Author Topic: New .15 fast design? (Read 9664 times)

Rich Perry · « **on:** February 23, 2017, 02:29:41 PM »

I will be working out a new design for a .15 Fast model. I plan to have these for the AMA Nats this summer. To start with, it will be a foamy. I want to be able to get that l.e. kill. A modified version of my old big block fast. My primary consideration (other than weight) will be to try to maintain as long a tail moment as possible. I have never been a fan of the way the Ukrainian models felt. To me they kind of bobble and do not point well. Regardless, I prefer to fly my own stuff, so here I am. I know that with the light .15 engine, it may be tricky to get the tail boom length that I want. So some design considerations will be to keep the tail area to a minimum, getting all of the weight out of the tail, possibly using thread to sew the tails on, as opposed to the wire, removable type. I am also considering sweeping the wing back, like we have done with 1/2 A designs to allow for a more aft CG. Right now my area is around 455 sq in. with a 52" span. This can be adjusted, but I have been told the hot FAI engines can handle it. Any thoughts on this?

Bob Mears · « **Reply #1 on:** February 24, 2017, 08:36:47 AM »

Several years ago I built a 15 fast that was an expanded 1/2 a. Very swept leading edge and straight trailing edge and long boom. Flew just like the 1/2A's. But that long boom was vulnerable. So much that I abandoned it. I'm building foamiew for fast at the nats again this year. They're copies of Riley's old Shadow and Sizzor. I use Phil's wings. Plane really flies great. I use the hardwood leading edge only about 6" in the center then switch to a soft balsa from there out.

Bob Mears · « **Reply #2 on:** February 24, 2017, 08:45:53 AM »

This is the fast ship design of Riley's I used before Nelsons. Works great for today's 15's

Rich Perry · « **Reply #3 on:** February 24, 2017, 09:22:01 AM »

Are the guys really that good at whacking your boom?

Dane Martin · « **Reply #4 on:** February 24, 2017, 10:19:37 AM »

Quote from: Rich Perry on February 24, 2017, 09:22:01 AM

Are the guys really that good at whacking your boom?

Rich, I'm certainly not good. Me and my friend Joey were flying practice matches with some boom type planes. I went for a kill and took his tail off. I guess it could happen either style of plane. That's my experience, but I really like the way they handle when flying.

Paul Smith · « **Reply #5 on:** February 24, 2017, 10:44:11 AM »

I'm not all that happy with the flipper-on-the-TE design, either.

I guess a degree of flyability has been traded for excellent crash survival. In an one-plane fast match, maybe that's not such a big thing.

Ken Burdick · « **Reply #6 on:** February 24, 2017, 11:55:16 AM »

if you can get hold of Jeff Rein, he has a well refined design called the R&B rippoff. It flies great for 2D fast and he's gone all the way through the long boom to short boom design.

Rich Perry · « **Reply #7 on:** February 24, 2017, 12:14:42 PM »

Here is an article on it. I will study and learn. I still like to design my aircraft to fly well, primarily, and survive secondary. I find that when you are winning, not much is breaking. A good flying plane helps to win. http://flyinglines.org/bbb.rbripoff.html

Ken Burdick · « **Reply #8 on:** February 24, 2017, 02:39:50 PM »

I'm the B in that model and it began life as my F2D attempt. Jeff made it useable for speed limit and fast using the same basic platform. The s/l has a smaller span. One really cool idea was to inject (using the glue bottle) Gorilla Glue into the foam under the spars just before gluing them in place. Use a 10 penny nail to poke holes in the foam in the spar notch. Then put GG into them then the 3/8 x 1/8 spar. It makes an I beam and the load testing showed it made a huge strength difference.

Keep us informed on how you are doing with the model.

Ken

Ken Burdick · « **Reply #9 on:** February 24, 2017, 03:11:33 PM »

almost forgot. Get a roll of SLC from Phil C. It's super light, has adhesive that works well enough for foam. There is a technique to apply it. Use a household iron. This was shown us by Mike Willcox. It works so much better than other methods. Lay the slc on the foam and with the iron, use large strokes to adhere it. Not edges first like other stuff. Amazingly simple once you get the technique.
All this stuff was learned "the hard way" by stubbornly sticking with what we knew before....... then we tried new ideas and began cranking out the stuff like a factory.

K

Rich Perry · « **Reply #10 on:** February 25, 2017, 01:37:27 PM »

I have been hearing about a new covering material that is better. I have never been a fan of the old seal lamin' stuff. It tends to wrinkle over time. My big roll of the stuff is now small enough to justify replacing it. Especially if there is something better. DO you have a link to an article or video describing this new covering technique? Starting in the middle kind of breaks all of the old rules about covering.

Ken Burdick · « **Reply #11 on:** February 25, 2017, 04:02:15 PM »

I wish I did....it's something you have to see to understand. I'll send a note to Jeff and ask if he can better describe it than I can. I tried it myself tacking it down and it took a bit of time....he did his in a fraction of the time with no wrinkles.

Rich Perry · « **Reply #12 on:** February 27, 2017, 09:12:27 AM »

Bob, I have heard about a PVC film that is supposed to be the cat's meow. Where do you find this stuff (Ebay?), and I had heard you had a video on how to apply it.

