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Author Topic: Bristol 72 Racer 30" span (1/10 scale)  (Read 2144 times)
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Bill G
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« on: February 06, 2017, 01:44:21 AM »

Found a Pres Bruning plan here, for the Bristol 72.  The plan is pretty much used as a reference point, making some modifications to make the nose length and wing location scale.  I also drew a precision notching template for the fuse formers.  At this point the retractable landing gear servos (FlyZone 17gm retract servos) are programmed and working, although I haven't actually tested them with the gear legs connected, as the center keels will need to be cut away. The travel/endpoint settings should be close.  When properly setup, the strut legs will be inline, and not slightly bent at the knee, as shown in the photo below.  Probably should buy more of these servos while Tower still has a few, as they're harder to come by, since most people use those heavy servoless retracts these days.  Thinking about a future build of the Cessna CR-2 with retracts, where there is a Dave Rees plan for the model.  Planning the landing gear mechanics was an interesting job, fabricating the the gear legs from wire and modified Dubro parts.

Keeping weight forward, the battery box was fabricated with the motor mount box, with the battery mounting vertically, as far forward as possible.  The box rear plate has soft foam, allowing for various batteries and pushing them fully forward.  The battery will be angled in from a top door mounted a bit aft of the box, behind the top cylinder engine vent outlet in the fuse.  The tail servos are also in the front bay, contributing to ballast weight.  The dummy radial will be made from acquired Williams Brothers cylinders, where I located enough on Ebay, along with a few I already have, to have enough for 9 half-cylinders.  A Rimfire outrunner was modified by replacing the shaft with a GWS shaft, threaded even further than stock with a die, to allow for mounting the unusual spinner on this subject.  Much of the frontal area will be inset planked, before 1/32" sheeting the model.  The front former will require being cut away to the stringers, to create the scale thin edge opening, as well as needing the inset planking for reinforcing around the cutouts for the scale engine vents in the fuselage.

http://www.airteamimages.com/pics/114/114601_800.jpg
Bristol 72 Racer 30" span (1/10 scale)
Attached files Thumbnail(s):
Bristol 72 Racer 30" span (1/10 scale)
Bristol 72 Racer 30" span (1/10 scale)
Bristol 72 Racer 30" span (1/10 scale)
Bristol 72 Racer 30" span (1/10 scale)
Bristol 72 Racer 30" span (1/10 scale)
Bristol 72 Racer 30" span (1/10 scale)
« Last Edit: February 06, 2017, 01:59:35 AM by Bill G » Logged
Konrad
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« Reply #1 on: February 06, 2017, 10:47:35 AM »

Now that is an ugly airplane! Oh, and the prop is spinning the wrong way! Roll Eyes

Is the output gear metal in those servos? looks like the landing loads will go through the servo output gear into the case then the servo mount. It looks like you are supporting the case with those block.

The way I land I'd need a bit more structure. I'd look at adding some plywood to the bulkhead that supports the servos. Use the plywood to tie the servo mounts to the keels (top and side).

Is Williams Brothers out of production again?
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« Reply #2 on: February 06, 2017, 04:37:27 PM »

Didn't notice the props until you mentioned it.  The Bristol Bulldog with the Jupiter radial also has CW (viewed from front) props.  The servos are metal shafted, not sure about the gears, although there is no servo gear load when the upper shafts are aligned straight, in the deployed position.  Again the photo with the legs not perfectly aligned straight is just a mock-up. The servo mounting plate gussets are fairly well aligned with the direction of the load.  The gussets are also double layer laminated for bi-directional grain strength (seen in 4th photo), providing 3/16" of gluing area to the 3/32" fuse bulkhead, which was selected from a hard grade of balsa which is probably almost as strong as 1/16" ply.  I'm particular about using different balsa grades for various apps. The failure point would probably be the gussets tearing away from the plate, which may not be a bad thing.  I thought about adding more attachment area with corner gusset stringers at the base of the gussets.  I'm not sure if WB is out of production again or not.  The parts do seem to be more difficult to come by though, with Tower probably not stocking as much as they did in the past.  I should buy more cylinders on Ebay, as they're not terribly expensive.  
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Konrad
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« Reply #3 on: February 06, 2017, 08:18:19 PM »

I see where you are trying to keep the load off the servo gear train. I've never had much luck with balsa as landing gear load bearing beams. Have you thought of adding servo blocks to the bottom side of the servo outboard. I'm assuming the servo will want to rock on landing.
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Bill G
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« Reply #4 on: February 07, 2017, 01:31:57 AM »

I see where you are trying to keep the load off the servo gear train. I've never had much luck with balsa as landing gear load bearing beams. Have you thought of adding servo blocks to the bottom side of the servo outboard. I'm assuming the servo will want to rock on landing.
If you look at it from the rocking perspective, the servo body would probably want to tear out the roughly 1/8" thick perimeter of balsa at the base of the servo.  There's not that much leverage to cause that to happen.  The servos protrude through cutouts in the fuse formers, which were necessary to align the servo horn with the struts. The entire nose will be 3/32" inset planked before a final full fuse 1/32" sheeting, which will make it unlikely that the perimeter of the cutout would break outward.  There's always the opportunity for a bit of CF hair laminate also, for areas like that.  I think it's difficult to examine the stresses/loads on this setup from photos.  It's one of those things you really need to have in front of you, to get the full picture.  For example, it took some time to work out the exact lengths of the struts (with a bit of adjustment) as well as mounting the servos with offset angles to the fuse former, in both directions.  That was necessary to align with the sweep path of the struts.  There's more to this than meets the eye.
« Last Edit: February 07, 2017, 01:44:35 AM by Bill G » Logged
Konrad
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« Reply #5 on: February 07, 2017, 10:52:40 AM »

There's more to this than meets the eye.
So true! That is why I often model geometric issues in foam or cardboard before cutting balsa. Exotic materials (carbon) is another option.
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« Reply #6 on: February 07, 2017, 11:31:29 PM »

There's more to this than meets the eye.
So true! That is why I often model geometric issues in foam or cardboard before cutting balsa. Exotic materials (carbon) is another option.
Absolutely!  Look at the transparent paper trace of the landing gear assembly, in the first 2 photos.  I probably had a good 50 hours in planning, before starting this project.  The paper gear trace swings using a pin, at the rotation center.  Crude, but it works.  The same diagram was used to determine the strut swing path, so that the struts would both swing inside the large wing farings without hitting, as well as being able to retract the gear with 180 degrees of servo travel.  I had one small miss, that turned out to not be a problem.  The pivot bushings on the lower fuse formers should be axially aligned, as well as being on parallel mounting plates.  Being only a few degrees off from ideal, there's enough clearance between the bushings and the ply mounting plates to make up the difference. 

Started working on the spinner, which I'll have photos of soon.  It's reminding me of building the Manzano/Peter Rake Bristol M1c spinner, which I made with a removable backing plate, so that the prop cutouts would not require being enlarged for prop servicing.  They got my fiberglass molded back up spinner and had Keith Sparks make a mold from it, so the kit now comes with a vacuum molded spinner.
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« Reply #7 on: February 08, 2017, 03:21:04 AM »

Mostly finished with the spinner now.  The tapered cone was made by thin CA gluing together two identical parts cut from thin clear plastic sheet, with overlapping seams, using an 88 cent Wal Mart oil funnel as a form. The seams are opposed 180 degrees, keeping the spinner in balance. All the plastic parts were scuffed before gluing, as some plastics do not glue well without roughing up. The clear backing plate was cut out from a CD disc cover, where the router bit cut holes provide cooling air for the motor/ESC. The holes were cleaned up, while also making sure to keep the disc in balance, after cutting them out. The plate will remain clear for semi-scale appearance, as the full scale spoked spinner obviously had no backing plate. The holes also lightened the part, as the backing plate was initially a whopping 10.5 grams. The entire spinner (less spokes) weighs 12.4 grams.

