Best way to strengthen an Excel Plus or Horizon 54

[firemanup]

Hi guys,

Some new questions for ya, I'm too chicken to put my BSD THOR up on a K motor i'm just afraid of something like what happened to the Jaguar. So to me basically I don't have a K capable bird, now that's a problem.. heh

So I'm considering an Excel Plus or a Horizon 54 for a new K motor/mach busting bird. I doubled the completed weights the respective websites have listed and i'm breaking mach in sims with most of the upper K motors.

Has anyone seen either of these birds fly on K motors..?

What I'm wondering at this point is how best to strengthen the bird to handle the upper K motors. I've not fiberglassed before but i'm willing to learn.

What i'm considering now is building stock with one or two wraps of 6oz glass, topped with one wrap of 2oz glass. I don't want to glass the nosecone so i'm wondering what kind of lip that will give me at the airframe where the cone meets.

2nd option is to double wall the whole thing with couplers.

3rd option is to double wall the whole thing with couplers and glass the inside of them with one or two layers of 6 oz glass.

With any of these i'm thinking i'm going to need some noseweight with the bigger K motors, so i'm considering filling the nosecone with 2 part expanding foam.

What is your opinion as far as what will be needed, and or which of the above modifications for strength would be the best bet.?

My preference at this point would be to double wall with glassed couplers, I don't mind finishing paper tubes at all and am a little worried about my finish on my first fiberglass attempt..

Thanks for any help suggestions.

 

[DPatell]

I suggest fiberglassing the tube with a layer of 6oz. followed by a layer of 2oz. Fiberglass the inside of your couplers with 2 layers of 6oz. glass by laying the fiberglass inside the couplers, then blowing up a ballon to compress the glass tight to the coupler.

Then I suggest fin tab to fin tab internal glassing with 6oz. glass, large epoxy filled with milled glass external fillets, along with a layer of 6oz fiberglass fin tip to fin tip, followed by a layer of 2oz for finishing, or just paint another layer of resin over it to fill the weave.

This will result in a VERY robust rocket, that should be able to handle the K motors. Mach is not nice to rockets

The lip will proably be 1/16" or so, not too bad. You can use bondo to build that up on the cone.

You will be surprised how much strength the 6oz fiberglass adds.

Also, I suggest making sure that your coupler fits are very tight, in order to prevent movement side to side if it cones. That will definately result in a shred.

 

[rocwizard]

Personally, I would recommend biting the bullet and glassing the exterior. It is really not that hard. I actually think it's fun to do As for getting a good finish, the weave can be filled in many ways, be it auto body filler <bondo> or thickened epoxy. WHat I recommend though, is to get a can of Kilz primer. It is VERY high solids and fills in voids very quickly. You mioght also want to try out some Super Fill or UV Smooth Prime which can be had from Aircraft Spruce or Shadow Composites.

I would recommend two wraps of 6oz. but that's just me.

HTH

 

[firemanup]

Dpatell,

Are you saying 6 oz and 2 oz on the outside then 2 layers of 6 oz on the inside of the stock couplers, or.....

Outside layers then double wall full length of the body tubes with couplers that have two layers of 6 oz inside of them..

Roc,

I'm not so concerned with filling the weave of the fiberglass, more so where the wrap overlaps, i'm trying to figure out a way to get the edges to match up without coming up short or overlapping creating a hump that has to be sanded down...

What is finishing epoxy guys...? is it basically any long cure time epoxy or is it a specific type of epoxy used for fiberglassing?

Without being a west systems guy yet, and not willing to invest in it YET i'd rather try this first, how much epoxy will i need..?

Currently I use bob smith stuff from the hobby shop, comes in two squeeze bottles that equal out to 9 oz combined, to put one wrap of glass on the outside of a 4"x36" tube am i going to use about 1/2 of that, all of that..???

I'm starting to think the fiberglassing supplies alone will add up to another 30 to 40 bucks..

Thanks for the quick replies and info...

 

[Justin Horne]

From what I've gathered, finishing epoxy is just a sandable epoxy. PML sells some, 20 minute. Almost all that I have seen is 20 minute, so that may be the only kind. It's also used for sealing wood fins.

Justin

 

[DPatell]

I'm sorry, I read it afterwards and had to double read it. Hope this will make a little more sense...


Body Tubes:
1 Layer of 6oz.
1 Layer of 2 oz.

Couplers (altimeter Bay, or zipperless coupler if thats how you plan to deploy):
2 layers of 6oz. glass internally

You could double wall if you'd like, that would make a stockier rocket. Build for the biggest motor you plan to put in there! Overkill is okay in this instance.

 

[Ryan S.]

