I had used high density foam to carve out a plug. I would like advise on how I can seal the plug before I lay on a layer of fibre glass material. Appreciate advise on steps to take to complete the plug.

Thanks.

Isaac

Hi Isaac

Packaging tape seems to be used for this purpose.

Jason

Hi,

Thanks for the reply. I am not sure if packing tape can be used for my case. I had seen them used for moulds for fuel tanks.

This is my first attempt at creating a mould and I am not sure if the overlapping edges of the tape will be be transfered onto the mould. I desire a smooth plug (mould).

By the way, I am trying to produce mouldings for a nacelle to house a K80 engine for a Learjet.

Isaac

Isaac,

I would imagine you would be fine just applying the glass to the foam once shaped and sanded, you might need to add another layer of resin once its set up but probably easier than applying a sealer of some sort.

marcs.

[link=http://www.monokote.com/]Monokote or equivalent film maybe?[/link]

There are a couple of ways you could go about this.

Tape/Monokote. Very simple but the edges will be transferred to your mould and would have to be sanded and polished out.

Another way is to seal the plug with fiberglass. This is the more professional approach as it would create a durable plug and no seams. However it requires a lot more work to lay up the fiberglass and then sand, paint and seal the plug to the required standards.

You can also seal the plug with autobody filler. The stuff sands easily enough and can be painted on. You would have to be very careful not to damage the plug as it would be very delicate.

Issac,

sand the plug to desire shape, to a smooth surface. Then lay your cloth using epoxy resin. Do not use polyester or your plug will melt. Sand, fill pin holes with a good light catalyze putty, spay a coat or two of epoxy type primer. Sand, check for more pin holes, if any sand, when everything is perfect, you can polish your plug. Then you can prepare parting board for the female mold. For any other tips go to composite forum. A lot of info there. Hope this help.

Happy Holidays,
Alex

Hello:

You can see my way in my Picasa album:

http://picasaweb.google.com/cmjets2007/MiBandit#

http://picasaweb.google.com/cmjets2007/MiBobcat#

Regards from Spain.

Carlos.
________________________________

http://cmjets.blogspot.com/

Ask Butch (Hustler58), he is the foamplugmeister!

http://www.nextcraft.com/j47_sportjet02.html


http://www.nextcraft.com/rcdesignandbuilding.html

.

Yes, I recently used brown tape for a lost foam molded canopy and it is fantastic.. easy to apply and before laying the fiberglass you can shrink any wrinkle left with a heat gun. Also latex paint can be used as a sealer for the foam, in case you are using a polyester resin wich will attack the foam.

Enrique

Hello Enrique:

You can see the brown tape in my lost mold Bandit.

Regards from Spain Amigo.

Carlos.
__________________________________

http://cmjets.blogspot.com/

Watch the 105 videos here and you'll be building like a pro, and get your questions answered....

Best work I've ever seen.

http://www.youtube.com/watch?v=HqTKJU6PlkA

Very nice Carlos! didn´t knew that you used this method in your Bandit. Right now I am using too this method in a Mirage and supposing it doesn´t turn into a goo mess, I will post the pics here.

Hi

Were there any more ideas on this one? I am trying to produce a couple of small moulds for football arials but cant get the packing tape to work well.!!!

help???

If you are using epoxy you don't have to put anything on the foam. Just lay your glass and resin right on the foam. If you are using polyester than you have to be real careful. I would take spray adhesive and aluminum foil. Spray the foil and apply to the foam. The foil will have small wrinkels but they will not be seen through the glass cloth. Then wax and put a heavy coat of PVA. Butch

Brown paper and PVA glue overlap the joints and when its all dry sand the joints flush, if the brown paper start to pill give it another coat of PVA, its cheap and a very good way to cover a plug or even for finnishing a foam wing prior to painting, low stress airframe only though.

Mike

Here are a few Photos of a Plug I made for Smoke tanks on A Fly Eagle F-15.
First photo plug in place in Fuse.
Second photo first layer of fiberglass cloth with Epoxy resin.
Third photo Heavy code of Bondo after fiberglass to make smooth. Most of which was sanded off
Fourth photo first half of mold being laid up.
Fifth photo first half of plug made.
Final photo finished Mold. The lines in the orange is because I could not find my Dump gun so I had to brush on the gel coat.
Its not a hard process but it does take some time sanding and getting the plug smooth. The finished part will only be as good as the plug.
Hope this helps.

I am not sure by your post if you are making a male plug to use to make a female mold or if you are going to try to make a finished part off the foam plug.

If you are going to make a female mold off the plug, do as Butch says. Lay up the plug with epoxy resing and glass cloth. The glass cloth needs to be fairly thick (stiff) so it doesn't flex too much when sanding the glass. I recently make some tank molds and only used two layers of 3.2oz cloth and the foam would flex when sanding and caused me a lot of work to get a good finish.

I have made a dozen or so molds of aircraft over the years, seal the plug with Epoxy . Just brush on , then glass with 2oz cloth , sand , prime to fill imperfection, spray epoxy paint , polish and your ready to move to molding.

Thanks guys! I will move forward with the epoxy idea. Just answwer the question. I have made the final part in foam so yes I am trying to make a female mould. The parts were just to small to try and get tape on but  brushing on epoxy and glass should be fine.

Thanks again everyone

P.S Butch. that is one hell of a project your doing...superb

Thank you all for your help and advices... I am producing a male plug to create female moulds to pull off castings...

I had moved on to glass the plug with finishing resin. I forgot the weight of the cloth but it has the same thickness as t-shirt material... I applied a second coat of resin to fill the gaps in the weave and when it had dried, I wet sanded the entire plug with 400 grit sand paper.

I located some low spots in the sanded plug. I will follow Bill's method of coating the entire plug with a thick layer of putty... I have no success locating bondo putty in Singapore.. so I am testing various brands of putty to find one which is easy to spread and will sand well... the pics show the plug after sanding down with 400 grit sandpaper and the various putties I am testing.

By the way, is there a trick on how to lay an even coat of putty into the plug?

One of the putty that i am testing (the darker grey one) in the pic above is from a brand called Dynatron.. I noted that the maker of this putty is Bondo Corporation... Is this Bondo?

I had used this putty before and had noted that even after prolonged drying, it does not dry to a hard texture... it remains slightly flexible and elastic (sort of rubbery...). It does sand smooth but it fouls up the sand paper very quickly. When sanded dry, it creates a lot of fibrous particles (fromed from the sanding debris).

If this is Bondo, please kindly advise on working with this putty.

Try using polyester spray filler,it like car body filler,only thinner,you will need to use a spray gun with at least a2mm fluid tip .This stuff sands really nice,3 coats will give good build,allowing plenty of sanding,watch the pot life,which is normally about 15 mins,less in warmer climates!If you dont you'll be buying a new spraygun,dont ask how i know!!!!

Mun - For filling voids I use a mix of epoxy resin and micro balloons. That mix sands very well.
If I have a deep void to fill I use a mix of epoxy resin and milled fiber glass.