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Jul 08, 2020, 05:40 AM
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Fuse 14: cowl


With the firewall trimmed out with vents, and the nose generally sheeted, I can start on prepping for my fibreglass cowl.

The designed space between the front of the cowl and rear of F4 is 143mm

With my Engine, I required

Engine Mount to front of crankcase = 123mm
Firewall = 7mm
Front of F3 to Back of F4 = 27mm
TOTAL COWL LENGTH = 157mm

My skyraider is going to be 14mm longer than the design.

Steps:

1. I made a 150mm square 'tower' of 7x 23mm pieces of Styrofoam for a total of 161mm length. This will be shaped into the cowl as a destroyable mould for my fibreglass cowl.
2. Sanded back the cylinder shape from the Foam block. A piece of 2" x 1" of around 300mm is a good sanding block to run laterally over the cowl mould
3. Remove the plywood ends and use a template of the cowl front radius to shape the front.
4. First coat of West System (105 resin / 206 hardener / Microballoons) and 4oz cloth. Allow to dry overnight
5. Sand off imperfections with 80 grit paper. Second coat and glass applied.
6. Sand off imperfections again. Final coat applied but lightly applied. Due to the slow hardening, I rotated the cowl 90 degrees every 4 mins for 32 mins total. The end result was very good.

I have decided to redo my cowl. The first one is just too cylindrical so i have started again to be more like the ziroli scale.
The new cowl is formed from a cylinder, like the first but transitions in 3 sections.
The rear third of the cowl is cylindrical, the middle third tapers by 5mm to the nose, and the last third is rounded off to a 110mm diameter opening. This looks much better.
Last edited by Vortrog; Aug 10, 2020 at 04:08 PM.
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Jul 13, 2020, 02:06 PM
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Fuse 15: Canopy


I am going to vaccuum form my own canopy (my first ever)

For this I am using PETG 0.04 thick I bought from my local industrial plastics. 1 lineal meter of this was about $30. I can make about 12 canopies from this sheet (lucky for me as I failed at my first 6 attempts)

To achieve this;
1. Form a blank from Styrofoam
2. Create a plug mould from Fibreglass
3. Remove the blank in the Plug Mould, clean the negative mould out then create a positive mould from Plaster
4. Vaccuum form the new canopy from my new plaster plug

SUMMARY OF SUCCESSFUL PULL
0. I covered my plug with candle wax as a mould release agent
1. Oven at 175 degrees C. It should only take 1 to 2 mins for the plastic to soften enough to pull (see 3 below)
2. your frame should have legs on the TOP side that are at least 75mm long
3, When the frame goes in the over (upside down on the legs), wait until the PETG has sagged at least 50mm before putting on the plug
4. Vacuum running before removing the frame from oven
5. dont place the frame on the vacuum box too fast. Lay it over evenly to prevent seams forming

The reason for my failures were:
1. PETG no hot enough (incomplete pull)
2. PETG not hot enough (then use heat gun to finish it, but the heat cracked the paint covering on the mould and stuck to the PETG. I had to bend the canopy to get it off the mould)
USING OVEN AS HEAT SOURCE
3. PETG not hot enough (Oven at 130 degrees C)
4. PETG Not hot enough (Oven at 140 degrees C)
5. PETG hot enough (OVEN at 175 degrees C) but I was too fast on placement and pulled down on the mould too fast resulting in seams (folder plastic) over the canopy. Paint sticking to canopy
Used Wax as a mould 'lubricant' (eg coated the mould by rubbing a candle over it)
6. PETG hot enough, but got wrinkles again as I put the damn PETG frame on upside down. Still getting pain on mould
DIDNT REMOVE PROTECTIVE LAYER ON INSIDE OF CANOPY
7. Success. Was able to strip away protective layer and all wax and paint came off. Slight spekling of canopy results but it is acceptable.
Last edited by Vortrog; Jul 30, 2020 at 05:24 PM.
Jul 20, 2020, 06:26 AM
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General: closeouts of build works


Anything still to be done before glassing the model is in this section.

