AS K-18

Almost finished!!!! It's Big and Beautiful!!!!

Jim stands next to his ASK-18 ASK-18 in the grass - full image
ASK-18 in the grass - zoomed image


Construction of the AS-K 18

by Jim Ealy, 2006

THE WING:

The laser cut parts are superb, not too tight of a fit, but laser cut just to hold together until glue dries. For the record, this is the easiest wing I have ever built - is too scale AND not over engineered! I used CA glue and 15 minute epoxy for this kit. I placed plans with wax paper on one of my long tables. These tables are framed up 2" x 4" with 1 inch plywood 30" x 108" and 5/8 "homesote" for ease of pinning. I have never felt that a piece of glass was worth the effort. My 10 year old tables are still flat and have been used for many excellent flying ships. Most of you will not have a 1/2 in plate glass top that is also 8 feet long. Also, the pictures are shot with flash and natural light. I just got a new digital and did not realize that the lens was fast enough to give pleasing and detailed shots in natural light. When I did learn this fact - I did not want to rip the wing apart to retake the shots. The remaining tail feathers and fuse will all be done in same lighting conditions.

  1. Decide if you are going to build the 2 piece or 4 piece wing.

  2. After making that decision layout the plans with wax paper on top.

  3. Take the 1/8 by 1/2 spruce spar material and cut to length. If you need to splice, make sure your diagonal cut is at least 2 and 1/2 times the width. (1/2 x 2 1/2) = 1 1/4 inch long. (Pic #1) I made the two piece wing, so I cut and glued a full length spar with 1/2 x 1/8 inboard and 3/8 x 1/8 outboard portion.

Spliced spar
Picture #1

  1. Then you need to attach a 1/2" by total length piece of 0.007" carbon strip. This will allow you to also winch launch and do aerobatics. This was done to both top and bottom spars. Whether it is best to attach the carbon on the inside of the spars or the outside of the spars is your choice and who you believe. Some suggest that carbon on top and bottom of each spar is better. Your call!!

Ribs on the top spar
Picture #2

  1. The wing is more accurately built upside down (Pic #2). The full scale ship has flat tops and up swept bottoms. While this is a much more difficult process - whether it is worth it, is really up to you. The ship also has dihedral and that really obscures the issue. It is almost impossible to tell the correct from the incorrect when the wing also has dihedral. With the Granau Baby IIb --- no dihedral, a flat bottom wing appears very different from the full scale ship.
  2. Full span webs are specified for the wing. It is a matter of debate, whether to place a rib, then the next web, and the next rib (Pic #3), etc or to glue all ribs and then add webs. I do both until I get bored, then I change. The end result is the same, if both are done carefully.

Spar webs
Picture #3

  1. The plans call for two wings tubes and rods off of the spar (Pic #4). It turns out that many large GREAT TD ships from the past used exactly this method. This spar design survived, when other part of the fuse and wing did not in a successful rekitting.

Wing tubes
Picture #4

  1. Place the sheeting over the plans. Make every effort to plot rib locations on the sheeting, as it will be impossible to see locations from the plans with the sheeting in place.

Wing sheeting planning
Picture #5

  1. Glue carbon/spruce spar in place.
  2. Add ribs and webbing
  3. I decided to use a single wing rod sandwiched between the spars with vertical webs epoxied in place with 3/32 ply web caps between ribs.
  4. I also added a 1/4" by 1/8" spar TE to the balsa sheeting. Others would suggest that a 1/4 - 1/2 " by 0.004 carbon strip would be better, sandwiched between the top and bottom sheeting. It would, but that adds additional cost that some may not want to endure. Both are probably not needed. However, my TE's get wavy after several years of flying in humid conditions.
  5. If you build the 4 piece wing you will need to add a wing rod tube to the inboard and outboard panel at the spar (Pic #6).

