2000mm Giant Scale B-24 - Silver

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  • Originally posted by xviper View Post
    I'm thinking about doing something similar to extend the nose so the motor can act on a longer lever, making it possible to use smaller batteries and eliminate the need for extra weight. It would be great if you could snap a pic or two along the way. I'd love to see how you're doing it.
    I'll do that xviper. I've taken a couple already, attached, but having sufficient time is my problem currently. The pics, not in sequence, should be self explanatory.

    It's not a huge job, but precision is important.

    The oval shape of the blank was marked by putting the cut end of the cockpit end on the foam and marking around it. The ends that slide into the fuselage are shaped by trial and error.

    I marked the cut line using a piece of light cardboard wrapped round the fuse just in front of the wing recess. By bringing the ends together, a 'straight' line is drawn around the fuselage, and I cut the glass fuselage using a fine hacksaw blade, rolling the fuselage as I went so that I was always cutting down and into the fuselage, and not from one side to the other, which would probably result in chipping because the glass is so thin. A Dremel with a cutting disc is not necessary, although could just as easily be used.

    I'll glue the blank into each piece of the fuselage, wrapping a piece of 1/16 balsa around the bottom half and securing it with rubber bands, and getting the alignment right by using the red stripes. I'll also wrap the visible part of the blank, that between the two fuse halves, in sellotape so that the fiberglass doesn't stick to the foam, making it easier to get the foam out. Most of that should come out by breaking it up, and the residue will melt out using acetone.

    My question above regarding the type of resin used in the original layup may have been solved, but I'd still like confirmation from somebody who has actually done fiberglass work on the fuselage. When I cut it, it had a distinctive polyester resin smell to it, quite different from that of epoxy, but not the green/ish tinge that poly normally has. I have plenty of epoxy and cloth of varying weights here, but need to pickup some poly resin, probably tomorrow, so I can get on with the project.

    Ben Jones, owner of rcairmods.com the guy who specializes in BoT mods, uses epoxy to attach his nose section mods, and says he hasn't had any difficulties, separations, etc., in spite of some heavy landings.

    I'm going to use a 42 mm spinner, and make my bulkhead of three thicknesses of 1/16 marine ply, glued in. The diameter of the motor is critical, and I'll probably use one of Ben's recommendations, a Cobra 2826 which should easily fit if the bulkhead is about 45 mm across. Because of the oval shape of the fuselage, there will be an 'overhang' top, or bottom, or both. I'll sand that to fair it into the spinner, and may even have an air inlet top and bottom, a very small crescent shaped opening.

    I'll post more as the project proceeds.

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    • Originally posted by brk6188 View Post
      I am not sure either but have read that " New Poly sticks to Old Poly and New Epoxy sticks to Old Poly BUT New Poly will not stick to Old or New Epoxy" Have never proven it one way or another, suspect age might be a factor ?
      I'd read something similar brk6188, but I'd prefer to use polyester resin if the original layup was in poly, just my conservative side.


      • Thanks, Ross. Very industrious and innovative. Looking forward to seeing the progress. Even more so, is to hear of your impressions of how it flies. I have heard that the "extended" version flies much better than stock but I've only heard this from one person.


        • I managed to find the time to get back on the project today, and made good progress.

          I had a second fuselage, damaged in shipping, and since I had to repaint part of the fuselage, even if I'd used the undamaged one, I decided to repair the damaged fuse, just a few cracks, and use it for the conversion, and the bonus is that I have a brand new fuselage in stock!!

          I glued the foam blank into both parts of the cut fuselage, and cut off the nose prior to doing so. If I hadn't done that, the whole thing would have become unweildy because of the ballast in the nose, and probably not achieved such a good result. I cut a couple of millimeters less, 'just in case'. The cardboard around the bottom section held in place with rubber bands and some masking tape gave good alignment, and I used a straightedge to line up the red stripe to ensure it was as close to perfect as I could get it.

          Pics are attached.....

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          # 1 Ready with the foam blank, cardboard and rubber bands to hold it all together while the glue dried, 6 minute epoxy, with some microballoons to bulk it out.

          # 2 The blank has been glued in and the fuse is held down with a couple of sand bags.

          # 3 is a drawing of the nose section plan and profile, to get an idea how it will look. The silverish blob is the steel shot used for ballast. There's barely enough adhesive in there to hold the shot together, and when it's knocked out, shot goes everywhere!!

          # 4 The fuselage lying on the drawing sheet giving an idea of how the front section will look. The crescent shapes will be holes for cooling air.

          I think it would have been a better idea to just shape the pieces of the blank that are glued into the fuse ends, and shape the 10 cm of foam to the fuselage shape after the block of foam is glued in. I shaped it before glueing, and there are a few low spots that will need building up. I'll probably just use layers of paper for that and hold it in place with masking tape.

