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May 08, 2017, 06:14 PM
Orco Skinny
Hi Naptalene
Balsa core foil looks nice. I'm a little confused, did you pre shape the balsa core by hand, or did you shape it on a mill , or some other method ?
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May 09, 2017, 02:06 AM
Registered User
I did it by hand lol.
I took a 3mm piece of balsa and pushed the mould halves onto it so it scored the planform. Cut that out with a craft knife.
Placed it back in the mould and clamped it together with quite a bit of pressure.
This compressed the balsa and gave me a rough idea of the foil shape but it was still too thick. So I sanded with 100 grit to fit into the moulds but left it slightly too thick ( the mould halves had about 1mm space without being clamped.
I used a lot of resin on the glass to fill any voids that my hand sanding created. All the excess resin gets squished out the little slots on the side of the mould as you compress it so it's fine.

Does that make sense? So the only fancy thing used was the printer for the mould.

The foam core using meat packing worked brilliantly. I just cut the foil shape and clamped it for 20minutes. It retained its shape and took the airfoil shape perfectly. I'll do one like that once I have some epoxy and report back. To my mind it would be the more technically correct shape ( says the idiot who has very little technical background)

Is there any other similar material that normal resin won't melt so I can try in the meantime?

Here is my autoclave......



Here is the foam core before I melted it with the resin. The shape was literally made by cutting the planform out and putting it between the mould whilst clamping. Pull it out and re-trim the planform.

May 09, 2017, 11:31 AM
Orco Skinny
Makes perfect sense to me. I once was making an engine cover for a vintage race car using fiberglass cloth and polyester resin. I was installing X bracing on the back side to give it some rigidity using styrene foam cut in to 1 inch wide strips. Then I covered it with 2 inch wide matt and polyester resin . What happened was the resin melted the styrene and the styrene outgassed leaving these perfectly shaped hollow cross braces. Sometimes it pays to be lucky rather than knowing what you are actually doing! I wonder if you used styrene in the sandwich with a light cloth and polyester resin if you would get a hollow rudder ??
MMB
May 09, 2017, 01:05 PM
a.k.a. Bob Parks
Depends on the resin used. Polyester resin may react to foams differently then Epoxy resin.

Look around building construction sites for blue dow insulation foam board sheet insulation scraps. The sheet foam is what RC airplane builders use for wing cores.

BP
May 09, 2017, 03:00 PM
Registered User
Dick L.'s Avatar
Quote:
Originally Posted by bbbp
Depends on the resin used. Polyester resin may react to foams differently then Epoxy resin.

Look around building construction sites for blue dow insulation foam board sheet insulation scraps. The sheet foam is what RC airplane builders use for wing cores.

BP

Unfortunately, polystyrene, whether extruded or expanded WILL react and melt when using polyester resin - including those foams suggested above. If you are determined to used extruded foam, use epoxy ! Any of the thinners or fillers with an ingredient listed as a "thane" - or - Acetone, MEK, or similar, will dissolve foam. So will gasoline - so you can "melt" out the foam (a very messy, gooey operation) if using a male foam plug if you want a hollow hull, rudder blade, keel, or airplane wing.. I haven't tried it, but it might be possible to coat a foam plug with epoxy, and then use polyester resin and glass over, but polyester isn't too good about affixing itself to epoxy. Besides, if you have the epoxy, why mess with polyester resin?

By the way, this issue of melting foam also happens when trying to use Bondo (or similar automotive body fillers) to fair foam.

Just a note of caution. Dick
May 10, 2017, 01:49 AM
Registered User

RG 65 Mass Build?


Thanks for the info Guys
I wouldn't have thought that bondo would melt styrene. A good one to remember.

If you want a hollow core, surely you could just cast both sides individually and then glue them together in the moulds?

I think I'm good to go for a keelfin mould now. It will be interesting to see how it goes as I will have to print each half in multiple pieces..... in theory it will all line up so let's see!!


Ps. I'm using the Polyester resin/chopped strand Matt for now as it's cheap and I blew this months budget on 3d printer bits.
May 10, 2017, 09:38 PM
Registered User

Manta RG65


Progressing right along
May 12, 2017, 11:53 AM
Registered User

Manta "Genesis"


Genesis (what I named her) is progressing slowly. Sadly living in the desert is limiting my building to just mornings lol. I could put a wall unit AC in the shop, but the AC bill would be a bit high. Fitted the bow and stern this morning and trimmed up the rear deck. Rood Ars from ARS Components (maker of the IOM Wedge, Tara and Nitro.. RG65 Sith) is making fins, bulb, keelbox and mast ram for Genesis . Hull and deck, ruff cut at this point is at 84g. This using 4oz fiberglass &4.5oz Terra Fiber.

My mini me IOM makes me smile just looking at it lol. I am not planning on using a swing rig for this version.
May 12, 2017, 12:35 PM
Registered User
RCphotoguy's Avatar
I like the shape of that hull. And some serious bling coming from Rood Ars!
May 12, 2017, 12:45 PM
Registered User
Google Ductless air conditioners - https://www.google.com/#q=ductless+air+conditioner
much more efficient than window units, some have heat to.



Genesis (what I named her) is progressing slowly. Sadly living in the desert is limiting my building to just mornings lol. I could put a wall unit AC in the shop, but the AC bill would be a bit high.
May 12, 2017, 04:56 PM
Registered User
Thank you Craig and Bob.
May 16, 2017, 10:55 PM
Registered User

Manta RG65


A little more progress on Genesis, fitting the deck and foredeck


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