LR4 Build

Been experimenting with some tube construction and now have the ability to make small diameter tubes suitable for booms and till extensions.

On the far left is a boom that can be used with a center sheeting system (weight is 32 oz.)

The three tiller extensions are (from right to left):all carbon, carbon/Innegra. and carbon/Kevlar. They are 9' long and weigh 16 oz. for the carbon/ Innegra to 20 oz. for the all carbon one. The carbon/ Innegra version is less likely to break than the all carbon one.

Lindahl Composite Design is going to be building another A Class catamaran, the LR4. Once again we are going to use a unique method of strip planking the hulls that eliminates the need for an expensive mold. There has been quite a bit of interest in our build method since it allows the garage builder to create a one-off prototype rather easily.
I will update this site with progress reports and photos of the build. I encourage people to ask questions or make comments. Click on "LR4 Q&A" at the top of this page if you have questions or comments.
This hull design came from Richard Roake who I have worked with for many years. Our first collaboration was the LR1, a strip planked cedar A cat I sailed in the 1987 Worlds. Now it's my son, Ian, who does the sailing and has contributed his "seat of the pants" feeling to the design, We work together on the building.
The LR2 and LR3 were built using this foam strip plank method and are documented at: LR2ACATS : LR2 A-Class Catamaran

The first step is to build a strongback. I used two 20' floor joists. They are straight and don't twist or sag. A plywood top holds the two together and is used to layout frame locations. The frames are spaced every 9 inches.

Looking forward after the building frames have been set up. A starboard outer hull half and a port inner hull half will get built with the frames in this position, and then they will be reversed for a port outer half and a starboard inner half.

We had a mold CNC'd for the first 12" of the hull.Made the shaping of the bow much easier and accurate to the design. It integrates nicely with the building frames.

Foam in the frames. Gorilla glue used to join the coved and beaded foam strips. Now you get an idea of what the hull shape is like.

Now carbon fiber has been hand laid onto the foam. the carbon is wet out with West System epoxy and carefully squeegeed into the weave. Done properly a very favorable resin to cloth weight ratio can be achieved. Reinforcements for deck hardware and bulkheads are also added at this stage.

   We built the starboard outer and port inner hull
     halves first and have now reversed the frames to
     build the starboard inner and port outer halves.
    Thanks to Tony Arends for that tip. It cut down on
     the number of frames that had to be cut and the
     switch over only took about an hour. It also cut
     down on the cost. The building frames and the
     alignment jigs for setting beams only cost $195.
     including materials.

A flange is created so the hull halves can be aligned properly when joined together and to add surface area to the bonded joint.

Local reinforcements for shroud attachments and blocks and cleats that will be installed on the deck.

Putting two hull halves together.

Integrated, finished bow Bottoms up Faring tools

Carbon dry Carbon inside and out, 27.5 lbs.

Hull check. What we've got matches back to the the original CNC cut frames. Accuracy to the design is insured. Fairing the foam was done very well. Gorilla Glue made the cove and bead joints one solid unit. Minimum amount of bog needed to fill the weave and get ready for primer.

Here's what the hull looks like: very fine entry, moderate rocker, nice and full under the rear beam, clean exit.

CNC cut nesting jig Hull fits Wet sanding primer

Ready to fix the beams One layer under beam One layer over front beam Rear beam
One tabbing, beam to hull

                                                                             Got it all together.
            Got boards and rudders. Got a mast and a new Bossett sail. Have to cut some wire and get the tramp.
                                                                                                                                  Then go sailing.

Got on the water at 8:30 Friday night for an hour. Loaded up on the trailer and Ian was off to a race on Lake Charlevoix at 5:30AM. This sure looks good through the water and the sail has lots of power.

Got some good video of the first sail and I put a couple of clips on YOUTUBE. Look for LR4 ACAT, Launch. If you use Skype send me your address and I can easily send more video. Unforunately I can't post it on this free website without spending big bucks.

Out of the paint shop

SOME DETAILS

MAST BASE/ROTATOR DELRIN MAST PIVOT & DIAMOND ADJUSTER ACORN NUT ON A THREADED ROD TAPPED INTO A COMPRESSION TUBE