Thread Tools
Nov 15, 2013, 11:34 PM
Pronounced "High Duck"
haiduk's Avatar
Thread OP
Build Log

SBD Dauntless Scratch Build


For me, this years winter building season has begun. I have always wanted a Douglas Dauntless dive bomber. I know there is an ARF kit available from Windrider, but I like to scratch build my own designs.

Usually, I start by creating a 3D model to test in RealFlight, but this time, I'm skipping the simulator step. I've got most of the 3D model sculpted, but only the wings and their internal spar structure have been programmed for CnC milling and laser cutting.

One of the limitations I have with our CnC router is with the bit length. I can cut up to about 1.5" in depth so all of the parts I cut have to be less than an inch-and-a-half thick. I will have to figure out a way to build up the fuselage from layers. I've got an idea, but I'll share more about that later.

On the full scale aircraft, the dive brakes / flaps are hinged at the surface with piano type hinges. I made a mockup to test an idea. I used coffee stir straws as tube and made my own "piano" hinges. The torque rod becomes the hinge for the air brakes. The lower flaps can be driven with a standard control horn in the middle flap and pins connecting the outer flaps. Let me take some photo's to help illustrate what I'm trying to say here.

I'll post my progress here in this thread for those of you who like to watch build threads. Feel free to offer ideas and advice. I like to think that people can learn from each other with these build threads.

EDIT (20 Jan 2014):
I finished with the initial prototype airframe. It came out much heavier than I expected due to the extra ballast added inside the cowl to get the plane to balance. I never did get the plane to balance at the proper CoG. I will be making several design changes and building another, much lighter, one. In the meantime, I decided to build a 1/20 scale micro SBD for indoor flying. Planning on getting back into the 1/12 scale version this spring.



(26 Jan 2014): Finished with the 3D modelling and CnC programming for the 25" Micro SBD Prototype. Started cutting parts.
Last edited by haiduk; Jan 26, 2014 at 08:14 PM.
Sign up now
to remove ads between posts
Nov 16, 2013, 08:28 AM
An itch?. Scratch build.
eflightray's Avatar
A beautiful plane the SBD.

My Scratch Built Depron version, (sorry, couldn't resit that ) --
Nov 16, 2013, 02:36 PM
Pronounced "High Duck"
haiduk's Avatar
Thread OP
Depron? Nice job eflightray. I've been thinking about final colors myself. I'm thinking blue on blue or blue on gray might be a bit rough for me to see. The trainer colors, however, might be a bit easier for me to spot in the air.

Did some building at the Senior Center. I ran out of basswood so I cut the flaps from some fairly heavy C grain balsa. Hopefully, they will be rigid enough. I could hit them with a layer of light fiberglass to stiffen them up a bit. That might be a good idea anyway. The center flaps will be driving the lower flaps so that one will definitely need to be solid. I may have to break down and order some more 1/16" basswood sheets or even consider using 1/16" aircraft ply for the flaps.

The wing spar crutch assembly (almost) fits into the foam wing parts. There are a few places where the cutter couldn't reach to slot the foam completely. I will use my hot knife to fix the slots later.
Last edited by haiduk; Dec 14, 2013 at 02:18 PM.
Nov 17, 2013, 08:14 PM
Pronounced "High Duck"
haiduk's Avatar
Thread OP
Fitted and installed the wing spar / landing gear assembly into the wing. Is nice having all of the slots line up perfectly. CnC is a nice tool. I really didn't run into any major problems so far. The wing went together nicely.

I plan on hiding all of the control horns and servos. Secret Horns have worked well for me in the past. Am using them for the ailerons of this bird.

Have to let the light weight spackle fully cure out and finish rough sanding the wing. I am planning on covering the wing with a layer of light fiberglass for the tensile strength as well as a bit of future hanger rash prevention.
Nov 19, 2013, 05:36 PM
Pronounced "High Duck"
haiduk's Avatar
Thread OP
Finished rigging the secret hinges for the ailerons. The starboard aileron came out about 1/8" short. I'll have to scab a bit of foam to an end and shape it to fix. Not a big deal. No exposed control horns so far. That's the goal.

The flaps and air brakes came out pretty good. They came out straight and are plenty rigid enough after getting a layer of fiberglass. Planning on painting then before I poke the holes out. The existing glass should make for extremely good masking. I will file the holes out after I paint the air brakes and flaps.

The only problem I encountered with the flaps was the mid flap doesn't quite line up with the outboard flaps. I may have to remove it and reapply it with better alignment. I will have to decide what to do before I cover the wing.
Last edited by haiduk; Nov 19, 2013 at 06:23 PM.
Nov 20, 2013, 07:53 AM
Warbirds Lover
Dreamcatcher's Avatar
Hi !

Great job, Congratulations !

D.C.
Nov 20, 2013, 02:38 PM
Registered User

Hey there Haiduck


You've got another senior citizen, scratch builder here, who has wanted an
SBD for ever so long......(electrified dontcha know)......

I was wondering if you would sell the plans (if you created some), or would
consider trading them for some other plans ( I have a lot of DXF/ DWF files,
some pretty raw, some close to finished). Also, interested in your Wurger ( FW190 ) and the AstroHog.

I am trying to convert all of my building to foam, with my second model ( Warheads Pink Beaver). Cheaper in materials, and power systems...........

Finally, you're doing something really interesting with RealFlight, which I have been thinking about. Like to know more about that if you've the time.

