sunnybreeze-inactive

Hey Bluenote,
Very good questions. First let me say I'm not designing any new system here. The boat building industry developeted the infusion system. Now the aircraft people have copied it. How the heck do you think the F117 was built? any how I will have to say it did take a try before I fiqured it out but once you go thru your learning curve it's no sweat.

I will agree with the fact that you use more resin. A lot is wasted in the flow medium and the catch container. The system is simply a better way to wet out the cloth because it will not soak up any more resin once it's wetted out. The weave of the cloth can still be seen and felt once you pull it out of the mold. That's why I use .06oz cloth on the outside for a smooth finish. Remember the ratio of excess resin is zero with no loss of strength. You can also do the same ratio by no infusion by wetting out the cloth in the mold the old fashion way and then putting on peel-ply and a layer of breather cloth and then vacuum bag. The excess resin will soak out of the cloth thru the peel ply into the breather cloth. This works well and I did it quite a bit in the past but is more messy.

If you study the site I gave it's all explained in detail. I vacuum infuse all the time.
I'm going to do my wing skin tonite so stay tuned.

Again do not hesitate to ask questions, that's how I learned this good stuff!!!!!!!!!!

Blue Note

Thanks for the info. I will stay tuned. I appreciate the ample use of pictures as well. So often critical things such as internal supports inside a hollow wing, servo retention and hatch, hatches, wing joiners, wing to fuse mating, etc are left out and we just get a series of pictures showing the outside looks. While still enjoyable, the 'how to' portion is always of more interest. After all, I trying to learn 'how to' do it for myself. By the way, what did you skin the wing and fuselage with prior to making your mold? I hope to tackle a similar project in the near future.

sunnybreeze-inactive

Both the fuse and wing were skinned with 2 layers of 2oz cloth and epoxy. Then into the vacuum bag at a max 8"hg otherwise you will crush the foam out of shape. Once it's hard I sand to 120grit and recoat all bad areas with filler and epoxy and sand. The final product needs to be covered with primer. Two or three heavy coats and wet sand to 360 or 400. It has to be super clean and shiny. Then 3 to 4 coats of partall and build your parting board. My parting board is covered with mylar and the entire parting and plug is then sprayed out with 2 heavy coats of PVA.

sunnybreeze-inactive

I've been away way to long but my first Hawker tempest wing skin has been formed. It went well but I'm somewhat disappointed with the total finished weight. It came out at 84 grams for a skin so four skins will result in 336 grams or approx 12 oz. I was hoping for something around 6 oz. I'm welcome to any ideas someone may have for weight savings. Here is how the wing was made. 1/16" balsa wing panel was precut from pattern. then I preformed by wetting out with windex and laying on in the mold and insert in vacuum bag and pull 30"Hg. left in for 12 hours and it held it's shape very well. I wetted out with epoxy and layed on two layers of 0.7oz cloth on the outside and a single layer of 0.7oz on the inside. I squeeqe the crap of all excess resin and apply peel-ply and breather cloth. Into the mold and bag for a full 30"Hg pull. The finished product is perfect other than the weight. The fuse halfs came in at 40grams each so I'm much happier with them. Again any ideas to save weight are welcome.

First pic is the fuse halfs and then the top and bottom of the wing skin

Blue Note

Welcome back.

Slow Low

How much epoxy was pulled out into the breather? You should be able to sum the total weight of materials that you put into the mould and subtract the weight of the finished piece. What I'm getting at is that the resin to cloth ratio on the finished part should be about 1:1 - the unsealed balsa likely absorbed more excess resin than did your breather - do you think that that would be fair to say?

sunnybreeze-inactive

SlowLow,
Yes I have to agree the inside with the peelply and breather came out lighter. The outside is glossy and retained more weight. What are you getting at when you say unsealed balsa? Do you know something I don't? Maybe I'm maxed out with how light I can get it but I don't think so. There has to be a way to drop to 45 to 55grams. Come on guys and give me some ideas!

Slow Low

The first thing I would try would be to thin your epoxy with 30-40% denatured alcohol after you've mixed the hardener into the resin.
If I still wasn't happy I would seal the balsa with some thinned out clear dope (maybe with a little baby powder) then I would repeat with the above.

What are you planning on doing with this wing and what kind of internals are you thinking about?

sunnybreeze-inactive

SlowLow,
That's not a bad idea. I'll make up some test panels and see what happens. The internals are two wing ribs in way of the wing mounted landing gear only. It's been done before by a friend of mine and it works fine. Maybe a different medium over balsa?

Slow Low

I'm not sure about your meaning of "over balsa", but if you meant rather than balsa, I would say that the balsa is pretty light and the grain is a major factor in providing your strength. If you meant a different cloth weight, or weave over the balsa, there might be a better weave for the application, but it wouldn't be worth the cost and effort for the negligible weight savings.
I'm looking forward to the next round. Be sure to record the weight of the epoxy that you apply; this will make you conscious of remaining conservative. Same goes for the balsa - record the weight before and after sealing. If you have the option, I would say spray the dope rather than brushing it.

sunnybreeze-inactive

Slowlow,
Thanks for the ideas. I'm going to do more research and testing before I move forward. One thing I feel I did wrong was not squeeze off enough epoxy from the outside of the skin. I feel I could apply some light hair dryer heat and remove even more epoxy.
This could easy be 20 grams or more. I may also try something other than Balsa core. I'm out of my shop for now due to my job on a deepwater dive vessel in the gulf of mexico. I'll be back home in march and back to plane building. One way or the other I'm going to get this wing down to 12 oz total!!
I want to see your wing mold ASAP so GET TO WORK!!!!!!!!!

Steve

Slow Low

Thanks Steve - I'm sanding like crazy over here! I'll do my best to give you some plane building to watch while your away from home. Pretty cool workplace you've got going on there. There was a time when I thought about diving for a living, but I settled for wreck diving in my spare time instead. When I was younger being away from home was one thing and now it's another. lol Stay warm. - oops didn't see you were in the Gulf - enjoy.

jamie_duff

That's very impressive composite work indeed.

Is there any reason why you didn't use some decent plans for your plugs though? It seems an awful lot of work invested in the moulds and, I hate to say it, it doesn't look much like a Tempest to me []

sunnybreeze-inactive

Jamie,
Good question as far as the design. This is a semi scale Tempest competition control line stunt plane. No way a scale plane would be competitive at a contest. The Tempest wing was VERY close to the spitfire wing and this is basically what it is based upon. In the world of control line stunt designers are forced to take liberties.

Steve

jamie_duff

Control Line?? Awesome! I remember my first steps into model flying were with control line.

I'm sure it'll do the job very well indeed! Best of luck to you