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Teach Me Please About Making Custom Tanks

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Teach Me Please About Making Custom Tanks

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Old 02-14-2018, 09:55 AM
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ravill
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Default Teach Me Please About Making Custom Tanks

Last year, I made a custom smoke tank for my F-86.

It was a HUGE PITA.

I am very happy that I have a conformal smoke tank that is tucked nicely in a perfect spot over the CG.

But I don't ever want to make one again. Why? Because, I don't think I made it right.

The tank was really rough on the inside(which was REALLY hard to fix), it had tons of pin hole leaks that needed plugging and overall, it was tons of work. I think I used the wrong fiberglass resin and cloth.

Can all you gurus out there teach me (and the rest of us) how to make them correctly?

Like from the simple stuff, what kind of plug material, how to prep the plug, which cloth (kevlar is nice too!), which resin, how to minimize pin hole leaks, cleaning out the inside of the tanks, how long to wait for each step, etc.....?

And pics would be appreciated please!

Here is the only pic I took of my building the tank with the foam after cutting the tank in half.

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The way I did it is below:

1. I cut and shaped foam to fit the spot I wanted the tank in. I didn't sand it tough...(would that have helped?) I wrapped it in blue painters tape. (I think aluminum tape would've been better)

2. laid out aluminum foil, laid the foam plug on the foil, I found foam safe fiberglass resin and bought cloth (too coarse?) at west marine.

3. Brushed on resin (after mixing with solidifying drops) on the foam plug, then laid the cloth on the resin and brushed as many bubbles out as I could

4. Let dry

5. Turn plug over, repeat brushing on resin and cloth. These steps were repeated until the whole tank was covered.

6. Cut in half, clean out foam bit that got stuck in the tank.

7. Put halves back together, lay on aluminum foil, cut out another fiberglass cloth strip to close the gap, brush more resin and join the halves.

8. Fix the 85708978787 pin holes and attach fittings.
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Old 02-14-2018, 10:16 AM
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rhklenke
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Rav,

I have a meeting in a few minutes, so I don't have much time to type detailed directions now (maybe later if someone else doesn't), but there are two major things you need to change:

1) make a proper *male* mold for the tank. If you were going into production, you'd use that to make a female mold to make the actual tank, but for a one-off, you can make the tank from a male mold. A proper mold is one that:
a) is glassed enough to be *rigid*
b) is filled with icing and sanded smooth
c) is primed with 2-part primer
d) is wet sanded down to 600 grit, at least
e) is waxed
f) is coated with mold release

2) cast the tank on the mold in 2-halves - that makes it easier to release from the mold, leaves the mold in tact, and there are a few tricks you can use to make the halves fit together neatly.

3) use *epoxy resin*, not polyester. West system is probably the best. I have good luck with US Composites stuff...

Off to my meeting...

Bob
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Old 02-14-2018, 10:31 AM
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ChuckC
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Having experienced the pinhole beast myself - I can tell you that doing a couple of layers, at least is best. The inner layer should be a fine/light weave to prevent pinholes, but you need a heavier cloth for strength.

The best way to not get pinholes is to vacuum bag the mess onto a good, smooth female mold; it distributes the resin very effectively without having to make it so dang heavy. But, to do that, you really need a proper female mold built. A lot of work for one or 2 tanks. However, if you're making a generic size tank that could fit multiple air frames (if that's even possible), then ...maybe?

Ditto above for method of making a plug; you want SMOOTH. Don't forget PVA release...
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Old 02-14-2018, 10:35 AM
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I used Kevin Whitlow's method with great results.

