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Old Aug 06, 2014, 07:34 AM
Life is a Hobby
Canada, ON, Delhi
Joined Aug 2012
852 Posts
The GP Extra Large 1.20-1.80 engine mount was attached to the firewall in post # 38. Time to drill and tap the mount for the DLE20RA.

Secured the 4 inch spinner plate to the engine as a reference to the right thrust in the firewall. Keeping both sides of the back plate equi-distant from the firewall ensures the engine won`t be slightly skewed in the mount as the drilling proceeds.

Have to drill and tap one hole at a time constantly checking the back plate against the firewall. Tempting to drill all four holes at the same time but this usually results in one hole being off-center. Used an 8-32 tap for the allen head mounting bolts. Didn`t go all the way through the hole with the tap which makes the bottom of the hole tighter on the bolts acting like a lock nut.

Once the cowl is on, the rear-mounted carb makes it awkward to get at the choke. Guys rig up various lever rigs but I want a servo doing the work. With the DLE mounted, proceeded to install the throttle and choke servos. Secured a standard servo in the servo plate for the throttle. A square battery hole in the plate was just the right size for a micro servo for the choke. There is no mention in the manual or the plans for doublers for the servo screws. I used some scrap 1/8 lite ply to glue in doublers.

Ball links had been secured to the throttle and choke levers on the Walbro carb. Lined up the balls relative to the firewall and the servos and drilled 3/16 holes through the firewall for the pushrods. Screwed nylon ball sockets onto the pushrods and cut the rods to length. Secured the rods on the servo arms with EZ links using 4-40 allen bolts.

Tested both pushrods for travel and binds. Digitals below of the Walbro carb control linkage.
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Old Aug 09, 2014, 08:08 AM
Life is a Hobby
Canada, ON, Delhi
Joined Aug 2012
852 Posts
Got the rear end pretty well finished. Now for the front end.

To start center lines are drawn on the back of the 4 inch spinner plate. The semi-circular 1/16 ply spinner ring that will form the front of the cowl top is centered on the back plate and tack glued to the plate top and sides with small scabs of 3/32 scrap balsa. The scabs ensure proper spacing between the cowl and spinner. The manual says use 1/16 scab but that is a little too fine for me. Don`t want a rub between the back plate and the finished cowl.

The DLE20RA is secured in its mount and the back plate bolted in place on the prop shaft. The ply spinner ring is open at the bottom, being about 60% of a circle. The ends of the semi-circle are lined up with the bearing surfaces on the arms of the GP engine mount.

The bottom edges of the fore deck have to be modified by removing balsa according to patterns on the plans sheet. This allows the plastic ABS bottom cowl to eventually fit properly in place. The new bottom edges line up with the bearing surfaces on the engine mount.

The top half of the cowl is made up of five 1/2 inch slabs of balsa. All the slabs supplied in the kit are medium soft so didn`t have to replace any. Start with fitting the two bottom slabs using the spinner ring, engine mount and fresh fore deck cut as a reference line. This is a fit and try process. The ends of the slab have to be undercut for the angle between the foredeck and spinner. Took my time for a good fit so there are no gaps which makes final glueing a pain. Tack glued the slab ends to the foredeck and spinner ring with thin CA.

Next fit the top slab then the two corner slabs. The manual says remove the engine and hence the spinner plate BEFORE glueing the top slab. This means cutting through the scabs between the plate and the spinner ring. I thought it would be too easy to put the ring out-of-flat while fitting the top slab so I removed the engine AFTER glueing the top slab.

The manual says bevel the edges of the bottom and top slabs to accept the corner slabs. This requires some very careful alignment of the bevelled edges to avoid gaps. Also means cutting these edges below the level of the foredeck and spinner ring. I preferred to bevel the edges of the corner slabs and fit them up from the inside against the other slabs. Easier to fit and avoiding gaps.

After all slabs are in place I ran thin CA all the way around the ends for a firm bond to the foredeck and spinner ring. There is no glue yet between the slabs to avoid a glue ridge in the final sanding. The final glueing will actually be the fuel proofing epoxy coat on the inside of the cowl.

With all slabs about 1/8 inch has to protrude above the foredeck and spinner ring to allow carving the proper curved surface of the cowl. Too little protruding and the cowl middle will be flat. Too much and there will be gaps where the corners of the slabs meet.

The edge of the 1/16 ply spinner ring can be chipped during the carving process if not careful. I ran thin CA all around its edge to harden it. When carving towards the ring lift the cutter just before reaching it and finish the shape while sanding. The manual says carve from the middle towards the ends to ensure the rounded shape and this method works well.

After carving finish by sanding with 100 grit to blend the slabs into each other, the foredeck and the spinner ring. Fill any gaps with LePage Light Oak wood filler that dries to a balsa colour.

Digitals below of the top cowl build.
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Old Aug 11, 2014, 07:29 AM
Life is a Hobby
Canada, ON, Delhi
Joined Aug 2012
852 Posts
On to the wing fillets, one of the major structural additions to WWII fighters in an attempt to go faster farther.

Start by covering the wing top with plastic to protect against glue. The fillet bases are pushed out of 1/16 ply sheets. The sharp TF stamping dies made that an easy job. The bases are trapped between the fuselage wing saddle and the wing using alignment marks.

Die cut formers are glued between the fuse and base at specific intervals. I found thin CA to be best for the whole fillet job. The rear of the base behind the wing TE is hinged to the front of the base so it can be moved into position against the fuse and glued in place. Then the front of the base is glued along the fuse.

Three fillet skins are cut out of 1/16 balsa. Cutting patterns are on the plans sheet for the top front and rear skins. The manual says there is a pattern for the bottom rear but there is none. I used the hole in the 1/16 ply sheet that the base came out of as a pattern. There is no curve in the rear bottom skin so this method gave the correct size. The top front and rear skins are curved so the holes in the 1/16 ply are too small for patterns. In fact the pattern for the top front skin is too small and I cut the edge against the fuse 1/4 inch wider.

Cut and fit to get all three skins properly sized and located. I did bottom rear first, then top rear then top front. The top front skin stops 4 inches short of the wing LE. This narrow portion is filled with tri stock and wood filler.

Went over all the skin edges with thin CA to bind to the fuse and base. After all is cured sand to contour.

Digitals below of fillet build.
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Old Aug 13, 2014, 08:55 AM
Life is a Hobby
Canada, ON, Delhi
Joined Aug 2012
852 Posts
Lot of structure in the wing/fuselage join area. On top are the wing fillets and below the fuse belly pan. In the full scale P40 all an attempt at streamlining to increase air speed and reduce fuel consumption. In the R/C model this means some careful cutting and fitting of 1/16 balsa skins over 1/8 ply formers.

The previous post covered the wing fillets. This post will look at the belly pan build. The wing is bolted to the fuse to make sure the belly pan is centered front and back. The position of the five 1/8 ply formers is transfered from the plans to the wing bottom. Former F1 is glued just behind the wing LE centered on the fuse and F5 is glued centered on the wing TE. A 3/16 balsa stringer inserts into the top of the formers and is used to line up F2,3,4 straight to F1 and F5. The formers are glued and then the stringer.

There is a pattern on the plans for cutting out the belly pan skin halves from 1/16 balsa sheet. The pattern was right on with just the right shape and amount of balsa. The 1/16 balsa sheet supplied in the kit is flexible medium soft, perfect for this part of the build. The sheet is cut from a balsa log which gives it a slight natural curve across its width. When cutting the skin care was taken that this curve was around the formers, not away from them.

While glueing the first skin half with thin CA it became apparent that F2 is either too long or its position on the plans is wrong. The height of the former is OK but there was a pronounced bulge in the skin at the base of the former. After some thought the easiest way around the problem was to cut a slit in the skin around the bulge so that the excess former stuck up above the skin. Then the former was sanded flush with the skin.

After both skins halves are on, the ends of the skins are sanded flush with F1 and F5. There is a 1/4 inch balsa cap on F1 that is glued in place and sanded to shape to line up the forward belly pan end with the wing LE. The rear end of the belly pan is faired into the fuse by carving a shaped balsa block glued to the fuse behind the wing TE. I wanted to fill and finish sand the belly pan created so far before glueing and shaping the rear block.

EDIT: easier to completely carve and sand the rear fairing BEFORE glueing it to the fuselage. Allow a 1/16 gap between F5 and the fairing for easy wing removal.

Digitals below of the belly pan build.
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Last edited by erie_flyer; Aug 13, 2014 at 04:58 PM.
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Old Aug 13, 2014, 05:21 PM
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upland CA
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Old Aug 14, 2014, 12:47 AM
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simply excellent looking work!!!!
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Old Aug 15, 2014, 07:40 AM
Life is a Hobby
Canada, ON, Delhi
Joined Aug 2012
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The large lower cowl that is a hallmark of the P40 comes in the kit as four vacuum-formed ABS plastic parts that have the flashing removed and then glued together. The glue must be a solvent type that melts the parts together. The seams will eventually separate with surface glues like CA or epoxy. Over the years I have found acetone to be the best. Use in a well ventilated area. If done properly the inner seams do not have to be reinforced with fibreglass strips.

The two cowl body halves are glued together first and then the cowl front. The assembly is try-fitted to the upper wood cowl and the fuselage. The ABS is thinner than the fuse sheeting so 1/16 scrap shims are glued in the fuse pocket where the rear cowl fits to level things out.