Wing tip joiner
Picture #6

  1. Use a 1/8 carbon rod for an alignment or a 5/32 wooden dowel. Use a hard balsa block between ribs 24 and 25 and ribs 25a and 26.
  2. Add aileron sub-spars (Pic #7). I increased the aileron sub spar length by one rib bay in both directions beyond the plans for extra strength and support (Pic #8).
  3. Glue the 1/8" false leading edge. Splice the false LE in the same fashion as the spars. Glue in place, and trim to correct height for total length with razor plane.

Aileron sub spar
Picture #7

Installing the false leading edge
Picture #8

  1. Continue adding ribs 26 - 43. Cutting aileron sub ribs and gluing in place on aileron sheeting.
Important Note: Use the triangular shaped spruce spar-splice pieces as jig pieces to lift up the wing tip to build in the wash-out. Do the same with the aileron outboard end. By moving these pieces in and out, you can achieve the correct amount of staggered lift to the TE of the wing to achieve the desired wash-out. This will be easier to do, if you build the wing in the flat bottom version. If you build the wing upside down, you will need to shim up the TE of the entire inboard section and pin down the wing tip, before you add the bottom sheeting.
  1. Trim the aileron sub-spars for airfoil shape guided by the top surface of ribs.
  2. Glue the remaining TE sheeting in place.
  3. Add the Aileron servo. I chose to attach the push rod inside the wing (Pic #9).

Aileron servo installation
Picture #9

  1. The spoilers are not difficult. You must however, choose whether to go with the barn-door or the Shempp-Hirth style (Pic #10). I decide that two pairs of Multiplex spoilers were too much of an investment for the first build. In later builds, I will add them to the top and bottom as per full scale craft. For the first build, I used the barn-door style (Pic #11) as per plan and on the top only. These will certainly be effective for the model.

Shempp-Hirth style spoilers
Picture #10

Barn-door style spoiler servo
Picture #11

  1. Add long TWISTED spoiler wires though holes provided (Pic #12 and 13). I decided not to use the four wire/one plug version. I will glue the end plugs together to prevent incorrect orientation at field.

spoiler_wires
Picture #12

Wing top sheeting
Picture #13

  1. Add top sheeting. Complete the spoiler installation. Trim the LE of aileron for top hinging. The gap should be at least 3/8" (Pic #14) at bottom of sub spars. This will allow for about 1 1/2" aileron and 5/8" down aileron.

Aileron gap
Picture #14

  1. Add the balsa LE. Plane and sand to correct shape. Wing will be covered with white Coverite and trimmed with latex paint.

THE FUSELAGE:

The Fuselage is even better engineered than the wings. This is a perfect ship for the first time "newbie's" scale kit builder. You will take great pride in the finished project. For those of us who remember Ambroid fondly – this will be a great joy!!! This is a combination of sound modern construction with the old "box-loc" of years past. The parts are cut perfectly with just enough tightness to ensure staying in place for the time needed to ensure straightness.

Picture #1
Graphic1

  1. Glue the horizontal plate (#11) to formers E and F.
  2. Glue the two braces (#17) to the plate and former E.
  3. Brace or clamp to ensure straightness! The straightness of these parts will ensure the straightness of the entire fuse.

Picture #2
Graphic2

  1. Glue former G to the plate, etc.
  2. Glue braces (17) to the plate and former G at the same time.
  3. Again, brace or clamp to ensure trueness.

Picture #3
Graphic3

  1. Here is where things get interesting... Dry fit ribs 10 and 10a (2) and vertical brace.
  2. Cut a piece of spar material (1/2 by 3/16 x 51/4)

These all fit together and need to be assembled, but not glued together. When satisfied with the fit and procedure, check again!

Picture #3.5
Graphic3.5

  1. Glue assembled ribs, brace and spar to top of plate.
  2. Check trueness -- adjust if necessary before glue dries.

Picture #4
Graphic4

Picture #5
Graphic5

  1. Glue 10b (2) to the vertical brace and plate. Clamp in place.

Picture #6
Graphic6

  1. Dry fit wheel-well support and keel in place. Mark positions of formers on both pieces, make sure that it is straight and accurate to the plans. Also make sure that the formers are still vertical and not bowed/bent. Only when you are certain that all is as called for on plans -- remove, add glue, and refit. CLAMP to ensure that all stays as planned!