1. Engine offset of 1.5 degree right should be achieved with the addition of a 3mm spacer to the left engine mount. I used 3mm plywood for this.
2. Fit off of Rudder using M3 bolts, and washers. Very imortant that you sand the leading edges to a curved shape to ensure the rudder has full movement without binding on the fuselage.
3. Second side sheeting of Rudder in 1.5mm balsa.
4. Cut outs for all wing servos completed. I reinfoced the 2x free edges of each servo pocket with 10mm x 6.5mm balsa strips (between Servo mounting ply and wing skin)
Last edited by Vortrog; Jul 22, 2020 at 05:19 AM.
Jul 22, 2020, 12:12 AM
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Finishes 01: Scheme and Finishes Type


For this model, I will be covering in 1 layer of 3/4 Oz Fibreglass Cloth, and West Systems 205 Epoxy (2 coats of 100% thinned with Methylated Spirits (or denatured alcohol)).

Painting will be with Automotive Acrylic (150% thinned)

Colour scheme I have decided will be the Navy Colour scheme as per the plans (Grey Upper, White underside and control surfaces, black), but with a twist.

This model will not compete in quality or scale to many others either manufactured or caringly and faithfull built by those who love this Aircraft (I specifically call out JMorgan on his brilliant work....I'll never match that). So I am going to deviate from historical markings on this model for something a little different.

Hypothetically, had the HMAS Melbourne been supplied with some Ground attack aircraft as part of its trip to the US in 1967 for operation in Vietnam after escorting the HMAS Sydney, what would they have looked like?

For starters, the greys and white are much the same as the US used. The difference is the change over to Australian designations and Roundels.

Anyone who loves the history of the aircraft will hate this idea, but I think it will be interesting.
Last edited by Vortrog; Jul 26, 2020 at 04:03 AM.
Jul 24, 2020, 05:39 AM
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Pre-glassing weight check


Model weight before glassing and painting is 3.699kg

If i can bring the glassing and painting in under 300grams that would be good

For comparison, my 1600mm FW190 was about 3.83kg (add battery weight to THIS POST weight at this stage and ended up weighing 4.2kg. So Glassing and paint added about 370grams to the model.
Last edited by Vortrog; Jul 24, 2020 at 06:12 AM.
Jul 26, 2020, 04:09 AM
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Finishes 1: Fibreglassing


Fibreglassing time

Cloth: 3/4 Oz
Epoxy: West Systems 205 Resin, 206 hardener
5 parts Epoxy Diluted with 5 parts Methylated spirits (for first coat)
5 parts Epoxy diluted with 4 parts Methylated Spirits (Second Coat)

Stages:
1. Bottom of Wing, Horizontal Stab and Bottom of fuse (cloth and Resin applied)
2. Right side of Fuse and Top of Wing (cloth and Resin applied)
3. Left side of fuse (Cloth & Resin). Control surfaces (Cloth & Resin). Wing (second coat resin)
4. Fuse (Second coat of resin). Control surfaces (second coat of resin). Firewall and Wheel Bays (Resin coat), Vert Stab (Glass and Resin)
5. Horizontal Stab (second coat resin), Firewall (second coat resin)
Last edited by Vortrog; Jul 30, 2020 at 05:30 PM.
Aug 01, 2020, 09:25 PM
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Finishes 2: Painting


After completing both coats of epoxy (first coat with glass), I sand all raised spots/bubbles and degreased all surfaces ready for painting.

As with my FW190 build, I used Concept Acrylic Primer and Paints/Thinner.

I took my son's Durafly Skyraider into my local paint shop and had them match the White and Gray to the following Concept Colours:
GREY - Achatgrau RAL7038
White - Signalweiss RAL2003
Black (left over from my FW190 Project)

FIRST COAT STAGE COMMENT: My balsa panel installation and sanding is pretty average so seam lines are visible. To be honest, although I sanded, I didnt really put the hours in I should have, mainly because this model is not intended as a display piece. Maybe my second one will be.

