This includes the vacumn bag and compressor which was pretested to ensure no leaks
a length of peel-ply material to prevent any escaped epoxy sticking everything together(can be substituted with a length of paper towel.
I have estimated that about 300/350 grams of glass cloth for both top and bottom skins. I will need about the same in resin , 30 percent less if you work carefully. Resin binds the components together ,excess resin adds no strength only weight, so work it in well and spread the excess with a plastic card (I use telkom telephone cards ,which I collect free from some pay-phones near my office.
I mix the epoxy in paper cups and have 3 x premeasured with 50 grams of resin in each
The first cup has the harderner added (slc 30) in this case with 30 mins pot life
and its "game on" .
The Mylar is still on the news paper with the two layers of cloth, I fold back "carefully the 163gr about halfway , smooth out the wrinkles in the first 106gr fine cloth and pour on about 2 x teaspoons of resin. I only work with a plastic card
no brush, and spread the resin as soon as a reasonable area is wet out , the glass stays in place and you can add more resin and spread/scrape it to the edges, working back and forth very soon the whole area will wet out, carefull near the edges that you dont pull the threads apart in the cloth.
You want it to look shiney and it can be a little resin rich.
I used about 30grs resin to this point, I now fold the top layer back down onto the wet out area and rub it down onto the wet out cloth under neath very soon it starts
soaking up the excess resin and you can see the areas change from white to shiney clearish. If a lot of resin comes through start working it in near the middle and add a little resin as you work outwards.The 163gr needs more resin to wet out and frays easily on the edges.
Soon the mylars are both wet out I used about 100gr epoxy per skin to this point
and its time to lay on the UD-carbon. The latex gloves which by now are all sticky come off and on go new ones, the carbon can become like spidersweb ,it comes of the backing especially where cut at an angle and can be a nightmare. You basically line it up on one corner and lay t down onto the wet below dont touch it unless you are happy with the possition.
Now you can press down on it and work it with the card through the pink plastic backing (not many people use UD carbon so if using any other woven cloth you would just wet out as per normal)
Shorty you will see the areas that have resin, I spend lots of time trying to pull the excess resin up into the carbon.Its worth the effort, we are about 2hrs into the proceedure.
The backing is lifted off and and some fresh resin mixed and poured on (sparesly)
This is worked in and then its time for a short break (5 mins) .
After 5 minutes when spreading more epoxy in you will notice the white binding threads that hold the carbon material together start to release and can be removed.
It takes some effort but the epoxy melts some sort of glue holding them and the come off, there are some lengthways threads as well which I also remove but which could stay in as they lie flush and wont show in the wing surface.
An off-cut piece of 163gr goes over the carbon at the wingroot to strengthen this area which also holds locating pins/ the ply rib etc. I have also put a piece at the very tip for the winglet .
At this time I have used all 300gr of epoxy and its time to possition the wing on
to the bottom mylar, the leading edge must line up , plenty of overlap on the trailing edge.
I now make up a mix of 50gr resin with micro/balloons about 20 percent to 80 percent
Cabosil/Aerosil this is a thickening agent mix in until you get a consistency of peanut butter ie quite thick paste.
This is spread along the trailing edge which now looks quite ragged, add extra where pieces are missing and spread with the plastic card.
, "morefresh new lattex gloves on" the top skin is lined up on the trailing edge and then in one motion flipped over, it can be possitioned to line up to the leading edge
I then attach some masking tape fron the top skin onto the bottom skin in three places tips middle and root ,I then slide the peel-ply cloth under the wing and slide the whole thing into the open end of the bag.
The possition of the skins is checked to see they havent moved , a second piece of peel ply is layed over the top and the bag closed and vacumn pulled. I then release the vacumn and spread out any wrinkles in the skins/peelply , vacumn re-applied .
Now some builders place the foam core outershells under and on top of the wing and weight the wing down while it cures overnight, I no longer use the outers and weight it down on a flat surface(floor) I position the weights carefully if the wing has built in washout as in this case.A good workshop cleanup and we are done for the day
The next day no1 comes out the bag and number 2 goes in , part 5 hope it all works.
Cheers
Mike
All materials used in this project are available from A.M.T. who are most helpfull
and can advise on the products they supply . Speak to a MR. E. Shaw there.
No comments:
Post a Comment