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The Doghouse Extreme by Dick Smith was discovered while searching for a new plane that was 3D capable and quick to build. This plane is a .40 - .50 sized aerobat. It is used by a few TOC pilots, Chip Hyde and Bill Hemple, as their practice planes. This plane has large control surfaces, all laser cut parts, and wood from Sig. After reading about the plane and talking to Dick via email and a few phone calls, the order was placed. A Saito .91 was ordered to power it after Dick said it was the best engine for the Doghouse for performing 3D maneuvers. There was a mix-up with the check that was sent to him but Dick sent the plane before receiving the check. This is a pretty classy operation. The kit arrived just before a 6 day trip so the instructions and plans were taken along for later perusal. The bottom line is that the plane looks super simple to build. Dick suggested putting the elevator and rudder servos in the tail to help balance the plane and avoid the dreaded lead weight. This led to the decision to make the servo cut-outs in the fuselage prior to anything else being done. This took about an hour to do for both servos. The remaining fuselage doublers were added on to the inside of each fuselage piece. The fit was perfect. All the angles and sides matched up with no trouble at all. After these pieces are installed, the locations for formers F1, F2 and F3 can be marked. These lines are transfered from the plans to the fuselage sides with a pencil and ruler. The plans even have the lines marked above and below the fuselage side drawing so when the actual fuselage side is placed onto the plans, the lines are visible around edges of the fuselage. This is a nice touch. Each former has two pieces of 1/4" triangle stock glued in front and in back for support. Former F1 was positioned on the lines then a piece of triangle stock was placed in front of the former and glued. The rear piece of triangular stock against F1 and glued. The former was removed and leaving a place to slide the former in that is perfectly positioned. This method was used for formers F2 and F3 on the right side of the fuselage. The fuselage had to be square and the formers had to match up pefectly. The fuselage sides were layed next to each other and were aligned so they were like mirror images. The triangle stock was added to the left fuselage. The formers were slid down from the right side so that about 3/4 of the former was now on the left side and 1/4 of it was being held in position by the already installed triangule stock on the right side. The triangular stock was then glued in place to the left fuselage side using the former for location. This ensured that the fuselage would be square and that the formers were at the correct location. The tail feathers were constructed next. There is not much to say about this phase. The rudder/fin are balsa sheets that just need to be hinged. The fin did have two pieces that needed to be glued together. There are two (2) options as to how to control the elevators; two (2) independent elevators controlled by two (2) servos or a single servo operation. If one (1) servo is used, the elevators have to be notched to accept a 1/4" dowel that joins the elevator halves. This method was chose to save the weight of the extra servo. Prior to gluing the three (3) formers to the fuselage sides, the location of the engine mount, throttle pushrod, and tank/fuel line positioning were planned. It is much easier to do this during the early stages of construction. Finally, former F1 was epoxied to the fuselage sides and F2, and F3 were were attached using CA. The remaining formers were added to the rear of the fuselage sides. These are just 3/8" x 1/4" balsa sticks that are glued to the fuselage sides. Then the tail was pulled together and glued. After that was done, the cross-member pieces were added to the top and bottom of the rear formers. The bottom sheeting was added next. There is a 1/8" pywood piece that is glued to the forward part of the fuselage bottom. This is there for added strength because the landing gear will mount to it. The remaining bottom sheeting is 1/8" balsa glued cross grain. The landing gear block was glued into the inside of the fuselage and the landing gear was mounted. The throttle servo is the only one mounted inside the fuselage so there was no need for rails running from one side of the fuselage to the other. A servo mount was constructed from lite-ply. This allows more room to adjust battery and receiver location without being limited inside the fuselage by servo rails. To mount the engine, four (4) #6-32 x 1" socket head bolts were used. After the engine was mounted, the throttle pushrod was connected. Finally, the needle valve extension location was found and the hole was drilled. The hatch that goes above the tank appears to be a part that would only take a few minutes to build but it took over an hour. The hatch is built in three (3) sections; a rear piece that is fixed, the removeable hatch, and a fixed front piece. All of these hatch pieces are 1/2" thick. The rear piece is glued first. The dowel that extends from the wing is supposed to pass through former F2, which is only 1/8" thick, and the dowel has to extend almost an inch from the leading edge. The rear hatch piece would interfere with the dowel because it is glued against former F2. This could have been drilled out later but it was easier to do before the piece was glued in. After the rear piece was glued in, the removable hatch was placed into position. Next, the front fixed piece is butted up to the hatch and glued. The problem is that if this is done, the hatch cannot be removed. The hatch is held in place by a tongue in the front and a bolt in back. To remove it, it is lifted out rear first. The hatch at the rear is 1/2" thick and since it butts up to the rear hatch piece, there must be a little bit of space it will not come out. A little space must be left between the removeable portion and the fixed front piece. A #2-56 x 1" bolt and a blind nut were used to secure the hatch at the rear. The front fixed piece and the first 1/3 of the hatch are tapered to almost nothing to match the line of the fuselage at the front. This was accomplished with a little sanding. Foam was placed in the hatch area and the tank was installed. Next, the top surface