rharshberger
Well-Known Member
I dont know, I have used perf film and peel ply both, I prefer peel ply especially on compound curves.
I think you about covered it, I dont know what to say.I have used 3M77 spray adhesive as well as Fiber-Tac, which is supposed to be formulated to not interfere. In the past I've had great results but a recent delamination has made me nervous.
View attachment 423552
There was a lot going on that could have caused this. Mach 2.7 with Aeropoxy and unprotected leading edges to name a few. But This was all stuck down with the Fiber-Tac beforehand. I can basically peel the rest of that off by hand. I don't think I got very good adhesion.
The link I posted for 3M 71 does say it specifically made to work for composite work.I have used 3M77 spray adhesive as well as Fiber-Tac, which is supposed to be formulated to not interfere. In the past I've had great results but a recent delamination has made me nervous.
View attachment 423552
There was a lot going on that could have caused this. Mach 2.7 with Aeropoxy and unprotected leading edges to name a few. But This was all stuck down with the Fiber-Tac beforehand. I can basically peel the rest of that off by hand. I don't think I got very good adhesion.
You can use the canister attachment on a Foodsaver, its the hose woth a barb on it, all thats needed is a port on the bag, a short section of hose and a valve in the hose. Plug the canister adapter into the hose an vacuum, once under vacuum close the valve and monitor the bag to see when re-vacuuming is needed. If the food saver going to be a permanent addition to the rocket construction equipment, then I would remove the end of the canister attachment and permanently plumb it for vac bagging.First let me say thank you for producing such an informative, and exciting, post! I really got a lot out of this and cannot wait to experiment myself with the information you were so kind to share. One question though, is there a vacuum/food saver device that you can recommend that’s large enough for laminating large high power fins, even if it requires that I do one fin at a time?
thanks again!
I've been using John Coker's FoodSaver method for a few years on little and medium-big rockets. Works great, adds little weight. 3/4 oz (or 1/2 oz if you can find it) fiberglass adds tremendous strength but little weight for small rocket fins. You do have to consider that you're stiffening fins, and that transfers what would've been absorbed flex to the root attachment: fins are less likely to break, and more likely to detach at the root from regular handling and dumb-ass rocketeer mistakes. Consider modifying your construction to TTW with this technique.With (FoodSaver) vacuum bagging (a la John Coker), I only saw a roughly 4g increase on some BT-80-sized Patriot fins. Starting weights were 3.1g (1/8" balsa) and 9.1g (1/8" baltic birch ply). So, at least with vacuum bagging, I didn't see a dramatic weight gain for a huge gain in strength.
If you want the fin edges beveled its best to do it before laminating. These fins have the leading edge of the forward fin beveled and the trailing edge of the aft fin beveled.
View attachment 414574
I have not had an issue with the parts being deformed, but I do remove them during the leather stage. It is also unnecessary to pull a full 30" of vacuum on parts, according to a "conversation" I had with John Coker iirc the number is about between 15-20" for our hobby purposes. The main reason for vacuum bagging is to remove trapped air and extra resin from the lay-up, while at the same time compressing the composite materials together. Typically I also don't vac bag parts with wide (deep) bevels, or if I do I support the edge of the bevel and do one side at a time.Do you have any issues with the pressure from the bagging deflecting the beveled parts toward your MDF platen and then locking in that deformation as the resin cures? Or does removing them from vacuum in the leather stage allow them to return to their unflexed form?
Enter your email address to join: