Mold Making Troubles

[A6INTRUDER]

I have tried many times to make molds but I always seem to have troubles.

Carving a plug isnt too tough but casting the mold seems to be my downfall.

I carve a plug, cover it in several coats of West system epoxy, paint it with Krylon, wait for that to dry for days or sometimes weeks, wax the crap out of it with meguires 8 mold release wax, spray it with several coats of PVA, then proceed to make the mold. Let it cure for a day or so, and when I pull the plug out some of the paint stays with the mold and usually my edges get messed up too. What am I doing wrong.

Recently I shaped a plug for a wingeron out of pink foam, covered it with
5 coats of epoxy,(did not paint it), sanded it with 600 and then polished it with rubbing compound, but now I'm reluctant to make the mold, for fear of the same thing happening again.

Do you guys have any suggestions?????

thanks

A6

[Tony D.]

You don't need to paint your plug.

After you have your shape finish sanded and you have applied a couple of coats of epoxy, you need to let it dry for at least 3 days.

Then shoot the plug with a good quality grey primer. (At least 2 coats)

Automotive primer works well for this.

Wet sand the plug with 400 and then 600.

Check the surface for any irregularities, dimples or holes etc. If there are any fill them (I use automotive Bondo) and then shoot it with the primer again let dry then sand with 400, 600, and if you have the patience 800.

Put on thin layers of wax and really buff it to a shiny smooth finish between coats of wax and leave plenty of time for the wax to dry between coats.

I only use 1 layer of PVA and I always apply the PVA after the plug is installed in the splitter plate so that there will be a layer of PVA at the boundary between plug and plate.

Make sure that your splitter plate has at least 5 coats of wax on it before installing the plug.

After you lay up your mold wait 5 to 7 days before you try to pull the plug out.

Hope this helps.



T.D.

[A6INTRUDER]

Thanks for the suggestion TD,

I have done most of what you said, but I think the major thing
that has caused problems for me is not waiting long enough
before pulling the plug out of the mold. I have only waited a couple
days at the most.
This time actaully I did paint the plug, just to see that it was
ready, but then I stripped it back down to glass, and now I have sanded with
400 and 600 and I have waxed it many times...
I will be trying it again in the next few days so I will wait longer
this time before removing the plug.

thanks again

TIM

[soholingo]

take some pictures so we can all learn...

Thanks,

Jay

[A6INTRUDER]

Ok
Here are a few shots, sorry they are not too clear.
It will take a while for this all to happen but I will post pics as I go.
I hope this does not turn out to be another failure.

TIM

[A6INTRUDER]

Also,
Any suggestions would be appreciated.
It would be nice to have one of these projects turn out good.....

thanks
TIM

[davidfee]

Looking good so far. Make sure you laquer the parting board so it's nice and glossy. What do you plan to use for filling the gap around the plug? If the gap is small, modeling clay works well. I've also had great luck using Bondo. You can see my website for some details about how I've done it. http://members.cox.net/davidfee/techniques.htm

What's your surface coat? It should be fairly viscous, and having it an opaque color really helps. I prefer black, others like different colors. Whatever the surface coat, use a brush to gently get it into the corner along the seam between the fuse and the parting board.

Ultimately, if some paint stays in the mold it isn't the end of the world. Just take it out with paint thinner and then polish if needed before waxing.

Good luck,
-David

[A6INTRUDER]

thanks for the ideas David,
I have looked at your web site before and it is great.
You have a talent for this stuff.
I had always used clay for the dam before but now that I see your idea about bondo I think I will give that a try. Seems like the plug would be more stable that way.
West system epoxy is what I have always used just because it can be bought localy,
and I have put micro balloons and black coloring in it for the surface coat.
That has yeilded alot of nicks and air pockets along the edges of my molds so this time
I think I will try, cabosil around the edges, as I think it is stronger than microballoons.

What methods can be used to make a recessed area in the fuse for the canopy to sit in? I have actually already pulled a mold off this plug, just in the area where the canopy will be, and my thought was to make a slightly larger canopy, and then
cut out the fuse plug where the canopy will be and then slip this slightly larger one in under the surface of the plug. Glue it in place and then it will create the recessed area where the actual canopy will reside. I am sure there must be more simple ways, does any one know one??

thanks again

TIM

[davidfee]

Don't use microballoons for the surface coat. It will be weak, for one thing. Also, the microballoons act like little ball bearings and the stuff will just slide all over the place. What you want is colloidal silica (also available from WEST Systems). It's a thixotropic agent. That means, it acts like the platelets in your blood and greatly increases the flow resistance (particularly in shear). This makes the surface coat "sag resistant."

