Jump to content

1:72 Grumman AA-5 Traveler


Recommended Posts

I thought I would share some progress on a current side project...

 

First I should explain that as co-designer of a prototype Human Mk 1 – currently at early testing stages, a long way off even taxiing, mainly focussed on the exhaust system at present – I am limited to 10 minute essential dashes into the attic, so my conventional modelling is basically on hold. However between 5.30 and 7.30am I do have a window where I can combine infant care with some laptop action, and have been developing some planes on CAD for DLP resin printing.  

 

I find it strange that there are not more single engine GA aircraft available in kit form in 1:72. Yes you can get things like the Bulldog or Chipmunk, but even the Cessna 172 I think is limited to one hard to find resin issue. I guess that the people that dig these planes are those that fly them, and have neither the time nor the inclination to bother with them in model form. But they are such ubiquitous aircraft, and fly over us all the time.

 

I’ve been tinkering with quite a few, but here is the Grumman AA-5 Traveler:

AA-5

 

Because of the print area of machines like the Elegoo Mars, my trusty steed, these sizes of planes work well, anything bigger would have to be highly modular. In this case, I can break it down into fuselage, wings, prop and wheels.

 

As a print, I am quite pleased. The resin is standard Elegoo grey, printed in 0.02mm layers with a 8 sec per layer exposure. The layer lines are still visible, of course, but not nearly as obvious as they would be with FDM printing:

2020-08-13_05-39-35

 

The fuselage is printed with supports on the bottom, which will obligate some finishing work:

2020-08-13_05-39-26

The wings are printed standing on their end – this makes the print rather tall, and long (ca. 14 hours) but means the finish is better. That said, the mating surface is not quite square, so there may be some sagging going on:

2020-08-13_05-39-03

Details can be done, but as a lessons learnt prototype, I will resolve to increase the size of panel lines, as these luggage doors barely register and will disappear with sanding:

2020-08-13_06-05-37

Also, I have printed the horizontal stabilisers and fuselage as one, but there seems to be a tendency for these to warp (I have seen this on other models), so will probably benefit from separation:

2020-08-13_06-06-35

There is also the matter of transparencies. I have been trying to print these too, using Monocure clear resin. These of course have layer lines too, which is not ideal for transparency. This isn't from the Traveler, but shows a part straight out of the printer after clean up with IPA:

2020-08-13_05-38-25

One possible solution is to brush with extra resin and expose to more UV (a nail gel lamp):

2020-08-13_05-38-52

 

2020-08-13_05-40-25

A smoother finish, but some manual polishing will definitely be required. I am comforted however by  a Mach 2 clear part I have to hand – I am just about at Mach 2 clarity! Also, I think those lumps in the surface are doobreys that found there way onto the part, so general modelling hygiene is a must.

 

As I say, I'm working on a few, really as a learning curve. Here is a Cessna 152 (yes I know there's a resin kit on the way!)

2020-08-13_05-38-38

All in all, exciting experimentations with learning points and a bit of an insight into the realities for those that actually design proper model kits. My hat is permanently doffed in their general direction! 

 

Circumstances dictate that I probably won't be sprinting to a quick RFI (poor form for a 9cm long model!) but I hope some of the above is of interest. There'll certainly be a reprint so if any eagle eyed Grumman afficianados spot any doosies do let me know, I am aware the top of the cowling is too flat. 

 

All best,

Harry

  • Like 7
Link to comment
Share on other sites

Nice to see the AA5 in model form. I flew one for a while and it was so much better than the PA28.

 

I also got a once-in-a-lifetime picture at Duxford next to four Grumman fighters. Something that Cessna and Piper pilots couldn't do!

 

Grummans_1000.jpg?width=1920&height=1080

  • Like 5
  • Thanks 1
Link to comment
Share on other sites

Those look fantastic.  I would love to see more kits if GA types in this scale.

 

Maybe we'll see 3D printing become more mainstream for model production as time goes on.

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

6 hours ago, Bangseat said:

A smoother finish, but some manual polishing will definitely be required. I am comforted however by  a Mach 2 clear part I have to hand – I am just about at Mach 2 clarity!

Very nice so far - could you not use your part to make a vacform canopy in lieu? It'd be a lot thinner and clearer.

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

I love these projects.

Currently I am in the process of making a Cessna 210 and Barron for 3d printing.

Was about to start with a Cessna 310 also, but fortunately a nice resin kit came out recently.

