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Thread: Mirage Tomcat Resurrection

  1. #21
    ExperiMental BYOBoat's Avatar
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    Quote Originally Posted by MonsterNine View Post
    Where do you get the sponson tip covers?
    It so happens I have a mold for the tips. I'll lay up an extra set when I'm building a few next month. You don't need them for sport use, but we are required for racing. When racing becomes rubb'n they pop off to leave a blunt surface instead of poking. With the original tips cut off we glass in a bulkhead, use foam and glass to make it roundish, then the tip slides over and secures with a couple screws
    mini tunnel boats for sport, now an experimental Sport C added to the fleet.

  2. #22
    Team Member MonsterNine's Avatar
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    OK so I have been doing some more work on the jig the last few days. I wanted to make a form for the bottom of the tunnel so when I glass the new core to the bottom there will be support. I don't want a big bow from the weights I will be putting on the core and I want to try to get the ripples out of it as much as possible so I am doing more filling than grinding when I fair that part.
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    Dave

  3. #23
    Team Member MonsterNine's Avatar
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    With the tunnel form made I think I'm ready to start tabbing the hull to the jig. Then I get to take off the deck and start cutting and grinding all the junk wood and glass out of it.

    And then? Start making a boat out of it again.
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    Dave

  4. #24
    Team Member MonsterNine's Avatar
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    Quote Originally Posted by BYOBoat View Post
    On the rigging side, I've found a mercruiser trim pump, and merc outboard ram off ebay work well. Most people use a rubber truck gear shift boot to keep the water out. I found glassing in an outboard well of sorts around the ram and bracket is more reliable for longer waits at the dock between races. I'll try to take a pic. Or some people have built trim ram mounts that are entirely external. Either way power trim is the only way to drive these. With the 40hp 2 cylinder Tohatsu they're good for 55-60mph, WOT full time, cornering and blowover prevention is all with the thumb controlled trim switch.
    Do you have any pics of the rigging? Cockpit, seat, fuel tank, battery, steering cables, trim pump set-up, motor mount? Do the motors use any set back?
    Dave

  5. #25
    Team Member MonsterNine's Avatar
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    Tabbed the hull to the jig. Took off the deck and everything seems to be held in place firmly. Angles are equal and elevations are level across the sponsons. Weather permitting I can start removing the bad glass and wood and start patching the many holes soon.
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  6. #26
    Team Member MonsterNine's Avatar
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    Did a bunch of grinding the last couple days. Still have a lot more to do. Interesting layup. First the gelcoat, then the skin coat, and then the cores (1/4 inch plywood) directly to the skin coat with just neat resin. Most of the slots cut in the cores to allow excess resin to flow through have little resin in them. Red areas under where the cores were is where there was no bonding. After the cores it looks like there is a layer of 1808 which is overlapped on the vertical side of the sponsons. Had to include the gratuitous picture of the rotted wood. The bulkheads came out pretty intact so I can make templates. I was thinking of using iso poly resin for the whole job but I think I will just use it for the outward hull repairs and then use vinylester or epoxy for everything else with an extra layer of fiberglass under the cores covering the entire interior of the hull. Finally found a place in Vegas that sells FG supplies but may have to get the foam for the cores and PW shipped to me.
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  7. #27
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    Some of these are not tomcat pictures, but all are typical hardware setups on Sport C boats. Official Sport C setups run teh 2 cylinder 40HP Nissan/Tohatsu motors, models M40C, NS40C and NS40C2. I think Tomcats were also run in Sport D years past with similar setups but using the 3 cylinder 40-50hp Tohatsu and Yamaha motors.

    Steering, typical setup is a pull-pull cable system. A 1" or similar shaft is supported on bearings. A steering cable runs from the motor steering bars, through guides (to reduce cable flop and rattle), through pulleys, around a drum on the shaft with 3+ turns/wraps, out the other side and back to the motor. Using steering bars, the cable should wrap from the bottom of the drum around, and exit off the bottom out the other side. If it enters from the top you'll steer left to go right

    Pulleys. Nydahl gimbal type are great, but with CAREFUL alignment during install you can also use Harken or similar sailboat hardware pulleys. I've found it's easiest to set up the steering after mounting the motor, assembled with steering bars, and set at about the right prop height.

