Wanted Fin fiberglassing (vacuum layup) service

[jhill9693]

I have a LOC 5.5" Patriot on the way, and I want the 1/4" ply fins glassed to prevent flutter at mach.

...but I REALLY don't like the idea of doing it myself, and I don't have any of the supplies required.

Anyone with the stuff and skillz willing to help me out on this? I'd pay for it, and would cover shipping, both ways.

 

[jhill9693]

Alternately, if someone has a set of supplies sufficient for this project to sell, I'd be open to going that route and doing it myself.

 

[3stoogesrocketry]

Alternately, if someone has a set of supplies sufficient for this project to sell, I'd be open to going that route and doing it myself.

Look into a cheaper vacuum food saver. Bags are disposable. I have a "MasterChef" unit that was like 60 dollars. You can make custom bags by attaching food saver bags to your bigger bag. Stock they do a 8x10 bag or a 3 inch tube

 

[rfjustin]

I have a LOC 5.5" Patriot on the way, and I want the 1/4" ply fins glassed to prevent flutter at mach.

...but I REALLY don't like the idea of doing it myself, and I don't have any of the supplies required.

Anyone with the stuff and skillz willing to help me out on this? I'd pay for it, and would cover shipping, both ways.

I can help you if "normal" fin to fin is acceptable. All fin to fin work I have done to date has not been vacuum bagged.

Do you have the kit in hand or not ordered yet? I have ideas for a twin.

 

[jhill9693]

That's some nice work, @rfjustin! I have the kit (it just arrived), and would need to assemble the fins to the MMT and ship it to you that way I suppose for the glass work. I was planning to add glass reinforcements on my own to the fin tabs and tube, so doing it tip-to-tip would accomplish that purpose also.

 

[jhill9693]

Look into a cheaper vacuum food saver. Bags are disposable. I have a "MasterChef" unit that was like 60 dollars. You can make custom bags by attaching food saver bags to your bigger bag. Stock they do a 8x10 bag or a 3 inch tube

The vacuum bagger is the easiest part, IMO. I can probably find one cheap (and my wife would probably end up using it in the kitchen). It's ALL THE OTHER STUFF that I'm not anxious to run out and buy:

• Epoxy (which kind?)
• Measuring tools (which kind?)
• Peel ply (which kind?)
• Batting

I mean, yeah, I could go to US Composites and get everything but I don't plan on doing a lot of this, and I worry about the leftovers just going to waste.

 

[rfjustin]

That's some nice work, @rfjustin! I have the kit (it just arrived), and would need to assemble the fins to the MMT and ship it to you that way I suppose for the glass work. I was planning to add glass reinforcements on my own to the fin tabs and tube, so doing it tip-to-tip would accomplish that purpose also.

If you want the fins beveled and worked on a bit before you build the booster, let me know.

 

[AlexBruccoleri]

I can help you if "normal" fin to fin is acceptable. All fin to fin work I have done to date has not been vacuum bagged.

Do you have the kit in hand or not ordered yet? I have ideas for a twin.

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Beautiful work. Do you let it fully cure and then sand or do you cut the excess while the epoxy is semi cured?

 

[rfjustin]

Beautiful work. Do you let it fully cure and then sand or do you cut the excess while the epoxy is semi cured?

If possible, I trim the excess when the layup is at the "leathery" stage. Single edge razor blade is my tool of choice and does a fine job.

 

[troj]

The vacuum bagger is the easiest part, IMO. I can probably find one cheap (and my wife would probably end up using it in the kitchen). It's ALL THE OTHER STUFF that I'm not anxious to run out and buy:

• Epoxy (which kind?)
• Measuring tools (which kind?)
• Peel ply (which kind?)
• Batting

I mean, yeah, I could go to US Composites and get everything but I don't plan on doing a lot of this, and I worry about the leftovers just going to waste.

I don't recommend using a Food Saver (or any other brand of the same) for both rocketry and food work. Should be one or the other, or you risk contamination.

I've used a Food Saver for "poor man's vaccuum bagging" and it definitely works. I've also just squashed things between a couple leftover pieces of stone countertop - go by a company that installs them, and see if they'll sell you the piece they cut out for a sink.

-Kevin

 

[Sandy H.]

Alternately, if someone has a set of supplies sufficient for this project to sell, I'd be open to going that route and doing it myself.

I have a full set-up for vacuum bagging (initially woodworking, but later rocketry fiberglass) that I can't get rid of, but I'm likely in your region based on your club affiliations.

I have peel-ply, mylar, bags and a vacuum system - also some old US Composites epoxy, but I would absolutely recommend doing a test batch or two before using it.

Due to really poor life/work balance, I can't help with the project, but I'd be glad to loan you the equipment for a few weeks if you pick it up. I'll likely need the vacuum system back within 1-2 weeks, but if that might help your project PM me.

