Beta build of a future BMJR kit of a half size Ed Kasmirski Taurus - RC Groups
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Jan 18, 2009, 09:46 PM
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Beta build of a future BMJR kit of a half size Ed Kasmirski Taurus


Brian Malin of BMJR Model Products (http://www.bmjrmodels.com) and I share an interest in the vintage pattern models that helped set the performance standards of the late 50’s and early 60’s. After reading about some of my half size versions of some of those designs he thought it might be nice to expand his line of laser cut kits to include a few. The idea of doing them at half size comes from transportability, storage, and flying site options. Their size and weight make them ideal for the smaller flying venues.

Brian invited me to participate in the kit development since I had some recent experience. As a result his first kits in the vintage pattern ½ series will be the three that I had in hand. These are the 1958 Fred Dunn designed Astro Hog, the 1960 Ed Kasmirski Orion, and the 1963 Ed Kasmerski Taurus. Photos have been provided of my one off models to given you a reference for the models involved.

Work started on the project back in November 2008 and the Kasmerski Orion will be the first kit released. I became immersed in that project to the point that I failed to do a build thread here in RC Groups. I wanted to change that with the next kit being developed for release. That is the Kasmirski Taurus. So after this long winded introduction, let’s get started with the beta build of the BMJR half size Kasmirski Taurus.

Paul Bradley
Last edited by PaulBrad; Oct 27, 2009 at 10:23 PM.
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Jan 18, 2009, 09:55 PM
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Beta build of a future BMJR kit of a half size Ed Kasmirski Taurus


A scan of the cover of my really dog eared issue of the January 1963 issue of Model Airplane News ( I actually bought the magazine in back then) has been provided for reference. It was that photo that started my love affair with this model. Like all modern kit builds, this one starts with a plan and a stack of laser cut parts. The production kit will include the construction materials, hardware, canopy, and a photo illustrated manual to go along with the plan and laser cut parts.

The half size model has a wing span of 36" with an area of 195 square inches. The flying weight is in the 16 ounce range. The model is intended to be flown on 80 to 90 watts. My model uses a 1320 three cell Lipo pack and a PJS 300 SFR outrunner turning a 7x5 prop. The model built from the kit will use an Atlas 2308/34 motor turning an 8x6 prop.

Construction begins with the assembly of each fuselage side. This involves laser cut parts and some 1/8” square balsa strip stock.

There are only three formers in the fuselage. Two are laminated plywood and the third is a lamination of 1/16 balsa with the grain at 90 degrees. Once these are made up the nose gear leg is made up from 1/16” piano wire. The nose gear is not steerable and gets lashed to the fuselage former that carries the motor mount. The model steers on a paved surface nicely from the prop wash over the rudder.

After the nose gear leg is lashed to the “firewall” former the motor mount is assembled in place on the same former. The original Taurus used right and down thrust. The same thrust lines were incorporated in the parts that make up the motor mount. Using the original thrust lines were found to be perfect for the half size that I have been flying.

Paul Bradley
Last edited by PaulBrad; Oct 27, 2009 at 10:23 PM.
Jan 18, 2009, 10:00 PM
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Beta build of a future BMJR kit of a half size Ed Kasmirski Taurus


Once the nose gear leg and motor mount have been added to the firewall former actual assembly of the fuselage begins. The three formers are placed on one fuselage side using notches in the laser cut parts as location guides. The second side is placed on the assemble and check for square before gluing in place. Once the two sides are in place on the formers the rear is closed and some 1/8” square balsa cross pieces are added.

The next step is to assemble the fuselage turtle deck. This is made up of five laminations of 1/8” balsa. After the turtle deck laminations are glued together the assembly is glued to the fuselage. Rough shaping of the turtle deck is accomplished using a razor plane. The plywood fuselage former located at the leading edge of the wing opening serves as a shaping guide for the turtle deck.

Paul Bradley
Last edited by PaulBrad; Oct 27, 2009 at 10:23 PM.
Jan 18, 2009, 10:06 PM
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Beta build of a future BMJR kit of a half size Ed Kasmirski Taurus


Once rough shaping of the turtle deck is completed the battery compartment hatch is assembled and shaped. The battery hatch is held in place with two pair of rare earth magnets. The magnet located at the forward end of the hatch needs a 1/16” spacer so the magnet will be flush with the bottom of the hatch. One of the drop out from the rear hatch 1/16” plywood former is used for the spacer. The forward magnet hold down support is made up of two 1/16” plywood parts that fit in notches located in the rear lamination of the firewall.

Small diameter Sullivan sleeves are used to support the pushrods and they need to be installed before the bottom fuselage sheeting is glued in place. To facilitate the pushrod sleeve installation the rudder and elevator servos are temporarily installed. A 1/32” piano wire pushrod is slipped into a sleeve and that assembly in inserted into the fuselage. A piece of scrap balsa is used as an anchor for the sleeve. These are slipped in place on both pushrod sleeves. Once in place and the pushrods are properly lined up the balsa anchors are glued to the former and the sleeves.

