A Tom Moorehouse design. Thank-you for purchasing the FireFighter.21. I believe that you will find it to be the best.21 rigger kit available. It has won 1 st place in the 2006 AMPBA nationals! It was designed with conservative design features that allow it to be fast and stable. The FireFighter is designed to stand up to years of intense heat racing. A great deal of thought and testing went in to making this a design that is easy to build, light weight and strong. If you have any questions about the boat, feel free to contact me at tom@firefighterboats.com Tom Moorehouse We are always improving our building instructions by using your suggestions. The most current version is available for download from www.firefighterboats.com. If you have suggestions on how to improve these directions please let us know. This is version #2 Special Thanks: I would like to thank Tim Duggan and Mike Poulsen for their help with the.21 FireFighter. Tim was a prototype tester and has provided valuable feedback on the design. Mike was also a prototype tester and has provided a bunch of the building pictures. Mike has also given valuable tips on construction methods for the kit. Recommended Hardware: Engine: Front and rear exhaust.21 size engines will work. Motor mount: 3 3.25 wide mount, Octura 3-30. Turn fin: C&D Machine.21 hydro turn fin. Strut: Speedmaster VM3 round bottom Rudder: Speedmaster.21 Mini Rudder. Fuel Cell: Walt s Hobbies Servos: Micro for throttle and high power mini for steering (example: Hitec HS81 throttle ; Hitec HS225 rudder). The rudder servo should have at least 50-70 OZ torque. Propellers: Octura 1450 or 1445 are good propellers to start with. Flex cable:.187 size with 3/16 stub. (Note:) Resource list at the end of these instructions (NOTE:) We recommend the Octura 3-30 motor mount. The boat has been designed for it specifically. This mount does however require significant machining to be used with a.21 size engine. You will see two cutouts in the engine bay tub side doublers. There is one cutout on each side. These are there to allow the mount to be removed. It is recommended you keep the engine as far forward as reasonably possible. A diagram is included at the end of the instructions to show placement of a MAC engine. Rear exhaust engines should be further forward.
General building tips: 1) It is recommended you read over the entire instructions before starting construction. This will familiarize you with the process. 2) You should lightly sand off the burning from the laser on edges that will be glued. This will allow for better bonds. 3) Some parts are oversize on purpose. This allows you to be able to sand the part to the correct size and angle for the part to work properly. Building the turn fin spar: 1) The turn fin spar needs to be very strong. This is achieved by gluing a 1/8 fiberglass plate inbetween two pieces of 1/16 plywood. The spar should be glued together with epoxy. 2) Before gluing the spar together you should rough up the surface of the epoxy glass. I do this with 60 grit sand paper. I also make some score marks with a sharp knife. The parts should be firmly clamped together while gluing. You need to use epoxy glue for this step. Building the front sponson cores: 1) The front sponsons are a wood and foam sandwich core with a plywood covering. For gluing the foam parts you do not need to use a lot of glue. 2) The following parts are needed to assemble to front sponson cores: a) 2-1/16 sponson insides b) 2-1/4 balsa inside doublers (Note: the turn fin side will have a cutout where the spar will fit inside) c) 2 - inner foam cores d) 2-1/8 plywood sponson centers e) 2 outer foam cores (Note: inner and outer foam cores are identical)
3) Pay close attention to be sure you are making a proper right and left side. Start by attaching the balsa inside doubler to the sponson insides. The part with the cutout is for the spar to fit inside. 4) Set the spar inside of the cut out on the left side sponson. Glue the spar in place with epoxy glue. 5) Now glue the inner foam cores on top. The side with the spar might need a little bit of foam removed where the spar is. I simply pressed the foam to the spar to transfer the shape. Then I used a knife to chunk away the area that was marked.
6) Glue the 1/8 plywood center on 7) Glue the foam core outers on. 8) You should now test fit the sponson tubes to make sure they fit. You can also do a preliminary check to see if they are square. Covering the front sponsons: 1) The following parts are needed to sheet the front sponsons: a) 2-1/32 plywood sponson tops. b) 1-1/32 plywood sponson back with a spar cut out. c) 1-1/32 plywood sponson back without a spar cut out. d) 2-1/16 plywood sponson bottoms. e) 2-1/32 plywood sponson out sides. f) 2 - sponson cores you made in the last step.
2) Sand down the sponson back to make everything nice and flat. Make sure you don t sand too much. The sponson back should be square with the sponson inside. Attach the sponson back. 3) Use the diagram and sponson angle templates at the end of these instructions to set the bottom angles. Glue the templates to some cardboard before you cut them out to make them more ridged. Holding the correct template on the bottom of your sponson examine the angle you have. Determine what you need to sand to match the template and sand it until they match. You might find it easier to measure the bottom angle if you hold the sponson bottom in place while checking the angle.