The center tube (white plastic tubing) will glue over the short white plastic bushing that is glued onto the front face of the backing plate. The bushing was sized to fit over the prop shaft with minimal clearance. The small nylon flanged bushing glued in the front of the white tubing has a small clear plastic disc behind the flange. The disc will ensure that the nylon coated silver beading wire spokes do not build up and pop over the flange, while spoking. The outer surface of the nylon flange bushing was also roughed up, as nylon does not glue well and I wouldn't want the spoke tension popping it out, when the spinner is not installed on the motor shaft. The spokes angle slightly rearward, toward the center hub.

When finished and installed, there are ample threads on the motor shaft to allow for a nylon locking nut. I may also drill a small hole near the center of the backing plate and glue in an indexing dowel pin, that will fit into a hole drilled into the flange bushing that is pressed into the front of the prop. The brown reinforcing ring that is glued into the front opening of the spinner was cut away from the bottom of a Rustoleum spray bomb cap. It was a mm or so larger than the ID of the opening, which was intended so that it would glue just behind the opening. Now to mark off and drill 18 small holes through the front of the spinner cone that are spaced at 22.5 degrees apart, for spoking. Balance wise, a few drops of glue added inside the cone were enough to balance the spinner. Interestingly, they were added along the seam which seemed to not have quite as much glue as the seam on the other side, which is exactly what would be expected. Final balancing can be a different story, as balance weight may need to be placed toward the front or rear of the spinner, which is what I had to do when balancing the Rake M1c spinner. 
Attached files Thumbnail(s):
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
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« Reply #8 on: February 08, 2017, 11:06:22 PM »

Correction to the last post, there are 16 spokes, spaced 22.5 degrees apart. 
The spinner is now spoked, rebalanced, and ran up surprisingly smooth. For the outer surface, I will attempt to spray a light coat of brown from a distance, over a base coat of silver. As far as I know, the spinner was made from sheet metal which had a light rust coating, before they painted it silver, which reportedly caused it to scatter due to the added weight.

The spoking was wound using two lengths of nylon coated silver beading wire, started 180 degrees apart. This was done to keep the rim centered and concentric, as it is somewhat flexible. A few inches of wire length was added to the calculated length, as you don't want to run out. Photo #1 shows one of the two start points, where the end of each wire is first inserted through a hole and glued inside the rim. The wires are then ran through the adjacent holes and the spoking begins. Photo #2 shows where the wire loops around the outer surface of the spinner, and back through the next hole. These "loops" were glued down to the outer surface of the spinner as each spoke was wound, to keep the wire from slacking. The key is to determine how tight to pull them, while gluing. What worked was to pull the first spokes so that the rim bowed slightly inward. The wires will still seem a bit sloppy, but as you continue to spoke and pull the spokes tight, they will both pull the rim outward where the previous spokes were ran, and also tighten them. Done properly, all the spokes will be tight and the rim will be concentric. Photo # 3 shows a termination, where the wire ends are glued to the outer surface of the spinner. They are also looped back through the start point holes and cut leaving about 10mm of length, which was glued to the inside of the rim.
Attached files Thumbnail(s):
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
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« Reply #9 on: February 13, 2017, 11:28:16 PM »

Finally connected the landing gear struts to the servos and tested the gear. The bottom (extended) end points are now set, where the top points will be adjusted as the wing panels are test fitted. Note the white plastic tubing wing plug-in tubes installed in the video link below.

Got another tedious task out of the way, creating the white "Bristol" graphics. I tweaked a traced print of the artwork that was on the plan, using a photo of the actual artwork as a reference. Enlarging the artwork from the available internet photo lost too much resolution to be useful. The tweaked tracing was then copied, for the second decal. Initially I planned to transfer these tracings to white decal material and then cut away from the decal material, which would be even more tedious and unnecessary. The paper decals were cut out with an exacto, and then sprayed with several coats of white enamel paint. The small portion between the "B" and the "r" will be cut away and joined with a small strip of clear tape, as it is now the only thing holding the decals together.

