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Stop/Give Way Delta Wing

by Mat Downs

Plan No.692

Plan Detail:
Plan No. 692
Price: AU$33.00 (3xSheets) 
plus P&H (AU$4.00 within Australia).

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Have a large enough flat building board that has a surface that can accommodate pins for holding the fuselage and wings etcetera, well, only a delta wing in this case. Craftwood, MDF or similar are good or even either of these then covered with compressed cork floor tiles will give a good flat surface and allow the holding pins to do their job.

Also necessary is a means of accurately transferring lines from the plan to materials such as tracing paper or better still, a photo copier. If you do get the plan photo copied you can then cut out the various components and lay them face down onto the required piece of either balsa or ply, then by applying heat with a household iron, the reversed image will be transferred to the wood. It is now only a matter of accurately cutting out the required shape.

Good quality material and adhesives go without saying. This aircraft can be built with basic tools and clamps so no costly machinery is necessary.

Study the plan thoroughly before commencing construction so that you have a full understanding of the way you are going to build the "Stop & Give Way".

Using this review as a building guide and you are sure to have a fun machine.
Although this plane is not your conventional wing, fuselage and tail assembly job, the principles of construction are the same. Keep weight to a minimum without compromising strength, (some builders weigh materials in their quest for lightness) and ensure twists and warps are not built in. In this model the potential for twists is significant as the shape of the wing can lend itself to the problem if you are not careful.

Getting Started
Start by cutting out the wing ribs. Transfer the outline to balsa sheet. I used yet another method of transferring the rib shape to the balsa. Using the wing rib photocopy, I rubbed a rag soaked with turpentine on the back of the copy to transfer the ink to the wood. Smelly but works just as well as the cloths iron method. There are only 5 ribs per half so balsa waste can be kept to a minimum by careful positioning of the transfer. You may prefer to photocopy from the plan, cut out the shape and use it as a template. Remember to place two sheets of balsa on top of each other when cutting pairs of ribs so that ribs are identical. Mark a centre line length ways through the ribs so that the leading and trailing edges can be kept straight when they are fixed to the ribs. Position each rib over the plan and bevel the leading edge to match the angle of the leading edge spar so that a larger surface area is available to glue to when the time comes.

Construction of the "Stop Give Way" plane is different in that the fuselage is constructed inside the wing. Each half of the wing is built separately over the plan. Protect the plan with cling wrap film or similar. Make sure that the centre line of the ribs at the front and back are straight to prevent built in warps. The centre ribs, which form part of the fuselage, are placed with an outward (top towards the tip) slant as determined by the dihedral angle. When the halves are joined these centre ribs sit vertically to attach to the fuselage sides.

Cut four spars per half as per the plan, the top two will be trimmed to accurate length when the halves are joined. Note the front two are spruce, not balsa.

The leading edges can be cut to length. Mark a centre line full length on what will be the inside of this piece. It should be tapered now, but leave oversize to allow for sanding after the leading edge sheeting is installed. Glue the leading edge in place ensuring that the centerline of both the leading edge and ribs match. Also prepare and fix the balsa elevon spar in a similar manner.

When both halves are built to the above stage, prepare the ply dihedral brace as per the plan and trial fit to both halves. When satisfied with the dihedral brace fit, put it aside. The leading and trailing edge top sheeting can be trimmed and fixed in place; this gives the wing some rigidity for the following steps. Again remember the potential twist problem. We install the trailing edge lower sheet when the centre sheeting is fitted. The top trailing edge sheet does not meet in the centre, as it has to accommodate former F5 passing through to the bottom of the fuselage.

The wing halves can now be joined. This is where trimming of top spars will be required to accommodate the dihedral, they are all butt joined. Remember the dihedral brace and consequent dihedral angle. Dihedral is built in by placing a 30mm block under each wing tip. The other important guide is that the centre ribs should now be vertical. Butt join the spar inner ends and glue, adding any required fillets for strength. The trailing edge join is strengthened by former F5.

The wing can now be turned over and the dihedral brace in glued place. The spar will hold the dihedral angle but be gentle. It is a good idea to check that nothing has moved by re-blocking the wing tips while the glue sets. The trailing edge and centre sheeting is ready to be installed. Start at the trailing edge and work forward to within about 30mm of the leading edge sheet. The gap left will make clamping of the fuselage and doublers easier when they are fitted. Now sheet the top centre from the trailing edge forward to where the rear spar comes through the centre ribs. The reason being the fuselage sides sit in top of this sheeting from this point aft.

I installed the 9.5mm block which supports the fin at this stage for added strength and in preparation for mounting the fuselage.

Fuselage. What Fuselage?
As stated before the fuselage is built inside the wing ribs. Prepare the balsa strip (6.5 x 3 mm), which covers the wing centre-sheeting join, it needs to be in two pieces as it crosses the rear spar. Also prepare formers F4 and F5. Fix the balsa strip over the bottom centre-sheeting join (inside) and glue F4 & F5 in place. Fit the second piece of balsa strip, taking care to have it centred.

