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Arsenal78

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I feel like a thread already exists but I can’t find it. I just purchased my first large fiberglass rocket (Rocketry Warehouse ARCAS) and I’m used to BSI epoxy but that would cost way too much for this. I’ve heard about US Composites and West Systems but have never used them and after looking them up and all the different types, I’m quite confused on what I would need. I see US Composites is much cheaper so I’ll probably go with them. I can get West Systems locally but it’s a lot of money. I know I’ll need milled fibers and stuff for it. Which resin/hardener set would I need for internal fillets and building it? I may use RocketPoxy for external fillets on this.
 

timbucktoo

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Here is a good thread.
 

timbucktoo

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Just do a search for epoxy. Here’s another.
 

mikec

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I use 635 thin with 3:1 medium hardener for everything.

I would also recommend getting a good scale and measuring by weight; skip the pump system.
 

Arsenal78

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Weight isn't an issue on this sized kit. I will look into getting a good scale though for smaller birds. I understand milled fiber is good for fillets but would it be needed for actually gluing in the fins?
 

NateB

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US Composites is very thin epoxy. Even for internal bonds, I thicken it with milled fiber and cab-o-sil. When it is just mixed from the 2 parts, it runs all over the place before it starts to cure. Good for laminating, not so good for structural work.
 

Tobor

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Weight isn't an issue on this sized kit. I will look into getting a good scale though for smaller birds. I understand milled fiber is good for fillets but would it be needed for actually gluing in the fins?
I believe mikec recommended the scale so as to insure more accurate dispensing of resin and hardener.
As to attaching fins, I would not suggest using any form of milled fiber as the fibers can interfere with seating the fin roots properly. Save the milled fibers for the fillets.
 

mikec

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I use milled fiber for internal fillets and cabosil or microballoons for external fillets. Any joint that is easy to get to and not visible (e.g., MMT to CR fillets) I use chopped fiber. I usually tack the fins on with something that cures faster (BSI 5-minute or even CA.)

Using weight instead of the pumps allows you to mix much smaller batches. Otherwise you'll end up wasting a lot of epoxy, even if you try to mark your pumps for fractional shots. By weight I can easily make 1/4 oz if that's all I need.
 
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rharshberger

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US Composites makes the 650 and 150 epoxies, 150 is a structural adhesive that can be thickened with cabosil or other thickeners/fibers but it is too thick to laminate with, 635 on the other hand is a near water thin laminating epoxy for layups and it wets out fg/carbon cloth very well, it to can be thickend and used as a glue. I built my L3 and 7.5" Nuclear Sledgehammer with almost entirely 635 3:1.
 

C.O.B.H.C.

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I have used US Composites Medium to build a bunch of rockets. For fillets I thicken it with Cab-o-sil and milled fiberglass or chopped carbon. For fiberglass or carbon fiber lay ups I use it straight with no additives poured out on a paper plate so it doesn't kick as fast. It is great epoxy.
 

SkyFire

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I use Hysol 9462 for everything; fillets, bulkheads, etc. Not only is it incredibly strong it's also thixotropic (meaning it doesn't run or flow like many epoxies) I have been using it for years on giant scale rc airplane firewalls (affected by high torque and vibration) and high stress landing gear support structures.
Hysol 9462.jpg
 

watheyak

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I second (third?) The suggestion for a good scale with a .1 gram resolution.

US Composiites is pretty nice stuff at a really good price. With the right additives it'll do just about anything you need it to.
 

Rob702Martinez

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Aeromarine 300/21 thin or 400/21 thick you can add kevlar pulp, chopped kevlar, milled glass, milled carbon fibre, chopped carbon fibre and color it. It's 70% of what I use for internal filllets on fins and rings, laminating and other needs. Otherwise its proline with or with out additives or add copper for leading edges, or rocket proxy with or without additives for external fillets. Etc.
 

TheTank

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I use Hysol 9462 for everything; fillets, bulkheads, etc. Not only is it incredibly strong it's also thixotropic (meaning it doesn't run or flow like many epoxies) I have been using it for years on giant scale rc airplane firewalls (affected by high torque and vibration) and high stress landing gear support structures.
View attachment 440302
I used this a ton back in my giant scale RC competition days. My old supplier is gone these days. Can you recommend another good source these days?
 

Conway Stevens

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I have used US composites for over 20 years. They have both a thin and a thick based epoxy. The thin works great for laminating fiberglass cloth or carbon fiber. even used it with Kevlar. Its to thin for much else. would take alot to thicken it. I like to utilize their medium hardener for this. Their thicker base is pretty thick. easy to utilize for fillets. BUT for fillets and structurally needed componets I really like Aeropoxy, Have used most everything there is out there over many years. West systems, jb weld, Panel bonder, Hysol and others. The US composites is good product and not alot of money. comes in various sizes.
 
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