JayW

Oh, I just noticed the cross section pics with the blue fishbowl!! Awesome, very helpful! Thanks Mike.

Looking awesome Pete.

Alright - these test parts are very important. This model is supposed to be primarily made from 3D print parts, so as to assure great accuracy of shape. But what I am finding is that my parts have inaccuracies if not outright flaws. Much of this was unexpected, and could be operator error. By that I mean I am not printing parts off as well as other real experts could - due to the resin I use, or the machine settings I have created (exposure time, lifting speeds, layer thickness, aliasing), or how I am orienting and supporting the part during the printing process. But it also could be I am expecting too much of the 3D printing process. I am asking for some serious exactness. Take a look at my prop spinner parts - I already learned from test parts, and have applied some lessons learned. Also Alain suggested I print the nose upside down, which I wanted to try. Recall the test parts: Terrible fit, wavy edges. Part of the terrible fit, BTW, are from some subsequently discovered small but nonetheless serious clashes with the prop roots. I fixed that for the "production" parts. Those wavy deformed edges are serious: If I do not get a handle on that, this whole project is going to be a no-go. Peter (Airscale) has been having similar issues with his 3D print work and is working on it in parallel. Somehow that has to be addressed - all my parts are going to have edges of course. The "production" parts: Note there are two nose halves and one aft half. The nose half to the right was supported in a traditional way, tilted about 45 deg with nose up, so that all the supports were on a portion of the aft edge. Compared to the test part which was supported the same way, I only increased the number of supports to try to get rid of the local waviness. It worked in that there is no waviness. You can see remnants of those supports along the edge. The other nose part was printed upside down at a slight tilt, where all the supports were on the nose surface itself. That ought to leave the aft edges pristine. You can see the little marks the supports made on the outside surface after snipping them off and sanding smooth, just off the "pointy end". The third part of course is the aft half of the spinner. To my great dismay, the traditionally supported nose half has a large deformity in the region where it was supported: No waviness, but a giant mismatch with the aft half of the spinner. This part goes in the trash can. Why oh why did this happen? Well, clearly it was stretched and deformed during the printing process. That corner was the first to be printed. And as more and more layers are then added, the part gets heavier and its weight is pulling on those first small layers. Also, after each layer is baked on, the build plate is lifted to allow resin to flow back underneath it so the next layer can be created. There is some stiction force associated with that motion, which also pulls on all the layers previously laid down. One or both of those phenomena might be causing this. Perhaps if I spun it 45 degrees so that the first layers are not coincident with the prop root cutout? Then the first layers should be more robust. I dunno... Or, maybe my exposure time (3.5 seconds per layer) is insufficient to give a good hard material? Again, dunno. That is the recommended exposure time for this stuff at 5 microns layer thickness. The aft half, which was oriented and supported in a similar manner, suffered the same fate although less severe. It is, however, a bit out-of-round as a result. That part will also go in the trash can. Then there is the other nose half, which was printed upside down: Now THAT'S what I am talking about. Thanks Alain - good idea! Good edges, decent match up with the aft half. That is a useable part. It has a bit of a rash from the supports: But some putty or CA will cover that up. So I think I am about 80% of the way there. A few more shots that seem to indicate a more hopeful situation: The prop blades are just laid in there loose for now. So, I have a useable spinner front half, and an un-usable aft half although quite close to being OK. Next post I hope to show a useable aft half which is perfectly round at its aft edge (currently it a bit off), and not wavy or deformed. And then I can declare victory and move on with some assurance that this 3D print process will actually work OK. Bear with me, some may find this a bit painful to follow. But it is here where I can determine whether or not this project will succeed. Stay tuned.

Mike that is some serious modeling going on there!! Mad skills! One of those modelers that accomplishes more in smaller scales than I can in larger scales.

Well shoot! So this B-17C - is it done? What does it look like?

Literally minutes ago, I began printing off my "production" nose cones! And yes, I thought about some sort of sacrificial edge as well. But this time at least, I left the parts at an angle without any augmented edge, and just doubled or tripled the supports down on the bottom where the print layers have a severe angle. Report out probably tomorrow. I see you have included depressions for rivet heads. Boy Peter - you set a very high bar. I'll think about that.....

So not to belabor the point, as many who are following are not conversant in 3D printing, but not knowing any better, I am using plain old Elegoo 8K standard space grey resin. It seems like great stuff, but what do I know.... And for transparencies I am using Nova3D High Transparency resin. I am having trouble with it, even after various tweaks to exposure time, lift speeds, and some other parameters. And, varying ways of supporting and orienting the part. And have yet to get a really good exposure test part (I've used several types). Have you done transparencies? If so, how are they and what have you used?