Fuselage sides can now be trimmed and fitted. Note they are in two halves. When satisfied glue and clamp / pin the rear halves FS2 in place. F3 can be glued in place as it will assist in holding the fuselage sides. A variety of clamps purchased from the local $2 shop are an invaluable building tool. The front halves FS1 are installed, note the fuselage sides stop at the firewall position. Next step is to fit and fix the ply fuselage doublers FD. Again take care with length and clamp well while glue goes off. At this stage the second formers F1, 2 and 3 and undercarriage block are built in, study the plan to fully understand what is required.

The bottom balsa sheeting can now be completed and top fuselage longerons fitted and fixed. Prepare ply sheeting UF which is used forward of the undercarriage block. Epoxy is the preferred adhesive as this is potentially a high stress area.

Shape the leading edges. I have recently purchased some of the ÒPerma-GritÓ range of tungsten carbide sanding, cutting and grinding tools and this is where the leading edge sanding tool came into its own. Being pre-shaped (concave), the job of getting a good uniform leading edge was made easy with this accessory. When first looked at this would seem a difficult task especially at the inner end as the edge is so wide and there is only 12.5 mm to work with. However, with a little patience a quite satisfying shape can be achieved. Now fit the wing rib caps.

T4s are fitted either side of the slot in F5. These pieces help support the fin. Sheet the fuselage top from F2 to F3, there is a hatch from F1 to F2 for fuel tank access, from F3 to the front edge of where T1 will be placed, there is another hatch. From the front edge of T1 over F5 and down over T4s sheeting is fixed. A slot will need to be cut to fit the fin.

Building the elevons and tail is quite easy. Follow the requirements of the plan. This is where a flat surface is again important. When complete, hinge slots can be inserted in preparation for covering and installation.

After sanding, cover the plane with a good quality product and make sure edges are well sealed around the engine area. The red trim is iron on covering over the top of the white base. For those not used to this process a cool iron is needed and work from one edge towards the other or from the middle out each way to avoid bubbles. If too much heat is used the shrinking will cause uneven lines along the edge. Fit the fin in the slot, removing the covering where glue is to be applied. Glue in elevons and the rudder.

Mount the motor with 2 degrees of right thrust. This is achieved with a small wedge behind the engine mount. Install servo trays and fit out with servos. Note the receiver and battery pack are mounted in the rear of the fuselage. Now install the undercarriage and tail wheel. You may prefer a steerable (with the rudder) setup as this will make the model easier to steer on the ground.

Centre of Gravity
Being an untried plan, the centre of gravity was not included, consequently it needed to be calculated. Using the formula from the book mentioned in an earlier edition of Airbourne where the Dassault Falcon was reviewed a theoretical point was established. As described later, this in fact was very close to the final point. Flying a prototype model the first time can be a bit nerve wracking. Is the airfoil OK? Is the motor matched OK? Are the control surfaces large enough? Do they throw far enough or too far? And most importantly is the centre of Gravity (C of G) somewhere near the all so vital balancing point? The last thing you need is a tail-heavy model!

Lets Fly...First Flight
The Hamilton area turned on a perfect day and there were ten or so members present to witness the maiden flight. Fueled up, radio range check completed, do the elevons work the correct way? Likewise the throttle and rudder. All had obviously been checked during building, but it still pays to check especially with multi model capable radios.

For this flight I fueled to the max, tested the throws yet and taxied out to the runway. The elevon throw was maximum at about 30mm each way.

Lift off was after a run of about 20 metres; basically it became airborne by itself. Move the elevon stick and Òtwitch twitchÓ, too much throw for a test flight and nose heavy into the bargain. When I let the elevator go, down would go the nose. Rolls were savage with such a high rate and the rudder had plenty of authority in that you could roll nearly as well with it as with the elevons! When on final approach to land almost all the elevon up was needed for the slow approach because it was nose heavy.

To achieve the balance during building and to meet the previously calculated C of G, the battery and receiver were mounted between the throttle and rudder servos. I now moved them to the rear of the fuselage to counteract the nose heavy attitude. Elevon throws were reduced to about 20mm each way and the rudder to around 30mm with expotential control.

Second Test Flight
The second flight was great, a shorter takeoff, more easily controlled flight characteristics and no dropping of the nose and still a good roll rate. Testing the slow flight speeds was impressive with no vices displayed. Slow passes were done for photos and a good range of aerobatics were tried, even a rough hover a fair way above the ground. With rudder and elevon input, diving spins were very fast, loops and rolls are easy and no stall traits are displayed.
On returning home the C of G was checked on the jig and found to have moved about 10mm from the point calculated.

In Summary
This is an easy model to build with no hidden obstacles. It would be easily constructed by a novice builder. It is certainly not a beginners model to fly, but anybody with solo experience would be able to manage OK, however a test flight by an experienced pilot would be advisable.

 

parts and plans

setting up wing ribs

2 halfs of delta constructions

2 halfs joined

wing sheeted

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