F-86 Sabre (90mm) Fast Foam - Page 2 - RC Groups
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This thread is privately moderated by Herb, who may elect to delete unwanted replies.
Oct 27, 2009, 04:34 PM
Family,RC Planes & Gym....
Get it going :-) Im waiting for the HET F86 to come out, that should be a fun build for me :-/
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Oct 29, 2009, 07:26 PM
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I only find time to work on this thing over the weekends ... and then if the weather is nice you know where I end up

I still have to order the motor. I am still debating on either a custom Neu 1415/1.5y with opend endbells (36.5mm diam) versus the standard Neu 1515/1.5y (39mm diam). The latter does not fit the WeMoTec MidiFan ...

This 101mm fan is I think a bit on the big side, because of the fuse surgery needed ...

Oct 30, 2009, 05:33 PM
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The front retract unit assembly is almost complete.

Need to reinforce the sides of the mount, add the pull-pull steering steel wires and mount the stering servo (hs-82mg).

Because of the standard 3.15 mm wire size, I can use either the spring lg or a normal steel wire lg.

Last edited by Herb; Oct 31, 2009 at 06:39 PM.
Oct 30, 2009, 05:39 PM
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The Neu 1515/1.5y fits the 90mm shroud I am using quite prefectly (39.5 mm diam motor opening).

Next I need to machine down the rotor to 89mm.

Nov 01, 2009, 09:12 PM
Registered User
herb...how do you cut your rotors down?...I know its kind of ghetto but i use alittle stand with a motor bolted to it,,then i attach the rotor i wanna cut, run it up about 1/4 throttle , and then hold self made sanding block( 4in by 4in block of wood with 80grit sand paper glued to it) on the rotor while it spins..... seems to work fine
Nov 03, 2009, 02:13 PM
corsair nut's Avatar
is that the fly fly shroud?
Nov 05, 2009, 02:58 PM
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Originally Posted by sheppard559
Herb...how do you cut your rotors down?...
A drill press is perhaps the best tool, but I have used just a dremel in the past as well.

You clearly mark where the cut is supposed to go on the rotor (with a bit of margin left) and then cut away. Has worked for me for years.

Flow around the rotor tip is highly turbulent, so the cut and finish need not be absolutely perfect ... The tip gap is not critical either, as long as it's < 1mm.

I am still considering sticking with the 101mm fan, it's a lot more rigid than the 90mm variants.

It will require quite a bit of foam surgery through; both the intake and the exhaust have to be modified.

Yet there is plenty of intake area, even for the 101mm fan (see pic below).

I did not like the fact that the Neu 1414 motor - which has a smaller 36mm diam can and therefor fist the WeMoTec MidiFan - has closed enbells.

Claims to the contrary notwithstanding, years of experience have taught us that rotor cooling in edf is a crucial longevity factor.

Steve Neu had kindly offered me a few months ago to make a custom 1414 EDF motor with open endbells to take care of the rotor cooling problems.

But in the end I decided to just go with the slightly bigger 1515, and use a larger shroud to accomodate the 39mm can. It took me just three days to get one from Esprit ...

Last edited by Herb; Nov 08, 2009 at 03:52 PM.
Nov 07, 2009, 02:36 PM
EDF Jet Jam 2017, June 15-18
Kevin Cox's Avatar
Very nice work Herb!
Nov 08, 2009, 02:48 PM
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Thanke Kev !

I finally glassed the wing bottom with 3 layers of 3/4 oz cloth; it will only be one or two layers max on top.

The persistent sanding and filling paid off, the wing surface still looks quite ugly at this point, but is in fact really smooth - as one can see when looking at it sideways.

I did a preliminary stress test of the wing, to see if further work might be needed, and it seems pretty strong. I cannot detect any flex now.

I am comparing ultra-thin adhesive aluminum tape to stick-on polyester film. The latter is a lot lighter, but does not conform well to compound curves. I might end up using both, and later use steel wool to cut down the shiny-ness.
Last edited by Herb; Nov 08, 2009 at 02:54 PM.
Nov 10, 2009, 03:07 PM
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Over the weekend I managed to do some priming and sanding....

Automotive primer (rustoleoum from ace) was used to fill in the weave. Most of it was wet-sanded away later, giving a reasonably smooth finish. I used a B&D Mouse to do most of the sanding work.

Nov 10, 2009, 03:12 PM
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Primer fills in the weave nicely.

You sand too much and the glass will comes off as well, which you want to avoid at all costs.

A side view of the wing shows nicely the thin epoxy - glass layer.

Nov 10, 2009, 04:58 PM
Never too much detail
fredo21's Avatar
Hi Herb

Following your build with great interest, looks great. I have a flyfly Sabre and have the objective of glassing it and finishing it in a spazstix mirror chrome paint. I am in the process of testing the finishing methods. My plan is to glass the plane, get a very smooth surface(priming and sanding). paint with hi gloss black/mirror chrome then multiple clear coats. I need to test this to determine the chrome effect achieved and the durability of the finish.

I tried WBPU and found, surprisingly, the automotive primer went through it and ate the foam. I knew the primer would eat the foam however I thought 3 coats of WBPU would protect it. I am considering using a laminating epoxy as you have suggested. Is the brand of automotive primer you are using "foam safe" or are you relying on the epoxy to separate it from the foam?


Nov 10, 2009, 05:24 PM
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Originally Posted by fredo21
... I tried WBPU and found, surprisingly, the automotive primer went through it and ate the foam. I knew the primer would eat the foam however I thought 3 coats of WBPU would protect it. I am considering using a laminating epoxy as you have suggested. ...
Good question.

No the primer I am using is NOT foam safe, it is standard (rustoleum) automotive prime. Cheap and very effective.

First let me say that I do *NOT* recommend anything but laminating epoxy.

I have tried all other methods (pu, wbpu, polycrylic), and believe me there's no comparison. No, you do not save any money either.

Laminating epoxy (Pacer in my case)

* is easy to apply (I mix it with rubbing alcohol to dilute)

* can be mixed with microballoons

* dries fast and hard (12-24 hrs)

* is tough and structurally very strong when combined with fg cloth

* sands extremely well, does not gum up sanders

* sticks to anything

* forms an impenetrable layer

How do I prevent the primer from eating the foam?

I deviate from JePe's method - he first puts the cloth on the bare foam, then paints the laminating epoxy on it.

I do the reverse, first I use a large (1 inch) paintbrush and apply the thinned epoxy everywhere. Then I put the cloth on, and apply more epoxy.

My method ensures that there are no bare foam spots left! This is crucial (btw JePe makes it all look so easy. It is not).
Nov 11, 2009, 04:17 PM
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The nosegar strut needs to be lengthened a bit, and the mains shortened just a bit.

Other than that, it looks good so far

Nov 13, 2009, 05:38 PM
corsair nut's Avatar
nice herb mysabre gained a little over a pound after alum finish. didnt seem to hurt performance at all though.

hopefully steve will do holes in the 14 series. i tend to agree with you on that as well. when i got my first one, i was like..."huh?" no holes? does well with a decent cool down run after flight to help with heat soak. i run a small heat sink on mine. i thought i cooked my 2y, turned out it was a broken wind like tumblers. the 1.5Y never gets close to cooking at 2.5kw on 8s without cooling holes. the 2y on 12s is a solid 3.5kw, and is pretty close to its limit.

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