JayW

Wow!!! Great 3D print parts. I know what goes into parts like that. Alot of research on the config, and alot of digital modeling time. How is it you are going so quickly? Takes me forever.

Golly Moses Chuck - you can be very proud of that seat. I mean really.

On Monday I expect to get two Malcolm hood canopies from Shapeways. A highly anticipated package I can tell you. Meanwhile - I learned enough from the Malcolm hood test to proceed with "production part" fuselage skin panels, with the Malcolm hood panel additions and roller bars incorporated into the parts. Here are the 3D printed parts: The P-51 expert will recognize the oval hole - the flare gun port. The angled edge is common to the firewall, and the other (aft) edge) is coincident with the station 146 frame, just like the real thing. Why not? A close-up of the roller bar: You can see some slight imperfections on the printed surface near the oval hole - no prob, remember this fuselage will be skinned in aluminum. There are groups of three "discs". The center disk is actually a large head for an attachment bolt, and of course the outer discs are the rollers. They scale to .875 outer diameter - it is an educated guess on my part. Or at 1/18 scale - 0.049 inch diameter. What you see is about half of the bar's length. The other half (aft half) will be either a separate part on its own, or incorporated into the aft skin panel. And I wasted little time bonding the skin panels to the framework secured on the jig: Put the windshield on there just to impress y'all. Of course these fuselage side halves can be removed from the jig - and now they have a bit of robustness so I can work on them: This was a thrill, I can tell you. A nice step towards a completed forward fuselage one day not too long from now. And a nice step forward to validate the idea of 3D printing an entire airframe. It was about this time that I noticed something disturbing. Do you see those double frames with the little intercostals in between them? Those comprise the station 104 frame, and that is where the wing front spar bolts to the fuselage at the lower longeron. Well, the LH frame is similar to but also different from the RH frame. The LH frame is designed to interface with the control pedestal mostly, while the RH frame is designed to interface with the spare lamp stowage container, and radio equipment. So their profiles are different. So what did I notice - in an act of amazing stupidity a couple weeks ago I attached the LH frame to the RH side of the jig, and the RH frame to the LH side of the jig. This after paying so much attention to each frame to make sure they are accurate. After putting out my hair fire, I settled in to fix-it mode. I have some ideas, and I think I can make it ok. Not perfect but OK. What I cannot do is disassemble it - the epoxy and CA are too strong. In the coming days, I will be working with the Shapeways Malcolm hoods soon as they arrive, and populating the side panels with cockpit stuff. Lots of stuff. I will start with the control pedestal on the LH side I think, and the nearby bomb release quadrant and support. It is this stuff that now must interface with a wrongly shaped sta 104 frame. Gonna require a magic wand. Then, I think, I will go to the RH side and figure out how to modify that frame to interface with what it is supposed to. Take care, this modeler is a little steamed right now. And motivated.

I have a question for the B-17 experts. Many of us are watching "Masters of the Air", and the show often depicts the top turret and ball turret rotating at an astonishing rate as the gunner tries to lead a passing fighter at high closing speed. I have to believe turret rotation was done manually somehow, without power assist, which would mean the show is inaccurate in that respect. Can anyone describe the mechanism for turning the turret?

What I think about every time I visit this build. The size would be just untenable - 69 inch by 50 inch by my calculations. It would half fill my office! It could however (Pat - listen up) be done in sections or pods. My 1/18 P-38 is sorta that way - tail booms, outer wings, and center section. Only human life span would stop you.

Yeah that's it Antonio. I think I saw that same picture in one of the pilot operating manuals or something. That looks like the handle of the light. But I wonder if 8th AF aircraft in the field had it....

Calling all P-51 experts - so many of you. Who can tell me more about this item in the P-51B/C cockpit (LH side by the seat): AN3089 signal light with several filters. And a mounting or stowage clip "A-2542". I do not believe I have ever seen these items before. The government spec for the light: Looks like some hand held item that is stored along the sidewall of the fuselage in the cockpit. Anybody have any pictures they could share? I ran out of patience searching the web.