Picture #7
Graphic7

  1. Add plywood false former ( ). This can be done as the very first step. I just overlooked/forgot it in my rush to get started!

Picture #8
Graphic8

  1. Add spruce stringers to both sides of fuse, add forward keel (), add formers: B,C,and D. I used rubber bands to hold in place. It is best to glue the stringers to formers E, F, and G. Again decide how you are going to best do this in the dry state. When you have it aligned, straight and true -- mark all positions on the keel and stringers. Again make sure the formers are vertical as per plan and perpendicular to keel. This is where you "position twice and glue once!"
  2. Do not add former A.

Picture #9
Graphic9

  1. Glue formers B, C, and D in place, rubber band and clamp. Trim stringers to correct length and glue former A to keel. Make sure it is aligned correctly.

Picture #10
Graphic10

  1. Your keel should look straight!!!

Picture #11
Graphic11

  1. Fit top keel (), align and mark positions. Glue in place.

Picture #12
Graphic12

  1. Clamp all parts in correct alignment.

Picture #13
Graphic13

  1. Dry fit the other stringers, be sure to make sure that the formers remain vertical and the fuse remains straight.
  2. Glue the stringers in place, clamp and or use rubber bands to hold in place.

Picture #14
Graphic2

  1. The plans call for hard balsa 1/4 x 3/8", I substituted redwood, light and stronger that hard balsa. You must stop gluing at former B, until you have added this stringer to both sides. Before dry fitting this stringer, trim the stringer from former C to former A. When the glue joints for both stringers have dried, wet the wood, this will make it easier to force the thick stringers to meet former A.

Picture #15
Graphic3

  1. Trim and glue the aft section of the 1/4 x 3/8 stringer in place on both sides of the fuse.

Picture #16
Graphic4

  1. Add the remaining stringers, glue in place ONLY forward of former G. When dry, put the remaining formers in place. DO NOT GLUE, YET. Align the aft formers in place. Check to make sure that they are aligned correctly in the vertical and laterally. After you are sure all is correct -- check with the plan several times. Mark each former's position on each stringer. Remove formers and glue each carefully in place. Add clamps

Picture #17
Graphic5

  1. When dry, add top and bottom stringer, check alignment. Make sure the aft section is straight and true. When all is straight, glue the top and bottom stringers in place.

Picture #18
Graphic6

  1. When all stringers are in place and the aft section is straight and true, add and glue the diagonal 1/8" x 1/2" strips.

Wheel Well and Sheeting

Picture #19
Wheel

  1. The wheel well is very solid. The plan shows the two half moon shaped doublers on the outside of the wheel well sides. They should go on the inside, so that the 1/4" square spruce supports will fit without notching as in the picture #19
  2. I used a brass tube that fits inside the wheel hub. I then glued a piece of carbon rod with OD equal to ID of brass tube in the brass tube.

Picture #20
Wheel well and former

  1. The wheel well fits nicely in the former E slot. The plywood support half ring also fits nicely and provides very good support.
  2. As is evident in this photo, I've covered the fuse with 1/64" ply sheeting instead of 1/16 balsa as per plan. I wanted the inside of the cockpit to show the ply of the full scale ship. The 1/64 ply is very strong and provides for more resistance to puncture. If the plywood is not important, then go with hard 1/16 balsa sheeting.
  3. I will glue a releasable tow hook in front of the wheel well and to the bottom keel. This two hook can be used for aero-towing or for winch launching. While the tow hook is too far forward for maximum winch launches, it will give reasonable height. You can always increase the line length.