A little 1/16” balsa and the bottom of the fuselage is closed up. All that remains in performing the fuselage assembly is to perform final sanding. Next up will be the tail surfaces.

Paul Bradley
Last edited by PaulBrad; Oct 27, 2009 at 10:24 PM.
Jan 19, 2009, 10:52 AM
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These are a great idea. A small Astro Hog would be a lot of fun.
Jan 19, 2009, 08:08 PM
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Thanks TRuss. As noted at the begining of this thread, a half size Astro Hog kit is coming.

Work was completed today on the built up stab. The stab on the half scale Taurus follows the same type of construction as the full size version. While a bit more tedious to build than a sheet balsa stab, the built up stab offers several advantages. First it very stiff in torsion and bending. The stab uses a triangular airfoil. This allows for easy shaping and also offers some aerodynamic advantages. The triangular airfoil of the stab helps reduce elevator sensitivity near the neutral position. While not as big a deal today with radios that offer exponential settings, that feature of the stab airfoil does still help the model's flight characteristics.

The core structure of the stab is a frame made from 1/8” x 1/4 balsa strip stock with diagonal ribs made from 1/8” x 1/16” balsa strip stock. The top and bottom spars along with the center section filler blocks are laser cut from 1/8” balsa. After the core frame is completed the spar components and center section filler blocks are glued in place. The stab is shaped by carefully sanding the triangular profile using the leading edge and spar split line as guides. Using a sanding bar make the process fairly easy.

The split elevators are joined by a control horn fabricated from 1/16” music wire. The elevators are hinged using CA hinges that are cut down to about 3/16” wide strips. As is typical for a model with split elevators, they are installed after the model is covered.

The fin and rudder are made from laser cut 1/8” balsa parts. This also follows the structural design of the original model.

The next assembly sequence will be the wing.
Jan 20, 2009, 03:19 AM
Light and floaty does it
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This is a good idea and I'll follow with interest. For those who like to build, and like me remember these famous models from first time around when we were kids and RC was REALLY expensive, there's a lot of attraction in having a clutch of compact, affordable reduced-scale versions that capture the spirit of the original, and with modern equipment ought to fly really well.
Jan 20, 2009, 05:16 PM
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I appreciate your comments Work. They pretty much mirror my thoughts when I did my first razor cut half size Taurus several years ago. I have some additional progress to report.

When Ed Kasmerski designed the Taurus he had several performance improvement objectives from his earlier Orion. One was to have a model that exhibited more consistent speed when performing maneuvers like loops. To help achieve that goal he used a rather thick airfoil. The section is 19 percent thick and that represented some challenges to build and keep the wing light. It also presented a challenge in maintaining a accurate leading edge radius along the span of each panel. The structural design he used involved wrapping sheet balsa around the leading edge of the ribs. This was actually a very efficient method both from a structural strength and weigh stand point.

For the full size model the leading edge radius at the tip was enough to make bending the sheet balsa around the rib profile practical. For the half size model this was a bit more problematic. To get around the problem I used two layers of 1/32” balsa adhered together with spray contact cement. This worked really well and yielded a light and strong leading edge like the full size Taurus. Other than the leading edge assembly, the remainder of the wing build is fairly straight forward.

The wing assembly begins with the assembly of several sub-components. The ribs that carry the mounting blocks for the main landing gear legs have 1/64” plywood doublers applied to each side. This provides considerable strength with very little weight gain. The landing gear mounting blocks are made up of three layers of 1/16” plywood. To form a slot for the 1/16” music wire landing gear legs the third layer is two pieces and a piece of 1/16” music wire is used to set the gap when the parts are glued together. The wing tips are made up of laminations of 1/8” balsa. The last sub-components that get fabricated before wing assembly begins are the leading edge sheets. Each leading edge lamination is made from two pieces of 1/32” balsa. The cutting pattern is shown on the plan. Four panels are made up from eight cut pieces. Two pieces are joined by taping them together with masking tape and then running thin CA along the seam on the side opposite the tape.
Jan 20, 2009, 05:29 PM
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With the sub-components completed wing assembly begins. The spar is a split design that locates each rib and maintains an unbroken load path along the outer edges. The lower half of the spar is identified with a raised tab near the root. Orientation or the spar halves is necessary to maintain the proper dihedral angle of the root rib. Ribs are placed in their respective slots along the bottom half of the spar. No glue is applied just yet. The root and tip ribs get installed after the top half of the spar is in position. The top half of the spar put into position next. After making sure everything is properly seated and in position glue is applied to each rib location.

After the ribs are glued in place the trailing edge sheeting is put in place. The bottom sheet fits in slots formed by the temporary tabs at the rear of each rib. After the lower trailing edge sheet is properly aligned it gets glue. Before the top trailing edge sheet is placed and glued in position some 1/8” x 1/4” balsa pieces are cut and shaped for placement at the aileron hinge locations. This provides some “meat” for the CA hinges. The top trailing edge sheet then gets positioned and glued in place.