Oh boy Craig - gettin' out the popcorn.

You know of course Peter that I refer to your 70+ page build thread all the time to see how you did it. You used your "mad skills" at scratch building for most all of your build. For this one, I am concentrating on 3D printing (cheating!!), unapologetically. Your Lope's Hope is IMO the world-wide benchmark for a model P-51. Thanks for looking in.

Like this Guy: Last I printed some parts, I oriented one part vertically with forward edge up, and one with aft edge up. The fwd edge up version worked best, because the supports had a more robust edge to attach to and left less local deformities (my aft edge has a stiffening bead, whereas the fwd edge doesn't). So nothing going on between layers - the length of the parts are good. Honestly I am baffled. One edge is supported, and one is just in mid air supported only by previous layers. But both appear to have shrunk in height by about the same amount. 3D printing does involve a bit of growing or shrinking, but not this much. Tilting the part is an option, but (a big but) with the bulbous shape this canopy has, any tilt will increase the angle of one side of the bulge while decreasing angle of the other side. In 3D printing, the more vertical a layer stack is, the better. Anything off vertical and unsupported leaves the next layer with some unsupported overhang, and the potential for deformity. So to minimize overhang angles, such that I would not need to place supports inside the edges (and marr the surface), I oriented the parts as you see. Thanks for your interest! I now wonder how Shapeways plans on orienting the part and the supports..... I told them I don't want supports inside the edges.

I would like to report out on my analysis of the .03 height mismatch I discovered on my Malcolm Hood test parts, FYI. This: First, I looked for an error in the Rhino modeling. It has been a few months since I created the Rhino hood model, and I had two versions of it, where I hoped to find the height error. Nothing. All is as it should be. So next I needed to do some careful measuring of the several parts I have printed up over the last few months. To do that exactly, I made a simple little jig to place the part in securely such that its height can be measured with calipers, and compare to the digital model. Extracting dimensions from a Rhino model is easy-peasy. Measuring the part, not as easy. Like this: Note that it controls the width of the part. Important, as the width will affect the height. And I found that with remarkable consistency, each part was short (the height dimension) by about .03 inch. Forward and aft edges. Some of my parts were made from the Nova3D clear resin, and some with the Resione G217 clear resin. Didn't matter - about the same shrinkage. Length (fore/aft) was about right, so no shrinkage or stretch in that direction. But shrinkage in height. Something is going on in the printing process which is causing that shrinkage - but I am baffled what it might be. Wish I had my old hood part made from gray resin, to check it too, but alas I threw it away months ago. Were I to use one of my own parts, assuming anything more I print will have the same anomaly, I would just make adjustments in the side guides, or rails to account for it. I shimmed the test parts to solve it - my real fix would be a bit more sophisticated than that. But I want a Shapeways part, and I do not know if the Shapeways part will have the same shrinkage. Probably not. So what I am going to do is go ahead and order the Shapeways part made from my unaltered Rhino model of the hood, and when I get it back, I will do the same measuring exercise with the same little jig. And depending on what height measurements I get, I will make whatever alterations necessary in Rhino for the side guides, and print version 3 of them. Hopefully the Shapeways part will be perfect and I will not have to do any re-design at all. Not optimum, but I don't know what else to do. Thanks for putting up with this tedious exercise. Next post I hope to report on a Shapeways part.

Oh my Pat - what a tiger you have by the tail. And I can relate to so much what you are going through, as we have very similar projects going at the same time. And, I see we are both employing 3D printed bucks - one for burnishing transparencies (mine) and one for burnishing aluminum sheet (yours). I love my printing machine. The possibilities seem endless.

Yeah what Chuck and Bee said. Some real wizardry here Peter. And when you show it eventually, prepare to take home some gold. Wow.