Picture # 21
sheeting

  1. The only way to add ply or balsa sheeting is to cut and fit, cut and fit. I suggest that you sand the edges of the ply skid to the proper angle to make a smooth transition. I did not, but will on the second build. You can see from picture #21 and the next Picture #22 that formers A, B, and C also need to be sanded to the proper angle.

Picture # 22
Keel

  1. The top keel also needs to be sanded to the former contour for the best fit of the sheeting.

Picture #23
Front Sheeting

  1. Add all of the sheeting and sand to smooth contour from former A to G. Be sure to have everything completed, BEFORE completing the sheeting. The top sheeting needs to be completed in two sections, from former B to C and from former A to B. The compound bends will not allow one piece from former A to C. The only sharp transition lines that show on the full scale are the two below the canopy hinge line.

FIN AND RUDDER

  1. The fin and rudder is a typical build. I started with the rudder.
  2. Trim a piece of very hard balsa or spruce with a plane.
  3. Add triangle gussets to the ribs and then glue rib/gusset combination to the spar.

Rudder/fin picture #1
Standing ribs

  1. Add TE and block it up with 1/8 pieces
  2. Add a small piece of balsa at top.
  3. Add large piece of hard balsa for bottom of rudder.

Picture #2
Pin back part of rudder

  1. Add 1/64 ply sheeting or 1/16 balsa top and bottom, on both sides
  2. Sand to shape

Picture #3
Fin next to rudder

  1. Trim another piece of very hard balsa or spruce to shape to match the rudder spar.
  2. I added ribs in vertical position just as I did with the rudder spar. Add triangular gussets.

Picture #4
Pinned rudder

  1. Raise the LE with 1/8 strips. Glue LE to ribs and top gusset

Picture #5
Clamps on rudder

  1. Add sheeting balsa to both sides. Be sure to have balsa sheeting exceed the fin spar to provide a hinge gap seal!

Picture #6
Rudder

  1. Sand to shape and contour.
  2. Trim top and bottom spars of the fin and rudder for brass hinge pins.

Picture #7
Brass I hinge

  1. Top hinge is a single strip of brass drilled for three screws. Two for fin and one for rudder spar.

Picture #8
Brass T hinge

  1. I added a small piece of brass to the bottom of the fin spar. I then soldered another piece of brass to the first piece to form a "T" with the vertical section of the "T" screwed to the rudder spar. I also clamped the brass strip down with screws.
  2. If you are going to use regular hinges, hard balsa spars would be OK. But if you are going to use this method of hinging, use spruce spars.

Cockpit/Canopy Refit and Fuse Twisting

  1. My fuse does not have the twisting, that has been discussed in several chat-rooms, as I used spruce for ALL longerons. This does make the tail heavier. But something I can live with. I do not believe that you need to sheet the aft section. If you used balsa longerons, diagonal bamboo skewers (horizontal and vertical) can be used in the aft section to stop the twisting and still maintain the scalloped formers look with the covering. You could also sheet "just" the fuse section under the stab, for additional anti-twisting.
  2. The plans have a significant mistake with the shape of the canopy and frame. HOWEVER, this can be corrected in about 2 hours of relaxed work, if you have already completed the fuse according to plans. I had, as per the building of the fuse section!!! If you have not started, it will require much less time.

    I built the fuse/canopy as per plans, but I had a funny feeling about the shape since I open the kit. I could not place the problem, if there was one. The full scale ship has the front canopy frame, CA, tilted forward, per the pictures on Ray's website. The plans show the canopy's front frame vertical. I have about 100 pictures of different ASK-18's and I still could not "place/see" the mistake on the plans......

    Use a Zona saw and "saw" down through the sheeting. After marking the sheeting with a pencil, start the cut, 1 inch from the vertical on the top keel. The cutting should be done slowly and carefully! Cut the top part of former C from the bottom part. Tilt it forward until it just fits under the sheeting and the top keel. At one inch, C is just perfect, the down slop of the keel allows C to once again fit correctly. See following pictures. LUCK!!!!!!!