As for the canopy, I've read so many good ideas that I've never tried... that I can't keep them straight. ;) Let me think for a second... ok, here's a good one: http://www.rcgroups.com/links/index.php?id=4138

[davidfee]

That guy who did the Bf-109 in the link is way more gifted than I will ever be! :)

-David

[Tony D.]

Tim,

I can highly recommend West Systems 404. (I think this is the same product David is referring to in his post)

It is better than cabosil, it is also more expensive but in this case you get what you pay for:

http://www.westsystem.com/webpages/productinfo/guide/

Canopys are a pain but with the plug you have you can use this method to good effect to make a perfectly fitting canopy:

http://www.charlesriverrc.org/articles/construction/stevefujikawa_perfecthatch.htm



T.D.

[A6INTRUDER]

thanks for the ideas, I will pick up some colloidal silica as soon as I can. I may have to order it as the place I get west systems stuff is very limited in what they carry.

Both of those hatch ideas are good ones.

T.D., while that is a great idea, I dont think it will work for me cause there will be no other opening in the fuse as this is going to be a wingeron or pitcheron plane. There would be no way to lay up the glass behind the hatch. That is a really simple way to do it though. The other idea would work, if need be.
I will be thinking about it some more.....
Any other ideas would be appreciated too.....

thanks again

TIM

[AirBornOne]

A6...
Your project makes me think your wishing you had a VS Sailplanes Xica.
Very nice looking plug.
Will be anticipating your progress.
Skies.
Jay.

[A6INTRUDER]

I got a chance to surf the net a little today and seem to find that Coloidal silica is the same as Cabosil. Is that true? If thats the case then I have some of that already.
My local(well, its 25 miles away) supplier of West products does not carry Coloidal silica (#406)or the graphite powder(#423) either. They will not order it so now I have to find the best place to order it.
David where do you get yours???
I tried putting moleling clay around the plug this morning before work and it seemed to
do well. That is what I have used before but I am still leaning towards trying the
Bondo method too.

more as progress happens

TIM

[A6INTRUDER]

AirBorneOne,

Well that was not my intention but I wish those were still around.
I saw one along time ago and thought it was an awesome plane.
Hey maybe Ed Berris could revive that one too.....

thanks

TIM

[Bayport_Bob]

A6intruder,

Since you live near Washington, one of the better suppliers of composite raw materials is Fiberglass Supply, Inc.

http://www.fiberglasssupply.com/

They carry just about everything, and they're usually the least expensive. Some name brand stuff is sold at regular retail, but most other products are very, very reasonable.

Just my opinion & everybody's got one. Bob

[A6INTRUDER]

Thanks for reminding me of them.
I had forgotten they were so close.
I just sent them an email to see what they say about Cabosil and Colloidal silica,
and they seem to have a generic graphite powder, so I asked if it was the same
as west systems.

thanks Bayport Bob

TIM

[davidfee]

Yes, Cab-O-Sil is Cabot Corporation's brand name for colloidal silica, aka fumed silica. It's all the same stuff.

The WEST microlite filler mentioned earlier is likely a blend... probably microballoons and something else. They say it's "lighter" than microballoons, so who knows. I haven't used it. I generally use as little filler as possible and, when I do use it, I want it to be structural.

Anyway, I get most of my fillers from CST, since they have competitive prices and I've known the owners for over 12 years. I also get some stuff locally at Diversified Materials Company (online, but no e-commerce).

-David

[A6INTRUDER]

Today I ordered some graphite powder from fiberglass supply in bingen wa.
I also decided to go with modeling clay to seal the plug to the parting board.
Here are a couple pics (sorry again not too clear) of the plug in the parting board.
I put lots of clay on the back side and then just pushed more clay in fromt he top side. Then I scraped it off with a regular putty knife and a razor blade.

As soon as I get the graphite powder I will be ready to do the molding.
I hope to have this done by the end of next week.

How long after I mold the first side should I wait until I do the other side???


thanks again

TIM

[raptor22]

Yes, Cab-O-Sil is Cabot Corporation's brand name for colloidal silica, aka fumed silica. It's all the same stuff.

The WEST microlite filler mentioned earlier is likely a blend... probably microballoons and something else. They say it's "lighter" than microballoons, so who knows. I haven't used it. I generally use as little filler as possible and, when I do use it, I want it to be structural.

Anyway, I get most of my fillers from CST, since they have competitive prices and I've known the owners for over 12 years. I also get some stuff locally at Diversified Materials Company (online, but no e-commerce).

-David


I've noticed them, and that they're epoxy is pretty cheap. They say its as good or better than west systems; have you used it?

--Alex

[A6INTRUDER]

HI Alex,
No I have not tried their epoxy, but you are right it is less expensive.
Maybe some one else might be able to tell us how it works.

