Jessie The Jeep Posted January 31, 2012 Share Posted January 31, 2012 Some of you will have seen pictures of my B-17 posted here. The story of the B-17 began in 1994, at the Elvington model show, with the decision to scratch build a 1/6 scale B-17 Fortress, to join my scratch built P-47D and a friends Galaxy P-51D. Wood cutting began two weeks later. After 10 years, August 1st, 2004 marked the last flight of my B-17G, 'Hang The Expense'. The Fort on its last flight at Seething airfield, coincidentally the location of a forced landing by the original wartime crew. Shortly after this, I became ill with asthma and a wood dust allergy, and transporting the B-17 to model shows was just too much physical effort. It took me two to three years to get better, by which time, UK fuel prices had increased dramatically, and that together will the loss of my job through ill health, meant that travelling around the country was not affordable. Over the past few years, the B-17 has made a few static appearances at local military shows, but with two Jeeps and a Dodge to look after, I no longer have the interest in flying any models. It's actually cheaper to run the Jeep and Dodge than it is to take the B-17 around the shows like I used to! The B-17 on static display in 2009 A second factor that has permanently grounded the B-17, is that UK model shows have now moved exclusively to 2.4GHz radio, and I don't have the money to invest in new radio equipment, especially with the limited use it would get. I have no regrets grounding the Fort, as building a large B-17 was my primary goal, when starting the hobby back in 1983. I've done that twice now with both 1/10 and 1/6 scale scratch built versions, plus a lengthy rebuild, so now I have little interest in going back over old ground and challenges. Military vehicles and astronomy is more than enough to keep me busy and challenged for now. With the recent purchase of a Ford GPW to restore, I needed the space in the garage that was occupied by the B-17 in its trailer, and so the B-17 and trailer had to move out. While the trailer can live on the drive, I didn't want the wooden airframe to stay out in the damp, so it looks like it has found a home at the North East Aircraft Museum. I would however need to do a little work to the aircraft before it could go on display. The engines and radio gear would be stripped out, and I'd need to fill the holes in the engine cowlings where parts of the 2-stroke engines poked out, and I'd also need to make some dummy engines. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 Here's the B-17 in its not so small trailer! The box is 12' x 6' 2" x 3' so takes up quite a big space in the garage. My original Jeep only had about 1.5 inches clearance each side when next to the trailer. Soon after I started to take it on static display, I decided the two blade flight props had to go. 1/6 scale Hamilton standard props aren't generally found on the selves of hobby stores in the UK, so I set about making some. I already had photos and measurements to work from, using my research from back in 1988 at the RAF Museum, Hendon. To start with, I carved a single prop blade from pine, and made a two part fibreglass mould of this blade. The first half of the mould has been removed while the wooden blade pattern is still in place. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 Each half of the mould was layed up with resin and a few layers of 48 gram glass skinning cloth. Before either half had gone off, I mixed a slurry of resin, polyester filler and chopped strand glass to act as a filler and joining compound. Any excess squeezed out of the mould when the two halves were clamped together. This 'flash' was trimmed off later once cured. Moulding the twelve prop blades was a bit of a chore, but certainly not as much as the 36 'Cyclone' cylinders for the dummy engines! One blade has had the excess taken off ready for final sanding while the other two are straight out of the mould. Quote Link to comment Share on other sites More sharing options...
private mw Posted January 31, 2012 Share Posted January 31, 2012 nice one mate you must have got the patience of a saint . nice work .:angel: Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 (edited) Cheers. I have loads of patience for things, but quite a short fuse with people!! Edited January 31, 2012 by Jessie The Jeep Quote Link to comment Share on other sites More sharing options...
private mw Posted January 31, 2012 Share Posted January 31, 2012 you have more patience than me you are always making things to the smallest detail , did you ever start or finish that model railway layout . :-\ Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 The pattern for the hub was also made from wood, built up from several turned pieces. A silicone mould was made from this, and four resin hubs cast. These would then be drilled to allow the moulded blades to slot in and glue. A jig was made to hold the hub and support the blade at the correct pitch so that all the blades were set at the same angle. With all the blades cast and cleaned up, and the four hubs cast, it was time for assembly and painting. Tips first using yellow. The cream coloured resin meant the yellow covered fairly well. Once dry, the tips were masked off and the black painted. I have some Hamilton Standard prop badges that I scaled and printed on photo paper which are yet to be attached. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 ....did you ever start or finish that model railway layout . :-\ That's an ongoing project, but the hours on it have been cut back for now as the customer had some unexpected property repairs to fund. It will continue, but will probably be completed in a reduced size compared to the original plan. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 Over the Christmas period, I started on the dummy Wright Cyclones. Years ago, when I started building my 1/10 scale B-17 ( seen below ), I bought the Monogram 1/12 scale Wight Cyclone kit as a reference for a dummy engine. In the end, I never got around to making 1/10 scale copies. The Monogram kit was useful over Christmas however, being able to simple double the measurements to create a 1/6 scale drawing of the cylinder. The plan was to cast the cylinders from resin, and make the crankcases from wood, then add the details such as the pushrod tubes and ignition harness from metal tube and wire etc. An M10 bolt would be fitted for the props to screw on to. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 With a piece of 2mm acrylic as a nice flat base, the basic cylinder outline was cut from 0.75mm styrene. Next was the very slow process of measuring and cutting half discs of styrene to make the cooling fins of the lower cylinder. These were also 0.75mm. The mounting flange to attach the cylinder to the crankcase is 2mm styrene. The cylinder pattern and ignition harness junction box complete. The upper fins on the Monogram model were thicker then the lower, so I used 1mm styrene for these. The notches for the pushrods were ground into the styrene with a small stone cylinder in a mini drill. Other details such as the rocker housings were from high density model board. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 The next stage was a styrene box around the pattern. Once done, it was time to work out how much silicone to mix. I placed a very thin walled plastic bag into the mould, and filled it with water until the mould was full. The water was then tipped into a measuring jug to see how many fl oz it was. From there, I could mix up the silicone without any waste. To assist air bubble removal, I placed a piece of 1/2 inch ply with a hole in the top, over the mixing pot. A vacuum cleaner hose was then placed over the hole to help draw the air out of the rubber. Once poured carefully into the mould, the vacuum trick was repeated, and finally the edges of the mould vibrated with an orbital sander. The following day, the rubber mould was removed from the pattern. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 The cylinders were made from polyester casting resin. The casting process took quite some time, with each cylinder taking about 30 minutes to cure enough before it could be removed. The two photos show the first cylinder in the mould and after release. I did wonder whether the resin would pick out the 0.75mm fins, but I'd worked the resin into the mould with a pointed wooden dowel to try and minimise air bubbles trapped between the fins. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 After a couple of days, I'd got two engines worth of cylinders. The mould was still looking good, with no signs of damage. At the end of the 27th cylinder, the 0.75mm fins in the mould had started to show signs of wrinkling, I presume from a combination of heat damage and stretching of the mould. The last nine cylinders got progressively worse, but not unuseable. In all, it took four days to cast them all, using almost half a gallon of resin. A few of the details on the ignition junction boxes didn't form properly, so another eight of those needed casting. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 The crankcases were next. Two layers of 15mm faced chipboard gave me the correct thickness for the area where the cylinders would attach. The discs were cut on the bandsaw and sanded close to the final size. They were then cyanoed together before final sanding. The exposed edge was sealed with cyano. Another layer was glued to some 1/4 ply for the tapered front of the crankcase. This was then turned in the lathe to give the taper. The circumference was divided into nine for the notches where the bolts are for the front casing, although there are only eight notches. These were sanded with a small drum sander in my mini drill. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 I forgot to seal the exposed wood on the tapered pieces before applying the filler. This allowed some of the wood fibres to expand during the first wet sand. The main body of the crankcases sanded well, having been sealed with the cyano. This picture was taken before the first sand. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 Time for another dry assembly for inspiration! The engine is around 9 inches in diameter. After a few applications of filler, primer and rubbing down between, they are looking good. There's a few more smaller parts to make for the crankcase before they can be assembled. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 By January 9th, I got into the trailer and got all four cowlings off the B-17. They were moulded in polyester resin, and after 18 years of sun, rain, vibrations and petrol exposure has taken its toll on the glass and paint. These couple of pictures show some of the openings that need filling. This picture also shows the inside edge of the cowl, near the gills. Each cowl has had this edge sanded with a powerfile so a new layer of glass cloth can be applied. Several of the gills have been caught on things over the years, and have fractured along their hinge line, so another layer of glass will reinforce them all. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 This shot shows how the paint has crazed in places due to pooling of overflowing fuel. The holes have all been glassed on the inside to give a strong base, and the holes will then be filled with polyester filler. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 All the gills have been reinforced. The front lip of this cowl needs work, but this will be done once the first area of glassing has cured, otherwise I know I'll end up in a sticky mess! This cowl had some weak areas in the front ring, so it was filled with the last of the resin in the pot, and some small strips of glass cloth stippled in. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 The holes in the cowls were filled next, and after it cured, the high spots were taken off with 80 grit used dry. This was followed by wet sanding with 120 grit. The old Flair Spectrum paint, baked from years in the sun, was incredibly hard, and it took five hours to wet sand the four cowlings! Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 All the cowls were given a first coat of grey primer to pick out the air bubbles and other imperfections in the glass. There are also still some places that need additional glassing to build up thickness after sanding thinned out some areas. A morning was spent with the fine surface filler going over all the pin holes and scratches which could be seen clearly with the grey primer on. Once dry, all the cowls were wet sanded again. The cowl on the left is shown just with the filler on, the right cowl has been rubbed down. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 By January 13th, the cowls were rubbed down again and re-primed, and were looking pretty good again. The cowl gills were also re-cut. I then moved on to the crankcase details. These were made from more resin model board, cut and sanded on the bandsaw/disc sander, or turned on my lathe. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 Four ply discs were also cut onto which the engines will be mounted. These in turn will be glassed into the cowls. Another inspiration picture, but still plenty more details to make and add before they're done. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 I decided it was probably worth double checking the engines would fit inside the cowlings! Even with the prop resting on the front of the cowl, the engine should still be clearly seen, and should look great once painted. Quote Link to comment Share on other sites More sharing options...
Jessie The Jeep Posted January 31, 2012 Author Share Posted January 31, 2012 Last thing done that day was to fill some of the gaps where the details meet the crankcase. I also found some nice little hex-head bolts to be fitted into the crankcase. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.