5m Supra XC ship - RC Groups
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Sep 17, 2017, 11:01 PM
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gliderguide's Avatar
Discussion

5m Supra XC ship


Howdy

Looking to do a bit of XC here in Australia. I have the XC Sagitta with a bob Sealy fuse etc, however I'd like something a bit newer. I looked at planes like SBXC, Icon2 and Royale as a starting point. Really hard to get here so I thought that I'd go home brew.

I've ordered a fuse from CLM Pro, pod 133, with a longer boom, 1250mm. Specified extra Kevlar in fuse and a bunch more carbon in the boom as from what I read, it's not a bad idea. Should stiffen it up sufficiently. I'll build the tail group and the wing.

For the wing, I'm considering something similar to a Supra but enlarged to around 5m. Foam core, carbon sandwich spars, vac bagged etc. I'm interested in other people's thoughts or experiences with this. Needs to be strong and handle ballast, both I'm comfortable with in my building skills. It's the validity of design I guess I'm really looking to get help on. Is this the right thoughts for airfoil, plan form etc or should I consider something else...

Cheers
Ian
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Sep 18, 2017, 12:02 PM
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TrekBiker's Avatar
Based on the experience over the last few years here in California I would recommend designing the wing to approx. 10" root chord and 19-21 oz/ft loading. That will limit your span closer to 4m. Supra airfoils are good as are most the F3J airfoils. Cant go wrong copying the Supra wing planform. Or just find any good F3J 3.8-4m wing and use it. Would save a lot of work. Longer boom is a good idea.
Sep 18, 2017, 02:57 PM
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gliderguide's Avatar
It's Australia. Finding anything good second hand is hard!!! I'm not looking to be contest legal, hence my desire to go a bit bigger. I like the base wing loading info. Ballast from there for penetration?
Sep 20, 2017, 12:09 PM
Master of the Wind
G Norsworthy's Avatar
I would not go any bigger than this.

https://www.rcgroups.com/forums/show...possible-wings

I've done a lot of analysis on these wings and the Supra airfoils are as good as anything out there. Once you settle on that part it becomes a game of wing loading vs visibility. The smaller the plane, the faster it will go but the lower your ceiling. 4m is a good span but you can play with the aspect ratio to vary the loading. Going to 5m will make it harder to stay under the 5 m weight limit. If that is not a consideration you can go bigger.
Sep 20, 2017, 01:06 PM
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gliderguide's Avatar
Thanks Greg!! I thought I'd read most of your stuff but I must have missed this one. The 5kg limit doesn't apply for me as I'm not looking to set records or fly contest. 5m is a practical span for me with a 2m centre and 1.5m tips. I'll reread your thread in the morning. It's 1am here and I'm sleepy!!
Cheers
Ian
Sep 20, 2017, 02:46 PM
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gliderguide's Avatar
Ok, sleep can wait.... if upper weight limit isn't an issue, is 5m span fine? I was thinking to have a chord of around 14" too. And on your fuse, what's the advantage of T tail? Is it just for protection on the rough out landings or is there an aerodynamic advantage? I was going to copy the supra style AMT mounted on the boom if I can get enough command authority, or place a small pod on the boom and use a split elevator if it looked needed. I have some MKS 6125's floating around that I thought would do for the rear, mounted in the fin for both ease and accuracy. I'll need to do some cg work when my fuse arrives to see what works with the longer tail moment. Trying not to need 5kgs of nose weight or the inertia...

Maybe sleep now...
Sep 20, 2017, 04:03 PM
Master of the Wind
G Norsworthy's Avatar
Hi Ian, as long as you are not capped by the weight limit you can go bigger. Keep in mind to get any velocity you will have to be over 5 kg. You may start to bump into the winch capability.

I like T tails to keep out of the weeds plus you have fewer angle joints for drag and the control setup is very easy with a carbon rod up the center of the fin. And the t tail nicely caps the fin. I do the initial test flights, fix the tail incidence, then finish the fillet.

You will want a rather large battery which should take care of your noseweight problem, but keep the rail as light as possible. None of my recent planes has come apart in the air so you should be safe following my structural examples.
Sep 20, 2017, 04:36 PM
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gliderguide's Avatar
Thanks Greg
Aesthetically I do like a T tail!! My concern is that I'm using a fuse from CLM Pro and although I've asked for a bunch extra Kevlar in the pod, and more carbon in the boom, that a T will have more moment to break the fuse at the base of the fin. Equally, the fin would need to be structurally a lot stronger and would therefore increase weight a bit. I'm trying to avoid making my own fuse for now. Mythought was to concentrate on wing construction but I'm open to making something later if it all works ok.

There's no competition here for xc. And I'm not a great pilot, I just enjoy flying andbuilding so I see this as a fun way to improve some skills. I've done plenty of balsa building in the last 36 years but not much composite work. I do have friends here who design n build DS stuff so they can help with bagging etc.

How long is your fuse? Are there drawingsin a thread?

Cheers
Ian
Sep 20, 2017, 07:23 PM
Master of the Wind
G Norsworthy's Avatar
Not sure I published drawings but I can send them to you. I'll have access to the files sept 27. I understand what you are trying to accomplish. I think you would be very happy with a copy of the plane we built, plus you would not have to design it, only copy it. Read the thread and check out Bill's comments in the way it flies.

I can show you how to make a light T tail.
Last edited by G Norsworthy; Sep 20, 2017 at 07:44 PM.
Sep 20, 2017, 09:10 PM
Registered User
gliderguide's Avatar
Cheers Greg. I'd love to have a similar plane. It looks great, flys well and is a good evolution so why would I reinvent the wheel...

Sent you a pm. Also noticed you carbon socked your spars. I was going to use a Kevlar wrap like the BD but the sock looks really good and more accurate too
Sep 30, 2017, 07:41 AM
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gliderguide's Avatar
Greg

Sent you a couple pm's. Not sure if you got them.
Cheers
Ian
Oct 04, 2017, 04:55 AM
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gliderguide's Avatar
Fuse has arrived. Won't be using the elevator or rudder on this project...

CLM Pro set 133, extended boom and lots of extra Kevlar in pod, and carbon in the boom . It's very stiff.


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