TIM

[raptor22]

I was hoping that David might be able to give a report of the DMC (diversified materials) stuff.

--Alex

[davidfee]

Oh yes, the stuff DMC sells is made by Jeffco Products (http://www.jeffcoproducts.com/), another San Diego company. I've used their epoxy for years. It works just fine, and they offer many formulations for different applications. I generally have gone straight to Jeffco's warehouse so I could talk to the chemist and get different systems DMC doesn't always carry.

For basic layups of fuselages and vacuum bagged wings, I have used Jeffco 1310 L-6 epoxy resin with 3102 (fast) hardener. For molds, I have used the same resin with slower hardeners, such as 3156 (med) and 3176 (slow). For mold surface coats I have generally used Jeffco 908 SC with 3102 or 3156 hardener. I used 1310 L-6/3176 filled with steel or aluminum powder to make metal-filled epoxy prop molds.

I've recently started using MGS epoxy for my layups, since it is lower viscosity (flows and wets out better) and it has a nice blue color. ;) I like the Jeffco better for some applications, since the fast hardener (3102) is a bit faster than the fast MGS hardener (285). Sometimes speed is good.

-David

[A6INTRUDER]

As I had said earlier, I made a quick mold of the area of the fuse where the
canopy will be. Just for fun, I layed up a couple different canopies to see
how much glass to use.
The red one is the mold, the middle one is two layers of 3.5 oz and one layer of 1.4 oz glass.
The right one is three layers of 1.4 oz glass.
The middile one seems to be just about what I want for thickness but the
right one is too light..
I made these way way too big cause I have not decided how large the
actual canopy will be.

As soon as I get the graphite powder I will lay up the first side of the mold.

more later

TIM

[A6INTRUDER]

OK today I received the graphite powder that I ordered from http://www.fiberglasssupply.com/

Ordered it last friday and got it today, wednesday. pretty quick.
Soholingo, if you have not purchased any yet, they have a pretty good deal on it.
Shipping was 5.61 cents and that included some other items I ordered too.

David, how much graphite powder is needed for molds. I read West Systems recomendation, but they seems to be using it for boats so I was wondering how much you use.

I will try to get one side of this molded this week if possible.

thanks
TIM

[davidfee]

Yeah, I don't think the WEST application is really for a mold surface. IIRC, they are talking about just decreasing friction and increasing the wear resistance on something like the bottom of a centerboard or keel, or something.

I can't remember a specific ratio I've used, but I think the <10% by volume listed on the WEST #423 can is about right. A little less is probably fine. Then you thicken it up by adding colloidal silica.

-David

[A6INTRUDER]

thanks David,
I will try it soon.
TIM

[DLD]

I would not recommend Bondo for your parting board, as it may want to stick to the board and the plug so much you may have a hard time getting it out. Clay or smooth spackling works best. Cabosil and silica are pretty much the same stuff, both work well. I ran a business for 6 years building kits with all fiberglass fuselages, built all the molds myself, some of which turned out thousands of parts and are still in good shape. One thing you might want to try is wiping the PVA on with a soft rag instead of spraying. I found that it gives a smoother surface and makes a better barrier. One good coat should be enough if the surface is smooth and waxed well. Make sure the wax you're using has lots of carnuba, it makes ALL the difference. Make the mold at least twice as thick as the intended part, for production molds I made them about 1/4 of an inch thick, especially the flange. I used West Systems epoxy exclusively for 6 years with no problems. For your surface coat, thicken the epoxy with silica until it is about like mayonaise or a little thicker, color with pigment ( my preference was red) and brush on always brushing in the same direction. This will help keep voids out, especially along the parting board. Make sure you arange for alignment between the mold halves while they are still togehter. I drilled alignment holes and trimmed the edge at this point. If paint comes off the part, don't worry about it, just clean it out of the mold, polish the mold and continue. One of the positives about painting the plug is that if it sticks a little, it just takes off paint and doesn't stick the plug to the mold. Plastic propellors make good parting tools for molds. I could go on and on, but hopefully this will help. Feel free to ask me any questions about making molds, I made many of them anywhere from hand launch gliders to giant scale USRA race planes like AT-6 and P-51. Good luck,

David Layne

[DLD]

I missed the part about the graphite earlier. I don't think it is necessary. I never had to use it in my molds. Just make sure your part is smooth (600 or better), well waxed and a good layer of PVA. Also make sure your surface coat is pretty thick, two layers if necessary.

David Layne

[shoe]

...I ran a business for 6 years building kits with all fiberglass fuselages, built all the molds myself, some of which turned out thousands of parts and are still in good shape...

David Layne

I remember when the Saturns were the planes to beat...of course I was just a kid then I'm not that old ;)

Thinking of going back into business David?