Retractable gear video: https://www.youtube.com/watch?v=35xn45eES2Y
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Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
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« Reply #10 on: February 15, 2017, 04:34:28 AM »

Started working on the fuselage infills around the landing gear arms. Almost got ahead of myself, as the 4 bottom cylinders have vents will exit the fuse in that area. I'll have to make a small mold to make the vent farings, using thin plastic sheet. The spinner is now painted to simulate surface rusted sheet metal. The only model I've found of this subject has the spinner painted a bit more brown that I cared for, so it got a light dusting of brown paint over a base of silver. http://www.aircraftresourcecenter.com/Gal11/10001-10100/gal10088-Racer-Stern/00.shtm
For the vote of confidence, I ran the painted spinner up on the motor with no prop, holding the motor mount by hand. Felt smooth at at a higher rpm that it should see, with the prop mounted.
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Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
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« Reply #11 on: February 15, 2017, 11:59:32 PM »

One for Konrad in the first pic.  Don't want to miss any opportunity to further strengthen the retract mounts as much as possible.  It's difficult to see in the photo, but the glue joint added (see pencil pointer) between the servo mount and the brace that runs across the fuse, is basically in the direction of loading that the strut puts on the servo.  This joint is in the perfect location to further prevent the possibility of the servo mounts tearing away from the fuse former.

Getting ready to start on the wing panels of tail feathers, for something different. The fill panels around the LG legs are mostly finished, although I'll probably delay installing last panels which cover the servos, as they block access to the inner fuse, if I need to get in there. One of these is shown tacked in place with tape, in the second photo below. Four of the individual cylinder cooling vent outlets will be installed in this area, where two of them will be located in the area of the two retract servos. The recessed vent farings were heat pulled from sheet plastic, using a sculpted balsa mold. The first two photos below show the approximate area where they will fit. The vent farings will obviously require notches, to allow for the gear legs to fit into them.

The red painted paper wheel covers are now glued to the wheels. I'd like to try painting the "PALMER CORD AERO TYRE" text on the wheels with white paint, although it would probably just make a mess of it. Could always experiment first using other "tyres". I printed a mirror copy of the right panel using the advanced CAD program MS Paint, for the left wing. I like to build both wing panels at the same time, which the plan didn't facilitate well. There were also features that I marked on the right wing panel, which could be traced onto the left panel sheet, by laying it over the right panel. The wing rib count will be changed per scale with more ribs, and will have a CF tube running through the ribs, which will plug into the fuse.
Attached files Thumbnail(s):
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
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Konrad
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« Reply #12 on: February 16, 2017, 09:34:49 AM »

To my eye, she is looking much better than I had first thought. I had imagined a huge cavity (gear doors) in the fuse. I know understand this is not the case.
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« Reply #13 on: February 17, 2017, 01:18:02 AM »

I spent a good few hours thinking about how I would deal with that huge cavity!  Turned out it wasn't as difficult as I expected, but fitting the engine vents in that area will still be a task. 
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« Reply #14 on: February 22, 2017, 12:41:00 AM »

Slowly moving ahead on the Bristol, due to lack of motivation, especially 1/32" fuse sheeting. The first photo shows 1/8" balsa stringer sections, used to keep servo harnessing away from the landing gear retract arms. The second photo shows the rudder, with the tail cone framing complete. There's also a small pad for the control horn (gotta think ahead about those small details). The third photo shows balsa blocks glued in place where the tail pushrods exit. The one that's sticking out a bit high was decked down smooth with the stringer. The 1/32" sheeting is a bit fragile to cut pushrod exit holes into, without the reinforcement underneath. The sheeting is now underway, with the total amount of scrap shown in the fourth photo. I may "strip plank" sheet across several bays at a time, for the remaining front portion of the fuse, while sheeting a single bay at a time is the most efficient, in terms of balsa usage. Note the small pieces of balsa used in the model, with Guillow's printing on them. No wood is wasted.