Pictures #0a and 0b: Plastic on frame and Correction on plans
Plastic on frame Correction on plans

Picture #1 Canopy frame vertical and the fuse corrected
Frame adjustment in wood

  1. If you use the canopy frame as provided -- you do not have to cut another CA. Picture #2 shows a one inch forward slant.

Picture #2
Upnose showing the adjustment

  1. The stretcher bar in the front of the canopy frame (picture #2) is useless and ugly. I cut this out and Ray and I both laminated CA with 0.007 carbon sheet for strength, as per picture #3 Trim to fit.

Picture #3
Laminating carbon

Picture #4
Up the nose

  1. In picture #4, the finished frame CA is in place. You must glue a 1/4 square spruce longeron to the bottom of the canopy frame for proper fit and strength. In the next section I will show you how to "up-scale" the cockpit with very little effort.

Up-Scale the Cockpit

The cockpit can be given a full-scale appearance with very little effort!! The instrument panel provided is un-like any I've seen in an ASK-18. I copied the instrument panel shown in Ray's website pictures. I added a floor for the instrument panel, pilot's legs, and stick. I also used a few bamboo skewers (painted with aluminum paint) to simulate the tube construction. (pic #1 and #6) The instrument panel can be stained with walnut stain with a cloth and by rubbing in several coats. The back of the canopy frame is not scale, but adds structure and support to the canopy. (pic #3) Therefore a few access panel holes are cut into the former E and canopy EA. (pics #3 and #4) EA is also stained with walnut. The canopy frame is painted black as per the photos on Rays; website. The seat is visible in pic #1 & #5 behind the pilot and #6. The releasable tow hook and servo are hidden below the seat, made from 1/8 lite ply. In pic #6, the seat can be seen, the metal tube structure, and the beginning of the well for the stick. I will also mount a camera on the canopy frame, cut in a sliding ventilation window, and a ditty bag. These extras may take 5 hours total, but they add so much to the overall appearance.

Cockpit picture #1
Empty instrument panel

Cockpit picture #2
Finished instrument panel with pilot

Cockpit picture #3
Holes in former behind pilot

Cockpit picture #4
Installing former

Cockpit picture #5
Former and pilot

Cockpit picture #6
Seat and faux aluminium poles


Stab and Elevator

  1. The stab and elevator are built the same way as the rudder and fin. Glue ribs to hard balsa spars. Glue the LE and tips to spar and ribs.

Framed up stab

  1. Do the same with the TE and elevator spar.

Framed up elevator and TE

  1. Add the gussets and elevator tips. Decide how you are going to hinge the elevator. You may wish to add a few blocks of hard balsa for the hinge points. If you are planning on using flat blade hinges, the spars are more than sufficient.
  2. >

Elevator with gussets and hinges

  1. Shape and sand all parts to a smooth outline to match the plans. Select light, but sturdy 1/16 balsa sheeting for the stab. I added a few more hard balsa and ply pieces to the stab root. I will attach the stab and elevator permanently. (Epoxy) Add balsa sheet to top and bottom of the stab and sand to a smooth contour.

Gluing on the bottom sheeting
Gluing on the top sheeting

  1. I used a pull/pull setup for the rudder. I also added bamboo skewers as cross braces and that stiffen the aft end of the fuse to my liking. I also added a piece of 1/32 ply under the stab on both sides for stiffness and a clean exit for the pull/pull cables. I have not decided on a skid, as per kit and plans, or a wheel as per several full scale ships.

Tail reinforcements
Tail control ports

  1. Servos in fuse/wing nacelle/turtle deck. Front half of fuse/wing nacelle covered and spruce strips add to aft section of nacelle for ply hatch cover hold downs. The front half will be covered with 1/64 ply. The 1/4; inch hole on both sides of the aft - nacelle are for the 1/4; inch dowel alignment pins attached to wings.

Tail servos - from side
Tail servos - from back

  1. The hole between the two elevator halves is the slot for the elevator horn.

Elevator horn detail


 


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