I would to essentially what dan said. put big internal fillets (thickened, really thickened eopxy) so when you do the tip to tip it will be easier for the glass to make the transition from fin to MMT. Definantly overbuild, it is fun I like heavy little rockets that can take big motors, it looks cool when the flame is bigger than the rocket itself

 

[daveyfire]

Finishing epoxy is a longer-cure epoxy that is also quite thin and is designed for lamination. It does not contain any of the fillers added to the hobby shop 5 and 30 minute resins to make them 1:1 mix and a lot thicker. It's very, very thin and runny. It is NOT, however, sandable. No epoxy is sandable, and if it is, it has been adulterated with some filler which will weaken the joint. I've found that covering the layer of glass with another layer of resin works to fill in the weave, but it's incredibly heavy and is quite brittle (we land on lakebed, and I bring my rockets down quick -- on rockets I've filled this way, it's a cosmetic repair every flight).

The way to fill in the weave is to use a high build primer, as Eric mentioned, in 2 or 3 coats, or to squeegee in epoxy filled with West System 407 Fairing Filler or similar. This is not only lighter than straight epoxy, it also will hold up better and be easier to sand. Dealing with the overlap isn't that bad -- just overlap the cloth about .5" to 1" and fill in with SuperFil or thickened epoxy. Sand it down (get a power sander if you don't have one yet -- you'll be needing it!) and it'll practically be invisible.

Epoxy-wise, I'd recommend just diving in and getting a high-quality marine or aerospace grade product. It has practically an infinite shelf life, is much stronger than hobby store epoxies, and is an incredibly versatile product -- from thin for lamination to incredibly thick for fillets, from unmodified to modified with carbon fiber, fiberglass, or kevlar pulp for fin fillets, etc. etc. etc. It's about $40 to get into the West System group A size, which will last you a while (until you become like Carl and start to build 5 big rockets at once!). This includes the handy pumps for measuring the 5:1 mix ratio. Aeropoxy is even cheaper and is designed for the aerospace industry -- it's what amateur aviators use to hold together their airplanes. It also has a higher temperature resistance than West System, and can be oven-cured in 90 minutes. Aeropoxy can also be post-cure treated for even better temperature resistance. It's about $30 to get a gallon of the stuff -- not too bad!

Enjoy the ride while you're glassing. It'll make your rockets a lot stronger for the high-speed flights and less-than-nominal landings

 

[firemanup]

Ok,

Browsing the internet another option just came up...

Looking at Giant Leap's website and found the Kevlar sock and easyglass socks..., emailed them to find out if one wrap of each would be similar in strength to two 6oz and one 2 oz layer of glass...

Now during the build when would i do what..?? LOL sorry but i'm unsure here..

I'm looking at building the motor mount fin can outside of the rocket then slotting the end of the body tube and sliding it up and in...

I'm wondering when to glass different pieces.. ie build the fin can, tip to tip glass the fins. Cut fin slots then glass or sock the body tubes..

Then insert the fins can into the rocket and do the internal and external fillets.. my only question is, how well will these fillets adhear to already glassed fins and body tube..??

or do i have te build order messed up..?

 

[firemanup]

I appreciate the replies and this is actually one of the first threads i've decided to print off..

I've decided to do this project for sure, should start in the next 2 to 4 wks.. and i will be taking, as close as i can possibly get, carl type build pics. The man just sets a standard ya know..


Davey,

Aeropoxy, comes in a one gallon can? I take it there's no mixing of this stuff..? or is there..? 30 bucks i'll fork out for this project..

With regular glass i'm starting to assume you must overlap for strength issues..? I was trying to figure out how to make it match up evenly and think i can do that..

3 layers of glass would you want to stagger the overlaps so they're not all on top of eachother..?

 

[daveyfire]

I don't like Kevlar Sock for any rockets under 6" diameter. Wetting it out is like pouring epoxy on a sponge -- it just keeps drinking it up more and more. I recommend doing a standard wrap -- it's a little tougher, but the end result is lighter and stronger.

I build exactly the way you have described, except I slot after I glass. If you extend the slots all the way out the back of the tube, IMHO, it's a pain in the butt to get the tube to stay in the right shape as you pull the glass over the surface. Epoxy will stick GREAT to the glassed surface -- if you don't fill the weave until after you've filleted, it leaves a bunch of nooks and crannies for the epoxy to grab on to. The only caveat is to sand a little bit to clean up the "amine blush". If you live in an area with any humidity, the curative will react with it and produce this oily layer on top of the cured laminate. Not a strength problem -- just a bit of an annoyance. I've noticed that Aeropoxy doesn't blush nearly as much as West System.

You can get Aeropoxy from Aircraft Spruce (https://www.aircraftspruce.com) or from ShadowAero (https://www.shadowaero.com) in 1 quart, 1 gallon, 5 gallon, and larger sizes. I've gone through one quart kit and am about 1/8 of the way into a gallon kit since I started out with the system in Decmber of 2002. Aeropoxy is a 3:1 mix ratio by volume or a 100:27 mix ratio by weight -- you don't get pumps, so you can either weigh out the resin and hardener on a scale (what I do) or do a volume measure (fill up a small cup with rice three times and dump it into a bigger cup each time, mark that level, and that's your resin and hardener amounts -- fill up the big cup to the line and fill up the small cup all the way, dump em together and mix). A little more work, but a quart of Aeropoxy costs $15 and a quart of West costs $40... you do the math

While you're there, pick up a kit of SuperFil. It's essentially Bondo for rockets. I'm always pushing this stuff on the forums, but I don't work for them, I'm just an incredibly satisfied customer. It mixes (by eye is OK) in a 2:1 ratio of part blue to part white and is very, very thick. It is also very, very light, weighing 3.3 lbs per gallon. The best part about this stuff is that it is epoxy based. Due to their chemistry, you can bond epoxy products to polyester surfaces, but not polyester products to epoxy surfaces. Bondo is polyester based (you can tell because curative is measured in drops, not in a proportion to the product), and as such doesn't stick very well to the surface. SuperFil is magic stuff -- it smooths out wonderfully and can be used to fill your overlap or fill the weave on small rockets. It's creamy smooth. I have had a quart kit for over four years and have barely made a dent in it. Best $20 I ever spent.