Back 1.5 Flat 4) Attach the sponson bottoms when you have the bottom angles matching the templates. 5) With a sanding block sand the sponson top so that it is nice and square to the sponson inside. Attach the sponson top 6) Shape the sponson outside. The sponson core needs to be shaped before attaching the sponson outside. Use a knife to rough cut off the majority of the foam. Use a sanding block to sand the foam nice and smooth up to the wood. You also need to sand enough of the wood so that it is angled for the sponson outside to be attached properly. A good way to tell if you have sanded enough is to make sure you have sanded all of the laser burn away.
7) All the way around the sponson outside you should create a little dent in the foam with your fingernail or a small stick. Use this dent to fill in with epoxy to act as a fillet to make the joint stronger. Attach the sponson outside. Sand it flush on all sides. Be sure to keep all bottom angles sharp. Do not round any corners as it will slow your boat down. Time to glue in the sponson tubes: 1) The best method we have found to glue the tubes in and keep everything straight is to glue both tubes and sponsons at the same time. Lay the sponsons on their tops on a flat surface. Dry fit everything together first. Be careful when pushing the tubes in to the sponson. If you push too hard you may damage the sponson outside plywood. You may need to use a round file to make slight adjustments to the sponson core to get everything lined up correctly. The tubes should go 1.75 inside of the sponsons. Make sure that the tubes are all square to the sponson insides. Make sure that the sponson tops are flat on the table. The distance between the two sponsons should be approximately 13.25 The tops should be flat on the table without the need for weights to hold them down. 2) When everything looks good mark the tubes to indicate what part will be inside of the sponson. Remove the tubes and roughen up the parts that will be inside to promote better adhesion. 3) Mix up a bunch of epoxy. I usually get big gobs of epoxy on a stick and drip a bunch in to each hole. Don t try to save weight by being skimpy with the epoxy on this step. Put the tubes in to the holes and get everything lined up and square before the epoxy sets.
4) You now need to cut the tubes and separate the sponsons. The sponsons should be cut apart 1/2 closer to the turn fin side. Centerline Cut Here.50 Centerline Cut Here.50 Building the tub: 1) The following parts are needed to build the tub: a) 2-1/8 plywood tub sides b) 2-1/8 plywood front sponson tube exit hole doublers c) 2-1/8 plywood engine bay doublers d) 2-1/4 plywood sponson blocks e) 1-1/4 plywood rear sponson block doubler f) 1-1/8 plywood engine bay front bulkhead g) 1-1/8 plywood tub tip bulkhead h) 1-1/8 plywood radio box bulkhead i) 1-1/8 plywood transom j) 1-1/8 plywood transom doubler k) 1-1/32 plywood tub top l) 1-1/16 plywood tub bottom m) 1 - nose block
2) Due to the shape and materials it would not be uncommon for the tub sides to be warped. You have to make sure you don t let this warp get in to your finished boat. This is the reason the tub will be boxed in while gluing it together. 3) Start building the tub by attaching the engine mount doubler and the front sponson tube exit hole doubler. Simply line them up and glue then in place. Make sure you don t make them identical. You need a right and left side. If you don t want the laser etched FireFighter logo on your tub side simply place them on the inside of the tub. If your tub sides are warped be sure the part is clamped to a flat surface while the glue dries. Depending on the motor mount you wish to use you may or may not want to use the entire engine bay doubler. The tub inside width with full doublers will be 3 If you want 3.25 you can cut down the doublers. Be sure to keep enough of the doublers so the rear sponson tube exit hole is still reinforced. 4) Drill the engine mount holes. A template is included at the end of these directions to show relative engine location. For rear exhaust engines the engine can be placed a little bit further forward. Don t go too far as it could upset the balance of the boat. Some people prefer to drill the engine mount holes after the tub is completed. You may do this if you like. I just find it easier to do it now. 5) Now attach the bulkheads and transom. All bulkheads are 3 wide. Place some on each tub side as that will make gluing the sides together easier. Use a square to make sure they are at 90 degrees to the tub sides. You may wish to use some triangle stock on corners to increase strength. Make sure you sand off the laser burn on these parts. You will need to glue on 4 parts:
a) Tip tip bulkhead (the smallest one). Glues to the very front of the tub. b) Engine bay front bulkhead. Glues.25 in front of the front sponson tube exit doubler. c) Radio box bulkhead (has a hole for the stuffing tube). The hole will be closer to the bottom of the tub. It is glued right against the engine bay doubler. d) The transom is glued right on the back of the tub. 6) Now it is time to glue the two tub sides together. This is a critical step. When gluing the tub sides together you need to make sure everything is square, and straight. The tub sides need to be even top to bottom, front to back. If you don t have everything nice and square you could have problems with the performance of your boat. I recommend boxing in the tub with something that you know is straight. Angle aluminum or iron will work well. Here a couple pictures showing how this could be done. The top of the tub is flat for a large portion of it. By placing the flat part of the top, flat on your building
surface, it will be easier to make sure everything is square and straight. I recommend using epoxy on this step as it will provide stronger joints. 7) Glue on the 1/8 plywood transom doubler. 8) After gluing the tub sides together and the transom doubler, use a sanding block to sand the tub sides, bulkheads and transom so they are all even and square. Be very careful when sanding not to change the shape of the tub sides. 9) Glue on the sponson tube blocks. The notch in the bottom of the tub indicates the blocks positions. For the rear boom block, the bottom block is slightly longer so that it will go all the way across the tub and fit in the notch. The top block is shorter to fit inside. When done you should run a drill bit through the tube mounting holes to clear out any glue.
