Skin for Blue

[WXYZCIENCE]

I was thinking about what Willib was saying about the poly resins eating the foam. I figured that a bag to protect the foam was required. Started looking around and found this leftover house wrap material. Here is what I came up with.







I started experimenting and found that the bag sealer in the kitchen worked on this stuff. Out to the shop to build a four foot bag sealer. Gathered up all the necessary parts and put the sealer together.







The unit is fifty two inches in length and uses a fine nichrome wire to heat the material. Also showing the transformer and light dimmer heat controller. A closeup shows the nichrome wire above a mica insulator that my brother Bill had purchased several years back for insulating transistors and fets.




A piano hinge allows the top to be lifted for loading the wrap into the sealing machine.

There is a felt strip on the bottom side of the sealer and the same mica insulator. A top view of the sealer closed and a close up of the tensioner spring connection.











I will now paint some epoxy on the blue foam wing, insert it in the bag and bond the two together. This will make the foam impervious to the less expensive resins. I will post more as developments progress.


Joseph.

[Shadow]

Wow! Youre very ingenious. Some Homewrap is 'breathable', meaning it is not air tight. Will that affect anything?  Good Job!

[SmoggyTurnip]

Very nice work.

I am not sure what the goal is.  Are you going to put resin over the sealed blade?  It won't give much extra strength if it is not bonded to the foam.  What am I missing?

.

[Titantornado]

It's probably a good idea to wrap the blades as you have.  I've never made blades from that blue foam, but dealing with it in construction several years back, I can tell you that it isn't UV resistant.  On homes sheathed with it, after a month of being exposed to the sun, you could lightly run your hand across it, and it would disintergrate and turn to powder.  If you used a finger, it would leave a groove, meaning it wasn't just superficial damage.  Rather, the UV had penetrated into the foam.  I didn't experiment further. (I didn't want to tick off the general contractor by rubbing holes into his sheathing)

I'd say for safety's sake, a UV BLOCKING product is mandatory.

[SmoggyTurnip]

Also I am pretty certaiin that resin will not bond to the plastic.

.

[SamoaPower]

Joe,

I may be a bit confused. I thought you were making plugs for a mold, but since you have three, it looks like you are doing actual blades.

If blades, I havent seen you mention any spar system. Glassed foam alone won't be nearly strong enough for the bending forces involved.

Your neat machine could be used to cut the necessary cavities for spars and there are numerous ways the spars could be done.

I'm not sure the plastic sleeves are a good idea. You really want to bond the skin to the foam.

Did you allow for the skin thickness when setting up the airfoil profile? If not, the airfoil will be changed, particularly at the trailing edge.

Looks like you're having good fun.

[SparWeb]

Stop!  

If you're not going to bond the skin to the foam, the blade won't work!  The foam gives shape to the blade, but if the skin can come away, you don't have an airfoil any more: you have a grocery bag.  Structurally, if the upper skin is in tension and the lower skin is in compression (bending), then there must be a shear load through the foam to make the blade act as one beam.  Thirdly (pausing to catch my breath) the compression side will just wrinkle up if it's not supported by the foam when the blade is loaded... Fourthly... heck, you get the picture by now....

[Experimental]

Hi Joseph,

    Again, really impressed with your enginuity !!!

But like the others, am confused with what you are trying to accomplish !!

    If you are just glassing the foam, epoxy resin will cause no problems, what the other fello ment by resins desolving the foam, only accures if you use polyester type boat resin on styrofoam...

    You can use polyester on polyurethane foam -- but be very carefull there as polyurethane foam can produce deadly fumes if hot wired -- while the styrofoam types work very nicely !!

    The blue and pink foams work great and as you have seen, hot wire beautifuly but you must use an epoxy resin on them -- as someone already mentioned, a really good epoxy is "West systems" -- after glassing West systems has a filler, you mix with the resin to form a paste, that you can smear on the finished blades, that will fill the weave and is very easily sanded -- it is tan in color and is called "Microlite #410" -- very nice to work with..

    Also was mentioned -- a spar !!

I have built blades without spars, by useing multiple layers of glass, but long blades, will flex -- a lot !!   That is why I mentioned glassing in the carbon fibre arrow shafts in an earlier post..

   If you want to make a mold, simply glass one of your blades, finish it to a glass like consistancy and use either wax or a mold release, called PVA (poly vinyl alcohol)

   The problem then is , you need a two piece mold, as removing the blade after glassing is not fun or nearly impossiable !!

   You do great work, have fun, Bill H..........

[SparWeb]

Seeing your subsequent posts - am posting a retraction.