Salty indeed. But I compare that to the hours upon hours I have spent on my previous efforts. And it is beginning to appear that they (Shapeways) have the magic clear resin - Accura 60 - that will give me the clarity and exactness I need, and am not quite getting from the two resins I have used. And that stuff is by all accounts prohibitively expensive to procure oneself except perhaps for mass production purposes. It's worth it to me if I can get a real good canopy. This project is one of those where cost is a secondary consideration, if that. I wish. No, its placed right. If you think about it, the forward end has to be considerably smaller than the aft end. The forward end, its outside edge (not inside), must take on the contour of the windshield, even a bit inside it. The aft end, its inside edge (not outside), has to be proud of the fuselage contour so that it can slide aft. The Malcolm hood has no hooked cam track to lift it out of the hole when opening, or plopping it back in the hole when closing, so the back end must clear the fuselage at all times. It just simply slides fore and aft. The Corsair BTW, the later ones after the birdcage versions, has just such a track shape, where the malcolm-style canopy lifts out of the hole to clear the fuselage when opening. Much more complicated than the Malcolm hood arrangement. Another dead giveaway is that the stiffening bead on the aft end is much more pronounced than at the front end. And the picture may be giving the wrong indication - the high point for my hood is indeed about in the middle. Just sayin'. Lots more to come with the Malcolm hood stuff.

I have been developing the fuselage side panels in Rhino, including the Malcolm hood additions with the roller bar. In so doing, it became more and more apparent to me that my rollers, and the width of the bar, appear too small. I have been struggling to figure out what diameter those rollers are. First, I am not aware of a P-51B/C Malcolm hooded model in any scale that actually has the rollers. Second, I am not aware of any technical data out there that would tell me. So all I can do is study all the pictures I have, like this (notice the rollers along the sides of the fuselage): Comparing roller size to other items in there, where I have an idea what their dimensions are, and I first came up with a roller diameter of .75 inch. Pretty small. Well, too small, it was beginning to be apparent. So I did some more measuring, and revised that diameter to .875 inch. I played around with 1.0 inch rollers in Rhino, and things were just not integrating well. So I am convinced a 1.0 inch roller is too large. Hence 7/8 (.875). Who knows? Being a British field mod, they may be a metric size..... Anyway, some of you might think I am splitting hairs, and you might be right. Here I spent a couple days changing everything affected by the larger rollers and roller bar: It looks better to me..... So it occurred to me that it might be wishful thinking to print up a couple of side panels either with the roller bar incorporated into them, or locating provisions for the bar, print up the Malcolm hood along with its side guides, and have it all fit perfectly to the already completed windshield. As exacting as parts can be when digitally defined and 3D printed, alot parts are in play and tolerances are going to add up. I need a good match-up. So I decided to make some test side panels, and do rev "A" of the side guides for the hood (I did some months ago but new larger ones required for the larger rollers): Here are the side guides bonded to one of my Malcolm hoods (that I will not be using, but now makes a good test part): Pretty nice looking for a test part.... Now to get those test side panels onto the jig and longerons: These are simplified test panels, so I cannot permanently bond them. Just taped. My finished windshield is on there too - taped in place. A couple things I wanted the test to tell me: 1. Will the hood fit onto and slide on the rollers? 2. Will the rollers retain the side guides such that the hood will not just fall off? 3. Will the hood fit to the windshield properly when closed? OK numbers 1 and 2 - When Rhino modeling the details, I took a guess how much clearance I needed between the track surfaces on the side guides, and the rollers. Too tight and the side guides will not fit onto the rollers, or if it does the hood might not be able to be slide fore and aft. Too loose and the hood will fall off; it is too flexible to just stay in place on its own. Here it is snapped onto the rollers: It wouldn't move! So I carefully pried it off and gave edges of the rollers and the track some light sanding, and tried again. It grudgingly was able to slide some, but the more I moved it, the easier it got. So victory. Now for the uber important number 3 - fit-up to the windshield. Boy did I get a surprise: A full .03 inch too low! WTF?? Also too low at its aft end: It is dragging on the top of the station 146 frame, where there should be about .03 inch clearance. Normal tolerances are not responsible for that. Something is wrong. What is it?? Why, why, why?? It's supposed to be perfect. So I began measuring everything. Where is the error? Is the windshield too tall? Nope, its right on. Are the side panels mislocated? Nope - they are fine. Is the hood too short? YES! Too short. By about .03 inch. There is the problem. But why? For some reason the part doesn't match the Rhino model. Did it shrink when being printed? Don't know yet. Fortunately, I have another couple of hood transparencies that I am not going to use, and I had printed a second set of side guides incase I ruined one. So I shimmed between the side guides and the transparency with .02 plastic, and retested with a now slightly taller Malcolm hood. Got great results: Wow!! What potential. Am I glad I did this test. Now I have to figure out what is what with the Malcolm hood transparency. I will do some critical measurements on all remaining parts (I have 5 total, none of which are clear enough for prime time) and see if that dimensional error is consistent. Now I am fixated on the Malcolm hood. I now have two 3D printed burnishing surfaces - one male and one female: They were not hard to design and print. About half a day's work. The transparency fits nicely into or over either, and I can sand and burnish and polish away. Next step is to understand how I got that .03 mismatch and make corrections, whatever they may be. Then, I will have Shapeways do my next transparency, in Accura 60 resin. The Malcolm hood transparency is just too difficult for me. I have come close, but no cigar. The quote is about $45 for one, $72 for two. I'm going to do it, and hope that is what gets me over the finish line. When the parts come they will require sanding/burnishing/polishing with the new tools. In parallel with that activity, I will finish designing the forward side panels. Lots of interior items that will interface with them - some I will incorporate into the panels, some I will just incorporate locating features. To worry about - control pedestal, flare gun port, electrical boxes, throttle quadrant, and pulley wheel brackets. Fun times. Stay tuned please!