Process:
1. Primer all surfaces (I neeed about 110ml of primer (mixed with 110ml of Thinner)
2. White to underside of wing, Horizontal Stabiliser. White to all of Ailerons (and I did flaps too) and Rudder. I needed140ml of white (plus 210ml of thinner)
3. Grey to all remaining areas (100ml of Grey (plus 150ml of thinner)

Planned to come
4. touch up coat of white
5. Black to upper cooler and antiglare panel, plus walkway on wing
6. Fix decals
7. Spray over decals with clear acrylic
Last edited by Vortrog; Aug 04, 2020 at 06:22 AM.
Aug 04, 2020, 06:11 PM
Son's Ground Crew
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Centre of Gravity


The plans show the centre of Gravity at 125mm back from the wing root.
I am going to start with 109mm

I ran my own calculations graphically.

Root Chord is 334mm
Tip chord is 183mm

Using grqaphics, the Mean Aerodynamic Chord (MAC) is about 263mm
The original recommended CoG is 34% of MAC.
25% of MAC (my plannedstarting point) is 65.75mm and is located about 101mm from the Wing Leading Edge (right on the Front Shear wall)

My back of limit would be 28% of MAC (73.64mm) which would be 109mm from the Wing Leading Edge.

Considering the recommended CoG is still rearward of this limit, I will start at 109mm
Aug 10, 2020, 04:23 AM
Son's Ground Crew
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Control fitoff


While I wait for my decal sheets, I installed my servos, landing gear and receiver, and aligned and set them all rest positions.

I am running a 6 channel set up with a Spektrum Dx7 and an AR620 Receiver using flaps, so I cant run dual aileron channels as I need the Aux port for flaps.

Port set up on receiver as follows
Port 0: Battery
Port 1: Throttle (12gram Servo)
Port 2: Ailerons - (2x 21gram MG servos via Y lead)
Port 3: Elevator (62G MG Servo)
Port 4: Rudder (62G MG Servo
Port 5: Landing Gear (2x Eflite rotating retracts)
Port 6: Flaps (2x 21gram MG servo via Y lead)

All wing servos are fixed in with Aluminium straps screwed into the ply mounting plates. I just used an aluminium can and cut it into 10mm thick strips.
Control horns are Dubro0716 Super strength T-Style control horns
Internal Rudder and Elevator Pushrods are DUBRO0500 Lazer Pushrods
External Flap and Aileron pushrods are DUBRO0108 Steel KWIKLINK on 30cm rods
Tailwheel system is Sullivan SULS861 Steerable Tail Wheel

I am using the battery as the final ballast for balancing the model. It location will be determined during the CoG balance.

I have undertaken a check weight with all gear installed and with exception of Canopy fitting and decals, I am at 4kg. I expect not to exceed 4.1kg (9 pounds AUW)
Last edited by Vortrog; Aug 11, 2020 at 04:47 PM.
Yesterday, 05:24 PM
Son's Ground Crew
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Balancing


I got a massive surprise on my CoG balance (based on my 28% MAC calculations of 109mm behind the leading edge at root). The model is very nose heavy.
I expected it to be a bit nose heavy due to the larger engine and redial mount, but not to the extent it is

Using the 135gram battery as a offset, I needed to place it 511mm behind the CoG (front of battery 250mm forward of the rear of the vertical stab)

My options are to A) add weight to the tail and increase the overall weight of the model by say 100g, OR B) add 30g of material and make a battery hatch in the underside of the fuselage.

I went with option B.

This meant I needed an extension cable through the Ribs F9 to F11, and confirmed I needed the switch to reside between F7 & F8.
Last edited by Vortrog; Yesterday at 06:36 PM.


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