[davidfee]

I would not recommend Bondo for your parting board, as it may want to stick to the board and the plug so much you may have a hard time getting it out.
David Layne

I'm sure I don't have as much experience as you, but the Bondo method was passed on to me by Chris Boultinghouse (Corn Dogger HLG, CAB Designs) back in '97 or so. I was having trouble getting seams which I found acceptable using the clay method. I have used bondo on at least 4 fuselage molds since then and on several smaller tools (spinners, other small parts). I have not had a sticking problem. I use wax and PVA on the plug to prevent sticking. I always use lots of wax... no magic.

On the graphite subject, well... you're right. It's probably not needed. But it doesn't hurt. Some people go so far as to use aluminum filled epoxy on the mold flanges and into the part line edges for improved strength. I've used a silicon-carbide filled surface coat for extra hardness on a propeller mold. Again, not needed... but some people will do it.

I like to include the locating pins and clamping hardware (threaded inserts and sleeves) in the mold flanges while I build them, rather than drilling and adding them later. Seems to make the alignment that much more positive.

-David

[Tony D.]

WADR DLD the Bondo method works very well, it is just a matter of having your plug and parting board waxed and PVA'd properly so that nothing will stick to it.

When using splitter plates I switched from clay to Bondo a few years ago and IMO there is no going back, the seam is superior to clay but of course YMMV.

For alignment I like to take a 6mm drill bit and hand turn small "dishes" into the first side of the mould so that when the other side is laid up it will automatically index with the first side. A pretty standard technique.

I was lucky to be taught moulding by a master mould/tool/layup maker who always stressed that it you did your Prep. correctly then you were most of the way home and everything else was just simple technique.
--------------------------------------------------------------------------
Going off topic here for a bit now:

I flew a Saturn for a while back in the day. A 2.9T with obechi wings. It was a refreshing change from the Selig section equipped gliders that were so abundant at the time. I flew mine at the slope lots of times with ballast and it would really move!

And I thought the plastic (or PVC?) wing tubes were a great idea.

Do you by any chance have any of the large aluminum wing rods kicking around? I no longer have the 2.9T but if the wing rods are available I would like to have a couple.


T.D.

[A6INTRUDER]

Ok so now you guys have me confused.

Graphite or not,
Clay or Bondo.
Spray the PVA or wipe it on

Well, I already have the fuse in the parting board with clay and it has been waxed many times, with wax that has carnuba in it.
I guess I am going to try it the way it is and also I am going to put some graphite in,
mostly for color but hopefully for strenght too. I will be mixing in Cabosil too.
I have always done Ok to this point before, but the trouble for me has always been
air bubbles around the edges of the mold, and the paint sticking thing. I never used Cabosil to thicken before, just used some micro balloons or some West system, fillet powder(410 I think). So maybe the Cabosil will make it all go well......

I am hoping to do the first side tonite(late) so I will post some pics tomorrow.

TIM

[Tony D.]

TIM, when you say "air bubbles around the edges of the mold" I assume you mean the plug/splitter plate junction?

If I am correct then what you can do is use an acid brush and "stiple" a bit of epoxy/cabosil slurrey in that area before doing your main layup. Just use the brush as a poker but go gently and work the E/C mixture into the joint. The E/C will sag a bit but enough will remain in the joint to make a fillet that you can lay up over and eliminate the air bubbles.

Wait for this to set up a bit and then do your main layup.

By the way you can use paper towel to apply PVA just don't "paint" it with to many back and forth strokes.

I am looking forward to your pics.



T.D.

[A6INTRUDER]

I layed up the first half of the mold tonite.
First I mixed up Epoxy and some carbon, then added in cabosil, until it was
about like mayonase. Then I painted that on the plug, trying to get it well into the edge where the plug and the clay dam meet. then I painted it onto the rest of the fuse using strokes in only one direction as suggested. While that was setting up, I cut strips of 2 oz mat and also one piece of 1.4 oz cloth and one of 3.5 oz cloth large enough to cover the entire thing.
When the first coat was getting tacky, I applied the one layer of 1.4 oz glass and then started putting pieces of the 2 oz mat on soaking them with epoxy and then when I thought I had enough of that on, I put the remaining layer of
3.5 oz cloth over it all. I soaked it with epoxy and then smooted it all out with my gloved fingers and I could feel the heat from the curing epoxy.

So far so good. Now the big wait to see how it turns out.

I will be away next week so this will get a little over a week to cure.

Should I then, lay up the next half without trying to take the plug out of the
first half to see if it is worth continuing on???????
The plug is only made of pink foam with epoxy over it so I think it will be
quite fragile. Maybe I will just have to take a chance and do the second half and hope for the best.......

