|Jul 01, 2012, 07:44 AM|
We have progress!
This weekend was a very productive one, well productive from my perspective. First order of the weekend was to sort out the vertical and horizontal control surfaces. The process for this is much the same as for the wings. 2 end templates and hot wireing.
Using scrap from the fuselage and wing foam blocks.
All cut out - I decided that I preferred a nice transition between the vertical stab and the tail boom so I ended up cutting off part of the leading edge and gluing a bit extra on - I think it looks a bit smoother. Horizontals were waaaay too big1
I glued the spinner on the front to get an idea of how to approach the finessing of the nose and to also see if I had the lines of the nose right - Not too bad I think? Kinda got the racey profile I was going for. It was beer o'clock by this stage so she got put away and I was going to pick it up again the next morning.
|Jul 01, 2012, 07:45 AM|
We got up and flew the AXN Floater and the trainer that we have (the little Cessna in the background of the first photo) - excellent wee plane the AXN - absolute joy to fly and certainly something to fill in the waiting time with. I'm looking forward to summer to see if I can get it to thermal.
Finessed the horizontal surfaces - added a nice transition and a bit of a sweep, and also put a nice radius on the wingtips.
Ended up doing a bit of work on the nose as well - I'm not sure if it's finished yet. I'm going for a bit of a scale look without adhering to a classic fuselage profile.
The next trick with the plane is really going to be filling and then getting it prepped for glassing so I think I've done as much as I can till some more supplies arrive. I think I have two options, one is to do the fuselage in a fiberglass sock and then attach the vertical after the event. I'm thinking that I'll use the lost foam technique. The main downside of this is that I won't really have any way of re-creating the fuselage again if either I or someone else wants one. C'est la vie. The other way is to possibly vacuum bag after the two are glued and the transitions filled. I guess it going to be a case of researching the options...
Putting the plane to the side I decided that it was time to get my hands dirty with some glassing. I need some pretty sturdy main landing gear so I set to making a mold for what I hope will be a nice bow style.
I grabbed some of my fathers glass scraps and some epoxy that he had spare - the day was really cold (about 5C or 41F) so it's not ideal conditions for glassing without a heater, oven or a warm room. Still I wanted to have a go. Going through a bunch of stuff he had sitting in storage I came across some interesting little bits and pieces.
Pulse jet anyone?
Here's the completed mold, peel ply and glass all laid out ready to go
Glass all wetted out - we had to keep a heat gun at the ready to keep the epoxy wetting through - it really wasn't ideal conditions. Two layers of 90 degree opposing grain glass then 9 layers of uni directional followed by another two of 90 degree opposing.
Laid into the mold...
...and compressed. Till next weekend on that one
Alltogether a very productive weekend It's an extremely cool process and I'm really looking forward to getting this beast into the air!
|Jul 01, 2012, 09:40 AM|
There is a cool factor when working with the composites like glass and epoxy. This thread started with those vintage wooden kits, but look at the warp speed trip into the future. Full blown composit builds! Way cool. Looks like it won't be long. Very nice.
|Jul 01, 2012, 04:42 PM|
Well we're standing off till next weekend and I'm not holding too much hope for the success of the landing gear - curing in 5C is not the best of conditions - I think some load testing is going to be the order of the day. Glassing the fuselage is going to be a whole other challenge... Building an oven and getting some fan heaters might mate that a far less painful job.
|Jul 02, 2012, 08:09 PM|
Woohoo - bagging stuff arrived, next I need 18g glass and some epoxy, a porcupine roller and a fairly large insulated box to use as an oven! And maybe a couple of fan heaters...
Once I get this process down I've got a few plans that I want to get underway, not the least a 2m flying wing. I get far too much jealousy from the Zypher 2 bunch - they look like a huge amount of fun!
|Jul 15, 2012, 07:02 AM|
So a couple of weeks down the line...
I left my camera in the hanger so I didn't have any photos with which to update the build log but that has now been rectified.
Where I left off was with the landing gear in the mold. It wasn't the prettiest of efforts, mostly because getting even pressure on the mold was not able to be achieved with the tools at hand. However it did yield a very usable piece of glass and after band sawing off the flashing and a bit of eyeballing next to the sander we have this!
I took to a couple of small blocks of foam to have a go at making some wheel pants. My first attempts were ill conceived and the result less than satisfactory. mainly because, like many of my builds, I approached it with a mental image and not an understanding of how these things are actually approached.
Sculpting wheel pants has a pretty simple approach (kindly informed by my father on this one - he has the grace to allow me to make a hash of it the first time and then give me gentle nudges in the right direction, after all we learn better from our mistakes do we not?). Basically you take a symmetrical airfoil and scale it around a wheel - makes sense too as you don't want the pants skewing your airflow - hence the symmetrical airfoil!
The weather was pretty sweet so we ended up hanging up the tools and going flying for a few batteries and then that was pretty much that for the weekend.
|Jul 15, 2012, 07:17 AM|
Fast forward to this weekend and we'd managed to source a number of items that should lend themselves to vacuum bagging. Mostly from Bunnings (hardware store here in Aus) so not really specifically for the task but sourcing this stuff locally and cheaply has a lot going for it.
My Franken Glider has been disassembled for parts and all I was left with was the wing. So what to do with a wing? Well, make it fly of course! Over the week proceeding this weekend I threw together a fuse for just this purpose, mostly because I have a hankering for a hand/bungee launched glider. End result?
Granted, she's not pretty but it was functional (and I say was because in 20MPH winds there wasn't much room for error... err...). Suffice to say, the fuselage is now pretty flexible and a few inches shorter! Still nothing wrong with a proof of concept and despite some pretty wicked wing flap at high speed bungee launches it was a lot of fun.
