HTB RC boats HTB-290 Tunnelhull

Radio Control Boat Modeler, Aug 2002 by Dunlap, Jerry

Tunnelhulls with powerful outboard engines are among my favorite boats, so when I was asked to review HTB RC

Boats' HTB-290 tunnelhull with a CMB 21 outboard engine, my response was a definite, "Send it right out!" HTB manufactures a line of tunnelhulls that, over the years, has captured many awards, and CMB Italia has manufactured inboard model marine engines that have powered many boats to national championships and speed records, so I was Sure that this combination would prove to be race worthy.

ON THE WATER

I used Wildcat 65-percent-nitro fuel and an Octura X460 prop. The first two runs were completed with a rich fuel mixture for break-in; opening the remote needle valve four turns ensured this When the two break-in runs had been completed, I leaned in) the mixture. With the leaner mixture setting, the engine proved to be very powerful. I've owned and seen some very fast 3.5 outboard tunnels, and the HTB 290 with the CMB 21 LS outboard pushing it across the pond was very fast. The ride attitude of the hull was slightly positive and very clean. Sharp corners could be executed at full throttle without hooking or spinning,

One way to evaluate performance is by comparison. I won the 2001 NAMBA 3.5 Modified I class running a Dunlap WOF 29 powered by a CMB 21 Gold Head engine: this combination obviously runs very well. For the 2002 racing season, the fast speed and good handling of the HTB 290/CMB 21 LS OLIII)Oard combination earned the starting position in 3.5 Mod Tunnel for Team Dunlap. Not too shabby!

THE TUNNELHULL

HTB offers tunnel boats in four sizes: with 27-, 29-, 34and 36-inch-long hulls. The hull for this review is the race-proven HTB-290, and like all HTB tunnel boats, it is constructed of vinylester resin and fiberglass cloth and features a high-quality white gelcoat finish. To complete the hull's exterior, you need add only trim stripes and a few decals of your choosing. Other gelcoat colors are available on request. A fiberglass radio box is included with the basic kit. Items such as steering rods, throttle cable and a fuel tank, which are required to prepare the hull for running, are available from HTB, as is a hardware package with all the components needed for rigging the steering and throttle.

BUILDING THE HULL

I had a wooden radio box that was ready to run, so I substituted it for the fiberglass radio box that's included with the hull. The directions recommend gluing the radio box to the center section. I prefer removable radio boxes, so I glued two 1/4x1/2x2-inch plywood strips to the bottom of the center section. I positioned the plywood strips at the front and back of the radio box and fabricated L-shaped, metal mounting brackets that I then screwed into the front and back of the radio box and into the plywood strips. I connected output arms from Robart Mfg. to a Futaba S9303 high-torque servo for steering. A servo with a minimum of 60 ounces of torque should be used to steer high-performance, 3.Scc tunnelhulls. I used a standard Futaba servo for throttle control, and wire linkages connect the output arms to the engine steering-control bracket. To provide adjustment, I cut the wire linkages, then overlapped them and secured them with wheel collars. For a solid connection of the linkages (including throttle) to the motor, I used ball-and-socket connectors.

I installed a Sullivan 8-ounce rectangular fuel tank. To improve fuel draw, I placed it on a piece of foam to elevate it. The foam is 12 inches thick and is secured with silicone glue. I bent wire into hooks for the rubber bands, and I screwed the hooks into the sides of the center section. Hook-and-loop fastener is also an easy method to secure the fuel tank to the foam.

To finish the hull, I masked off the windshield on the cowl and spray-painted it. Sponsor decals and press-on racing numbers completed the hull. I added downforce wings to the front of the cowl. (See "Outboard Corner" in the February 2002 issue of RC Boat Modeler for an explanation of how to install wings on tunnel boats.) To properly balance the hull, I needed to add 4 ounces of lead, so I cut an access hatch in the bottom of each sponson and glued 2 ounces of lead to the inside tip of each.

CONCLUSION

I'm looking forward to racing the HTB 290 tunnelhull with the CMB 21 LS outboard. Test runs of this hull and engine combination have provided outstanding performance in both straightaway speed and cornering. A high-quality engine bolted to the transom of a high-quality tunnel boat is the formula for a winning combination.

CMB; distributed by Tidewater Engineering.

Du-Bro Products, P.O. Box 815, Wauconda, IL 60084; (800) 848-9411; fax (847) 526-1604; www.dubro.com; rc@dubro.com.

Futaba; distributed exclusively by Great Planes Model Distributors Co., P.O. Box 9021, Champaign, IL 61826-9021; (800) 637-7660; futaba-rc.com.

HTB RC Boats, 1616 N. Parkway, Jackson, TN 38301; (731) 424-4597; fax (731) 424-2717; HTBboatsvaol.com; htbboats.com.

Irwin Performance Products, 7809 S. Sun Mar Dr., Muncie, IN 47302; (765) 747-4190.