I am not good a waiting so being away will force me to let it cure completely..

I attached some pics but as usual they are not very good.
Hope you get an idea of how it is going.

Thanks for all the support

TIM

[A6INTRUDER]

here is a couple more pics

[davidfee]

Tim,
It looks good so far! I'd like the mold to be thicker, myself, but it will certainly be fine this way.

Yes, definitely leave the plug in place. For one thing, being pink foam, you are likely to damage, if not destroy, it in the process of removal. Also, once you pop it out of the mold half, you won't be able to get it back exactly the way it was (or hold it there), so the second mold half will be too deep, by the amount that the plug is sitting high in the first half. Confused? ;) Just leave it in place and trust that you did a good job.

-David

[A6INTRUDER]

HI David,

Yes I think I should have made it a little thicker too, but I decided to try this and see if it works, since I have had so many falilure.

I know I should'nt have done this-- but-- this morning I went out to see how it looked and just for fun I lifted the edge of the mold from the parting board, just a tiny bit, to see if it was going to be stuck there, and the whole mold popped right off the board. Then while I was looking at it I twisted it slightly and the plug popped right out. So now I am stuck with having to try to get it back in there properly to make the other half of the mold. The good news is that the mold turned out really good. I am happy with the results so far.
It is much better than any I have made so far, no air pockets around the edges and it looks really smooth.

thanks to everyone for all the help, and I will be doing the other half when I return.

here are a couple pics

TIM

[Tony D.]

A6, as my nephew always says "Sweet"!

How are you going to do the indexing?

You can take a 6 or 8mm drill bit and make shallow "dishes" in the mould flange so when you lay up the other half of the mould it will make small "pins" that will index perfectly.

T.D.

[davidfee]

A6,
Congrats! It looks like the nth time is a charm. ;) I suggest you follow Tony's advice and drill/grind little dishes in the mold flanges. Two or 3 per side will be plenty. Sand these smooth and then put a lot of wax on them, since they will be a little rough. They will provide good indexing.

For getting the plug to stay in the mold, you may be able to "glue" it in place with PVA. I have had limited success with that. I think it was limited mostly by my impatience. If you wax the plug and mold again, you may be able to tack the plug in place using little dots of CA. Good luck!

-David

[A6INTRUDER]

I decided that everything was going so well and I had the time,so I layed up the other half of the mold tonite. Wax on- Wax off 6 times, then PVA, let that dry about an hour, then layed it up just the same as the first side.
I indexed it as you suggested T.D. so we will see how this all turns out.
It is curing in the garage now.
Cant wait to see how it turns out too.
It would be so cool to have one of these projects turn out to my liking..........
I am kind of a perfectionist in some ways so my past molds just didnt make me happyl.
Hopefully this one will.
If I can get a few fuses out of it I will be happy......

thanks again for all the suggestions and I will write more about
it when I return in about a week.....

TIM

[PDX Slope Pilot]

Very nice work Tim!!

[A6INTRUDER]

Well I had a little time this morning before I had to leave so I checked on the
second half. It was the same as the first. It popped right off and the plug
popped right out too.
NO air pockets or bubbles around the edges either.......

WOW success at last.

I trimmed the edges with my band saw and then ran them around the belt
sander to make them exactly the same size.

Now just a little clean up and some time to cure more, and they will be
ready to use.

The indexing pins work great, I think next time I will make them a little bigger though.

thanks again for all the help and I will post pics of the first fues when I
do it.

TIM

P.S. the brown furry things(deer) were in my front yard last nite when I was laying up the mold, just could resist putting in a pic.

Hey PDX you might be flying one of these soon>>>>>>>

[Tony D.]

Glad to see it worked out so well TIM, your Mould looks great.

It's all in the prep.

If you really want to go the distance and/or there are some small rough areas you can take some fine rubbing compound and use it to buff the mould surface, this is not a necessary step but it makes for a glassy smooth surface to layup against.


T.D.

[A6INTRUDER]

Thanks TD
I will do that cause I want it to be as good as it can be.
I have several ideas for small wingeron or pitcheron planes from this fuse.
Now that I know I can do it right I will be working on some other ideas I have too.
I fly mostly slope planes and I get tired of having to buy new parts after the crash or bad landing so now I can make my own.......
take care

TIM

[A6INTRUDER]

P.S.
Hey DLD I used your idea about the plastic prop for splitting the mold and it worked
great too.

thanks again

TIM

[davidfee]

Looking good, Tim!

[hayman]

I'm curious as to how you plan on joining the two halves?