If that is not one of the most awesome period pictures of a mustang, well I'm a monkey's uncle! Cutting daisies indeed! Thomaz, once again you have provided me with a treasure trove of pictures and information. Great to have you on my team! I think by now I have a pretty good idea of the basic shape of this Malcolm hood. Soon I will do one up in Rhino, but first I need to do the fuselage and windshield surfaces that surround it (you know - using all that point data I described in my first post).

Thanks Thomaz - Great pics (I have some of them already). Can I assume that hood is newly made (somehow)? If so, do you think the "Impatient Virgin" hood is "overblown"? The side bulging is more severe than scale models I have seen with the Malcolm hood - looks just like a fishbowl. And I have found no period pictures where the side profile is in evidence. I inquired at Aircorps Library to see if they had anything, as their sister company Aircorp Aviation does restorations (Lope's Hope being one of them - a greenhouse canopy C-model), and of course have a giant documents library, but they don't have anything on the Malcolm. I was told however that modern restorations, if the item is usable, will refurb it. And if it is unusable, reverse engineer what they have to work with - suggesting some of the old hoods actually exist but are unsuitable for repair. I'll bet you can count them on one hand and divide by two. Either way that suggests what we see on "impatient Virgin" might be correct, whether restored or remade. Thoughts? The mechanism. Yes. What a mod that must have been. And somehow the LH chain must be slaved to the RH chain (the RH has the handle crank). I don't know how they did that, but I would guess there is a torque shaft behind the seat armor with a sprocket on either end, fixed to the bearing brackets on the airframe, and those sprockets engage both chains. ???? Wish I knew, I would attempt to model it because it might be in sight. Also, I'd like to know what the means of attachment to the chains is, or at least how hidden (or not) it is. Personal preference as to the look. I personally like the look of the Malcolm hood better. Should I go with the B-model (have not decided yet), one of my goals is now to convince you. It does have the look of a mod I will concede.

True Peter. Looking for you to break trail for me with the P-39! I'll thank you in advance. Oh I think you would like that unit! I like my 2. Thanks Mike. Small world - Tim Perry helped him with this - the very person who provided so many of the 3D print parts for the Corsair. Yup, I will add this to my growing collection of all things Malcolm. And I will contact Alistair. Hi Guy! Yes I will keep that in mind. However this is not going to be a complete 3D print kit. I don't have a good plan yet, but I am pretty sure that some of this build is not going to directly involve 3D printed parts. For instance it could very well be that the sidewalls around the canopy will have scratch built skins over 3D printed frames. As opposed to the engine cowl, which is probably going to be fully 3D printed. And the wings - I have no idea at the moment how I am going to address the long wing spans, the gear bays, etc. There will be scratch building as well as 3D print. Anyone who would be interested in parts I create would have alot of work to do to integrate them into his/her own build. Yeah - at this point I just don't have a plan. I want to create as much CAD surface as I can, then go from there. As for B/C differences, as Mike stated they are essentially the same, only built in two different factories. Did you perhaps mean B/D differences? If so, they do share a good bit of geometry, but from the windshield back, they diverge alot. Except the radiator scoop area which again is the same for both. The tails are about the same too except the fin root which has to match with different fuselage contours. The B/C wing is same basic wing, but the extended leading edge is completely different leading to different landing gear doors and alot of other stuff in the leading edge. Also there is four guns versus six guns. Yeah, a modular approach would be pretty extensive. B/C/D/K aside, within each variant is a dizzying amount of change, just like all these vintage WW2 aircraft production runs saw. A P-51D-5 has many differences compared to a P-51D-20, for instance. But pretty sure you know that... Once I decide on a B or a D, then I must pick a subject, with its serial number, and once again strive to give it the right parts. It isn't very hard - the NAA drawings are not shy about specifying serial number blocks in which parts are effective on. Goodie goodie!! I need 3D print experts watching this build. Stick around! I am going to substantially redesign the spinner parts, where each will probably have internal "roofs" which would not have the benefit of lying directly on the build plate; thus would require supports, and would spoil any plans to print straight off the build plate. To date, with the exception of the "rook" chitubox file that came with my printer, I have never made a part that is directly on the build plate. However it's an option worth considering. Another person suggested printing the forward spinner part upside down, with supports. That would give me a much more accurate interfacing surface to the aft part, which would be done right side up either directly on the build plate, or at an angle. My flat surface on the test part of the forward half of the spinner was, like you said, affected by gravity during build-up, and was not flat at all. It was however minimally supported. Whereas the flat surface of the aft half part seemed just fine. It was not affected by gravity. Next post you will see my next try (or tries). Thank you all for your interest in this - there are challenges to come. I hope to be successful.

Stunning!!!!! So tell me about the beefy rings around these parts. I have not seen such a thing before.

