to get the job done. I bought the attached file.

Once I had prepared a long, flat surface that I could attach 5 DuraKore boards to, I mixed the glue.

The epoxy resin I chose to use was 105 West System manufactured by Gougeon Brothers, Inc.

It is a clear, light amber colored, low viscosity epoxy resin that can be cured over a wide temperature range to produce a high strength rigid solid that has excellent cohesive properties and is also an excellent moisture barrier.

There are two types of hardeners formulated for use with 105 resins.

Hardeners 205 and 206 require a mixing ratio of 5 parts resin to 1 part hardener. Hardeners 207 and 209 require a 3 to 1 ratio and a solid state of 6 to 8 hours.

I used hardener 205 which is used primarily for general bonding, barrier coating, and fabric application. It was also formulated to cure at lower temperatures and produce a rapid cure that develops its physical properties at room temperature. Its shelf life is 9 to 12 minutes at 22 degrees C. And in solid state from 9 to 12 hours.

Hardener 206 is a slower hardener and provides a longer work time, especially when working in higher temperature climates. Its shelf life is 20 to 25 minutes at 22 degrees C.

Special pumps can be purchased to dispense the correct amount of resin per 1 full stroke of the resin pump and the correct amount of hardener per 1 full stroke of the hardener pump.

The temptation is to mix larger amounts, to save time mixing all day, but this resin generates heat once the hardener is added and stirred, and with higher volumes of epoxy in the container, the greater the reaction and the shorter the life. Useful. Before you know what has happened, your hand is hot and the epoxy is hardening in the pot.

The epoxy must be thickened to bond the scarf joints so that it does not come off the joint before curing, and the West system provides additive powders to allow for this. Powders 411 are suitable for this.

I mixed about 4 pump strokes of resin and 4 pump strokes of hardener together, and while mixing I stirred the powder until I had a peanut butter consistency.

Mixing containers can be purchased, however I preferred to put my money in the can rather than the garbage can. I had my wife and our neighbors keep plastic milk bottles and other suitable containers for me. My supply of milk bottles was insane at times. I cut the lids off those to make suitable containers.

Five boards were glued and laid flat along a flat floor and a straight edge template for curing. This was important as the finished board needs to be straight, or else the hull will have a lot of humps and gaps to fill, which will make the fairing work bigger than it should be. Those finished planks were just under 12M long for the 9.M hull, which was fine because it is important to stagger the scarf joints when the hull is being decked, and waste will result from that.

Those long planks then had to be cut to a width of mostly 50mm so that the planks could be laid over the male frames of the mold to form a round bilge core. In fact, what you really have are many small backs, which are hardly noticeable, and disappear completely once the fairing is finished.

Around the bilge areas of the water line area I had to cut the width of the planks to 25mm and a torque to 12mm to go around the narrower radius.

Once I had a good stock of slats made, it was time to start installing them in the mold.

I first ensured that the helmet could be removed from the mold frames at a later date by applying electrical tape to the edge of all the mold frames.

The first board was important, as its location along the hull would depend on how well the next boards were placed around the curvature of the hull. I screwed the first board into the deepest point of the concave frame curve for each frame, and with a little trial and error it became apparent where the best fit was.

The edge of the first board was covered with thick glue so it wouldn’t run off and also filled the gaps at the edge joints. The next board was lifted and put in place, making sure that the sheer joints of each board were not aligned with each other, and only then was it bolted to the temporary frame.

I also found it necessary to screw plywood slats through the planks to keep the edges aligned in the areas between the runs of the temporary mold frames.

This edge gluing process was continued for approximately 6 to 7 weeks outside of business hours until the entire DuraKore core was finished. A cordless screwdriver made this job easier for me.

As the decking progressed, it became apparent that I would have to stop in the area I was filling at the time, because it became impossible to place the long planks around the bilge curves as the plank was starting to rotate like a propeller blade. and resist sitting flat against the edge of the mold frame.

Then I had to fit a new 25mm board along the highest point of the convex curve along the waterline, bow to stern and screw that board as my new edge to glue. The next 25mm board was glued on the edge and placed on the bottom edge of the new board, and I continue to make the board towards the old area, slowly increasing the width of the boards to fit the curve and thus , filling the long elliptical void that was left. As the gap closed, I found that I had to type the end of the boards so they could fit against the bottom board, and as the elliptical gap closed, each subsequent board shortened. You can see the photos showing the tables on my website.

Once the entire hull core was in place, thousands of screws were removed and the hole was filled. The glue joints were lightly sanded, being careful not to remove any hardwood veneer. Manual sanding was the safest method, as machines tend to dig too easily.

My next article will be on the placement of fiberglass in the main hull.

admin

Related Posts

fallback-image

Pilates Classes With Flexible Scheduling in East Sheen

fallback-image

Can Botox Jawline Improve the Appearance of a Double Chin?

fallback-image

Is Practical Training Included in an Aesthetic Doctor Course?

fallback-image

만성 전립선염에 대한 마사지

No Comment

Leave a Reply

Your email address will not be published. Required fields are marked *