  • Like 1
Link to comment
Share on other sites

8 hours ago, Bell209 said:

Very nice so far - could you not use your part to make a vacform canopy in lieu? It'd be a lot thinner and clearer.

Yes it would. A skill yet to master, really I'd like to get one of those small dentist's vacuum formers but I haven't found one at the right price yet. I do think there's mileage in printing clear though, especially for awkward window shapes such as the rear ones on the AA5, also the complex front transparency of the 152 which forms both the pilot's windshield and the leading edge of the wing centre section.

 

28 minutes ago, Rizon said:

I love these projects.

Currently I am in the process of making a Cessna 210 and Barron for 3d printing.

Was about to start with a Cessna 310 also, but fortunately a nice resin kit came out recently.

Great to hear. Do you own a printer, and what CAD programme are you using?

 

Would be great to have a dedicated 3d model maker's space for sharing these niche and probably totally uncommercial creations, it looks like this is developing in the 3D forum right now.  

 

 

@TJJ - great pic! Yes, a Grumman pilot can definitely claim a bit more runway cred. Just missing an F-14 from that line up...

  • Like 1
Link to comment
Share on other sites

9 hours ago, Beggsy said:

Those look fantastic.  I would love to see more kits if GA types in this scale.

 

Maybe we'll see 3D printing become more mainstream for model production as time goes on.

I'm sure we will, although I think there will always be a market for a well crafted kit of a whole aircraft. The real low hanging fruit is things like aftermarket seats, engines, wheels - easy to design, and once DLP printers get below £100 (and they will, they're not actually that complicated) anyone who regularly spends £15-20 a time on accessories to upgrade their kits will surely be tempted.

Link to comment
Share on other sites

57 minutes ago, Bangseat said:

A skill yet to master, really I'd like to get one of those small dentist's vacuum formers but I haven't found one at the right price yet.

You can get manual vac forming kits off eBay for fairly small money consisting of a frame and the vacuum box, you just attach a Hoover and grill the plastic to soften it. Alternatively it’s pretty easy to make your own vacuum box, If you look on YouTube there are many videos. Also the Mattel vacformer is supposed to be pretty good, they come up on eBay from time to time.

 

Vac forming isn’t that difficult the biggest things are to make a good form, don’t be too ambitious on fitting it in the frame ie make sure their is plenty of space around the form and make sure the plastic is sufficiently soft.

  • Like 1
Link to comment
Share on other sites

On 8/14/2020 at 10:33 AM, Bangseat said:

 

Great to hear. Do you own a printer, and what CAD programme are you using?

 

I do not own a printer as yet, currently relying on friends to print for me.

I tend to start my modelling as far as possible using Excell and / or Matlab to define and scale the sections. I then port the info to CAD. I normally use Rhino, as I prefer to work with surface modelling, instead of the Solid Model usually used. Comes from being an aerodynamicist where I work with surface geometries, rather than manufacturable components.

  • Like 1
Link to comment
Share on other sites

2 hours ago, Rizon said:

Comes from being an aerodynamicist where I work with surface geometries, rather than manufacturable components.

Funnily enough I find solid modelling easier. I did do a lot of CFD ( inkjet fluid flow) a number of years ago and this forced me to do surfaces but generally I found it much harder to manipulate.

Edited by Marklo
  • Like 1
Link to comment
Share on other sites

4 minutes ago, Marklo said:

Funnily enough I find solid modelling easier. I did do a lot of CFD ( inkjet fluid flow) a number of years ago and this forced me to do surfaces but generally I found it much harder to manipulate.

Depends a bit on the software also I guess. I cut my teeth on ProE doing Helicopter Air Intakes. That was a lot of fun. Recently had to do some work in Solid Edge using surfaces - an experience I can not recommend!

Link to comment
Share on other sites

I’ve used so many Cad programs over the years, started with Autocad, Claris cad, Ashlar vellum, pro e, solid designer, solid works. My favourite being solid works, but the bulk of my work would have been tooling and mechanical design with very little surfacing. I’m considering taking up Fusion 360 mostly because, it’s free to home users ( I think) that said I don’t have a functioning pc at the moment so I need to cross that bridge first.

Edited by Marklo
  • Like 1
Link to comment
Share on other sites

I also like Solid Works, its the most intuitive CAD I've ever used.  Now that work has gotten me used to Catia though, I don't think I'll ever be able to go back to anything else without missing one tool or another.

  • Like 1
Link to comment
Share on other sites

I've used t-squares, triangles, and French curves.  On mylar and vellum. 😆  And Autocad too but that was many winters ago.