Most of the wing parts are cut, where the ribs will need to be notched for the stringers, LE, and drilled for a CF rod main spar. Parts remaining to be cut are the aileron headers and short rib sections at the very front of the wing, located between each main rib, similar to the Bristol M1c wing. It probably wouldn't look right without them, and they form a better leading edge profile, so I decided to add them.

Built the tail feathers, with cap strips added and sculpted. I'd rather not have the added weight of the cap strips, but I decided having tail feathers without form would not look right on this model. Doing a preliminary balance check with a liberal amount of weight added to the tail, the gear forward design should accommodate the tail weight and fuse sheeting, with little to no ballast required with the 3s-1300 lipo. Of course I'd prefer to shave a bit of weight on the battery if possible, but it likely may not happen. Looking at photos, the tailskid seems to resemble an ancient horn with a golf club driver head at the end. The tailskid was made from spring steel, with balsa glued on, sculpted, and then wrapped with carbon fiber and CA, then re-sanded. A few coats of sanded fill primer should clean it up. The attachment will use a screw, threaded into a CA hardened hole in the rudder base.

The drawing was used only for the perimeter outline, which was modified as the horizontal stab tips were too flat, and the rudder shape a bit off. A bit of area was added, when correcting the horizontal stab shape. The mating surfaces to the fuse were marked on the drawing, as they have be pretty much dead on, or the parts would require a good bit of padding for proper alignment. The rudder construction gets even more interesting, as the rudder has to properly mate up to the top and bottom vertical stabilizer parts, which will be attached to the fuse. They were sized to account for the added 1/32" sheeting, yet to be added on the fuse. The fuselage center point also was determined for the rear cone and marked on the rudder. This cone essentially amounts to the rear tip of the fuselage chopped off, and attached to the rudder. The balsa disc in the photo will be cut into halves (accounting for rudder frame thickness) and glued to the rudder frame. The cone will be formed using 1/32" balsa sheet, glued over the disk and framing stringers, seen added in the second photo. The stabilizer hingeline frames will be notched roughly 3/4" from the fuse mounting points, with CF spars glued in place. The spars will also be glued to the rear fuselage former disc, to reinforce the stabilizer attachments.
Attached files Thumbnail(s):
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
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« Reply #15 on: February 22, 2017, 10:53:37 AM »

Does the fuselage fairing on the rudder move with the rudder (ALA the Ryan STA)?

I noticed some grain support strips on the fuselage formers. Is this more effective (strength to weight) than making the bulk heads out of balsa plywood?

I've often made my 1/16 formers out of two laminations of 1/32 balsa biased at 90°.  There is a weight penalty with the laminating glue. But I've found that I can thin the bulkhead (make the center hole much bigger) and in the end actually have a lighter and stronger former.
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« Reply #16 on: February 24, 2017, 02:10:02 AM »

The rudder has a cone that is part of it.  It's basically as if the rudder was built onto  The cone will require some clearance between the fuselage, for adequate rudder deflection.  The small gussets at the horizontal center of the cone base were added, as the cone will require notching to fit over the elevator joiner bar, when turning the rudder.  

The short, curved support strips at the perimeter of the bulkhead are there since the wing bracing cables will run through that area, requiring reinforcement behind the 1/32" sheeting.  The 1/16" stringer laminates are there to reinforce the weak areas where the grain does not run favorably, partly for added strength during the construction phase.  Once fully assembled, they are not as critical, but during construction the weak cross grain areas will break fairly easily if a former is bumped, before the stringers are added.  You could probably end up with a comparable former using laminates of 1/32", if the glue was used efficiently.  One advantage of 3/32" is that it's wide enough to allow for seaming sheeting on the formers, if desired.  I've done that with 1/16" (actually just did on my last build) but it's quite a pain. Normally I wouldn't care to use formers thicker than 1/16" on a model this size.  In this case, they were used due to the unusually wide fuselage diameter.