Full recovery Mike!

Yes I have. It will not be very long before I try it out.

That throttle pedestal - awesome. That took some CAD doing! And is it not amazing the detail a good 3D printer can print? May I ask about what diameter are the thumb switch posts? I have many to do in my Mustang cockpit, and I don't want to be snipping off pieces of wire for them (like I usually do) if they print up well.

Pat - as you probably know I am struggling with my own 3D printed transparencies. May I ask what resin you used for the nose glass? It looks wonderful. Wait! Never mind. I just saw your newer post.

Yeah OBG - this build is not the same so far. It is almost like a manufactured plastic kit where I make each part (3D printed with its own sprues), and then fit them together. There will be some more traditional scratch building though here and there. Sure is fun, trying to build up a forward fuselage very similarly to how an actual one is built up, even with a jig. But extremely time consuming digitally creating all these parts, and printing them. This week I intend to make a male and a female buck (3D printed from standard grey resin) shaped so that I can sand and buff the interior and exterior surfaces of the hood transparency much more effectively. That gray resin is at least as hard as plastic (the same stuff my other gray parts are made from). The clear resin seems a bit softer. Again, and I have been standing my ground on this - I have seen 3D printed transparencies that are good enough for me. I just have to have the right resin, and the right polishing technique. I think my resin is going to be OK And in parallel I am thinking of reaching out to Shapeways to see what it takes for them to make a couple for me. Maybe I get a pleasant surprise; maybe not. I have no confidence that a blown clear plastic part will have the accurate details I must have, like that forward lip that fits inside the slot on the windshield frame, and the interface with the heavy side tracks. So I will not be reaching out to any of our vacuform experts. Instead I am kind of committed to a 3D printed transparency. If I can pull this hood transparency off, my Malcolm hood mod is going to blow some people away. BTW, thinking some about its chain drive which is very visible nested inside the upper longerons - I do not think I will get away with scratching out all the links like I did for the Corsair's tail wheel door mechanism (if you will recall). Must come up with something....

Oh man! I have been using contact cement out of a can. Which is what Airscale uses as well. About how long does it take to set up? With the contact cement, depending on how thin the layer, you don't have much time to get the part in the right place - just a minute of less. And of course it goes on with a brush. Any downsides?

