Sprint Cat 42 FE Rebuild

[Mike W]

I took a personal interest in this build when it came my way because I had previously flush-seamed one back around 2000. It had twin Picco 67s and a widened turbine cowl to cover both Irwin pipes.

This one was a nitro boat and had several areas of previous damage needing rework and the deeper the owner got into fixing them right the worse the proper repair options became. So we cut the deck off, rails out, transom wood out, and cleaned up all the old repairs to start with this:

[Mike W]

Next step was to prep the major repair areas for repair laminations.

[Mike W]

After I cut materials and mix epoxy I like to take some epoxy and mix a filler with milled CF and microspheres to prefill areas adjacent to the existing material and create a smoother transition to the new for less finish work later.

[Mike W]

Repairs in place. Some holes and gouges filled.

[Mike W]

Deck underside repairs and existing rough mat were sanded and a layer of 6 oz. cloth added. Center sections were omitted since they'll be getting further rework later to fit this deck onto the hull bottom flush.

[Mike W]

Hull bottom was sanded and a thin filler epoxy layer added to the tunnel bottom. This smooths grinder marks and lends a much nicer appearance to the finished CF inlay.

[Mike W]

When sanding is complete I wash the hull down with Dawn, a red scotchbrite, and a microfiber. Hose out and dry well.

[Mike W]

The bottom will be laminated in 3 pieces. First I prefill tight inside radiuses. These are never able to be sanded easily or very smoothly and I sand them mostly with a ball carbide on the Dremel. So they get smoothed with a prefill fingertip of epoxy filler. A heavy coat of resin smooths them further.

[Mike W]

A 2mm CF transom is bonded on with an additional 2mm in the center.

[Mike W]

Just because the original layup had deck sponson tip CF reinforcements they were added again.

[Mike W]

Rejoining the hull is done with 3 reinforcement layers on the inside of the seams up to about the front hatch flange opening. The front will be finished later. Considerations are clearance to fit 6S 5000s into the sponsons so the transom was raised slightly.

[Mike W]

Properly laminating up front will require deck sponson sides be removed.

[Mike W]

Front center deck was removed and hatch flanges cut to allow a proper hull fit for flush joining. Here they are repaired. The front lip gets a CF strip doubler underneath.

Transom original upper pieces are epoxied back onto the new CF transom doubler.

[Mike W]

Completing closing up the front center area required some work. CF deck sponson insides are bonded to the hull bottom and deck, and a CF tunnel leading edge spanned across between them through two holes and flush on the backside.

A GFK deck support is bonded under the hatch flange. Everything is filleted and the deck support wrapped from tunnel to flange with CF.

The rear hatch flange cuts required to raise the deck and provide battery clearance are repaired while glassing the transom to the deck above the tunnel with CF.

[koen]

looks very good mike, these boats are so good. i have 36" use to run it with a cmb 90 now its rebuilt to electric ,and the funny thing is its now faster(i use a lehner 2260)

[Dirk Jan]

Great work and thank you for sharing photos and how to.
What kind of setup are you planning for thus hull?

[Mike W]

This will be a NAMBA T Offshore single.

[Dirk Jan]

I'm from Europe, and not familiar with the different NAMBA classes. What kind of motor and esc will you use and what kind of prop?

[Mike W]

Oh, it will by a 10S setup with a 56mm ~800-900KV motor on maybe a X462 or 2215-ish prop and a SF300 Pro+ Lite ESC. Not my boat I'm just restoring the hull for a customer. You can see my builds on FB Otto RC Marine. I post a few here to generate interest in this type of work, share some techniques, and hopefully learn something new if someone knows a better way!

Got her cleaned up again. Sanded seams. You can see the slightly increased rake in the hull and narrowed hatch flange to make battery clearance. I'll add a hatch opening edge support brace about in the middle for extra strength and to hold the necessary clearance.

The rear lamination came out great where I cut that long notch to allow some curvature. I taped over it with scotch tape before prefilling the radiuses along with this notch and laminating the reinforcement on. You can run your finger along the flange and not even feel it!

[srislash]

Fabulous job pal. I love these big guys ripping at 70 and hammering corners full tilt.

[Mike W]

Fabulous job pal. I love these big guys ripping at 70 and hammering corners full tilt.

Thanks Shawn!

Tacked in some deck supports last night. These will need glass reinforcement later.

Today I closed up the nose and created the center front deck flat. First I cut and fitted the foam along with another 6mm CF tube ahead of the 12mm. A quick fillet along the front of the deck support and the first layer began there and up. Then the foam was fitted and the initial layer of 6oz glass laid across and just around the front edge.

Radiuses we made on the top and back sides of the foam since the laminations could only butt up the sides. These were then prefilled for bond strength to the sides and back, and subsequent layers applied for a total of four over the foam. The first including the deck support and slightly wrapping past the front and underneath. the second over the foam only, The third from the hatch flange about an inch past the radius underneath and the third from the hatch flange 2" past the radius underneath.

Filler work and primer is next!

[fweasel]

Damn that's a lot of work. Is the owner attached to the hull? Regardless of the why, the how is awesome to see play out.

[Mike W]

Damn that's a lot of work. Is the owner attached to the hull? Regardless of the why, the how is awesome to see play out.

He is now. I get carried away sometimes with these builds. Finished up the bodywork it's ready for primer.

[koen]

looks very good mike

[Peter A]

Just wondering about the actual hatch now (what it looks like) the front deck has been flattened?
I have just picked up an undrilled hull. It came with a sprintcat hatch and a gas hatch mould. Neither of them I like. I am thinking of putting an F1 style top on it.

[Mike W]

looks very good mike

Thanks koen!

Just wondering about the actual hatch now (what it looks like) the front deck has been flattened?
I have just picked up an undrilled hull. It came with a sprintcat hatch and a gas hatch mould. Neither of them I like. I am thinking of putting an F1 style top on it.

Yes, I was waiting for primer to post another pic. It is a very basic long low bubble canopy.