10) Sand the bottom edge of the sponson boom blocks so that they match up with the tub sides in preparation for attaching the tub bottom. Be very careful not to change the shape of the tub sides. 11) Drill the Sponson booms. This is a very critical step. Take your time here measure and double measure everything before drilling. The smaller diameter tubes that are glued in to the sponsons meet inside of the tub. They are joined inside of the tub by fitting inside of the larger diameter tube. It may be necessary to slightly sand down the tubes to get them to fit inside. The screws hold everything together. Use the drawing to set the sponson placement. Then use clamps to hold everything together. Drill through the sponson blocks first then through tubes. You should be drilling from the bottom side of the tub towards the top.
Sponson Spacing Diagram 5.062 4.562 5.125 4.625 13.250 12) Attach the 1/32 tub top. Keep your tub boxed in when you glue on the tub top. The tub top will determine how square and straight the tub will end up. There is no going back at this point so make sure everything is perfectly square. When everything looks good glue the top on. The tub top will extend past the tub sides a little. You can sand it flush with the tub sides when the glue has dried. Hatch Lid Supports: 1) Parts needed and identification:
Engine Bay Back Support Engine Bay Front Supports Engine Bay Rear Supports Radio Box End Support Radio Box Side Supports Radio Box End Support a) 2 Front engine bay supports b) 2 Rear engine bay supports c) 1 Engine bay back support d) 2 Radio box side supports e) 2 Radio box end supports 2) Glue in the 1/32 hatch lid supports. Glue these strips so that 1/8 of an inch sticks out to support the hatch lid. Clothespins work well to hold it in place. 3) If you plan on using the Octura 3-30 motor mount you will need to cut away a small section of the engine bay hatch lid support to allow it to be removed. The cutout should be on one side only. It should be as wide as the motor mount and directly above the side cut-outs in the engine bay doubler. 4) The front tip of the engine bay hatch cover is held in place with a little tongue. Glue it in place.
More Tub construction: 1) At this point you should seal the inside of the tub. This is done because after you glue the tub bottom on, it will be very difficult to seal the top inside of the radio box and engine compartment. 2) Box the tub in like you did before. At this point you can still twist the hull slightly if needed to get a perfectly square tub. Make sure everything is square and even. Be sure you sand off all the laser burn and attach the tub bottom. 3) Drill holes through the tub bottom following the holes in the sponson blocks. Use a drill bit the same OD as the screws that were included in the kit. 4) Attach tub nose block. You will need to sand the tub nose to a nice round profile. Here is a trick to keep your tub top and bottom plywood looking nice. Put masking tape on top of the plywood just behind the tub tip while sanding. The masking tape will help protect the plywood from sanding through layers while shaping the tub tip. Time to build the rear sponsons: 1) The following items are needed to build the rear sponsons: a) 2 Rear sponson foam cores b) 2 1/32 plywood rear sponson insides c) 2 1/32 plywood rear sponson tops d) 2 1/32 plywood rear sponson backs e) 2 1/32 plywood rear sponson 2) Both the rear sponsons are made the same. They are mirror images of each other except for the bottom angle. 3) Attach the 1/32 plywood. sponson inside to the foam. Make sure it is all lined up and held against a flat table so that it won t warp.
4) Attach the sponson back. Sand the sponson back so when the sponson back is attached you have a nice flat surface. It should be square with the sponson inside. 5) Set the bottom angle. Use the templates at the end of these instructions to set the sponson bottoms. Glue the templates to some cardboard. Carefully cut out the templates. Use them to measure the sponson bottoms. The right sponson should be at 1 and the left at +1.5. Use a sanding block to get the correct angle. Back 1.5-1 6) Attach the sponson bottom.