Having said the above, I've never bagged an assembled fin can. Maybe it's a thing, but it seems less than easy. I've bagged flat fins, installed them, done fillets and then done tip to tip with decent results, but never tried to bag an assembled fin can.

I'd guess if @rfjustin is offering help, you'll get way better results working with him than anything I could do or you would do the first time with my equipment. Heck, with proper bribing, you might get him to send you some legit cheese curds back after he's done with the fins!!!!

Hope you find a good plan. Feel free to reach out if you want to do some of it in-house and are near-ish to south Charlotte.

Sandy.

 

[AlexBruccoleri]

I know this is off topic but what motor are you planning to fly and what dry weight are you expecting?

 

[jhill9693]

I know this is off topic but what motor are you planning to fly and what dry weight are you expecting?

Good questions. I'm upgrading to a 75mm engine mount, and plan to fly a Cesaroni L1030 and then a Cesaroni M1490 (Mach 1.24) or AMW M1850GG (Mach 1.13).

This may be my L3 project (if not, a 7.5" LOC V-2 kit bash will).

 

[jhill9693]

Since I've got your attention, here's where the plan is right now. Obviously I have to get it approved, also still trying to decide whether to do this under NAR or Tripoli (I'm NAR L2 currently).

 

[AlexBruccoleri]

Good questions. I'm upgrading to a 75mm engine mount, and plan to fly a Cesaroni L1030 and then a Cesaroni M1490 (Mach 1.24) or AMW M1850GG (Mach 1.13).

This may be my L3 project (if not, a 7.5" LOC V-2 kit bash will).

If it’s a L3 you need to make sure you are not violating the rules if someone else helps you too much. Your TAP/L3CC will tell you but certainly let them know in advance. You could just keep this as an L2 rocket and get some experience with @rfjustin and try fiberglass reinforcement yourself on a follow up project.

 

[jhill9693]

If it’s a L3 you need to make sure you are not violating the rules if someone else helps you too much. Your TAP/L3CC will tell you but certainly let them know in advance. You could just keep this as an L2 rocket and get some experience with @rfjustin and try fiberglass reinforcement yourself on a follow up project.

Yep, that's one of quite a few outstanding questions that I have.

 

[lr64]

Fiberglass is not the greatest material for preventing flutter. It's no stiffer than birch, though that stiffness is in two directions instead of one. On the other hand, fiberglass is more than twice as heavy. Weight increases the chance of flutter, at least out near the tips of the fins. If the fins are cut correctly, the faces will have their grain running parallel to the spanwise direction. In that case, the torsional stiffness may be less than you'd like. So a layer of 1/64" ply applied at +/- 45 degrees would probably reduce the chance of flutter more than the same weight of glass. Maybe this is why people paper their fins. I don't know the shear modulus of paper, but I bet it's better than 0/90 plywood or fiberglass. If you want to vacuum bag a composite onto fins to prevent flutter, I suggest light carbon fiber. At +/- 45, it's very stiff in shear, and of course it's stiff against tension and compression at 0/90. On flat surfaces, you can press instead of using a vacuum pump. Just clamp your fin with the glass on it between two rigid, flat objects, with some plastic to prevent sticking, and maybe Styrofoam sheets or something to even out the pressure. You will need to clamp pretty hard. About half an atmosphere would be appropriate for vacuum bagging, which is about 7.5 lbs per square inch. If your fins are, say, 200 square inches, that's a total of 1,500 lbs.

REALLY flutter resistant fins might be made by gluing a layer of thin ply at +/-45 to a tapered foam or other light core with a layer of veneer running spanwise over that. I see that some motor choices result in subsonic flights. For these, an airfoil shape, maybe 8 percent thick, or perhaps even a thicker laminar foil, if you are willing to shape very carefully, will be lower drag. Looking at the picture you put up, though, an M class motor will put you supersonic unless you add drag. And even with the smaller motors, low drag might require a higher altitude clearance.

 

[KenECoyote]

I personally would highly recommend that you try a bit of the traditional non-vacuum tip to tip yourself. You can even start with a small rocket and you just need 3 things: epoxy (West Systems or similar - you'll want slow set), fiberglass cloth (I got this off Amazon since I was in a rush), and peel ply (also Amazon).

I watched this video (as well as a few others) and did it for the first time a few months ago on my L3 project and found it fairly easy and results very good.



To me, L3 should be researched well in advance and preparation for it used as a learning tool to advance your skills.

As an example, I used my V2 as a test and learning tool for several things including glassing the tube. It came out ugly and rough and I made some mistakes...



but when I next did the same on my L3 build, it came out great!



Also I personally wouldn't recommend the V2 for an L3 attempt because, while I LOVE the rocket, the fins really extend out back and usually will be TTW against a plastic tail cone, where the bond isn't good, so chances of broken fins and cracked fin joints & fillets are much higher (I think that happened to Upscaler/Braden in one of his videos...maybe twice). You can use a bigger chute, but then it has higher chance of longer recovery or end up in a tree or lost. Finally, it doesn't have much space for a traditional dd bay when using a large motor (the Loc 7.5 bay set up inset on one side may work, but you'd have to research).

