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Old Mar 07, 2012, 02:02 AM
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New Zealand, Waikato, Hamilton
Joined Nov 2011
285 Posts
Hey,

I am nearing the stage on the build where my f22 needs covering and I was thinking either depron with a layer of glass over that or balsa with glass over that. Anyone have any recommendations for me (as this is my first scratch build)??

Cheers,

Matt
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Old Mar 08, 2012, 06:00 AM
it wasn't me flying that plane
Hover or die's Avatar
United States, NC, Wilmington
Joined Mar 2011
704 Posts
Matt,those are your two main options...you can also take a look at liquid sheeting..hard shell that goes over foam...also known as styrospray..awesome stuff..if i can get away with it i will do without glass andput a couple of layers of styrospray on my raptor..
Hope that helps.....chris
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Old Mar 08, 2012, 06:06 AM
it wasn't me flying that plane
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United States, NC, Wilmington
Joined Mar 2011
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Matt,
I also wanted to mention that you might want to get all yourelectronics,servos and linkages figured out before you cover.it is a thousand times easier to do this with the model uncovered..just thought i would mention it to ya...
The way nem has the servosyou will have to have a dozen access hatches and this is the reason for me refiguring most everything to do with electronics..i want my stuff accessable for limkage adjustment and servo replacement...
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Old Mar 08, 2012, 01:26 PM
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Denmark
Joined Sep 2005
865 Posts
Hi Chris

You are doing a fantastic job on your F22, it is a pleasure to follow you work.
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Old Mar 09, 2012, 02:07 PM
it wasn't me flying that plane
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United States, NC, Wilmington
Joined Mar 2011
704 Posts
Hey Frank! I hope you are doing well...I have 1 duct plug nearly done and thhe other is cut and being glued together and will be ready for filling..Iw they will not be exactly perfect but they will be pretty close when I finish...I have a few small flaws to fix on the first but I am really happy so far!!!The fans fit perfect and should slide right in when done..These being my first I will probably go a little heavy to be safe..I do have plenty of carbon tow/fibers to wrap both as much as is needed..
And also a big thanks for all the help you have provided me simce i started here..Very nice of you to help a new member out like you did Frank..
Rich as well,lots of help...
A few pics...
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Old Mar 09, 2012, 03:51 PM
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Crystal River Fl.
Joined Jul 2008
3,681 Posts
Chris, really looks great there! Coming right along, ducting is really good!!!! w.
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Old Mar 09, 2012, 07:48 PM
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St.Catharines, Ontario
Joined Jan 2009
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Chris

are the plugs the same diameter as the inside of your shrouds, or the outside of your shrouds? can't really tell from the pics, but thought I'de ask. ideally, you want them the same diameter as the inside of your shroud, then use 1/4 inch wide strips of electrical tape to build up the the edge of your duct to the outer diameter of your shroud, then add about another 1/4 inch to the length of the duct. this way, once you've laid it up, there will be a ridge created that will slip over the top of your shroud and create a nice seal. maybe you already knew this, but thought I'de add the tutorial anyway. someone else may read and learn how. LOL.
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Old Mar 10, 2012, 01:01 AM
it wasn't me flying that plane
Hover or die's Avatar
United States, NC, Wilmington
Joined Mar 2011
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Rich,
It actually has a strong taper right at the end and the fan should slide in about a quarter inch before bumping the taper in the duct..the ducts were ruled minus the center cone so they are a little smaller than the fans until the reach the taper where it grows to just where the fan will be able to slide into the duct just a little before bumping into the taper wall..if you look close at the pics you cancsee the duct expand right at the end..
I really think it will work out well..either way the experience will be well worth itlol..i have a ton of glassing experience by building my own offshore grouper boat from just a 33 foot navy hull..i like the epoxy resin much better than the poly!!!So much nicer to the senses...i did a couple of test runs to see how much glass i will need for a rigid duct and it looks like 2 wraps plus a run of the carbon tow for good measure....
Hopefully it goes well...ive started filling the second duct and it looks to be a good mirror image of the first..im really enjoying the process of doing ducts..
Thanks for the heads up Rich!
Take care......chris
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Old Mar 10, 2012, 06:00 AM
I'm BIG on micros
R.M. of Peel, ON
Joined Mar 2011
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What will you form the ducts out of?
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Old Mar 10, 2012, 06:30 AM
it wasn't me flying that plane
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United States, NC, Wilmington
Joined Mar 2011
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What you see above is a plug that will be wrapped in fiberglass and epoxy..this will form tubes once removed from the plug...hope that helps..
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Old Mar 10, 2012, 06:38 AM
I'm BIG on micros
R.M. of Peel, ON
Joined Mar 2011
517 Posts
Cool. I thought you would use plastic or something. Well, I'd better stick to my Champ for now, WAY too inexperienced to do this one.

Caps off to you, you are doing great!
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Old Mar 10, 2012, 03:03 PM
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St.Catharines, Ontario
Joined Jan 2009
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duct

the problem you may face with sliding the fan inside the duct, is that it'll be hard to seal and you may end up with seepage. unless of course, you glue the duct to the shroud with epoxy and it'll become a permanent seal. the other problem associated with this style of seal, is that it leaves a little ridge inside the duct, which acts like a bit of a damn. imagine a rock in the water and you can see eddy currents swirling around it. this will happen with the ridge of the shroud and could possibly send eddy currents right into the blade tips, robbing some power from your fan. ideally, you want to set up your ducts like I described, since it creates a perfect seal without being permanent. because it's a slip fit, it'll be tight and only need sealing with tape. here's a crude drawing for you.
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Old Mar 10, 2012, 03:28 PM
it wasn't me flying that plane
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United States, NC, Wilmington
Joined Mar 2011
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icI understand what you mean and will see if i can get it right before glassing..if i understand right you are say when the air hits the fan shroud(the lip thickness all the way round)it creates turbulance..it needs a smooth transition right to the *inside* of the shroud..without bumping its"edge" so to speak.....I think i can fix er' right up.....i had planned to use 1 wrap of the narrow gorilla tape around the shroud the make sure the seal was pretty air-tight...But this would only increase the lip height air must travel "over" and into the fan...
All i have to do is make a quick template to hotwire back to the point in the transition where it reaches the ID of the shroud..then go with the technique above to get the proper lip...should be pretty straightforward..Thanks Rich for explaining it's importance to the flow of air.............................chris
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Old Mar 10, 2012, 11:20 PM
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St.Catharines, Ontario
Joined Jan 2009
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yeah, you got it right.

I just make a template of the inner shroud diameter and make the plug to that diameter. don't forget to make the plug about 1/4 inch longer than required, since the slip fit will be 1/4 inch over the top of the shroud. you can make it a bit longer if you want. I've gone 3/8 inch and it was good. another point to bring up, is that the slip fit should be as tight to the fan as possible, so as not to have any gaps between the duct and the shroud face. push it in all the way and seal it up with tape. I use hospital tape for my planes and boats, since it also happens to be waterproof. LOL.
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Old Mar 13, 2012, 08:27 AM
it wasn't me flying that plane
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United States, NC, Wilmington
Joined Mar 2011
704 Posts
Finally decided on landing gear set from Shulman and also picked up a few extras like gear door hinges epoxy plate for gear doors,ect..
I'm hoping my motors show up this week as well..and possibly get the ducts and fans positioned in the airframe by weeks end but will have to wait and see if the 2nd motor shows up thisw week..
Lots to do anyways.........chris
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