Kevlar fuel tanks
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Old 02-14-2018, 11:09 AM
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Make a pattern out of some foam block and send it to Gary.....

https://www.jettechusa.com/collections/fuel-tanks-1
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Old 02-14-2018, 11:26 AM
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Originally Posted by Zeeb View Post
Make a pattern out of some foam block and send it to Gary.....

https://www.jettechusa.com/collections/fuel-tanks-1


++1. Best advice yet, Ha!
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Old 02-14-2018, 12:00 PM
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I can't find the other method I used and I don't remember who posted it.
  • You make a mold out of foam and cover it with a low heat film (like Econokote)
  • Wax it a couple times
  • wrap the entire mold with several layers of wet glass cloth (I used West Systems)
  • wrap the whole thing with shrink wrap
  • Once it is dry, I used a cut off wheel to barely cut through the fiberglass around the entire mold (making 2 halves)
  • removed the glass parts from the mold and install any fittings
  • epoxy the halves together with some fiberglass tape
Here is a pic of the mold, an internal shot with baffles installed, and one with the glassed tank wrapped in shrink wrap. Can't find a pic of the finished tank
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Old 02-14-2018, 12:53 PM
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Originally Posted by grbaker View Post
I used Kevin Whitlow's method with great results.

Kevlar fuel tanks
Yep, carve foam plug(s), cover with econocote (or any other low heat iron on covering) and lay up the tanks using fiberglass, kevlar, carbon fiber, or any combination of the three.
It's actually a little more involved than that depending on the size and shape of the tank being built (you have to plan ahead for part extraction, and joining lips, etc), but it is a relatively simple and quick process.

I have made many tanks using this method. I made at least 4 or five sets of tanks off of the molds from that 16 year old thread. I still have them in the attic, and I am sure they could be used again if needed.
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Old 02-14-2018, 01:14 PM
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Hey Raffy,

I think your general steps are fine, especially for a one off tank. The devil is in the details I guess.

First it sounds like you used polyester resin (your reference to "adding drops" sounds like adding the MEK catalyst). While I don't know anything specifically wrong with polyester in this application, I use epoxy, usually west systems with very slow hardener. You need a lot of time to do a good job.

Second, I don't use blue tape, but either low temperature iron on film, or packing tape. I glop the wax mold release on this heavily

Now I use a relative light cloth for the first 2 layers, usually 2 ounce, then follow up with 6 ounce satin weave for maybe 4 layers after that. I have everything precut to go on the plug before I mix anything.

Now this is where I think you introduced your pinhole problem. At this point, I wrap a final layer of teflon coated cloth (the resin does not stick to it) over the whole plug, then finally wrap the whole thing with either ace bandages or vet wrap my wife uses on the horses (like an ace bandage but sticky, I don't know how else to describe it). this last step compacts the layup and helps get rid of the voids and pinholes.

After cure, I then cut the plug in half with a band saw and the taped foam come right out. I clean the interior, inspect for any bubbles and repair with resin if needed. I mount the bung hole, I then join the halves back together with fresh thin CA, and cover the joint with a couple of layers of fiberglass tape and resin.

After that I mix up a hot batch of resin (fast hardener), thin it with heat and slosh it all around the inside of the tank, rotating it periodically for about an our until the resin sets.

Only think I could not follow in your sequence is the aluminum foil, I am not sure how that factors in.
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Old 02-14-2018, 04:21 PM
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Rav,

I made custom smoke tanks for my SM F-16 using lost foam method. The build thread and photos are in the 1/5 SM F-16 build thread here:
Skymaster 1/5 Scale F16 Build Thread
Start at Post # 461

It took some time but was not that hard. I had no plans for making more so the lost foam method was much easier than making a mold. Good luck, post photos.
Gary
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Old 02-16-2018, 11:25 AM
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This is why I love RCU!

I have so much to learn from all your replies guys!

Thank you!!

A couple of more questions please.

Where do you guys get your west system stuff? All online? Auto Parts? West Marine?

I had a hard time finding the lighter, finer fiberglass cloth and as I'm such an ignorant noob, I didn't trust myself ordering stuff online, do you guys get your kevlar, fiberglass cloth(s) at the same place you guys get your epoxy resin?

When you guys "apply wax" is that just regular car wax?

I use freedom form release (aka conosol 260 from fastenal) as smoke oil, if a releasing agent is like this conosol 260, how do you keep the first few layers of fiberglass/kevlar from absorbing the fluid?

Matt, where do you get teflon coated cloth? And I used the aluminum foil to catch the fiberglass resin and towards the end (as I was learning) I was able to use the foil to hold corners onto the foam mold.

And Zeeb, I have tons of Gary's tanks, and some of us LIKE to build! Crazy right?!