 

Fascinating topic Bangseat, and commendable efforts.  A few years back I followed Westlake Publishing's finescale railroad modelling forum, which had much intelligence re. 3-D printing. They were using Sketch-up mostly.  The state of the art has advanced considerably since then.

 

Wish I still had my Rapidograph pen set though.  

  • Like 1
Link to comment
Share on other sites

Great start. I'd be tempted to form the whole of the clear area including rear windows with a vac formed part. You don't need to buy a machine, I made my own, does the job quite well. It's a plastic tub rainforced with MDF and a hoover attachment siliconed in. The hard part is making a former and it looks like you have that nailed already. I'd just make the former undersized to accommodate the transparency. 0.5mm PET plastic does the job nicely, it's thick enough to handle well but thin enough to form easily. 

 

spacer.png

 

  • Like 1
Link to comment
Share on other sites

Some proper design pros here, I'd better just make the disclaimer that I'm nothing even close to an engineer or product designer in real life. I sometimes think maybe I should have ignored my maths teacher and tried, then again, much as I love doing these planes, I'm not sure I'd enjoy designing vacuum cleaner attachments and cup holders quite as much!

 

That said, someone from Onshape rang me today, having clocked how much I'm on there (big brother is watching you) and tried to flog me a commercial license. Damn, my evil plan to make millions out of 1:72 Grummans without paying a software license, foiled! 🤣

 

Slow pace of work continues but I have done a second draft:

2020-08-18_05-12-45

The vertical tailplane has been thinned out, the cowling made slightly more curvy although it's hard to tell, the horizontal stabs separated, wingtips improved as I'd done a poor job before. This is solid modelling, quite often I end up creating a basic shape and then whittling away at it with negative extruded in various directions. The cleverer I get with the various features, the closer I get to the real shape. The propeller is tiny, and the blades are really just generic blade shapes (stacked ovoid profiles twisting progressively about 45 degrees) made without any serious reference to the genuine thing. At 11mm long per blade, I'm just pleased to have something that looks like a prop but I've got a few tricks to learn for the future.

 

Speaking of future...the glass has had several coats of floor polish and although its lumpy due to bits getting in the resin when i 2nd coated it its otherwise rather Ok, and I think I can get a decent part if I reprint. 

 

  • Like 2
Link to comment
Share on other sites

  • 3 weeks later...

Still chipping away at this. It is an iterative process (iterate, swear, iterate, swear and so on) but with each new print I learn something different...

 

I've assembled some alternative components to make different versions of the AA-5 (like many GA planes, this had a long and evolutionary production life).

GAA5 2020-09-03_01-53-19

Printing well - I can get all the different components, bar the canopy and windows which of course are different resin, on one print bed. The print is about 12-13 hours. It now has an interior too:

2020-09-03_02-18-05

 

However there are still some fixes to do as I realise I have missed the exhaust outlets on both cowlings, and the landing light on one. Looking at the model side by side the real thing:

2020-09-03_01-51-44

The biggest problem I see is the tail - I might have undersized mine, then again, there may well be different tails out there from different decades! I certainly followed my drawings, but an easy fix if necessary. Also the spats need reshaping. The nose gear I am undecided on - it is obviously not spot on, but I could never print a part of that scale thinness and expect it to have any strength - and that is a weighted nose (about 8 grams of tugsten putty no less!) There are also limits to the way I can make the profile of the leg sweep in Onshape. It may be better to leave as is, and if a particular modeller so wishes they can easily make something more prototypical with wire. The canopy has been slightly reprofiled already, to be less of a bubble, I just need to clear my print queue before I can print some more clear parts. Also missing - footsteps and the tail bumper. No excuses, just left them off the print by mistake!

 

I just need to get it absolutely right, finally, get a good print of it and then actually sit down at the bench and do the building and painting. And decals!

 

AA5decals

Lots of good schemes for this, but VH-FXU is particularly irresistable - participating in the Australian Air Race 1976, Benson and Hedges sponsorship logos, slightly rude sounding reg - it just screams "Hold my Beer"... Won't post a pic due to copyright but if you stick the reg in Google you'll see what I mean!

 

All best, Harry

  • Like 1
Link to comment
Share on other sites

Looks good. I reckon your engine firewall is a bit too close to the front of the canopy as there seems to be a gap in the real thing. The tail does look different but I think the nose is sitting slightly higher in the real thing.

  • Thanks 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...