Two screws on each side secure the rear cowl in the fuse pocket. A small wood block is inletted and glued into the sides of the upper wood cowl to accept a forward screw. The ABS material is not perfectly rigid and can be a little wavy along the edge with the upper cowl. I used some scrap 3/16 square balsa to glue a fence along the edge of the upper cowl to straighten out the edge of the ABS lower cowl. Then a little sanding on the upper cowl to even out the edges.

The cowl supplied in the kit has the partitioned lower cowl front opening of the D and E variants. The F variant that I am building did not have these partitions. Removing them might weaken the opening a bit. Packing the inner lip with chopped fibreglass and epoxy would negate any weakness.

After the lower cowl has been screwed to the fuse the ABS cooling gills are glued to the rear of the lower cowl making sure the gills are centered on the fuse bottom. Then the seams between the ABS parts are filled with Bondo and sanded smooth. I didn`t fill the seam with the rear gills. It is fairly smooth and looks like the seam on full scale P40 photos.

Next step is to fit the cowl to the DLE20RA engine.

Digitals below of the lower cowl build.
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Old Aug 17, 2014, 07:40 AM
Life is a Hobby
Canada, ON, Delhi
Joined Aug 2012
852 Posts
The P40 has distinctive pods on the wing LE to cover and streamline the mechanism that swings and rotates the landing gear to the back of the wing. The pods in the TF balsa kit are vacuum formed ABS plastic that are cut out of their flashing and then two halves glued together for each pod. The seams are filled with Bondo, sanded smooth and then the pods are fitted to the wing LE and the LG bases.

The landing gear bases are housed in a sturdy framework of laminated projections from ply ribs W3 and W4. Based on my experience from 12 years ago, what is not so sturdy is the rail system for screw attachment of the interchangeable fixed LG and Robart 615 rotating retracts. The screws are small and the ply rails narrow. Doesn`t take much of a bounce to pull the screws out of the rails. I decided to modify the way the ply rails are glued to the rib projections hoping for a more secure screw base.

As for retracts, I installed Robart 615s in my previous P40 and they didn`t last long. The plastic mechanism causing the rotation takes the full force of a landing. Retracts would have to be sturdier (read heavier, expensive). I always maiden a warbird on fixed gear anyway and install retracts at a later date after the plane is trimmed out and I am used to its landing and flight characteristics. The wheel wells are installed under the wing skin. Just have to cut away the skin if I decide to install retracts.

The P40 LG has the same width as my TF Spitfire so should handle OK on the ground. I don`t remember any ground problems with my previous P40. The TF Spitfire has its LG wider than scale or it would be impossible to handle on the ground. Comparing the TF P40 to a 3-view, the model`s LG appear to have a scale width.

Digitals below of the LG build.
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Last edited by erie_flyer; Aug 18, 2014 at 06:43 AM.
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Old Aug 24, 2014, 08:02 AM
Life is a Hobby
Canada, ON, Delhi
Joined Aug 2012
852 Posts
Covered the wing with black SolarTex. For anyone not understanding the colour look back at post #1.

Preped the LE and TE first with finishing epoxy thinned with alcohol. This hardens the balsa and gives some tooth for the covering`s glue adhesion. SolarTex is my fav covering. Strong. Doesn`t become brittle in cold weather. Melts around compound curves. The colour is in the fabric, not in the glue like the mylar coverings.

Standard covering sequence - bottom first then the top overlapping the bottom covering at the LE and TE. Used the trim ends to cover the ailerons in the same sequence.

Hinged the ailerons with strips of SolarTex. These are called live hinges - very flexible with no air gaps. The aileron LE is undercut like a flap instead of "Ved". The aileron is placed in position fully rotated on top of the wing. The inside strip of SolarTex is ironed into place between the aileron LE and the wing TE. Then the aileron is rotated back down to its normal position. Another strip of SolarTex is ironed between the aileron LE and wing TE.

As previously explained I replaced the manual`s old fashioned single central aileron servo and outer bell cranks with two servos out at the ailerons. Gives a much more direct connection to the ailerons with short stiff pushrods.

For aileron servos I am using Hextronik MG-16s. These are metal geared ball bearing micro servos that are the same weight and torque as HiTek 85MG and are slightly faster. Attached 12 inch servo extensions locking the plugs together with heat shrink tubing. Don`t want them coming apart inside the wing. The servo arms are angled forward for differential throw.

Short 2-56 pushrods are supplied in the kit which are just the right length for threading a Sullivan brass clevis at the aileron horn end and bending an "L" at the servo arm end for securing with a keeper. This is different than the manual which says solder a threaded brass clevis coupler at the servo end. Lot simpler to use the "L" method.

Digitals below of work on the wing.
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