Rebuilding a Sport C Raceboat

If all goes as planned, this will be Megan Halver's new ride next summer. She is hoping to make the jump from GT Pro to Sport C in 2013.

This Yeeha/Flyer tunnelboat was built for SST 45. A few years ago, a previous owner re-configured the deck in search of a little more lift for Sport C.

More about Sport C HERE.

This is a virtually identical Sport C boat showing the original deck line.

The final product.

Dave Halver bought the boat a while later, and gave it a new look. But he was unable to get any good performance out of it.

We tinkered with it at my place a couple of summers ago without success. Then he sold it...

... and then bought it back again, and brought it back to my shop.

This time the bottom is getting re-worked.

The main goal of the project is to widen and flatten the sponson pads.

First, the destruction.

I removed the original pads from the transom to a point not quite eight feet forward of the transom. I will blend new with old at this point.

Adding new wood has already begun.

The main goal here is to build up the chine. The tunnel side, on the other hand, needs only a sliver of new wood, enough to create a bevel for the the new, lower-angled sponson pads.

I've also added a wedge to the face of the tunnel side to help widen out the structure.

Here I've added a bit of plywood to the bulkheads. The new stringers fit into notches in the rebuilt bulkheads and tuck under the orginal plywood at the forward end.

The new pads are formed with two overlapping parts. The raised edge at the overlap creates a sharp corner that acts as a spray rail.

Here the outboard part of the pad goes on.

The inboard part completes the pad.

Here's another look at the overlap.

Also seen here, the degree to which the pad deadrise was reduced.

The pads completed.

The first coat of epoxy.

After three coats of epoxy, I sanded off the high places and applied some additional resin to a couple of low spots.

Now I've applied a finish coat of 10 percent epoxy/graphite mixture. I may go with a second coat of this mix.

And we're done.

I ended up using three coats of graphite mix. The first two sanded through in spots, so a final coat was needed.

I'm thinking next time I'll use graphite on all coats -- or at least after a first clear coat.

Right side up again.

The job here is to remove the deck and the re-design done a few years ago.

At minimum, the deck needs replacing due to delamination. It has been my observation that "exterior" grade luan plywood sold at some of the big box stores is at best "moisture resistant." It comes apart very quickly once it hits the water.

Let the destruction begin!

The worst delamination, not suprisingly, was at the tunnel extensions (the area under my glove) and along the lower edges of the sides. At the bow, too, as can be seen in the picture above. Higher up on the deck, the plywood was solid and didn't come away easily.

The coaming is in trouble here too -- the cracks in the surface veneer can be seen. Likely water entered through the slot along the top edge where the rear cowling mates with the coaming.

Largely done with this side, although plenty of cleanup needed before rebuilding can begin.

The coamings are made up of three layers, the middle layer being recessed along its top edge forming a groove to hold the rear cowling. The outer layer on both sides was delaminating, so replacement was necessary.

On the port side, the middle layer also turned out to be in trouble with a large pocket of rot just forward of the motorboard.

Once this was peeled away, the inner layer proved sound.

Here I'm working on a new middle layer for the port side, with the rear cowling in place for a test fit.

When the deck was redesigned several years ago, the bulkheads were slightly reshaped. A bit of plywood added to each one was all it took to re-establish the original outline.

Gluing on the bulkhead additions.

Time for a new set of stringers.

And the new outer coaming layer.

The stringers are all installed, as are new side pieces for the sponson tips. These sides lead to the deck fin which helps guide airflow along the deck.

The hull sides are tacked in place and ready to be installed.

Sides and coamings installed. Now the deck is temporarily in place.

This project is quickly winding down.

Deck installed and starting to trim the edges. It's all details, now.

Hope to have this thing outa here next weekend.

Trimmed, filled and sanded.

The first coat of epoxy.

Now that it's been lovingly rebuilt, toss it out into the cold and the snow. More to come this spring and summer.

Spring arrived a month late, but finally came the time to get back to this project, along with repairs and upgrades to my own Sport C boat.

Here I've mocked up the the transom extension. This was originally an SST 45 boat -- the 45 motor has a 12" mid-section.

Mostly checking for motor height at this point.

Transom extension temporarily in place with aluminum angle inboard and outboard.

The trim cylinder bracket mocked up.

This very nice bracket was on the motor when it came to my shop. I don't know who made it. Apparently hand cut from billet aluminum.

Putting it all together. The transom extension and trim system are fully installed and functioning as intended.

A look at the business end.

Almost ready for testing.

June 2, 2013:

Dave came over, and we took the boat down to the lake. With me at the wheel it performed nominally well, which is all we were asking for at this point. Megan is a good deal lighter than me, and that will make a very big difference.

VERY optimistic as to the boat's potential.

Not sure when we will get Megan behind the wheel. Maybe not until the eve of racing in Detroit Lakes in two weeks.

Megan's first ride in the boat came in Detroit Lakes, MN. Fifteen minutes later she was racing. With no testing, no adjustments, no prop tryouts, she stayed on the lead lap and showed improvements thoughout.