Just caught myself almost making a fatal error!  I forgot to install the retract servo horn screws.  They were left off, in case I needed to reposition them.  Fortunately there's enough room that I can get in there with a phillips head driver bit, and loctite on the screws.  Usually items like these are added to the checklist, so they don't get lost by the wayside.

The wing kit is now pre-fabricated as much as possible, so I'll see how well it goes together soon.  Slowly to continue with fuse sheeting also.  
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« Reply #17 on: February 24, 2017, 10:53:23 AM »

Just caught myself almost making a fatal error!  I forgot to install the retract servo horn screws.  They were left off, in case I needed to reposition them.  Fortunately there's enough room that I can get in there with a phillips head driver bit, and loctite on the screws.  Usually items like these are added to the checklist, so they don't get lost by the wayside.
You're not alone in this.  Undecided I just flew a series of maiden and test flights on a high performance 2 meter glider (900 watts) with the rear servo screws left out.  Shocked Luckily the spline to horn fit was tight. BTW the brand of servo was KST http://alofthobbies.com/kst-x08-servo-2-8kg-38-oz-in-09-sec-8-grams.html I'm really liking these for my mid-level planes. If you land like I do you should check for availability of replacement gears. I'm finding that with the cost of servos being so low, these days, that service parts often aren't available. In the larger picture it is more economical to just replace the servo.
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« Reply #18 on: March 02, 2017, 02:05:29 AM »

Yep, these were pretty tight too, but you never know.  Those look like quite a servo, for 8 grams.

The dummy radial Bristol Jupiter is now constructed, using Williams Brothers cylinders and a thin plastic cup, with an inner reinforcement ring cut away, from an already cut away portion of an EDF intake lip. Putting scrap to good use. The front fuse former will be cut away soon, creating a thin edge at the fuse opening for the radial engine to fit into. The Dremel cutoff wheel trimmed portions at the top of the cylinders (3rd photo) will not show, as there is sheet metal ducting encasing the cylinder heads and valve rockers. The inner ring faring, where the cylinders mount, has cutouts for scale valve pushrods. The actual engine crankcase would be inside of this sheet metal faring. After cutting away the thin plastic cup faring, you still have 6oz of useful cup, albeit flimsy, for other applications.  The fuse is now over half sheeted.  I may start on the wing, as slowly adding precision fit sheet sections gets old after a while.  Took a sheeting break and fitted the battery door with spring slide latch, to get another part out of the way.
Attached files Thumbnail(s):
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
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« Reply #19 on: March 02, 2017, 09:43:46 AM »

Wow, your hand gives scale to just how large the fuselage is on this 30" model!
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« Reply #20 on: March 03, 2017, 07:58:40 AM »

Mostly finished with the spinner now.  The tapered cone was made by thin CA gluing together two identical parts cut from thin clear plastic sheet, with overlapping seams, using an 88 cent Wal Mart oil funnel as a form. The seams are opposed 180 degrees, keeping the spinner in balance. All the plastic parts were scuffed before gluing, as some plastics do not glue well without roughing up. The clear backing plate was cut out from a CD disc cover, where the router bit cut holes provide cooling air for the motor/ESC. The holes were cleaned up, while also making sure to keep the disc in balance, after cutting them out. The plate will remain clear for semi-scale appearance, as the full scale spoked spinner obviously had no backing plate. The holes also lightened the part, as the backing plate was initially a whopping 10.5 grams. The entire spinner (less spokes) weighs 12.4 grams. 

That's a pretty good trick, thanks for sharing that.  I can imagine using that myself.

Surely an interesting aircraft.  It's nice to see some off the beaten path AC once in a while.

