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Aug 25, 2019, 01:08 AM
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Yes, no one addressed the hot glue pitfall. That stuff is absolutely off the table for this kind of build. Gorilla glue (the slow drying kind) is much lighter and much stronger - but you've got to wait a long time for it to dry and you need to practice at how to apply it (do a search regarding this and other similar brands).

I think its obvious by now that the major challenges will be keeping weight and drag down.
Don't know how far you're willing to diverge from "scale" details. Example: If eliminating all those struts (from wing to fuselage, etc.) is an option for you, that will reduce drag and weight.

Obviously, other issues will arise, but these are the ones that should be addressed "up front".

Good luck!
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Aug 28, 2019, 10:48 AM
Registered User
Thread OP
Quick Update,

I ordered a cheap laser cutter and mini 3d printer from Amazon. Now I cut out the model as many times as necessary in as many configurations until it is right. I will now be able to 3D print all the small bits I need as well.

After I looked up the cost of laser cutting services I realized I should get the laser cutter. It works out to be much cheaper one time payment but I pay in the form of have to put in the time to set up/ figure out the new tool. I could get away with the cheaper one because I'm just cutting foam, however I think it can also cut Balsa wood. I'm hoping it can cut vinyl stickers with out melting it, well see.

I got the Mono Price mini 3D printer because of the price and it is 99% ready out of the box. There are a lot of little things I want like tools I can print, add on components to my radio and parts for the plane so it should pay for it self over the course of my time of this hobby.

Aug 28, 2019, 11:47 AM
Registered User
tspeer's Avatar
Originally Posted by robotproject
...I ordered a cheap laser cutter and mini 3d printer from Amazon. Now I cut out the model as many times as necessary in as many configurations until it is right. I will now be able to 3D print all the small bits I need as well. ...
Are you concerned about fires when you laser cut styrene foam?

To avoid this problem, I laser cut cheap utility plywood (0.1" thick) to make templates and then use a vertical hot wire (set up like a scroll saw) to cut the foam. The templates are placed on the foam with double-sided tape and it's quick work to run the wire around the template.
Aug 28, 2019, 02:11 PM
Retired CAD guy
birdofplay's Avatar
I tried one of those 5w lase r diodes.
It would cut Blue, Pink green and black/grey foams
but would not even touch the White depron or MPF.
Black , no surprisingly was best/easiest/quickest.
But no more black Depron so ...
C'est la vie !

That wavelength Light just bounces of the stuff.
I'm told a CO2 laser is necessary.
Aug 28, 2019, 03:51 PM
Registered User
Thread OP

RC Groups is like having a hundred Mikes in the background pointing out something I might have missed. I was going to set the laser cutter up at work on one of our steel work tables with the welding curtains up. I was worried about the first few times I cut the foam that it might catch fire but I assumed after I got a feel for the laser settings it would be less of an issue. However if I can not cut the foam because the laser is under powered or of the wrong wavelength to cut through I will take the advice from above and cut templates and then cut by hand.

I thought about returning it but I cant have the 3D printer and laser cutter if I get the bigger more expensive laser cutter.

Aug 28, 2019, 06:57 PM
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tspeer's Avatar
By all means, keep the laser cutter. It's very useful for all kinds of things. It's just polystyrene foam that is an issue. For foam, a CNC router or needle cutter is the ticket.

With the template approach, I can cut much larger pieces than I could with the laser. The laser makes precise puzzle joints that allow me to glue template pieces together to make a large template. For example, I've broken a fuselage side pattern into four pieces and glued them together to get the template for the complete fuselage length. If I were cutting the foam directly with the laser, I'd have to splice together the foam pieces themselves. So I might be using the template approach even if fires weren't an issue.
Aug 29, 2019, 09:12 AM
JureZ's Avatar
look at this Spruce Goose , as a reference for you and your buddy ( your nemesis)
RC Spruce Goose 1/20 (5 min 38 sec)
Aug 29, 2019, 07:58 PM
Held by Grace
BDOG1's Avatar
Hi Mil :
For your glue check out - Foam Tack
You will find it is a must have on your building bench

You might also consider using brushed motors as they are easy to run in pairs,quads etc with just one esc and can reverse the directions by changing polarity ( Laddie M ) used them quite a bit on some of his multi engine projects
They are also pretty. Cheap to purchase as is a brushed esc fro HK
I put a GWS DC- 3 together years ago and ran the 7.4 volt motors on 3S (12v )
It took off like a rocket at wide open throttle , cruised at 25% power
Lots of guys probably still have them tucked away in their work shops
Good Luck on your project !
Sep 01, 2019, 01:04 PM
Short bursts, Don't waste ammo
RCAV8R1964's Avatar
This can be done but you will probably need to scale it up some. If you go too small wing loading will become a problem as well as cost of components. The propellers on the Do X are 3.55 m (139.76 in). If you use a 5 in prop you will get a scale of 1/27.952. The wingspan is 47.8 m (1882 in) . At this scale your model will have a wingspan of 67.329 in. If you use a tractor pusher setup with the propellers should rotate in different directions. This should cancel out the torque moment. If you keep the thrust lines close to the centerline of the fuselage you shouldn’t need to enlarge the vertical stabilizer. A 4 - 5 in prop should give you a good compromise between size, wing loading and cost. At that scale your wing loading should be fairly low which means you could probably fly it like a trainer. As far as the foam goes are you peeling off the paper first? After you finish building you could cover it with a much lighter paper. Just my .002 cents.
Sep 02, 2019, 11:20 AM
Registered User
Thread OP
Your guys suggestions are the best, Thank you.

I have never tried Foam Tac but will order a bottle to try it out.

That video of the Spruce Goose is amazing.

As for scale, I know your right and I'm going to check with my friend if that will fit within the bounds of our competition/non-competition thing. Its more for bragging right s than anything and I may have to submit to a smaller model and then build a much larger one later. Remember he will have the same problems with scale, weight and wing loading I'm having. I have become fixated on rocking twelve motors above the wing and am considering an FPV set up on a 1.7-2 meter wing span plane. But first thing first... Based on all the really good advice from this form, a smaller two motor very light weight and nice looking model seems achievable. So I will focus on that, still no small task.

I have received the mini 3d printer and mini laser cutter in the mail. I will have to spend some time setting those up. I need to build a table an a pallet and bolt down my new tools so I may forklift it on to a rack out of the way at work but, pull it down to use when I need it.

Things are moving along in Illustrator.

I built the Corsair from Flight Test because I had the foam and hot glue on hand. I am trying to understand better how they set up their plans and why. It was fun and easy.

I hope you enjoyed the Holiday weekend,

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