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Mar 11, 2018, 07:53 AM
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Andrew207's Avatar
Question

rolling pod and boom as one?


I have been watching/reading a fair bit about rolling carbon booms, but I have not found an example of rolling the boom and pod as one unit. Is there a reason I could not turn a wooden blank on a lathe and use this blank to roll the boom and pod as one unit, with the exception of a separation at the front of the pod for access to electronics (and to be able to remove the plug)?
I am wondering if this is a reasonable approach or maybe I am missing something that is obvious to those in the know, just not to me.
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Mar 11, 2018, 08:39 AM
Lift is where you find it.
I don't know any good reason not to do it, but on the other hand, if it was a good idea people would probably be doing it that way. Interesting to see what responses you get from others with more knowledge of the process...
Mar 11, 2018, 09:41 AM
Kyle Clayton
Wave Glider's Avatar
I really don't mean to sound like a smart @ss here, but why not just make a one piece fuse with a mould?
Mar 11, 2018, 11:19 AM
Come out swinging
sporter's Avatar
How would you remove the wood plug?

Sean
Mar 11, 2018, 11:59 AM
Adam
xStatiCa's Avatar
Termites .
Mar 11, 2018, 02:40 PM
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Andrew207's Avatar
I was thinking of using the plug to form two separate pieces. The main boom and primary pod, then the front/nose of the pod which would slide over the rest of the pod. I would turn a slightly larger diameter onto the plug where the joint is.
Mar 11, 2018, 03:37 PM
Registered User
It could certainly be done though as you noted getting the plug out would likely require cutting the fuse then rejoining and eliminating the convenience of a one piece fuse. Using a lathe would also decrease your design options. If you look at most pods you will find they are rectangular in cross section not circular. Everything we put in them is a rectangle ie servos, rxs, some batteries. Making a circular cross section large enough to fit the gear ends up with a lot of wasted volume/space (drag).

Pod and boom is a gold standard as it requires smaller (easier to fabricate) molds and allows for rolled booms.
Mar 12, 2018, 04:42 AM
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Andrew207's Avatar
Austin,
That is just the kind of info I was looking for. As a person new to the hobby I always figure there is something I am overlooking. I may give it a go anyways as experimenting with building techniques is part of the fun and learning process. I could of course use the lathe to turn something that is oval in cross section. It is a simple technique that involves placing the piece between the spindles of the lathe off center (e.g. 1/4" to the left of center), then re-chucking the piece equally off center again, but in the opposite direction (e.g. 1/4" to the right). This is how you get tool handles that are oval instead of round.

Thanks or the input.
Andrew
Mar 12, 2018, 08:18 AM
Closed Account
I have never bothered to turn a boom section on my lathes but I have turned many a pod plug. The really nice thing about turning a plug is the symmetry. Once you have it symmetrical you can then flatten the top or the bottom on a belt sander to get a nice shape for holding gear. Just a few years back many of the pods were perfectly cylindrical with tapers on both ends.

My only concern with rolling and wrapping a complete fuse would be the transition area. It would need to be a long taper or as you apply your compression wraps they would migrate down the taper. It would need to be a wrap due to the extreme diameter differences.

Kyle, that is a good question and in a nutshell a full fuse mold is 10X more difficult and time consuming than rolling a boom. I can order the mandrels and then roll three booms in less than 30 minutes. I have been working on a new mold for close to 3 weeks, . It takes time because things need to cure between steps, then a flaw is found, more filler and so on. Some days I feel like a cat chasing a laser pointer, I will nevr get what I want but I cannot help but try.

Andrew, I would suggest you try turning a pod plug. CA makes a great finish you can wet sand to a nice gloss. You can use that to make a basic mold and roll your booms on STEEL golf shafts. What has worked well for me is to cut off about 2" of the butt end of the golf shaft and use that as a tenon for the boom. When turning your plug simply turn a tenon to match the I.D. of the golf shaft cut-off. For rolling your booms you can use a drill to build a simple lathe. I used a $30 variable speed drill and I use VCR tape for compression. You can even set it up with a foot peddle if you wish. Make a holder for the VCR tape reel, with enough pressure it can get quite warm in the fingers while spinning...
Mar 12, 2018, 04:27 PM
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Andrew207's Avatar
You guys are great. You have brought up a lot of nuances I would not have been aware of until I got myself in trouble. Thank you.
Mar 13, 2018, 02:59 AM
Rusty
Rusty Nail's Avatar
Shaper Dave has a tutorial here: https://www.rcgroups.com/forums/show...s-by-Dave-Hill
Mar 13, 2018, 04:59 PM
Registered User
My guess is that there are about a gazillion good ways to make a DLG fuselage, depending on your materials, skills, tools and ideas. There are even more bad ways, but that's another story.

I've got a mandrel for Supra booms and have tried making a few. So far, mine have ended up on the heavy side, and ugly. One thing I've learned is that I need to break the boom free from the aluminum mandrel before post cure, or else I'm faced with a very tough problem!

In general, structural performance, especially stiffness, may be better if you can use unidirectional materials, though of course all elements of the layup shouldn't be oriented in the same direction. I think if I was making a DLG boom, I might add a bit of thin, precured or pultruded carbon on the sides to make the boom stiff in yaw. OTOH, for all I know if it's stiff enough in torsion it may be stiff enough in bending anyway.

If you're using 2.4 gHz radio gear, you may want to make the pod from something radio transparent, but it would be hard to do better than carbon for the boom. If you use all carbon, you'll have to put those little whiskers outside, causing drag.
Mar 13, 2018, 05:48 PM
Closed Account
Quote:
Originally Posted by lincoln
My guess is that there are about a gazillion good ways to make a DLG fuselage, depending on your materials, skills, tools and ideas. There are even more bad ways, but that's another story.

I've got a mandrel for Supra booms and have tried making a few. So far, mine have ended up on the heavy side, and ugly. One thing I've learned is that I need to break the boom free from the aluminum mandrel before post cure, or else I'm faced with a very tough problem!

In general, structural performance, especially stiffness, may be better if you can use unidirectional materials, though of course all elements of the layup shouldn't be oriented in the same direction. I think if I was making a DLG boom, I might add a bit of thin, precured or pultruded carbon on the sides to make the boom stiff in yaw. OTOH, for all I know if it's stiff enough in torsion it may be stiff enough in bending anyway.

If you're using 2.4 gHz radio gear, you may want to make the pod from something radio transparent, but it would be hard to do better than carbon for the boom. If you use all carbon, you'll have to put those little whiskers outside, causing drag.
Great points ! I never thought of putting pre-cured carbon in my booms when I rolled them. That could have made them much stiffer.

On your large booms, try chilling them before you remove them from the mandrel. the aluminum should shrink a little and allow them to release more easily.

Paul
Mar 13, 2018, 06:08 PM
Team Horizon Pilot :)
Paul do you roll your booms like carbon fly rods. 2 flat surfaces to roll it
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Mar 13, 2018, 09:05 PM
G_T
G_T
Registered User
You can go from pencil and paper to completed molded pod in 2 weeks with a mold that is good enough to pull another 50 parts from.

It takes about that long to get a boom all worked out, from making tooling through testing and breaking a few tailbooms.

Gerald


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