# For small HPR gluing, I like Bob Smith's epoxy. What's a better option?

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#### jcsalem

##### Well-Known Member
Yes, it's yet another epoxy thread but I've never seen a good answer to my problem.

I know from my TRF postings that for large epoxy needs West Systems and Aeropoxy are highly recommended. However, the standard dispensers for West Systems mix up almost an ounce at a time. That's far more epoxy than I use for my typical HPR rockets (e.g., unglassed 2.5" to 4" rockets). It seems like a huge waste and expensive to use West Systems in this way. And it's too much of a pain to measure out smaller amounts (particularly since my scale is only accurate to 1g).

For all my HPR gluing needs, I've used Bob Smith's 15 minute epoxy for years. This is the kind they sell at many hobby stores. Yes, it's significantly weaker and smells nasty but it's very easy to mix up just a gram or three at a time which is usually all I need. I've had relatively few epoxy failures over the years. My biggest problems are that occasionally a fin fillet will crack on a hard landing or a plastic-wood joint will shear apart. To avoid cracking, I wish Bob Smith's was slightly flexible when cured.

I'd love to find a better option, but West Systems just isn't practical for me (unless someone has an easy way to mix just a few grams at a time). There are a bunch of others out there as well: Epoxy 88, System 3, NHP, etc. But they either appear to be roughly the same strength as Bob Smith's or are designed for mixing >= 1oz batches.

Suggestions?

Jim

PS: BTW, I know a lot of folks use the 5 minute epoxy but I generally don't work fast enough for that. It's also not supposed to be as strong.

#### stantonjtroy

##### Well-Known Member
Devcon makes a 15 and 30 min. both good. Also Hysol 1C is very good, about a 20-30 min work time.
FWIW
Troy

#### rocket999

##### Well-Known Member
Yes, it's yet another epoxy thread but I've never seen a good answer to my problem.

I know from my TRF postings that for large epoxy needs West Systems and Aeropoxy are highly recommended. However, the standard dispensers for West Systems mix up almost an ounce at a time. That's far more epoxy than I use for my typical HPR rockets (e.g., unglassed 2.5" to 4" rockets). It seems like a huge waste and expensive to use West Systems in this way. And it's too much of a pain to measure out smaller amounts (particularly since my scale is only accurate to 1g).

For all my HPR gluing needs, I've used Bob Smith's 15 minute epoxy for years. This is the kind they sell at many hobby stores. Yes, it's significantly weaker and smells nasty but it's very easy to mix up just a gram or three at a time which is usually all I need. I've had relatively few epoxy failures over the years. My biggest problems are that occasionally a fin fillet will crack on a hard landing or a plastic-wood joint will shear apart. To avoid cracking, I wish Bob Smith's was slightly flexible when cured.

I'd love to find a better option, but West Systems just isn't practical for me (unless someone has an easy way to mix just a few grams at a time). There are a bunch of others out there as well: Epoxy 88, System 3, NHP, etc. But they either appear to be roughly the same strength as Bob Smith's or are designed for mixing >= 1oz batches.

Suggestions?

Jim

PS: BTW, I know a lot of folks use the 5 minute epoxy but I generally don't work fast enough for that. It's also not supposed to be as strong.
I use NHP epoxy on mid power/small high power rockets without any failures on the epoxy itself (except on a rocket that the parachute didn't deploy).

The materials used on HPR rockets are generally weaker than the epoxy itself. Combine that with good build techniques and you generally get a strong rocket without the need for expensive top of the line epoxy.

I don't see the need for these expensive epoxies unless you are going for extreme flights (large minimum diameter, carbon fiber, ect.). If I am woried about a joint I just throw some fiberglass on it.

This is just my :2:. I have only been in the hobby 6 years, so it will be interesting to see what more experienced rocketeers say.

Sam

#### rdmmdr

##### Well-Known Member
estes gets build with thick ca.
mid power gets five min epoxy
high power gets built with west using pumps. you can mix smaller batches using digital scales, the are about 10$on ebay #### troj ##### Wielder Of the Skillet Of Harsh Discipline, Potent I use nothing but Fibreglast System 2000, or the dregs of the West I still have around. Buy a postal scale and measure small amounts that way. My family knows that yogurt containers, margarine tubs, ice cream buckets -- they all get saved for use for mixing epoxy. Yes, I've mixed close to an ice cream bucket full before.... For the smaller batches, I just measure it out by the gram or ounce, depending on amount needed, on my postal scale. -Kevin #### m85476585 ##### Well-Known Member I measure small batches on a little scale with .1g precision and up to 500g capacity. I got it on Ebay a few years ago for about$15. I use US Composites thin epoxy or Aeropoxy ES6279. I think Aeropoxy ES6209 is easier to find (GiantLeap sells it) and a little cheaper, but it cures slower than ES6279. I use pumps for bigger batches of US Composites for glassing, but I leave the pumps on all the time and use them to dispense just what I need into a mixing cup weighed on the scale.