          I hope to be laying up the glass tomorrow, and sanding back on the weekend, painting some time next week.

          I've sanded the gelcoat using 100 grade wet and dry, and gone right through to the fiberglass mat in some places. I took some advice, and conducted a few tests inside the fuse, and epoxy takes well to the original polyester resin, so I'll be using epoxy, probably one skin of 4 oz cloth (woven rovings), and a couple of finishing coats of 1/2 to 3/4 ounce cloth to make the fairing into the original easier..

          I'd better get on and order the few bits I need from Ben at rcairmods.


          • The project is coming along nicely, with the glassing finished, and the fuselage ready for paint...almost. Before I can paint, I have to manufacture the motor bulkhead, and to do that I need the spinner and motor. Both, along with other required parts, are in the mail, some from rcairmods, and a couple from Hobby King. I'll be using automotive adhesive pinstriping, 6 mm wide to replace the original stripe, in lieu of trying to accurately paint a stripe the length of the fuselage.

            I used two layers of 4 oz cloth, overlapping the original fuselage ends by about 3 cm on the outside, and 6 cm on the inside, with three layers of 3/4 ounce cloth on the outside to fair it into the original, and get a fine finish. The 3/4 ounce cloth overlaps the 4 oz cloth by about 3 cm each end. The 4 oz cloth was sanded, and faired into the fuselage before the 3/4 went on.

            I've made the front of the fuselage more round by squeezing the top and bottom, resulting in the sides splaying out. It's not completely round, and can't be because of the geometry of the fuselage, but it will make the fairing of the bulkhead into the spinner an easier transition. Prior to modifying the shape, it was 57 mm high and 43 mm wide, now 53 mm X 46 mm.

            The spinner is 42 mm, and the width of the fuselage now 46 mm, so only a 2 mm reduction each side. Top to bottom the fuse is 53 mm, so there will be a small reduction, about 3.5 mm top and bottom, required. The same all round would have been ideal, but is not achievable.

            I'm quite enjoying this project, time consuming, but I think the result will be well worthwhile, aesthetically pleasing, and functional.

            I think I'll only use a 2200 mA battery, reducing dead weight, and giving a flight time of about 5 minutes, but that will be 10 climbs to 1300 feet based on ecalc calculations.

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            • Really great work so far. Kudos! I can't wait to see the final results both static and in the air!


              • Incorrect info in my earlier post.....

                I think I'll only use a 2200 mA battery, reducing dead weight, and giving a flight time of about 5 minutes, but that will be 10 climbs to 1300 feet based on ecalc calculations.

                That should be 5 climbs to 1300 feet, probably a LOT higher than I'll be flying it, so 10 climbs to 650 feet.


                • It's difficult to think of all the contingencies when building something new. In an attempt to get the front of the motor bulkhead close to round, I extended it by a couple more pieces of ply, but when the motor arrived, it became obvious that with a 20 mm shaft, and a 17 mm thick bulkhead, there was a problem, but model flying is about problem solving, so I figured the best way round this was to cut a couple of laminations off the front, and cut a hole in the remaining 14 mm so that the motor could be brought forward. That not only fixes the problem, but moves the CoG a little further forward also.

                  Of course a cut through the laminated nose section is difficult to get completely square, so I had to true both pieces up on the disc sander, and put another piece of 2 mm marine ply in to make up for the cut and sanding of both sides.

                  The holes in the front piece of the bulkhead are four small countersunk for the bolts to fix the motor, the four larger holes are for cooling air to the motor, and the centre is obviously for the shaft.

                  That's all done, and it's ready to epoxy it all back together.

                  The order from rcairmods arrived in 6 days from the US (Australia Post can't get a letter from Sydney to Perth in 7 days!!), the motor and other required bits were couriered from Hobby King, so it's all set to go. Ben at rcairmods peovides great service, and outstanding communication.

                  Next stage will be epoxying the elevator mod from rcairmods in the fuselage, and on to painting, then putting it all together. Hopefully I'll have it flying in a week or two.

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                  • Work continues on the project, and I've made good progress.It's ready for paint, but I think it will be a good idea to strengthen the rear fuselage with a couple of skins of 3/4 fiberglass cloth. I have to repaint the fuselage anyway, so it's little extra work.

                    Since I used a damaged fuselage, I had to replace the ply stiffeners, and that's a huge job without having the old damaged ones for templates. I foolishly threw them out!!

                    If anybody is using Ben's (rcairmods) tail assembly kit, the original sleeve can be left in place because his sleeve is a nice fit in the original.

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                    • The fuselage is finished, a couple of minor imperfections, but overall, a good finish, and the fuselage is now 105 mm longer than the standard BoT, and I have a brand new fuselage in stock!!