7) Attach the sponson top. For the parts where you have an adjoining wood side use your thumbnail to make a small dent in the foam. This will make a nice fillet that you can fill with epoxy. Sand the sponson top so the plywood and the foam are nice and even. Make sure the sponson is not twisted when you make the attachment. 8) Shape the sponson outside. With the top, bottom, and back as a guide you can shape the sponson outside. Rough-cut the sponson outside with a knife and sand it to shape.
9) Glue on the sponson outside. This part is oversized. It is very important that the sponson bottom have sharp edges. Do not try to round them. This will cause drag and slow your boat down. All the way around the sponson outside you should create a little dent in the foam with your fingernail or a small stick. Use this dent to fill in with epoxy to act as a fillet to make the joint stronger. Attach the sponson outside. Sand it flush on all sides Installing the stuffing tube: 1) You need to have the boat setup basically the way it will be when it is ready to run to have the stuffing tube properly in position in preparation for installing it. Complete the following steps to do this. a) Install your sponsons with 4 shims under the rear sponson tube and none under the front. b) Install your engine mount and engine. c) Install your strut centered on the transom. 2) Set your strut height with the following diagram. Use a very flat table. The rear tub height measurement point should be 1/8 higher than the front tub height measurement point. You are measuring from the top of the table to the top of the tub. The strut bottom should be flat on the table or 0 degrees. 21 Distance "A" Distance "A" + 1/8" 4 Shims Front Tub Height Measurement Point Rear Tub Height Measurement Point 3) After you have your boat setup like above and your tube (not fiber glassed in yet) in place insert your flex shaft. Tighten the engines flex coupler to the flex shaft. The strut on one end and the flex shaft on the other should now support the stuffing tube. You can now make sure the stuffing tube is nice and straight and glass it in place. 4) Since the hole in the bulkhead by the engine was a little oversize you can now fine tune the alignment of the engine and tube. After it is lined up perfectly you can use another small piece of wood with a correct size hole and glue it into place.
Radio Box Setup: 1) Below you will find some pictures of my radio box setup. There are a lot of personal preferences in this area. I will not claim my method to be the best. This is simply what works best for me. Sealing and painting the boat: 1) If you are unfamiliar with this process you should do some research first. A good finish on your boat will help it last a long time. You will need to use a paint that is fuel proof. How to set the boat for it s initial run: 1) You should set the boat up just like you did to install the stuffing tube. Have 4 shims under the rear sponson tube and none in the front. Have the rear tub height 1/8 higher than the front measurement point. The strut should be flat on the setup table or 0 degrees. You should measure the distance between the setup table and the tip of each front sponson. The heights should be the same. You may need to shim only one side to get this correct. 2) The rear sponsons should not be permanently attached. Double sided foam servo tape should be used to attach the rears. See the diagram below for the general method. We recommend you have the rears 3/16 off the top of the setup table as a good starting point. Slide the loose block back and forth until the sponson top is parallel with the tabletop. Slide the sponson in place and get a good idea of where the tape should go. Attach the tape to the sponson and then attach the sponson to the tub.
Parallel to table top Loose Block Fixed block Flat Setup Table Top 3/16" Stacked scrap plywood 3) We recommend the.21 size C&D Machine turn fin. With your boat on the setup table the first bend in the fin should be 1/2 below the waterline (the surface of the setup table). The bend line should be parallel to the tabletop. When running your boat, if the turn fin side sponson appears to lift slightly in the turn, then you can rotate the fin so that the rear is slightly lower. This will help hold it down in the turns. 4) For your first run it is recommended to start with a small propeller. A stock Octura 1445 would be a good choice. The boat is designed to be very adjustable. Experimentation will determine your final best setup. Resources: Speedmaster: www.rossisales.com 1325 Carol Drive, Memphis, TN 38116 USA PH(901) 396-7485 FAX(901) 346-8923 C&D Machine: www.cdrace1.com catmay@sbcglobal.net David Preusse 3509 Greenleaf Ave. Island Lake IL. 60042 PHONE: 847-533-4694 FAX: 847-526-4694
Walt s Hobbies: kwb@powernet.org Walt Barney P O Box 206 Cedar Bluff, Al 35959 The End: Thank-you for building a FireFighter.21 I wish you much success with your new boat. Feel free to contact me with feedback at tom@firefighterboats.com Sincerely, Tom Moorehouse Tom@firefighterboats.com Sponson angle Jigs 1.5 degree jig -1 degree jig Flat jig
Engine Placement Diagram 21
Stuffing tube basic shape (reduced size) Back end 6"