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Jul 12, 2019, 11:03 AM
More gadgets please.
pete914's Avatar
Thread OP
Placed an order with Callie-graphics for the sticker set for the "ED" Airforce livery. Stoked!

Looking at airfoils. I'm still leaning towards something non-symmetrical; I think I'm going to need some lift for this big girl.
What do you guys think about the RG-15?
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Jul 12, 2019, 03:50 PM
Dont forget the velcro straps
corsair nut's Avatar
Probably wouldnt be too bad...just really thick. Mine has a semi symetrical. Its pretty thin though
Jul 13, 2019, 10:03 AM
Registered User
Ed Waldrep's Avatar
I used an Eppler 224, 7.1% thickness, hot wire cut with lite ply templates.

With that Dollar Tree foam, you can remove the paper from one side and then bend the foam around a cylinder like an oatmeal tube container or over the edge of a bull nosed (rounded edge) counter top. Bend it away from the paper. The paper keeps it from creasing. You can pull the paper off after if wanted.

https://www.rcgroups.com/forums/show...tch-built-2007

Good luck!
Jul 14, 2019, 07:00 AM
More gadgets please.
pete914's Avatar
Thread OP
Thank Ed! I'll look into that airfoil.
It's going to have to be thick. My landing gear needs 50mm, I could maybe get away with 45mm which means I'll probably be around 9.8% thickness

I'm going back and forth between cutting my own wings or trying to find someone to do it for me.
Jul 15, 2019, 08:02 AM
More gadgets please.
pete914's Avatar
Thread OP
Quick question for Brent, et al...

I need to extend my battery leads at least 16"
The castle creations cap pack is only rated to 53v...that's not enough as I'm hoping to run 14s on this beast. I ordered it but I think I'm going to have to return it.

If I extend my battery leads to 16", do you think 4 or 5 of the 300uf 63v capacitors will be enough to save the ESC?

I blew up a 14s YGE for this reason (I think).

I don't see how else I can make this work without extending the battery leads.

Any thoughts?
Last edited by pete914; Jul 15, 2019 at 08:11 AM.
Jul 15, 2019, 08:17 AM
More gadgets please.
pete914's Avatar
Thread OP
Oh, canopy is glassed and solid. I'm still planning to cover it with the Styro Spray 1000. They said it should stick if I rough up the surface of the fiberglass.

I attempted my first high-tapered hot wire cut and it went as planned...which means I failed and it looks like I cut it with a hacksaw.

Wire got slack and hung up on my formers...basically, I did everything wrong.

Attempt #2 tonight
Jul 15, 2019, 10:41 AM
Dont forget the velcro straps
corsair nut's Avatar
one thing about thickness on the wing..if you move the gear fwd like I did to aid In the ease of rotation....it puts you in a thicker part of the wing. I moved the gear quite a bit fwd from scale...reason being...every f5/f20/t8 family jet ive had with mains in the scale location...was hard to rotate. if your seen videos of my big t38 you know that's not the case. the main gear only sit a couple inches aft of the cg
Jul 15, 2019, 01:18 PM
More gadgets please.
pete914's Avatar
Thread OP
I have noticed your T-38 rotates like a dream. I definitely want that.
I will plan to put the LG just behind the CG.

Keep the advice coming, thanks Brent...
Jul 15, 2019, 04:16 PM
Dont forget the velcro straps
corsair nut's Avatar
no problem man. I just want to see your model be successful
Jul 16, 2019, 08:01 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by pete914
... I blew up a 14s YGE for this reason (I think). ...
Can you see which component(s) failed Pete? Are you certain measured current at WOT wasn't too high?

Quote:
Originally Posted by pete914
... I don't see how else I can make this work without extending the battery leads. ...
I assume you cannot move ESC close(er) to battery and extend motorwires instead?

Quote:
Originally Posted by pete914
... The castle creations cap pack is only rated to 53v...that's not enough as I'm hoping to run 14s on this beast. ...
Capacitor voltage rating same or higher as input caps already on ESC.

Quote:
Originally Posted by pete914
...If I extend my battery leads to 16", do you think 4 or 5 of the 300uf 63v capacitors will be enough to save the ESC? ...
Rules of thumb for extra capacity, instructions, expert opinions
too long wires batteryside will kill ESC over time: precautions, solutions & workarounds - RCG

Vriendelijke groeten Ron
Last edited by Ron van Sommeren; Jul 16, 2019 at 08:21 AM.
Jul 16, 2019, 09:25 AM
More gadgets please.
pete914's Avatar
Thread OP
Ron,

The ESC was specifically procured from YGE for the intended application. The company that built the 120mm EDF selected the ESC specifically for 14s and around 200 amps peak current draw.
The ESC has the full cap pack that YGE makes but the leads to the battery are likely around 18".

I've read your thread a few times; thanks for putting up such good info and replying here as well.

Without your thread explaining DC inductance on battery leads I probably would be unaware of the issue.

Brent suggested moving the fan forward to shorten the leads. I will do so to help alleviate the problem but I can only move it so much.

Things get pretty bunched up with the landing gear so I know I'm going to have to add at least 12" to the battery side to make switching out batteries and positioning the ESC in airflow possible. Based on your suggestion of around 220uF caps per 4", I think I'll add 4 caps.

How bad is extending the motor wires via splicing and soldering in a longer wire vs attempting to desolder the wires from the ESC board?
I would rather not as most ESC manufacturers seem to use a solder that requires a blow torch to melt.
Jul 16, 2019, 01:28 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
You can't see which component(s) failed? Picture(s, or have you already binned the ESC?

Vriendelijke groeten Ron
Jul 17, 2019, 07:04 AM
More gadgets please.
pete914's Avatar
Thread OP
Ron,
I haven't pulled it out of the glider yet. I was frustrated so just put everything away for a bit to cool off about it. I will try to post some autopsy photos here as I'm taking a break from the T-38 to get the glider up and running for an event this weekend. I will say the capacitors on the failed ESC all look fine. No desoldering of the wires, everything looks fine. No smell of smoke, just no power when plugged into the batteries. I'm sure something is burned up in there though...

I really need to make sure my ESC wiring is optimized in the T-38 as a failed ESC will probably result in a crash landing

So attempt #3 and I think I have a workable airfoil for the vertical with some sanding!

I downloaded the templates for the airfoil (free online web application) from: http://airfoiltools.com/
This site rules! It makes a printable form for your home computer that you can tape together if the airfoil is longer than 11".

Any suggestions on mounting the vertical to the fuse? I don't want to put a post through to the bottom of the fuse as I will be right in the middle of the single exhaust tube...
Last edited by pete914; Jul 17, 2019 at 07:09 AM.
Jul 17, 2019, 10:28 AM
Dont forget the velcro straps
corsair nut's Avatar
I had a post for my vert. so youll have to make a partial or full bulkhead that has a built in spar. maybe some good 1/8 ply or maybe even 1/4"
Jul 17, 2019, 05:17 PM
Classic jets rule
AIR SALLY's Avatar
Brent Clear your Pm's it is full.
the 38 is looking good


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