I needed to do a reality check on this ambitious dream I have here. To get a better idea what I am up against. How well did I model the engine cowl surfaces, including the "smiley face", that I have created so far? How well is the printer set up (exposure times, etc), and how well have I designed my supports and is my part orientation for printing acceptable. So I designed and created some test parts. Already I had a part defined for the cuffed propeller, done a couple years ago just for kicks: I could go on and on with this effort. It was a ton of fun. To make a long story short, Airscale Library has some Hamilton Standard data on prop blades including the one used for P-51's. Data is available for cross-section shapes at various prop stations from root to tip, and their twist angles. Create curves in Rhino of all these shapes, at the right angles, loft between them, do some tweaking, and you get what you see. Then I had to define other test parts using the cowl surfaces I created over the last few days, which I described last post. And also the spinner surface. Here: And after many hours of 3D printing I got these parts: Except for possibly the prop blades (they are practically perfect), these are merely test parts. Parts I make for the model will be much more detailed. So this was a test. What did I find? The printer is probably set up about as well as I can do it. No print failures, and part quality looks good. I certainly expected no less; I have already produced some parts for the Corsair. The "smiley face" part has excellent surface smoothness. no lumps, no ripples. What a victory! But it didn't print that great. More work to do on that score.... The cowl surface is actually pretty good. There is one seam between patches where I didn't do a good job of getting it smooth (I can fix that), and some edges are a bit ragged as can be seen on the smiley face part below. I hope I can fix that with a locally more dense array of supports on the 3D print file. I am a bit concerned about that. It could possibly be addressed with some putty though. Here: Fit between the two parts is pretty good, but I was expecting perfection. The 3D printing process is not yielding theoretically perfect results. Any imperfections will show up when trying to mate two parts together. And I do not like those ragged edges. Hope I can get that taken care of. I should say now that I intend to skin this model in aluminum litho sheet. So the final fuselage parts (wing too) will be under the defined surface by .005 inch to allow for the thickness of the litho sheet. And that will cover up some imperfections in the 3D printed parts. And speaking of imperfections: The spinner halves didn't fit together worth a sh_t. And edges are ragged similar to the cowl parts. The spinner will not be skinned so it has to be right on. Again - more supports locally should help with most of the shape problems. Also, the prop blades didn't fit in their holes at all. The holes need to be a few thousands of an inch larger, just like holes for a bolt need to be slightly larger than the bolt diameter. Instead of being exactly the same diameter. I am a dummy. Also, I am finding that 3D print parts might be just a tad expanded - so the prop blade roots might be a tad oversized, and the holes a tad undersized. On the bright side, these parts look very cool, and have the potential to be transformed into excellent ready-for-primetime parts. I will be doing some substantial redesign, and will probably make the prop blades and spinner my first effort at production parts. A stand-alone unit that will gather dust for a long time waiting to be installed on a complete fuselage. I combined test parts to see how it looks: I am both encouraged, and discouraged. It sure looks like a Mustang - that's great. But fit-up is going to be a challenge. This is not going to be as easy as I envisioned. But we all experience learning curves, and I hope to experience that here. Stay tuned - I will post progress on a greatly improved prop before long. Meanwhile I have alot of surfacing work to do on the computer.