Last edited by ravill; 02-16-2018 at 11:27 AM.
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Old 02-16-2018, 03:15 PM
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Rav

Look here for samples

https://store.acpsales.com/categorie...gging-supplies

or amazon carries just about all of the items mentioned.

you will want to wax first with a parting wax, then spray with parting solution called PVA then do your layup.. ... your conosol is for forming concrete, a little different.
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Old 02-16-2018, 03:22 PM
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Raf, carnuba car wax would work(avoid oil). I like the method pointed to by Gary and I would also bag it and use dress liner as the outer mold(does not stick to the glass and helps avoid pin holes). You can get all your stuff glass and ez lam resin from ACP in Livermore
https://www.acpsales.com/home.html

Darren
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Old 02-16-2018, 03:37 PM
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Rav,
Parting wax is similar to car wax, but it is usually pure carnuba wax where car wax has other additives. I usually try to wax (wax on / wax off) a new mold at least 10 times before it's first use, then 2-3 times before subsequent layups. Wax alone is sufficient if your mold has an absolutely mirror finish, but if it is less than perfect (which mine usually are) you will also need PVA (polyvinyl alcohol). PVA is a water based liquid that gets applied after the last waxing and is allowed to dry completely before laying up the glass. It will form a thin film between the part and the mold and makes removal much easier. Supposedly it can be brushed on, but I always get fish eyes when I try to brush it, so I usually spray it on in light dust coats.

Here are some links to companies I use for materials:
Fiberglass Supply - Product Catalog
https://store.acpsales.com/
Some good tutorials here:
CST - The Composites Store | Page 1 of 1
These two carry West Systems Epoxy:
https://www.fibreglast.com/
Pilot Supplies and Aircraft Parts from Aircraft Spruce

I'd suggest you read as much as you can (and search for youtube videos) on composites, that will give you the best idea of how to get started. Then you just need to start trying some of it and figure out what works best for you.
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Old 02-16-2018, 05:17 PM
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do you guys get your kevlar, fiberglass cloth(s) at the same place you guys get your epoxy resin?
I used glass cloth from here:
https://www.thayercraft.com
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Old 02-17-2018, 12:13 AM
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I've made many tanks in the past, no need to cut the tank in half to release the plug and re-join just use a hard foam plug and once in the right shape apply 3-4 layers of release PVA (different to the normal white PVA) allowing to dry between coats, stick a pipe into he plug where the tank fitting is going to be and then apply as many say n this threat a few layers of thin cloth followed by 4 or so layers of a heavier cloth. I use a small white foam roller to apply the resin (West System) and keep working the resin until you get a nice even coating, this will also help the pin hole issue.

Once fully cured pull out the supporting rod and dig out as much of the foam you can near the opening then pour in acetone and dissolve the foam out. It needs a fair amount of acetone and its messy by once you have done this and washed the tank out with warm water to remove any PVA you have a tank thats in one piece and no need to join.

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Old 02-17-2018, 09:29 AM
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When I make tanks, like Kevin, I shape a one piece tank that fits the space available, and has space for fittings where I want them (don't ask.....). Then I split it and add a base on the female/outer part. Cover with Solartex, (really low temp covering), wax and PVA. When the layup is cured I insert a beach/basketball filling needle along one side and GENTLY squirt a blast of air and off pops the part. Can reuse the mold almost immediately for another tank..

Greg
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Old 02-17-2018, 12:09 PM
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Wow, you guys have blown my mind.....

I have a ton of reading and experimenting to do. Its exciting that I'm going to learn so much.

Darren, again you know of local places that have all sorts of cool stuff! Thanks man.
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Old 02-18-2018, 06:07 AM
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If you really want to learn how to make a fuel tank... Start here..
There's about 10 more vids to follow. Bob is simply the Best!
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Old 02-20-2018, 02:27 PM
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Hello, if you need help, I can help you.
write me to:

contact@cmjets.com

Regards from Spain
Carlos

www.cmjets.com
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Old 02-20-2018, 05:05 PM
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Hi Raf,

As others have stated, ACP and CST are good sources. Thayercraft is great once you know what you want and need volume and a great price.

I also like Fiberglast. They have a lot of educational material as well.

https://www.fibreglast.com/category/Learning_Center
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