                      I figure it's taken me about 14-15 hours labor, but some of that was attributable to repairing the damaged in transit fuselage, and there was significant damage in places. I manufactured a fairing to cover the leading edge of the wing, previously covered by the rear of the canopy. Making the ply stiffeners to brace inside the fuselage was also time consuming.

                      The final coat paint is on, pin striping to go, and then start installing the rcairmods tail mod, motor, etc. It's looking great.

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                      • Labor of love. Nice job. Can't wait to see it all complete and with video!


                        • Pics taken on the way through the buiding process

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                          • You live in a nice part of the world Warbirdaholic. I spent some time in Seattle back in 87, at Boeing for a few weeks, and did a lot of driving throughout Washington state and up to Vancouver, and only clipped one deer in the hire car!!


                            • Thanks, yes I love my region for the most part. The rainy/windy/mucky/cloudy weather from November through April is a drag for sure but the beauty of the area is worth it.


                              • If you're going to modify a BoT.... Go serious!


                                • The project has stalled because my house has sold and I'm packing to move interstate.

                                  It's almost there, painting done, pin stripe (automotive, self adhesive off ebay) stuck on, servos installed, and receiver ready, but time is the problem.

                                  The pin striping looks good, and eliminated the need to try to get an accurately painted stripe the length of the fuselage.

                                  I'm currently making a wing bag, almost finished, and I'm still hopeful that it will fly within a couple of weeks.

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                                  • That looks real good, like it came out of the box that way. I'm doubting I have the skills to do this mod.


                                    • Originally posted by xviper View Post
                                      That looks real good, like it came out of the box that way. I'm doubting I have the skills to do this mod.

                                      The secret to good glassing is to start with a perfect surface xviper. My foam blank was a little low in places, so more glass and more sanding to get it right, and although there are some minor imperfections, I'm more than happy with the result. If I did something similar again, I'd fit the foam into both ends of the fuselage first, and then sand it to a straightedge laid across the fuselage ends, instead of trying to get the blank right before glueing it into the fuselage ends.

                                      I cut my teeth on a 2.1 meter span Martin Mariner, Keith Sparks' design, glass on blue builder's foam, except the wing where it was glass on balsa over foam. That's as near a perfect surface as you'll get except out of a mold. There are thirteen skins of .5 ounce cloth around the engine nacelles, down to four over most of the rest, and there was a lot of sanding involved there.

                                      I'm up to my ears in packing crates and boxes currently. I have four fuselages in a crate 1.6 meters long, 1.3 wide, and 1.1 high, and another three smaller crates with wings and fuselages. The longest, 2.2 meters, is for the single piece Mariner wing.

                                      I figure the entire volume to move will be about 42 cubic meters!! I've accumulated a lot in the 26 years I've been in this house.


                                      • Well, it's ready to fly, but the weather forecast doesnt' look as though I'll be doing so for at least a week, heavy rain and high winds forecast. Balance was right on the button,
                                        9.5 mm from the leading edge, with the battery and ESC placed centrally in the cockpit. The time spent on this project has been well worth it, and a larger battery wasn't required to get the CoG right.

                                        I'm using a 3S 1300mAh LiPo, and the weight comes in at a touch under 1.9 kgs, 4.1 lbs, as close as can be deetermined on bathroom scales, and I'm happy with that.

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                                        • Originally posted by Ross M View Post
                                          Well, it's ready to fly, but the weather forecast doesnt' look as though I'll be doing so for at least a week, heavy rain and high winds forecast. Balance was right on the button,
                                          9.5 mm from the leading edge, with the battery and ESC placed centrally in the cockpit. The time spent on this project has been well worth it, and a larger battery wasn't required to get the CoG right.

                                          I'm using a 3S 1300mAh LiPo, and the weight comes in at a touch under 1.9 kgs, 4.1 lbs, as close as can be deetermined on bathroom scales, and I'm happy with that.
                                          9.5 mm? Typo? I just looked at my manual and it says 95.3mm. Mine is finished (for now) except for the spoilers. I want to see how it flies first. In stock form, with no servo in the tail, using a 3000mah, 3s, Graphene battery, it still needed many oz. of lead stuck to the nose just to balance. I've wrapped the nose with white electrical tape to camouflage the lead. There's no way of shoving that much lead inside and get that big battery to fit. Besides, anything further back than the very tip, would require even more weight.
                                          Yours is the best solution (lengthening the front section) to make the lever longer on that end. Mine is the lazy man's way and I think if it flies OK, I may try the Radian XL fuselage option one day. I just wish the fellow who did this would have answered my question about how it flies compared to the stock XL. The absence of an answer tells me there may be something not good about that option. I also never liked that rubber band method of holding the wing on - looks like a toy and very primitive.
                                          This was and still is a classic shape but it was a poor design for electrifying.