Exquisite skinning Peter. What adhesive do you use?

The forward fuselage framework is now the subject of my efforts. Four stub frames and four full frames have been Rhino designed, 3D printed, and fit onto the longerons in the jig. The full frames were interesting - at stations 168 and 184, they are located well behind the seat and armor plate, and interface with the radio/battery compartment, and the fuselage fuel tank. Freshly printed and cured: As can be seen, there are left hand and right hand parts, which connect at the crown. There is a slot provided for a centerline stringer that will be integral to my crown skin panel, when I get to it. And further populating the jig: The stub frames are bonded to the longerons now. The full frames are dry fitted only. They are fragile without the skin panels, so I will wait until the time when they have to be there. That is all the frames. Now for skin panels. Lots of interfaces to worry about - the aft window, cockpit items, and the trapezoidal shaped Malcolm hood skin addition for the roller bar: Yessir. I am very excited about the skin panels and the Malcolm hood mod. Looming though, like a dark cloud, is the Malcolm hood transparency. I have printed off five so far over several months, and I still await one that I will go with. Somehow I must buff out the cloudiness - it needs to be the most clear of all the transparencies. Maybe Shapeways.....

Guy - this is turning into one splendid model. Love the stencils! Wish I could get a bunch for a 1/18 P-51!

Last post, I was pretty heavy into the windshield and surround, and the IP, and the gunsight. This post I can show you some completed items (or nearly so). First, the gunsight needed to be completed and installed, while the window panes were still not there (more access). Here is that picture from the parts catalogue again: Man - what is up with those two mirrors? Reminds me of a reflecting telescope. Note the lower one is stabilized by a long thin bolt. Well I have faithfully represented all that, and after all that clap-trap was installed, then in went the window panes - here: Note I did not include the rear view mirror - this aircraft sported one of those British Spitfire-style exterior mirrors instead. Also not included is the manual ring sight. A bracket exists for storing that thing, so consider mine stored. The windows didn't fit quite as well as I expected, and the joints look a bit of a mess. But they are going to be OK. The big victory here was no contamination of the window surfaces with epoxy or CA. Always a big risk, and with the tons of elbow grease I have expended on them, I'm glad for that! The IP, as you can see, is now installed. Easiest IP I have ever done I think. So then I just had to cover those window joints, which meant some challenging aluminum skinning. The side panels were straight-forward. The three pieces directly below and to either side of the flat bullet-proof glass were tough little compound curved SOB's. But the most cantankerous was the one you see below - the member that separates the flat glass from the top glass: The already cut out part is a fail; my second (successful) try has been outlined on tape, ready for cutting. And here is the finished windshield: I am very pleased that nothing broke, the windows were not contaminated, and the rabbeted edges of the window panes worked slick, allowing the exterior strips to be pretty flush (not proud of contour). Wahoo!! The three removable access panels in front of the windshield will be skinned later after I do the firewall. That way I can match them up to the already complete engine cowl. On that last picture, notice the circumferential slot around the aft edge of the windshield frame, provided for by the overhanging exterior strip, and a flange on the frame. Normal production -B's had a narrower strip that didn't overhang aft, so the hinged greenhouse panels could drop in and bear against the inside flange. But part of the Malcolm Hood modification was to replace the production exterior strip with a wider one for the hood to seal against as it slides forward and closed. A check of this feature with one of my (many) Malcolm hoods shows that the fit-up is good: Getting a much clearer Malcolm hood still eludes me. The big problem is that I cannot put enough pressure on the detail while sanding and buffing. I think I will 3D print a couple of "bucks" of sorts - one male and one female - to rest the part into or onto so that I can apply the necessary pressure to buff out the cloudiness. Why not? In the end, it may just have to be vac-formed.... In the mean time - it is time to build up those fuselage side panels (already started really, as can be seen in the last two pictures). You will see that next, I believe. Until then take care and stay with me.