Bill

[davidfee]

Details... ;)

I was wondering the same thing, since there are no openings in the mold yet. It could be as simple as cutting the tail open so a stick could be inserted. It may be worth making step flanges also. I think Tim is out of town, so well probably need to wait for his answer.

-David

[A6INTRUDER]

Wow this forum has been busy since I was gone.
Great to see that it is growing.
My idea for joining the halves is this.
I want to make a canopy opening. So I plan to make both halves of a test fuse and then just CA them together. Then I will decide just how big to make the canopy hole. I will cut the canopy out of the test fuse and then separate the halves again. Then I will put the test fuse halves back in the molds and cut out the mold halves for the canopy hole. That will allow me access into the mold when I lay up more fuses. My dilema is still that I would like to make a recessed lip around the canopy opening so the canopy will fit flush. I have thought about glueing in a thin layer of glass(or something) about one quater inch wide all around the canopy opening on the inside of the mold so when I lay up the fuses it will leave the recessed area in the new fuses.
Any body have any other ideas???
Thanks

TIM

[davidfee]

Sounds like a plan.

To get your recessed lip, use a few layers of striping tape along the perimeter of the opening. Then wax the tape along with the rest of the mold. This will give you the lip you need to have the canopy fit in place. For a more permanent solution, you could epoxy a strip of laminate (cut from a fuse) to the mold and then wax as before. The tape is easier, and it will work.

-David

[A6INTRUDER]

Thanks DAVID,
I had thought about some kind of tape but was not sure if it would stay in the mold
I will give your idea a try.

TIM

[davidfee]

Yes, the tape works. That is how I've made the recessed "pocket" on the lower surface of the control surfaces on molded wings and tails... to make room for the gap seals and ensure that the surface "telescopes" into the wing/stab.

-David

[A6INTRUDER]

I laid up both halves of my test fuse this morning before work.
one layer of 1.4 oz glass and two layers of 3.5 oz glass.
now I will wait a while and see how they turn out.

here are a couple pics

TIM

[A6INTRUDER]

I took both halves of the test fuse out of the mold and they turned out great.
Then I taped both halves of the test fuse together. I made a paper template of the canopy, and taped it to the test fuse. Then I shot some paint aroung it to mark the area in the fuse I would cut out. I cut out that area and then a strip about 1/4 inch wide around(you will see it in the pics).
I cut out the mold halves where the canopy will be and then I epoxied the strips in the mold wherer the recessed lip will be.
Also even though the pics dont show it, I cut the tail of the molds off so
I will be able reach in there to press the seams down when I join the two fuse halves in the future.

Here are a couple pics.
Hopefully the next pics will be of the first actual fuse.....

Gettting exciting now.

TIM

[A6INTRUDER]

I layed up the first production fuse yesterday and took it out of the mold today
It looks pretty good with the exception of some air bubbles along the
seam where the two halves meet. They are only on the surface so maybe I didnt get the seam pressed down good enough. It is hot here and the epoxy kicked off sooner than I expected. I guess some slower hardner will be necessary

Thanks to everybody who contributed ideas and hints.
I am sure my next fuese will be better.
here are a few more pics

gottal go for now

TIM

[Coligny]

Nice,

but how will you produse the canopy, since you cut this part of your mold out?

Maybe you will make a seperate mold of that area on the original plug?
Did you use any PVA in the prosess?

Regards

Coligny

[A6INTRUDER]

HI Coligny,

You are exactly right. Back in my posts you will find where I already
made a mold of the section of the plug where the canopy will be.
I made it way too large and now I will refine it a bit so the canopies will be a closer
fit.

Yes I used PVA. first I waxed the molds about 4 times then I wiped in a layer of
PVA with a soft cloth, like David Layne suggested.
When I separated the mold this morning it popped right off the fuse.

This has been a fun learning experience for me.
I am looking forward to seeing what others do too. I hope we get more people
posting their molding projects here on the Zone.

TIM

[Coligny]

Tim,

Do me one favour when you paint this thing. Make the hatch the same colour as the fuselage. It is a hatch and not a canopy. I always think it looks ugly when hatches are painted another colour to simulate a canopy, although the shape does not resemble a canopy.

Thats just my opinion.

Regards

Coligny

[A6INTRUDER]

HI COLINGY,
Yes I know what you mean. Sometimes they just dont look good with fake canopies.
I attached a couple pics of two planes I built from scratch. The little one
on the left is the one I am making this fuse for. The original fuse was a lost foam fuse and I just never liked it. But you can see how I painted it.
That is probably how I will paint the new fuse too. I did make a carbon hatch for this fuse and it looks Ok, mostly just because its carbon.

thanks for the input

TIM

[SoarNeck]

HI Coligny,

You are exactly right. Back in my posts you will find where I already
made a mold of the section of the plug where the canopy will be.
I made it way too large and now I will refine it a bit so the canopies will be a closer
fit.