    Drill a hole through the cockpit in line with the bottom of the steering drum. Keep in mind the cable will be on the front of the drum on one side, the back on the other, so left and right side of the boat the holes won't be the same distance off the bow. Wrap the middle of the cable around the drum a few times, through the holes, loose pulleys, and back to the motor. If your steering bars are built right trim angle won't make much difference on steering bar/cable end location. With the cables snug, you can then drill the mounting holes for the pulleys, with them lined up with the cable. Once that's done add a couple guides (sailboat hardware, half loop straps, plastic with a hole in the middle, etc) spaced evenly between the pulley and motor on each side. Keep in mind that if your prop height estimation is off by a couple inches, things will not line up as well later on, so estimated prop height is important. The pulley's should be ok, and you relocate the guides with a backing plate that's larger to hide the original holes.

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    mini tunnel boats for sport, now an experimental Sport C added to the fleet.

  8. #28
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    Looks like your jig will save a lot of time. Nothing is more frustrating than driving a twisted boat that won't handle. I've found, besides overall boat shape, the last few feet of the sponson bottoms must be STRAIGHT unless hook or rocker is intended, and the vertical inside sides of the sponsons should be straight and smooth to avoid funny jerking while turning. The straighter and stiffer the rest of the boat is the faster it will run and better it will turn.
    mini tunnel boats for sport, now an experimental Sport C added to the fleet.

  9. #29
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    Here's some typical Sport C hardware, as set up on the Tomcats and other similar boats.

    Basic overview. Steering is a pull-pull system with steering bars on the motor. Always use a foot throttle. F-N-R shifting can be mounted anywhere convenient but out of the way. Fuel tank just behind the driver bulkhead, to be shifted fore-aft as needed during testing (always strapped down with a seat belt for each test run) to help balance weight. A lawn tractor battery, and mercruiser or similar power trim pump mounted aft.

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    mini tunnel boats for sport, now an experimental Sport C added to the fleet.

  10. #30
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    The center of the steering cable (3/16" stainless cable is common?) should have a least 3 turns around a drum. I've used garage door spring/cable drums mounted on a 1" stainless shaft, but any variety of drums well secured to the shaft will work. Each end should then pass through the cockpit side, turn 90deg around a pulley, run aft through a couple guides (to reduce cable wiggle and rattle), and end on the motor steering bars. Nydahl makes nice gimbled pulleys, or if aligned CAREFULLY during installation Harken and other sailboat hardware pulleys work fine.

    Here's how I do an install. Mount the seat in the boat. Install the steering shaft into a pulley on the dash and another on a frame towards the bow. Install the steering wheel, and make sure the shaft is located so the wheel is a comfortable distance from the seat. Locate the drum at a convenient place on the shaft, and secure with a through bolt or such to the shaft. The cables must lead off the BOTTOM of the drum on both sides, or you'll turn left to go right . Drill a hole in each side of the cockpit, remembering the cable will enter the from of the drum on one side, wrap a few times, and leave the back of the drum on the other side, so the left and right holes won't be the same distance from the bow of the boat. Wrap the center of the cable around the drum, and run each end though the new hole, through a pulley, and aft towards the motor.

    The motor with steering bars should be mounted on the boat/jack plate or other arrangement you plan to run with. It is important to have the motor height approximately set. Otherwise, when the motor is jacked up, the pulleys won't be in line with the cable any more.

    Attach the cable ends to the steering bars with light tension. Then the pulleys can be held in place, rotated to align with the cable angle, and drilled and bolted. NO SELF TAPPING FASTENERS. Use through bolts or machine screws with nuts. Ive found #10 is sufficient, but self tappers will definitely work loose.

    The steering wheel should turn roughly 180* hard left to hard right. If all is good, undo the cable ends, thread on a couple guides, and reattach with moderate tension. Space them out on the cable, drill and bolt to the cockpit sides. These guides reduce cable flop in rough water, and rattles when idling before a race start. They can be sailboat hardware, half loop straps, plastic with a hole in the middle, eye bolts (use the 2 bolt the single stud type will eventually twist and bind on the cable), or such. A larger sloppy hole is better than too tight. The alignment will vary slightly as prop height is changed during prop and course setup changes.

    The motor ends of the cables must be secured well. Typically loop through a cable thimble or shackle. Then secure the cable to itself with a 2 clamps. One isn't enough, if it vibrates loose you're swimming home...or worse. I like to wrap electrical tape around the clamps to cover hard edges and help keep their nuts from coming loose.

    Optional: some people like to put a turnbuckle on one side of the cable at the motor attachment. This way you can snug the cable up without renting a gorilla to pull on the loose end while tightening the cable clamps.

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    mini tunnel boats for sport, now an experimental Sport C added to the fleet.

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