Last weekend we went out to Doonside with some of the NSWRA rocketeers but only equipped with lawn mowers and brush cutters. All the tall grass is now gone from the launch area so it is a lot nicer to move around and set up. Phil also installed permanent launcher bases which will make setting up much easier and there is less gear to bring each launch day.
While we wait for the new flight computer PCBs to arrive (Apparently they have now been shipped) we have been continuing to build the Acceleron V booster. We have mostly been testing and reinforcing the 2L spliced pairs. The booster uses 9 of them. We splice a pair together and then hydro test it up to about 80 psi. If there are no leaks we then add the neck reinforcing rings and wait a few days for them to dry, before testing again to 130psi. This way if the original splice fails at the 80 psi we don't waste time and bottles reinforcing the necks. The neck reinforcements are necessary as at about 110psi stretch marks begin to appear around the neck of the 2L bottles.
We are making a few spare spliced pairs in case any need replacing. The spare ones can later also be used for the new bigger Polaron boosters. A couple of the pairs are all-sikaflex splices so we are keen to see how they hold up.
I have also had my first go at fiberglassing. I wanted a simple project initially to learn the technique and so decided to make a ring fin that should be able to withstand a bit of punishment during tail-first landings under parachute. It was quite easy to do but I can see I need to pay a bit more attention in getting all the bubbles out and work a bit more at getting the resin in all the way through. But overall I was pretty happy with the results. The ring fin is 37 grams, 0.8mm wall thickness and uses 3 layers of fiberglass matting. It is significantly stiffer than a PET ring.
Here is the ring fin after the first rough sanding. I'll spend a bit more time making it smoother before painting it. The ring fin will be attached with CF struts to the main rocket body.
The next few fiberglass projects will likely to be fin strut attachment supports for the pressure chamber, and reinforced balsa fins. When I get a bit more comfortable working with it, I'll have a go at reinforcing some pressure chambers.