If you want, you can e-mail me [email protected]
Nov 20, 2013, 02:40 PM
Registered User

Hey there Haiduck - Vers 2


Sorry - dumbthumbed the e-mail.....

address is [email protected]

Thanks again - Mike Smith
Nov 20, 2013, 03:00 PM
An itch?. Scratch build.
eflightray's Avatar
Mike, there is/was ?, the Freewing Dauntless, Wingrider Dauntless, and the ESM Dauntless models with threads in the -- Electric Warbirds froum -- if buying one helps.
Plus there are probably a few others around as well.

And no, I didn't produce plans for mine either. The build thread's here if that helps -- https://www.rcgroups.com/forums/showthread.php?t=890889
Nov 20, 2013, 05:01 PM
Registered User
I thought the yellow wing color scheme was just the pre-war standard paint job. Tails were different colors depending on the aircraft carrier the plane flew from.

howell
Nov 20, 2013, 07:00 PM
Don't look at me like that....
62pilot's Avatar
Blue FFF and a foam core wing from an old Midwest P-40 profile plane and a bowl from the wives cupboard for a cowling. Mechanical retracts and flies on four cells with a 550 watt SKS motor. I do believe the canopy is to tall, so am currently reworking that part. One of my favorite planes.
Nov 21, 2013, 04:35 AM
Pronounced "High Duck"
haiduk's Avatar
Thread OP
Have been busy working on the wing. I finished with the fiberglass and prefitted all of the linkages to the ailerons and all five flaps. Works great so far, but not a whole lot to see other than the photos I've already posted.

Now it's time to think about how I'm going to do the fuselage. Remember I can only mill up to 1.5" deep. I am using the inch-and-a-half thick pink foam board. The fuselage, including the fairing, is roughly 7" wide. I wont be milling the fuselage out of a single piece.

The question is how to arrange the pieces. I could vertically laminate 5 sheets, but keeping them aligned might be a problem. Also, feather thin edges don't mill well in foam. The fuselage is just over 5 inches tall, not including the canopy and the vertical stabilizer. It might be easier to laminate 4 pieces from bottom to top, but again, the alignment might be difficult to get perfect and there would still be feather thin edges.

I've been thinking about using a built up wooden (balsa) structure and simply mill two foam sides, a foam top, and a foam bottom. They could be keyed to fit perfectly into the wooden structure. The pro here would be everything should line up without issues and the fuselage would be quite rigid. Con would be the structure might be a bit heavier than laminated foam.

I'll spend some more time tomorrow and play around with some ideas in 3DS Max and see how I can chop up the fuselage for milling.
Nov 21, 2013, 01:58 PM
Jer. 29:11
jeffsch's Avatar
Haiduk, what a terrific subject and really fascinating attention to detail! Those dive brakes are going to be awesome.

For the fuse laminations, some sort of crutch seems the way to go, something to key alignment slots / holes in the various milled foam parts. If you're concerned about weight, the crutch could be made from 1/4" sheet foam -- it just has to be strong enough to support straight / square assembly with the milled foam (and perhaps its covering) providing the final strength, right?

P.S. I really wish rcgroups had a feature where you could subscribe to new threads started by friends!
Nov 21, 2013, 03:29 PM
Registered User
SNice's Avatar
wow Haiduk! Looking great so far! The dive brakes are amazing! I have nothing to add but just wanted you to know that I am watching and learning! Would you mind sharing the details of your cnc setup? Your laser cutter? Are they commercially available? I'm. Looking to go cnc in the near future and am looking into options.

Keep up the great work. Subscribed!!!
Nov 22, 2013, 03:26 PM
Pronounced "High Duck"
haiduk's Avatar
Thread OP
Quote:
Originally Posted by jeffsch
...
For the fuse laminations, some sort of crutch seems the way to go, something to key alignment slots / holes in the various milled foam parts. If you're concerned about weight, the crutch could be made from 1/4" sheet foam -- it just has to be strong enough to support straight / square assembly with the milled foam (and perhaps its covering) providing the final strength, right?
I made the decision. I am going to design a basla/ply crutch and piece together a foam skin. Have been deep in design mode last couple days drawing up just that. Not a whole lot to see yet, but I promise to post images as soon as I have something worth looking at.

How does one make a suggestion like subscribing to friends new threads automatically? That would be an amazing forum feature here.

Quote:
Originally Posted by SNice
wow Haiduk! Looking great so far! The dive brakes are amazing! I have nothing to add but just wanted you to know that I am watching and learning! Would you mind sharing the details of your cnc setup? Your laser cutter? Are they commercially available? I'm. Looking to go cnc in the near future and am looking into options.

Keep up the great work. Subscribed!!!
Thanks SNice. I think the dive brakes will be fun too.

We've been using a 5th Generation Hobby Laser from FSlaser and a BlackToe CnC router from BuildYourCNC. We've made several mods to the CnC router, but it's mostly stock. You will also need the computers to drive the two units and software for designing and controlling. The laser unit comes with a very nice controller program called RetinaEngrave, but the CnC router does not. I recommend Mach3 ($150) for that. I am planning on building yet another CnC with a larger bed (4'x8').

I personally use DraftSight and 3DSMax for the design work and CamBam to program the cutting paths (GCode). Wish I could afford SolidWorks and MasterCam, but that's really not an option. Those two programs alone cost as much as a house. I refuse to use pirated software.
Last edited by haiduk; Nov 22, 2013 at 03:43 PM.


Quick Reply
Message:

Thread Tools