Hello all! Recently I purchased a 3D printer - Elegoo Saturn 2 - which has the potential to transform my modelling. Those of you who follow me know that my recently completed 1/18 scale build (F4U-1A Corsair) benefitted from a good bit of 3D printed parts almost all of which I designed myself but had printed by a capable fellow in the UK. Since then, I now have the means to do my own printing, if only I can get good enough at it. So my next project, if all goes well, is to create a very accurately shaped P-51 in 1/18 scale. At this point I am undecided whether to do a B/C variant (razorback) or a D variant (bubble canopy). My first choice would be a -B with a Malcolm hood modification, followed by a -D as a second choice. I would prefer not to do a straight up -B razorback (or maybe better known as a "greenhouse" canopy version), as Peter Castle (Airscale) has done his incredible Lopes Hope in 1/18 already, and I would prefer not to tread on that hallowed ground. The only available kit I know of a P-51 in 1/18 is from 21st Century toys or whatever it turned into over the years - a D model. They are long out of production but can be found on E-bay for inflated prices. I actually have one, but I will not be using it because it has too many inaccuracies. Years ago, though, I heavily modified just such an animal resulting in "Miss Velma": That satisfied my goals at the time, which was to take an existing large toy model and do my best to make it look real. Miss Velma, like many P-51 models in many scales, has shape inaccuracies, and can be greatly improved upon, and that is what I intend to do. So I have three important ingredients in which to do this: 1. Aircorps Library - they have a full set of engineering drawings for the P-51 variants, including "ordinate" drawings, which are tables of point coordinates that define the shapes of the outer surfaces of the aircraft (and even some inside shapes like throats of intakes). These ordinate drawings will allow me to create surface definition in any scale very accurately. 2. CAD modelling software - I have been using Rhino 7 for a couple years now, and it is indispensable for layouts, part definition, and 3D printing. I am no expert user, but I get by. 3. 3D Printing. This will be the first time I will have tried to make 3D printed parts the primary components of the build. Previously I have used it simply to augment an existing model. This is my weak link. I am a bit of a newbie when it comes to 3D printing. To start, I am in the process of converting point data, obtained from vintage engineering drawings, into Rhino surfaces - hopefully for the entire airframe. Here are examples of the point data vintage 1940's: There is also wing data that I have not shown. I can produce points in space from those tables, and connect them with curves in Rhino - like this: Very laborious and monotonous, I can say. Not too surprisingly, the Rhino model is showing what looks alot like a P-51. It better - the good folks at North American back in the '40's used the same data to build the tools used to manufacture the airframe. From there, and after some time-consuming schooling on primary surfacing, with classes available on YouTube, I used those curves to create a bunch of patches: Clearly I am not finished. Those patches can be combined to make a single compound-curved surface, or larger surfaces. I also have wing lofts, done a different way: P-51 wings have single curvature which is to say they are defined by straight line elements. Which is to say that you can have a contour at the inboard end, and a similar smaller contour at the outboard end, and you have fully defined the wing surfaces simply by lofting between them along straight line elements. That is what I did above. You see two lofts - the basic wing, and the inboard extended leading edge - a feature of the -D model, but not the -B model. That extended leading edge is also single curvature. Far and away the most difficult detail to surface so far has been the carb air intake below the prop spinner. After days of applying everything I learned in most of 14 classes I took on primary surfacing techniques, and episodes of tearing my hair out and occasionally walking off in a huff, I got this: It is not perfect, but any inaccuracies are measured in hundredths of an inch at full scale - which is infinitesimal at 1/18 scale. So, unlike a whole lot of P-51 models out there, this "smiley face" detail is deadly accurate. BTW - the Tamiya 1/32 P-51 has a very accurate smiley face, and I am convinced their designers had access to the point data that I have used. Next post you will see a test part of this detail, in 1/18 scale. I also have a complete surface for the prop spinner, done months ago: That was a breeze compared with the other surfacing efforts to date. Just a contour curve rotated around the thrust axis. In theory, if I can have a fully defined set of surfaces for the P-51, defined in Rhino in full scale, I can scale to 1/18 and create just about everything from them. A pretty exciting prospect, and easier said than done! Next post I will show the results of some test parts. I hope this build generates some interest; it's going to be a big challenge. P.S. - if any of you Mustang experts out there have any information on the Malcolm hood - like shapes and cross sections, well that would probably clear the way for me to do the B-model!

What a mess!! Sooo, the Helldiver had slats??? I don't know of any other American aircraft of that era to have slats.

I am considering building a P-51B or C in 1/18 scale, and would love to do a subject with a Malcolm hood canopy. Since nothing like that exists, I will have to try to scratch build it. Only thing is, I have no technical data on it. There are pretty good photos of it on restored aircraft, which helps. But what I really need is drawings of cross sections, details, sliding mechanism, airframe modifications, etc. Anybody know anything?

Congrats to Airscale!!

Dude! This is turning out to be an outstanding project! Testing on mules is a great way to go, isn't it? We cannot ruin a project where we have invested our life in.

I can't believe that little engine. Such wonderful Tamiya-like detail!

When I did my contrasting between metal and fabric on my 1/18 effort, I looked at a whole lot of old pictures. Oddly, I saw everything from fabric darker than metal to fabric lighter than metal to fabric looking same as metal. So I just painted the top coat it all the same. Turned out that my alum skinned panels ended up with an unintended different hue anyway, which was OK with me. I think you ought to leave it alone and weather the devil out of it with stains and dirt.

Wow Woody - seems like just yesterday I was doing my own version of that exterior painting. Looking very good.

How assuring it must have been to have those bad boy F4U's covering you. From a guy who has familiarized himself greatly with the F4U. Earlier in the conflict those would have been Dauntless's and Wildcats. I tell you Peter - I am liking the Helldiver more and more as I follow your build thread. Great shot.

Happy Birthday Kevin! Really appreciate you attention and support here on LSP. Oh - and nice birthday present!

Good grief man - the Stirling looks to be a flying bomb-bay. Love the Evergreen engineering taking place here. I can relate!

Ah yes. Gotta protect that 6. I do believe the Avenger had alot more rearward firepower though. Hopefully they had interrupters - without it I would not trust that young man to let up with the tail in the way! Not when an EA is on your 6 trying to shoot you down.

No expert on the Helldiver but are there guns at that aft position?