Yes I used PVA. first I waxed the molds about 4 times then I wiped in a layer of
PVA with a soft cloth, like David Layne suggested.
When I separated the mold this morning it popped right off the fuse.

This has been a fun learning experience for me.
I am looking forward to seeing what others do too. I hope we get more people
posting their molding projects here on the Zone.

TIM

Hi Tim,

Nice work so far, looks good. Just wanted to suggest that you invest in a tub of Dolphin wax from Harold Sattler @ H&M Racing:

http://www.superminnow.com/hmracing/racing/index.html

Don't know if it's on his site yet, but it's not expensive. Using that you can eliminate the PVA step, which makes painting in the mold much easier.

I look forward to these composites threads too, and hope to see more. I'll add my own as soon as I'm done lofting fuselage formers for my F3B Frostbite design, which I hope to start construction on reasonably soon.

[A6INTRUDER]

HI SOARNECK

So how does Dolphin wax work, I saw a thread by Soholingo a while ago, here in the
composite forum and it seemed like about 10 coats were needed to make it work.
Also it seemed critical how it was buffed out.
I only use 3 or 4 coats of Meguires 8, and then wipe in one layer of PVA.
What method of applying and buffing do you use, and how many layers too

Looking forward to seeing your posts about your upcoming plane too.

thanks
TIM

[Coligny]

Those pics looks great, thats how I would do it as well, those shapes lend themselves to not having a canopy, just a hatch...

[A6INTRUDER]

Here are a couple pics of the first fuse out of the mold and what I have done with it.
It is replacing a fuse on a little pitcheron plane that made a while ago.
It has two sets of wings, one 42 inch and one 50 inch.
V tails are solid balsa and they will get bagged up as well.
They are attached to a small carbon tube that gets glued into the tail of the fuse
Shooting for an AUW of about 19 oz.

Tim

[SoarNeck]

HI SOARNECK

So how does Dolphin wax work, I saw a thread by Soholingo a while ago, here in the
composite forum and it seemed like about 10 coats were needed to make it work.
Also it seemed critical how it was buffed out.
I only use 3 or 4 coats of Meguires 8, and then wipe in one layer of PVA.
What method of applying and buffing do you use, and how many layers too

Looking forward to seeing your posts about your upcoming plane too.

thanks
TIM

Whoops, sorry Tim, I guess I didn't notice this come in.

I rarely use more than 4 coats of wax, and have NEVER had a problem with release. If anything, this stuff goes on quicker because you're not supposed to wait very long between application and buffing. The big time savings is in not having to apply PVA and wait for it to dry, and not having to clean the resulting PVA off the mold and part afterwards. Painting is also much easier I'm told, but I don't have first-hand experience with that yet.

Let me put it this way - I got a dixie cup full from a friend as a sample, and when that ran out, I waited until my new shipment arrived before molding anymore parts. I had 2L of PartAll wax still on the shelf!

Dolphin (note: not its real name) is really great stuff - even Phil Barnes (of bagging DVD fame) switched after hearing about it.

I'll let you know when I start on my model. Almost finished the design, but I'm house-sitting right now, so the CAD work is on hold. Plus it's too nice outside to be building :)

[davekra]

A side note about using Bondo to make the parting board.
It can soften paint! I've used the stuff before for other things and should have remembered that.

I made a pattern for an Apogee fuse out of pine and used the spray can sandable primer from the hardware store to fill and smooth it.
The pattern was sanded to 800 and waxed several times then pva was applied.
The Bondo went on easy, man does it kick off quick, anyway.
After a couple hours I removed the pattern and the paint that was under the Bondo had softened and pulled off when the plug was removed.

Now I have to repair the pattern and try again. I did sand the top of the parting board and it did produce a beautiful sharp edge that, if the pattern had not been damaged, would produce a wonderful seam.

Thanks,
davidk

[GaryO]

The last time I checked Dolphin wax was not on the web site, but he does have it. Email to verify. I think I paid about $15 for 8 oz. Magic stuff.

[Boldav42]

Does anyone know how the Dolphin wax compares to the Safelease 20L. I attended a build seminar put on by Oleg Golovidov (Taboo XT DLG), and he used the Safelease for both the mylars and the fuse mold. He swears by the stuff. I watched him put only 1 coat on and then wipe it off with some paper towels a few minutes later. That was it! He's done hundreds of wings and fuses with no problems. I haven't gotten any of the stuff yet, but I plan to when I get an order together for CST.