of the fuselage was sheeted. There is nothing unusual to report in this step of construction. It is done the same way as the bottom of the fuselage was done. Once that was done, the stabilizer was glued onto the fuselage. A piece of 1/8" balsa is then added to match the upper surface of the stabilizer with the 1/8" top sheeting of the fuselage. This piece was made to fit prior to gluing the stabilizer. That way, it would match the contour of the fuselage. The remaining pieces of the tail filler were made leaving room for the elevator dowel to fit through. Finally, the tailwheel was installed and the rudder and elevator pushrods constructed and connected to each surface. This was pretty easy to do with the rear mounted servos. Du-Bro #2-56 swivel ball links were used at the servo end and a metal clevis at each control surface. Control surfaces were set for as much deflection as possible. This way, the dual rates can be set later to the desired throws. One problem that was encountered with the rudder was that the rudder is 1/4" thick and the rear of the fuselage at the tailpost is over 1/2" wide. The problem is that of setting the control horn where it needs to be and not having interference with the rear of the fuselage. A notch was made in the fuselage in this area to allow the control horn to move to full right travel. This was not a big problem but it was much easier to fix before the covering was applied. The 1/2" thick wing hold-down plate fits inside the fuselage right under the trailing edge location. There is not any built-in support for this plate. As a precaution, epoxy was used to install it the two (2) small holes were drilled through the fuselage sides and into the the side of the plate. Epoxy coated toothpicks were pushed into the holes, allowed to cure, and sanded flush. This took about ten (10) minutes to do but the hold down plate will never come out. This completed the fuselage construction. The plans show one reference to engine location. On the side view of the fuselage, there is a thrust line drawn. The location seemed a little high. In response to this concern, Dick Smith, the designer, lowering the engine would have no affect on performance. The prototype had been flown with several different engine locations with no ill affects. With this in mind, the engine was located on the center on former F1. This was expected to be a kit that caused no complaints but that did not hold true. The trailing edge of the wing is a 3/8" x 1/2" balsa stick that has to be sanded to match the contour of the ribs. This piece is 27" long and takes some effort to get correct. It would be better to charge a little more for a kit that had pre-shaped pieces. According to the instructions, the first part of the wing is built "floating", meaning that the spars and ribs are not pinned to the surface at first. Rather than following this method, the spar was pinned to the building board then each rib starting at the root was placed onto the spar and glue down one at a time. Making very sure the When that was done, the rest of the wing is pretty conventional. The capstrips were added on the ribs that needed them and installation the servo for this side of the wing was done according to the plans. The instructions recommend a paper tube for the aileron servo wire to slide through. After the servo is installed, 1/16" balsa is used to sheet around it. When both wing panels are complete, they are trial fitted together then joined. This is done by cutting slots in the center rib of one wing panel to accept the diherdral brace and 1/4" dowel that protrudes into former F2. The slots are cut the brace and the dowel are glued into one wing panel. After the epoxy cures, slots are cut into the other panel and the wing panels are joined together. After the wing joint had cured, the shear webs and center sheeting were installed and the holes for the wing hold-down bolt were drilled. The ailerons were straightforward; built-up and sheeted. All of the equipment was installed with the exception of the battery. That will be the last item so that it can be used for balancing. Installing everything prior to covering is much easier than trying to install radios, mounts, etc. after the covering has been applied. Monocote was used for covering. Since most of the plane is fully sheeted, it makes applying covering very easy. There is no need to apply Monokote over Monokote. The lines were drawn where the Monocote was to be applied to create the design and the colors were applied. Seams are overlapped by 1/8". After the covering was completed, the equipment was reinstalled. The balance point came out at the rear of the recommended range. No extra weight was required for balancing. The first flights were made with a lot of throw in all control surfaces using no exponential then the adjustments could be made from that point. The roll rate was very fast and pitch is somewhat sensitive. After the first flight, the dual rates were set to 70% for the elevator on low and 100% on high with -30% exponential. The ailerons were set to 50% for low and 85% for high with -30% exponential. The rudder was left at 100% for both high and low with -40% exponential. The plane tracks well throughout all maneuvers. It was somewhat windy so it bounced around a little. Hovering and TR's on the first flight were a little jerky due to the 0% exponential but after adjustments were made, it calmed down. During elevators and harriers, it tended to rock the wings back and forth fairly hard as it was descending. A little back and forth rudder was used to reduce the rocking. Elevator/flaperon mixing did not seem to make that much of a difference in the performance. The flaperons may not have had enough movement. The Saito .91 pulls the Doghouse around with authority. Most of the flying was done at half throttle. It seemed to Hover and TR at just under half throttle. This plane is going to be a good one. It was super easy to build. The parts fit was really good. The quality of the wood in the kit was excellent. The only complaint was having to shape the trailing edge pieces for the wings. It is super aerobatic, and yet can be very gentle. The size of the surfaces makes the 3D stuff a lot easier than a typical design of a .40-.50 sport plane. The Doghouse Extreme is highly recommended for anyone who is looking for a good 3D trainer/stable sport plane. |