 

[David Schwantz]

Justin does great work. But glassing is very easy. Ken's video is a good start to learning. Supplies are cheap, you can get everything at auto parts stores, other than a tight weave cloth for the finish layer. Any hobby store will carry that, or online. In rocketry, it is a very good skill to learn, has many uses other than just fins. Glassing tubes, making parts, and such. I suggest you at least give it a try on some scrap first. Good luck.

 

[John Kemker]

The vacuum bagger is the easiest part, IMO. I can probably find one cheap (and my wife would probably end up using it in the kitchen). It's ALL THE OTHER STUFF that I'm not anxious to run out and buy:

• Epoxy (which kind?)
• Measuring tools (which kind?)
• Peel ply (which kind?)
• Batting

I mean, yeah, I could go to US Composites and get everything but I don't plan on doing a lot of this, and I worry about the leftovers just going to waste.

I like US Composites or Aeropoxy laminating epoxies.

Measuring tools? To measure what, exactly? The fiberglass? No need. Just cut with an Olfa or similar wheel cutter about a 1/2" outside the fins. For the epoxy? If you get the US Composites, buy their pumps. Three pumps resin, one pump hardener and you're good. If Aeropoxy, 3:1 by volume. Don't bother with weight.

Peel Ply? I bought mine off of eBay.

Bleeder cloth? Same thing.

 

[Sandy H.]

I like US Composites or Aeropoxy laminating epoxies.

Measuring tools? To measure what, exactly? The fiberglass? No need. Just cut with an Olfa or similar wheel cutter about a 1/2" outside the fins. For the epoxy? If you get the US Composites, buy their pumps. Three pumps resin, one pump hardener and you're good. If Aeropoxy, 3:1 by volume. Don't bother with weight.

Peel Ply? I bought mine off of eBay.

Bleeder cloth? Same thing.

I also support US Composites and an Olfa pizza cutter. Personally, I did choose to measure by weight, but I don't know it was the right direction. If I were doing an L3 size project, I probably would buy the pumps and test/verify, as the weight method is both tedious and messy. My projects were most often 2.5-3" dia, with occasional 5.5" tip to tip (one set at a time) and they got tedious. If you're moving a bit of epoxy, I bet the pumps would be super helpful, but have never tried them, so can't comment from experience. I can say you'll spend an hour a session cleaning your scales, floor, cups and hands if you're as sloppy as I was using a scale. . .

 

[John Kemker]

I also support US Composites and an Olfa pizza cutter. Personally, I did choose to measure by weight, but I don't know it was the right direction. If I were doing an L3 size project, I probably would buy the pumps and test/verify, as the weight method is both tedious and messy. My projects were most often 2.5-3" dia, with occasional 5.5" tip to tip (one set at a time) and they got tedious. If you're moving a bit of epoxy, I bet the pumps would be super helpful, but have never tried them, so can't comment from experience. I can say you'll spend an hour a session cleaning your scales, floor, cups and hands if you're as sloppy as I was using a scale. . .

I used to use the weighing method for Aeropoxy until i read that you could use a 3:1 by volume ratio. MUCH easier than weighing, even if you're not using a pump. The pumps are VERY easy for the US Composites system, as both pumps measure out the same volume per stroke, so 3:1 strokes. If you bought larger sizes of Aeropoxy (1/2 gallon resin? Gallon, definitely.) you could use the same pumps, if the mouths of the bottles are the same. Just remember, don't short-stroke the pumps. Full strokes each time.

I used to use West Systems with the pumps and they had theirs calibrated for a stroke of each. Nice, but the US Composites is just as easy.

 

[lr64]

Sometimes I measure epoxy using a small balance I made for the purpose. Glue a small, disposable cup to each end of a stick. Glue a piece of pencil or something round to the bottom of the stick as a pivot. If the mix is 3 parts resin and 1 part hatdener by weight, put the pivot 3 times as far from the center of one cup than the other. Put an empty cup of the same type in each of those cups, and ballast the stick so that either end will stay down if it contacts the work table. Now put a bit of the hardener in the cup furthest from the pivot. Then fill the other one with resin until the first cup starts to come up. Take out the cups, pouring back and forth and mixing vigorously, scraping the sides and bottom of the cup and each surface of your mixing stick. If you want to make it extra precise, use something smaller in diameter than a pencil, or put spacers under the ends of the balance stick so it can't move much without touching the table. I don't know if Dixie cups are ok or not. I use disposable plastic cups that hold about an ounce.

White vinegar is quite good for cleaning up uncured epoxy.

Try to minimize skin contact with uncured epoxy. I once saw someone at work lying on the floor, gasping for air. I found out later that she'd become sensitized to the epoxy used in the assembly of the connectors our company made. The safety precautions weren't always the best there. I hope she got workmen's comp and a different, safer job.