Best of luck with her,
Bulldogger
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Bill G
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« Reply #21 on: March 06, 2017, 12:53:41 AM »

Thanks for the comments Konrad and Bulldogger. After stringing the spinner by starting from opposite sides with two lengths of beading wire, versus using one single wire length, I'd like to try building more wheels using the method.  Much easier than in the past, using a single length of beading wire.
This fuse is massive.  It's even larger than it appears in the previous photo, as my hand is at the front of the photo.  OTOH it's over 7" diameter at the widest point.  The engine is now temporarily "stuffed" in place for the photo below. Finally got around to sanding the fuse, where the 1/32" sheeting provided enough latitude to fill the low area behind the carbon fiber ring at the nose opening, after decking down. The fuse opening lip will need to be cleaned up, now that the front former has been cut away. The upper landing gear fill plates still need to be glued in place, in the fuselage.

The battery/rec access door is also fitted, with the hinge slot cut in the fuse also, angling downward into where there is some mass of balsa, since a scale fuse vent is located in the same area. The door and the fuse opening will be notched to minimize the hinge gap, with the hinge pin aligning with the top edge of the fuse and door opening, once fitted in place. I had a piece of red painted aluminum tubing which worked well for the spring assisted slide latch, so may as well put it to good use.

I finally cleared the old Cole tanker desk today, and started on the wing construction. It's the cleanest the build "desk" had been in several years.  The old desktop is made from a slightly rubbery plastic material, which allows for pins to be pressed into it, using it as a building board surface.
Attached files Thumbnail(s):
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
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« Reply #22 on: March 08, 2017, 09:05:14 PM »

Built the wing panels and removed them from the board.  The inner rib (actually 1/2 rib) on each panel was left loose, and will not be glued to the main spar (CF rod) and trailing edge, until the wing panels are fitted in place. It would have been torture to work out their exact positions ahead of time, when they will be buried underneath the thin balsa sheet wing walks. Much of the top inner wing will also be buried underneath the large farings that house the wheels, when retracted. The wing panel CF rods were sized to set the correct span of the wing panels, with the last (outer) rib just glued over the rod, with the end of each rod flush with the rib outer surface. Since the plug-in wing rods do not quite meet in the exact center of the fuselage, this several mm discrepancy was taken into account, making specific right and left wing rods. The ailerons will be constructed as the shortened version, when Bristol shortened them to about 40% of their initial length. The wing panels will also have functional cable bracing.

The hand cut parts fit well, especially considering the precision required for the wingtip ribs and the wingtips to fit together well.  Note the small lengths of balsa stringer laminated to the wingtip ribs, along the notches cut into the front of the ribs, which were laminated to the ribs before assembling the wings.  The wingtips would have otherwise likely broken off the small amount of balsa remaining around the notches cut into the ribs, when installing the wingtips into the notches.  The short ribs at the LE, which are located between each main rib, are installed after stringing the wing panels.  I started installing a few in the photos below, which fit well.  There's ample room to install them at an angle, and then position them in place for gluing.  The short ribs (1 per panel) at the tips had to be loosely fitted over the wingtips, before stringing.
Attached files Thumbnail(s):
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
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« Reply #23 on: March 10, 2017, 09:55:54 PM »

Test fitted the wing panels. The wheel bays will now need to be fabricated into the wing panels, which will require some cutting into the inner ribs. I'm more optimistic about this subject, now that I can see the actual wing area. The optimistic way to look at it is a model with a large fuselage, versus a model with small wings, granted that the AUW can be kept reasonable.

Installed the remaining fuselage filler plates, which fit between the "wishbone" gear legs.  The bottom four cylinder vents are also now installed in the fuselage.  They were easier than I expected to fit in place, and did the full installation without cycling the gear legs.  There are small notches cut into the vent farings to accommodate the gear legs, when retracted.
Attached files Thumbnail(s):
Re: Bristol 72 Racer 30" span (1/10 scale)
Re: Bristol 72 Racer 30" span (1/10 scale)
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« Reply #24 on: March 11, 2017, 01:39:52 PM »

 "wishbone" gear legs

That is so descriptive - love it!
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Cut it twice and it's still too short!
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