Next up is the first layer of leading edge sheeting. The installation process begins by placing one of the prepared panels under the wing. It is aligned with rear edge of the spar. While applying a small amount of hand pressure to the top of the spar CA is applied to the joint between the 1/32” balsa panel and the spar along the length of the spar. The assembly is then removed from the building board and water is applied to the outer face of the leading edge panel with a wet sponge. Several applications will likely be necessary to allow enough water to soak into the wood to make it possible to wrap the panel around the leading edge radius of each rib. As the water soaks into the wood it will begin to curl in the desired bending direction. Let the water soak in for several minutes with several repeat applications.

When the leading edge panel has soaked for several minutes you can start wrapping it around the ribs. Do this slowly making sure the wood has become pliable enough to make the bend without cracking. Thin Ca can be run down each rib through the openings in the spar to secure the panel. While the leading edge panel is wet the wing is held down to the building board with weights to make sure it does not warp.

Application of the second leading edge layer begins by wetting the outer face of the second panel. Like the first panel, several applications of water may be necessary to allow enough soaking to occur for the wood to become pliable. When the wood is pliable enough to bend easily apply a light coat of spray contact adhesive to the inner face of the panel. Also apply a light coat of spray contact adhesive to the outer face of the panel already in place on the wing. The second leading edge layer is then placed on the first starting on the bottom along the rear edge of the spar. The entire wing assembly is then simply rolled on to the second leading edge layer. By rolling the wing on to the panel it is easier to get linear contact along the span.

Wing construction will continue with addition of the trailing edge cap and tips.
Last edited by PaulBrad; Jan 20, 2009 at 10:08 PM.
Jan 20, 2009, 10:05 PM
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With the leading edge now in place the trailing edge cap is glued in place. The trailing edge cap is a piece of 1/8” x 1/16” strip stock. A few strokes of the sanding bar has everything nice and smooth on the top and bottom. The landing gear mounting block is glued in place followed by the installation of the center section sheeting. Laser cut parts help make that step a bit easier. When the center section sheeting installation is completed the wing rib cap strips are added. The cap strips are made from 1/4” x 1/16” strip stock. The last step remaining in the basic assembly of the wing panel is to attach and shape the wing tip.
Jan 21, 2009, 09:56 AM
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Paul, Looking good!

PAT
Jan 21, 2009, 10:39 AM
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I could get really interested in the little Astro Hog. Some where I have some plans for a 1/2 size version of it for glow power. Always wanted to build it for epower.

Now it seems it will be even better as a laser cut kit! I have fond memories of the original version from my glow days... ( yes I am old!)
Wes
Jan 21, 2009, 12:24 PM
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This is so cool. I can remember seeing an Orion that had reeds and maybe a Fox .59 flying at Langley AFB in about 1964. Also a Lil Rascal with an escapement of course. The first propos were just starting to show up. How far we have come!

Great job Paul. Can't wait to get any of the three.

Bob
Jan 21, 2009, 02:31 PM
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I very much like your solution to the sheeting going right round the LE, without a separate LE member, even at this smaller radius. It looks as if you're having real fun building it.
Jan 21, 2009, 11:30 PM
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1987tc - The half size Astro Hog is a great flier. Then again all three have been a blast to fly. Each has fully satisfied my desire to experience these designs in building and flying.

C550Driver - I appreciate your kind words. The Orion should be available soon. Heck an e-mail to Brian at BMJR may get you a kit now.

Work in Progress - Thanks for your encouragement. I scratched my head for a while on how best to duplicate the leading edge of the full size Taurus. The Top Flite kits that were sold back in the day had moulded balsa leading edges included. The double lamination of 1/32" balsa has worked out great and has proven to be quite strong. My orignal half size Taurus has stress tested the leading edge on several occasions. In each case the leading edge was undamaged.

I do have some additional progress to report on the project. Both wing panels have been completed so they get joined. That step begins with the installation of the wing servo mounting rails. Two rails are cut from some 1/4” x 3/16” spruce stock. The rails are slipped into the rib notches on one panel but not yet glued. Epoxy is then applied to the face of the root ribs that will make up the center joint. The wing joint is closed and some masking tape is applied to the bottom to hold things in place. The wing is placed on the provided dihedral jigs to allow the epoxy to set.

Once the dihedral joint is fully set the wing is removed from the jigs and the servo rails are glued in place. The dihedral joint now gets a wrap of fiberglass tape. The fiberglass tape is applied with some thin CA.

Wing assembly is completed with the set up of the strip ailerons and their torque rod assemblies. The torque rod assemblies are made from 3/32” tubing and 1/16” music wire. All push rods are 1/32” music wire with 90 degree bends retained with DuBro Mini E-Z connectors. As a result the aileron torque rods get a cap on the pushrod end for the pushrod. The cap is simply a piece of the 3/32” tubing that has been flattened on one end. A 1/32” hole is drilled in the flat end for the pushrod. The cap is attached to the 1/16” music wire with CA.

The wing trailing edges are grooved where the torque rod assemblies are attached. The torque rod assemblies are glued to the trailing edges. The joint is reinforced with some fiberglass tape.

Next up will be installing the tail surfaces and preping for covering.


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