Off topic, but Aeropoxy only has like 10 products, why do they need such long numbers?

#### MarkII

##### Well-Known Member
Aeropoxy is a division of PTMW Industries, which produces a variety of other products. My guess is that the combination of individual digits in Aerpoxy's product numbers represents a system of coding that indicates particular characteristics of the product, like, for example, the type of product, its recommended use and the unique formulation of the product, with each digit in the number standing for something specific and significant. If this is indeed the case, it represents a more precise and reliable way to identify each product than using descriptive names or simple sequential product numbers would do.

MarkII

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##### Well-Known Member
I really like the West System line up. For a more flexible bond use G/flex. Their G-5 is a really good 5 minute epoxy as well. Check out their website because they have tons of information and customers projects. As others have mentioned you can meter the 105 series by weight. One of the best features of the West System is the wide range of fillers for various bonding and filleting applications, and if you want or need to glass you still use 105 to wet the glass and do your lay up. https://www.westsystem.com/ss/

Another great epoxy that is used in aircraft building is System Three T-88. This is a structural adhesive, takes overnight to set but worth the wait and the expense. This is a far superior product than the hobby shop epoxies. https://www.systemthree.com/members/tds/T-88_TDS.pdf

#### AKPilot

##### Well-Known Member
Jim, there's absolutely nothing wrong with using Bob Smith's (local hobby store variety) epoxy for HPR. Why would you not think it's okay? Granted it doesn't carry a 'designer' label but, if you get the actual product information from their company it rates fairly close to Zap and others.

I've met Bob Smith at iHobby in Chicago each October and we've talked about his adhesive line. If used properly they have an enormously high success rate. The key is in the preparation of surfaces and resin/hardner. The failures Bob has told me about deal with rookies not mixing it properly.

So keep on buying it with confidence, and simply use a postal scale to measure the amounts and you'll be golden.

If you want something more 'deisgner' wise, go for West Systems (which I also have) but, let's face it - on the field I don't know too many people who start the conversation with epoxy talk. The design and finish of your rocket generally takes over . . .

#### jcsalem

##### Well-Known Member
Thanks for the great info, folks! Just what I was looking for.

Does the NHP or T-88 epoxy smell as nasty as the Bob Smith's?

#### troj

##### Wielder Of the Skillet Of Harsh Discipline, Potent
FWIW, a lot of epoxies can also be measured out easily using syringes. 20cc or larger work best, in my experience.

-Kevin

#### Sailorbill

##### Well-Known Member
FWIW, a lot of epoxies can also be measured out easily using syringes. 20cc or larger work best, in my experience.

-Kevin
That is what I use. I just go to the "Farm" store. They are usually in the vet section. I also have a postal scale to measure out small batches of Aeropoxy.

A friend of mine and I were have a build session recently and he was using some 20 min epoxy to tack some parts together. Problem was the temperature of the garage and the size of the container made the epoxy kick faster than he thought it would. Almost had an oops.:y:

#### MarkII

##### Well-Known Member
Thanks for the great info, folks! Just what I was looking for.

Does the NHP or T-88 epoxy smell as nasty as the Bob Smith's?
I use BSI epoxy quite often, and I have never noticed a strong, let alone nasty, smell from it. I think that it has an odor very similar to Devcon 2-Ton epoxy. I have used the Quick-, Mid- and Slow-Cure varieties. I haven't tried their Finishing Epoxy yet. I agree with Troy; BSI epoxies are fine for most building needs. I still like to use Aeropoxy 6209 Structural for some things, though.

MarkII

#### terryg

##### Well-Known Member
I use devcon 30 min epoxy for attaching fins and other quick setting uses. I use aeropoxy for fillets and general structural uses. It is very slow setting and is so thick that it stays where you put it. I use large syringes to dispense it and if I mix too much, it goes into the freezer for use the next day.

#### 5x7

##### Well-Known Member
The West systems I got a few weeks ago says it can be mixed in a 5:1 ratio by volume, so I got two 10 cc medicine syringes from the drugstore (the kind with the plunger). I have mixed several 6cc batches (5 resin 1 hardener) with very good results.