[A6INTRUDER]

Well I finally got the finnished product done.
It is a pitcheron plane, it has two sets of wings. one 50 inch and the other 42 inch. Also two hatches, one painted and one carbon...
Got to fly it last nite for the first time. First flight was real short but after adding a bit of nose weight it flew GREAT.
Very quick and handled very well. Still need to do some trimming out.
Thanks again for all the help and suggestions.
TIM

[Ward Hagaman]

Beautiful!
Did you make the linkage yourself?
Where did you put the wing rods at (% of MAC).
What servos?

[davidfee]

A side note about using Bondo to make the parting board.
It can soften paint! I've used the stuff before for other things and should have remembered that.
... snip ...
The Bondo went on easy, man does it kick off quick, anyway.


While it's entirely possible that the Bondo softened the paint (polyester resin can do that sometimes), I suspect that the heat was a primary problem. You can control the cure rate (and heat) by using less catalyst.

If the Bondo really softened the paint, that means it made its way through your PVA and your wax.... so I'd suggest being more careful with the release agent application.

good luck,
-David

[A6INTRUDER]

HI WARD,
Thanks for the compliments.
Yes I made the linkagae myself. I have a Mach1 and now also a Shrike kit and I just
kind of copied what they did. My Cams are made of printed circut board type material, I found some about 1/8th inch thick and I used two layers. It is tough to cut them accurately though. I will need some practice to make them perfect.
Do you know where I can buy some already made ones, that dont cost tooooo much??
The wing rod is at 25% MAC but when I flew it last nite I had to balance it a little bit
ahead of the rod. I put it in a couple pretty steep dives and didnt seem to get any flutter though.
I am just using HS85MG servos. They seem to work fine especially since this is a pretty small plane. 40 oz each servo, so a total of 80 oz of torque, I think that is enough for this plane.....

thanks again

TIM

[davekra]

While it's entirely possible that the Bondo softened the paint (polyester resin can do that sometimes), I suspect that the heat was a primary problem. You can control the cure rate (and heat) by using less catalyst.

If the Bondo really softened the paint, that means it made its way through your PVA and your wax.... so I'd suggest being more careful with the release agent application.

good luck,
-David

I don't think it was heat, there wasn’t that much bondo and I was in contact with it during the whole process. Also the bondo I used to position the plug in the plate was very thin. I had 3 "ribs" that supported the plug and used bondo to glue the plug to them. After those were set I bumped the plug and it came out, this was before the bondo surrounded the plug. The paint had already discolored and was soft. The pva had come off the plug so I had to spray it again before surrounding it with bondo. I’m making another mold for an apogee fuse and the sides are rather straight so it was going to be somewhat difficult to extract from the splitter or the mold.
The plug was painted 3 days before waxing so the paint was dry. Several coats of wax and the pva dried for a day before using the bondo. The bondo its self doesn’t penetrate the pva, only the solvents do. The pva is permeable and the solvent can get to the paint and start softening it. The wax layer is only going to be a few molecules thick so it's not going to stop the migration of solvents. I'm not an expert, I don't even play one on tv so this is just my guess at what is happening.

Either way, I was able to repair the plug and put it back in the sanded parting board. There was a slight gap now but after spraying pva it was fine and the mold came out looking quite nice.

Thanks,
davidk

p.s. Is there a way to make a jogle gasket that is more precise than trying to mark it or going by feel? I was thinking of using some tape arround the top of one side of the mold and trying to cast a plug that I can then cast a gasket from.

[davidfee]

The bondo its self doesn’t penetrate the pva, only the solvents do.

There should not be any solvents in your Bondo... it should contain polyster resin (styrene monomer... which can soften paint) filled with milled glass, clay, etc.

The pva is permeable and the solvent can get to the paint and start softening it.

PVA is used as the primary release agent in many polyester-based applications. It generally works very well and should not be permeable to any considerable extent.

The wax layer is only going to be a few molecules thick so it's not going to stop the migration of solvents.


This is true, especially since we'd be talking about organic solvents, if there were any. This is a main reason why I suggest that people do not thin their epoxy with any solvents. However, that barrier, which is only a few molecules thick, is generally sufficient to provide a reliable release for both epoxy and polyester systems.

In my experience, that inexpensive sandable primer from the hardware store tends to soften/separate/outgass/etc. at pretty low temperatures. Maybe it was the heat... maybe it was the styrene... maybe it was a combination or something else. Regardless, I'm glad you got good results in the end.

Is there a way to make a jogle gasket that is more precise than trying to mark it or going by feel? I was thinking of using some tape arround the top of one side of the mold and trying to cast a plug that I can then cast a gasket from.

How about using a couple layers of tape around the inside of one mold half to approximate the layup thickness (plus room for epoxy) and then go by feel to match the gasket to the tape? Kind of an educated guess. Seems like less work than making a special plug.

-David