RE: Bluejay XLT question
 

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Just got done running two tanks thru the Jett. . . all I can say is WOW.  I started with an 11 x 7 and without touching anything got 15.5K on the first tank.  I switched to a 12 x 6 and got between 14.5K and 15K.  I'm sure the neighbors are lovin' me!!! . . .
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All of this without going thru the whole tuning instructions and the pipe sliding back and forth whenever I changed RPM.
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Obviously Dub is right about running this engine on a test stand before putting it in an airplane.  Much easier to notice and fix issues on the stand. . . like the sliding pipe and header bolts loosening . . . I can also tell that I'll need to seal the engine compartment will since the carb likes to spit fuel.  Got a little work to do on the transition between now and then. . .
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After only two tanks I can tell that it is loosening up nicely.  Can't wait to hear this engine in the air!!!<br type="_moz"/>

RE: Bluejay XLT question
 

Awesome!!

I noticed in your test stand picture you don't have any zip-ties or clamps on the silicone coupler...You may wanna think about using them to keep stuff from sliding around...I've actually seen a pipe slide out of the coupler while using zip ties that weren't tight enough...

The silicone coupler will eventually "grip" and need to actually be peeled off the pipe once it has run a little bit...But if that seal is lost it will be loose until it re-seats itself...I have to remove the pipe in order to remove my wing's so I use a clamp on that end and zip ties on the fixed end of the coupler...Even with the clamp it can still slip until it seats...I like zip ties better cause you can tighten the snot out of them but it's sorta a pain to have to cut them off everytime...

Just my .02

Chuck

RE: Bluejay XLT question
 

Chuck,

Yessir . . . I figured that out 1.5 seconds after the first time I ran it up to full power. The coupler slipped off the header (BWWWAAAAAAA!!! - you know the sound!!) and then I went into the garage and got the zip-ties. The pipe was still sliding around a bit so I added another zip tie to the pipe holder help hold that. All part of the learning curve and I'm glad I'm learning them on the test stand.
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It's good to hear that the coupler will seat. I don't think I'll need to remove the pipe on this plane once I get it set the way I need. I ran two OS 1.40 RX's on Icepoints for a couple years. . . I have become a big fan of piped two-strokes. Once those OS's were set up, all I ever did was add fuel, light the plug and bump the prop. From what I've seen so far, this engine is going to be just as good.
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I've already found a couple really great features of this engine. The needle valve is a separate assembly from the engine. I have the needle valve mounted right now to the "firewall" of the test stand, and I still have to find a place for it in the plane, but it is nice to have the needle mounted to a solid surface and let the engine shake away on the Hyde mount. I guess "shake away" was a bad term. . . this engine is actually very smooth at all RPM's. The only movement I could see was the cylinder tilting left as it ran up to full power due to the torque from turning the prop.
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Another neat thing is the prop mounting bolt has a recess in the end for a hex wrench. You can hold the prop shaft in place so you can really get some torque on the prop nut. I can't really describe all of the other differences forward of the front bearings, but there are many as compared to an O.S. The spinner backplate is a replacement for the usual thrust washer, so you don't have the slipping when they are two separate pieces.



</snip>

RE: Bluejay XLT question
 

Not much to report over the weekend. . . starting to finish up all of the little tasks that have slipped under the radar so far. CST's glass cloth arrives tomorrow so I can start finishing this bird. . .
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Realized I didn't install hard points on the ailerons. . . same method as the elevators. .