The up-front on these materials is a little high, but they last a long, long time. I highly recommend starting out with the right stuff!

Overlap is more of a technique question than a strength question. When I started out, I always tried to get the 'glass to come right up to itself again on the overlap. I never could -- I always came up short. Problem with the coveted "exact wrap" is that 1. the glass shrinks slightly when resin is applied, and 2. the weave is inevitably pulled out of the glass, unless you tape it off like Carl does (but then you get to cut off the tape!). It's not a problem and glass layers are about 0.006" thick, so it's pretty easy to get a decent finish over the overlap. I've heard of a method where you bring the cloth around and pull out the weave so that the two ends of the cloth mesh together and it becomes perfectly smooth, but I've never tried it -- by the time I reach the overlap, I'm done with the tube and I toss it in the oven. I just let the power sander take care of the rest! When you put on layers, you indeed stagger the overlaps to prevent the tube from becoming egg-shaped. That's no fun!

Hope this helps more than it confuses

 

[firemanup]

Davey,

Can the AeroPoxy be used as regular old epoxy for building also..or is it just for laminating..?

 

[firemanup]

Also am I looking for E glass or S glass or does it really matter, I'm finding from the web that the E glass is stronger, but a little stiffer to work with,

Which is the preferred for rocketry..?

 

[Ryan S.]

I dont think it matters, I got the cheaper of the two at www.uscomposites.com

It works great.

 

[daveyfire]

Aeropoxy can most DEFINITELY be used for building! You'll need some sort of filler to thicken it up and keep it from running all over the place (West 406 is what I use, cheap and available locally, but any sort of fumed silica or microballoons will work), but it's incredibly strong. On my new 3" minimum diameter all-fiberglass rocket, I've just begun the reinforcement process on the fins. Using Aeropoxy with chopped carbon fiber added, the fillets are now on. I was out sanding them smooth for the next layer of reinforcement (5.7oz carbon), and walked away briefly to get some fresh sandpaper. The booster (4 ft long, weighs ~3 lbs) fell over on its side, hitting the concrete, and bounced four or five times. No damage to the surface mount fins. I've also done a surface mount demonstration for the uncertain with my Kick Me rocket. It's 38mm minimum diameter with G10 fins on it. I had the fillets completed with Aeropoxy and fumed silica when I performed the "test". I picked up the rocket and whacked it on the ground as hard as I could. No damage either On its second flight, it ripped out the shock cord and came in quick from 5000+ feet. At last, one of the fins cracked at the root.

Good, strong stuff, that! It's the beauty of a true epoxy system, because you start with a basic, very thin epoxy that has excellent strength characteristics, then build it up into whatever you need it for -- fillers, fibers, pigments, cloth, whatever. It's much more versatile than thick hobby shop epoxy, where it starts thick and stays that way. It's easier to thicken thin epoxy than thin thick epoxy. Wow, that's confusing!

Sorry, I was also off on the Aeropoxy price... it's $35.90/gallon for resin and $12.95 for hardener to cure it, so overall it's about $50ish. A gallon of resin is a lot, though... think of how many hobby shop bottles that is!

E-glass vs. S-glass... it doesn't really matter for our applications. I typically use S-glass just cause it's cheaper, and have had no problems with it so far, even on some pretty wild flights.

Hope this helps some!

 

[strudleman]

This has been the most interesting thread! Thanks to everyone who's posted ( questions OR answers!), I'm eagerly awaiting my first chance to try glassing!

 

[scm86]

Jason, sorry to add another option but, you can get the fiberglass or carbon or carbon/kevlar sleeves from https://www.aerosleeves.com. the advantage to these is that the loading of the fibers is in the direction that you want it, and there is no overlap at all, just wet it out after putting on the tube and strecth it out. that simple. Im told that a single layer of the carbon stuff would withstand mach on its own, without anysort of paper tube attached to it.

As for epoxy, Dave Muesing sells really nice epoxy called Mr Fiberglass epoxy. I use the 3:1 ratio stuff, thats the slow i think. Perfect for laminations since its thin, and is awesome for general construction. the phenolic microbaloons he sels are good for making large fillets that are strong and light. www.mrfiberglass.com


Oh, one last thing, do the slots after you glass and fill/sand the tube, that way theres no chance of sanding too hard and crushin the tube at the weak points where the slots are...

Scott McNeely