With that small distraction out of the way and it being waaaay too windy to go flying a little foamy like the AXN, there was nothing left to do but work. With the motor glider pretty much ready for glassing I needed something to use as a test for the bagging technique. Luckily I had one that I prepared earlier!
At the start of this thread I talked about some balsa trainer kits and again about my lack of experience in building. I also showed a fuselage that I had put together out of foam board and subsequently some wing cores that we had hot wired, again very much as a 'feeling it out' process.
Once again the trainer has come to the fore, ironically in a training capacity! Here I have the three cores joined with a 2 degree dihedral only in the centre. I guess I could've given it polyhedral as it is in 3 sections but it's added complexity with the bagging and the aim here is to learn so why complicate the process?
Gorilla glue is pretty good stuff but I've found that I have to keep re-compressing the join as it foams out - am I doing this wrong or is there a better way to join wing cores?
Here is the same wing with the trailing edge cut.
And here mocked up on the trainer fuselage
|Jul 15, 2012, 07:34 AM|
On to the exciting stuff!
Wing laid out on the prep table with glass getting cut to size. The plan here is to use one layer of unidirectional laterally the length of the wing with 45 degree bidirectional on the leading edges and tips. It's all experimental stuff to see how little we can get away with and still have a pretty robust wing.
The perforated 'Peel Ply' - really high tech stuff here, it's clear vinyl table cloth from bunnings - I have no idea how well it will work but this is why we're doing this on a test wing and not the pretty one!
Applying Peel Ply
It puts the wing in the bag...
It applies suction... You can see some epoxy already making its way out
It puts a tent up and takes the wing camping... wait... what?
Yes it is a tent - since it's pretty cold here at the moment and trying to heat a hanger is a little much for a fan heater, we shot down the road and for $19 got a 3 man tent to use as a bagging oven. In with the pump, a fan heater and a thermometer and we have a good constant 35 degrees C or 95F. The wing is chocked up for a couple of reasons - to keep the air circulating all around it and to help maintain the dihedral.
5-6 hours later out of the ove..ten...hmm tent oven! By this stage the epoxy has gotten pretty solid and as you can see quite a bit of it has come out which is exactly what we were after.
Unfortunately this is where I have to leave it. It will be a couple of weeks before I can update it again due to having prior commitments for the coming weekend involving a friends birthday and potentially a pretty decent hangover... yay!
It took a huge amount of restraint not to tear into the bag and check out the finish but apparently you shouldn't do that till about 12 hrs down the line. Not to say that we didn't open the bag and pull aside some of the wadding, despite the apparent lack of resin visible on the outside there was actually quite a bit around the outside of the peel ply, this is a good thing. The more on the outside of the PP, the less in the glass and the less weight we have in the wing.
I think a good place to leave it More in a couple of weeks!
|Jul 16, 2012, 11:36 PM|
Thank you for the update and the photos of all the testing. Looks like it is working out pretty good. Hope to hear what comes out of the bag sooner than 2 weeks!
|Jul 17, 2012, 12:08 AM|
I'd love to Fred, but it's a two hour drive out to the hangers. My father could well be going out this weekend so I could get him to take a few shots. Either way, it's getting to the business end of one of the builds. The wing is considerably longer than I planned on, just shy of 71" when the plan called for 49", so it could be an interesting flyer. I'm hoping that it will be pretty docile but I'm concious of the fact that more mass generally means a harder impact when you get it wrong and I'm really not sure about the impact strength of the uni glass. I'm hoping that the bidirectional will serve to protect the leading edges and tips from impact damage but I really don't know. It's funny, as much as it's just a test bed for the techniques, I'm actually pretty well invested in getting it looking and working great. I figure that if the wing flies really well that I might re-visit the fuse and build that out of foam as well. Give the poor thing some 'street cred' rather than the 'poor cousin' of the nice glass wing
|Jul 22, 2012, 06:58 AM|
With all the promise and expectation of success it was with deep regret that we arrived at the hangar, grabbed the wing, and discovered that the vacuum bagging process had failed. There were a number of reasons for this. The primary reason, I believe, was using the wrong materials for the job.
Rather than using the correct perforated peel ply, I decided to give it a shot with some thin clear vinyl table cloth covering bought from Bunnings (Aus hardware store). In theory it could've worked but I suspect that due to the nature of the plastic, it didn't behave well in the tent/oven and expanded 'self healing' the perforations that I had put in it. Rather than allowing the epoxy to wick away from the glass layout, it trapped it in leaving us with exactly the opposite effect of what we were after.
As you can see the epoxy has pooled in spots and sits way too thick on both the leading and trailing edges. This made the wing quite heavy and meant that I was to spend the first day sanding the whole wing to strip back as much of the epoxy as I could. To add to the fun it also showed that some of the glass had lifted from the foam somewhere in the process and left us with peaks in the layup that when sanded left us with unacceptably thin glass. The solution to this? Cut it out
Luckily it was only half the wing that had the lifting glass, unsurprisingly the side that I had worked on. The side that my father had worked on was too all intents and purposes entirely workable. It shows what experience can do for you. I'm not too upset by this as it was my first glass layup on foam. However, is it too much to ask for for it to be perfect first time? Haha... obviously so...
Too cheer myself up I took an hour or so to chuck together a simple delta which turned out to be a bundle of laughs, if only in that it really keeps you on your toes when you're flying it. It may actually be the first plane that I've chucked together that will get a paint job!!! Big thanks to Dekan for posting this one - bloody genius in it's simplicity - what a cracker of a design.
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