RE: Bluejay XLT question
 

Its been a couple weeks, so I'm going to try to catch up with where I'm at with this build. A couple reasons for the delay, first is that my employer made me an offer I couldn't refuse. . . the second is that I discovered that I had figued out a way NOT to apply the West System and microballoons and didn't want to post until I had either 1) recovered successfully, or 2) started a new fuselage. . . Luckily I was able to recover to #1. . .
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I started by applying the 0.7 oz. cloth from CST with the 3M 77 spray. I know this is initially a pain in the rear, getting the cloth to lay down smooth, but once you get it down it stays put thru all further handling. The only downside is that if you get any little wrinkles in the cloth, it is nearly impossible to get out. Then I used the original firewall and a piece of PVC pipe to make a fuselage holder while I work on the fuse. Another little trick I picked up elsewhere was to cut little hinges out of mylar to keep the slots open thru the finishing process. . .
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OK, here is where I went "off the reservation". . . I mixed the West Systems and microballoons before applying to the glass cloth. I didn't realize that the microballoons would thicken up the epoxy, but I was able to get the mixture down with the help of a hair dryer heating the mixture to a thinner consistency. With hindsight, I should have added some acetone to the mixture to thin it out and help it flow.
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Anyway, after the whole mess cured for a couple days, I started wet sanding and was able to get it down to a nice smooth surface that I believe is ready for the primer coat. . .

RE: Bluejay XLT question
 

Like they say in the simulator. . . "New jet, new day". . . On to the wings!! This time I applied the epoxy with a roller to a nice even consistency and then used Handglider's technique of rubbing in the microballoons after it set up a little. I ended up using much more of the microballoons than before, but the end result is a much easier job sanding the surface down. I'll post some more pictures when I get the wings done and ready for primer. . .

RE: Bluejay XLT question
 

Keith,

good stuff! I've never seen MB that color. Any different than the white ones?

What happens to the wing center - not painted?

David.

RE: Bluejay XLT question
 

Those are phenolic microballoons. The white ones are made of glass. You don't want to breathe the dust of either type, but especially the glass ones.


Ed Cregger

RE: Bluejay XLT question
 

No kidding! Thanks Ed.

RE: Bluejay XLT question
 

Ed,

What is the difference in the types of balloons? I just ordered them from West Marine, didn't know there was a difference. Hopefully the primer will cover the brown . . http://www.rcuniverse.com/forum/js/f...bout_smile.gif
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I do know that these were darn hard to blow up!!. .
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RE: Bluejay XLT question
 

Yeah, they are hard to blow up. I keep inhaling them...

The white ones are stronger and hold a set of threads better if you need to drill and tap the material, although I've used both the phenolic and the glass to hold nylon wing bolts and both types held up just fine.

Allegedly, the phenolic balloons are a tad lighter than the glass balloons, although I suspect that varies from one manufacturer to another. Both are great products.

Oh, to me, the phenolic balloons are easier to sand, although both work just fine for contouring, etc.


Ed Cregger

RE: Bluejay XLT question
 

Ed,

Thanks!!

RE: Bluejay XLT question
 

Although I have not got to this point in finishing any of my airplanes yet I do like Handgliders technique very much...You mention you ended up using allot more microballoons which is a really good thing!! More microballoons means less resin which in turn means less weight...

When the time comes I thought I would attempt weighing my cloth and used exactly that same weight of resin hoping to achieve a 50/50 cloth to resin ratio...I'll probably have to experiment on some test panels just to see what that "looks like"...Ultimatly I would like to cut that back a little more than 50/50 if I feel I can get the cloth wet out sufficiently...I know of pre-preg materials that are along the lines of 38% resin to 62% cloth...It's a little tougher to achieve the ultimate resin/cloth ratio while doing a wet lay-up process...

Not sure until I start monkeying with it if my mental picture of how things will work is valid...I may find that you need that extra resin to bind the microballoons together?? I don't know...Although I have allot of composite experience this will be different than what I'm use to doing...It should be pretty fun...

Your plane is looking good and look forward to the rest of the finishing stages...

Chuck

P.S. I think it's already been mentioned but be sure to where a respirator when using microballoons!! Or any of the other common fillers such as silica, flox, graphite powder ect...

RE: Bluejay XLT question
 

OK, the following images are not suitable for viewing by women of good repute, small children, or exclusive ARF builders. . .
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After rolling on the West Systems and rubbing in the microballoons, I allowed the wing to cure for a day. Then I did the other side and allowed another day for curing. Once I was sure everything was nice and solid, I broke out the 120 grit paper and began wet sanding. Even though it makes as big of a mess as you are imagining, it seemed to be a faster way to get down to a smooth surface and keep the paper from clogging up. Since the weather was nice outside, I just took the wing outside in the grass every once in a while and hosed it off. Does anyone know if microballoons have any fertilization properties?
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And yes, I was tempted on more than one occasion to break out the pressure washer you see in the background. . .

RE: Bluejay XLT question
 

Wow,

bring it on! That's what I call a finishing job...

Keith, when you're done, she'll be as smooth as a baby's bu*. :D

David.

RE: Bluejay XLT question
 

Reminds me of how I spent several Saturdays in the garage last summer. I used the polycrylic and 0.75 oz. cloth technique. Does the epoxy give a much more harder and dent resistant surface? I used talcum powder and polycrylic mixed to fill the weave in the cloth.

Jim

RE: Bluejay XLT question
 

The epoxy seems to make the surface pretty tough . . . hopefully its not adding too much weight.
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The control surfaces are curing right now, so once I get them sanded down I'll post another weight spreadsheet.
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I'm ready to put West Systems and microballoons in the rear view mirror . .

RE: Bluejay XLT question
 

Now that's funny.....:D:D Keep up the great work.

David

RE: Bluejay XLT question
 

Spent yesterday working on the control surfaces. . . same mess as the fuse and wing. I mixed up some epoxy and microballoons to fill in all of the little spots around the plane that bubbled up or needed a little repair. Hopefully I'll be able to shoot primer on Monday. The weather is getting nice and I want to get this bird up in the air!!
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I also posted the weights I have so far in the PDFfile. The second page is a record of the airplane components that are getting covered. Iam weighing at each step of the way and posting.I don't know if I'm in the ballpark or not as faras weights are concerned, so I'd like some feedback if possible. One place some parts of the airplane picked up alot of weight was absorbed water during the wet sanding. Maybe I'll set the plane out in the sun this weekend and dry it out some?

RE: Bluejay XLT question
 

Keith,

I would definitely not want to apply anything sealing (e.g., primer) if there is water inside the airframe. I'd let it evaporate out in the outside on a balmy day but not in direct sunlight. Check to see how much weight the airframe has gained after you feel any water has dried out. If it's under 2 oz each for fuse and wing you should be ok.

Your weights seem fine to me. It looks like a slightly more than ~55 oz airframe at the moment which should turn into a 60-65 oz finished model. Double that and you'll be in your AUW weight range ~120 oz for a nice 7.5 lb model. With your use of composites, I'm sure she'll end up lighter than average.

David.

RE: Bluejay XLT question
 

hmmm plane to dry out... sounds like a (AA) advertisment... :)

looking forward to seeing the plane..

so when you going to have a CPA event out in your area ??? hint hint

scott

RE: Bluejay XLT question
 

LOL. . . twelve-step process for R/C airplanes. . .
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Gotta work at track meet tomorrow, so its another good day to let it dry out and do some more sanding in the PM. . .
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RE: Bluejay XLT question
 

Keith,

speaking of surface prep and the 12 step process, are you out of the messy part?

David.

RE: Bluejay XLT question
 

OK, I'm really hoping that I'm done with the microballoons until the next airplane. . .
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I suspected that the control surfaces had absorbed alot of water during the wet sanding process so to make sure I went to Hobby Lobby and picked up a bag of silica dessicant. I dumped the whole bag of dessicant into a clear garbage bag ,added the control surfaces then sealed it all up with a zip-tie. I then left the bag out in the sun all day in the driveway. The total weight of the control surfaces was 199 grams at 8am, and then 194 grams at 7pm. I think it is safe to say I got all of the water out.
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I then spent the day working on the canopy, finding a place for the remote needle valve, and fitting the pipe support. A couple more test fittings of all the pieces / parts and I should be ready for primer. . . Maybe. . .

RE: Bluejay XLT question
 

Keith,

she's looking sweet!! Actually those phenolics make her look down right mean! Trim scheme in mind yet?

I'm surprised you lost only 5 of ~200g in drying the controls. That's only 2.5% weight reduction. It sounds like they might have not absorbed that much after all. This is a good sign that your glassing job was nicely done - a good example of a well sealed surface; great for paint, not so much for plastic covering.

David.