Ken Burdick · « **Reply #13 on:** February 27, 2017, 09:22:18 AM »

here ya go Rich. I just got this from Jeff on how he applies slc from Phil.

OK Ken, here is how I do it.

I start cutting a piece of SLC about 4 1/2 feet long. I place it over the top of the wing leaving about 1 inch to route around the leading edge. I then take a standard iron set to about mediem, which would be approximately 300°. I tack the SLC from the trailing edge to the leading edge right down the middle of the wing to secure it in place. I then take the iron and place it down on the wing and swiftly move from the center of the wing towards the wingtip and trailing edge. I do this in about three strokes, and it is attached. I then repeat the same from the center of the wing towards the other wingtip. Note you must keep the iron moving, or you will melt the foam. I then use scissors or an X-Acto knife to cut around the motor mount, the tail boom, and at the tips of the wing where the SLC is going to be folded over. I then hold the plane vertical and while pulling the SLC tight around the trailing edge I run the iron along the trailing edge. I do the same for the other trailing edge. I then take scissors and cut off the excess. I then take the iron and pull the SLC tight around the leading edge and with several swift strokes I rap and seal the SLC around the leading edge with the iron. I then make appropriate cuts with the scissors and seal all the edges and then finish off by shrinking the SLC on the top of the wing. I flip the wing over and repeat. Sealing all of the edges and very important. That is it. Good luck!

Ken Burdick · « **Reply #14 on:** February 27, 2017, 09:43:37 AM »

one more addition just arrived:

Just tack it in the center with the tip of the iron from the spar to the trailing edge then run the iron flat on the surface from the center out to the tips swiftly.

Rich Perry · « **Reply #15 on:** March 02, 2017, 12:35:50 PM »

I should be getting my engine soon, then I will start messing with this design. For some reason I thought this event was on 60' lines, but they are actually F2D spec, around 52'. That makes a big difference. Should be a lot of fun.

Ken Burdick · « **Reply #16 on:** March 03, 2017, 03:59:37 PM »

what engine did you buy?

Rich Perry · « **Reply #17 on:** March 03, 2017, 09:09:22 PM »

A Fora 2014, and I will have an 8mm muffler for it.

Ken Burdick · « **Reply #18 on:** March 04, 2017, 03:50:10 PM »

That will work. APC 7 x 3 pull very well and don't cost $4.00

Rich Perry · « **Reply #19 on:** March 05, 2017, 07:54:22 AM »

Thats good to hear. It is nice to be able to buy props locally as well if necessary. I also got a shut off. I will have to learn how to deal with that, as I have never used one.

Ken Burdick · « **Reply #20 on:** March 06, 2017, 09:36:52 AM »

if the shut off is a swing arm, keep the spring unflexed when not in use. They fail regularly. My preference is a line tension type for mechanical, I have not tried any electric shut off's. Do your research on the shut off. So far, the most reliable is the H&R made by Tony Huber and Jeff Rein. They use an on top of the wing system with a motor mount and rod that extends back some to mount the bell crank that is also the shut off. The whole thing changes out with the mount. Lines go directly to the bellcrank. One primary advantage to this system is the latch. You get full and smooth control while taking off and landing. Other earlier "wand" type line tension shut off's are hard to land because the spring tension is now directly to the lines. The simplest is "the spring thing" By Pete Athens. You will have to find an article on it but it's shown to work very well and is cheap and simple to make.

K

Rich Perry · « **Reply #21 on:** March 06, 2017, 02:34:16 PM »

I have heard good things about the H&R, but they seem to be unobtanium. Like so many things in this hobby. You pretty much have to make it yourself. The shutoff is the reason I quit flying 80 mph combat.
Thanks for the tip on keeping the arm in swung. That is the type I got. As time goes by I am sure I will get exposed to better things, and learn the shortcomings of the one I am getting. I am hoping it will be easily transferred to another plane, as for now I will only have one engine.

Bob Mears · « **Reply #22 on:** March 07, 2017, 10:20:14 AM »

Quote from: Rich Perry on February 27, 2017, 09:12:27 AM

Bob, I have heard about a PVC film that is supposed to be the cat's meow. Where do you find this stuff (Ebay?), and I had heard you had a video on how to apply it.

The links I have are no longer available for the colored PVC. Now I cant seem to find it. You need 100 gauge pvc for open wings, 75 is good enough for foam. It shrinks at 100 degrees so its really foam friendly. It has no glue, so 3m77 will do the trick. Whish I had bought more colors when I could find it.

john e. holliday · « **Reply #23 on:** March 07, 2017, 12:14:55 PM »

Bob, trying to help you out I did a search on PVC Film and several sites show colored film but I can't read Chinese or what ever language that is. By the way you sure make it look easy.

Rich Perry · « **Reply #24 on:** March 07, 2017, 12:30:45 PM »

This is where I got mine. I just wanted clear though, and did get the 75. http://www.uspackagingandwrapping.com/Heat-Shrink-Wrap/PVC-Shrink-Wrap/colored-pvc-shrink-wrap-500-ft.html

I will experiment this weekend.

Bob Mears · « **Reply #25 on:** March 08, 2017, 07:47:31 AM »

Cool !!! Thats the place I got it before. But my old link woudnt get me there. Glad you found it. Might be time to order another color.

Rich Perry · « **Reply #26 on:** March 11, 2017, 08:59:04 AM »

Been practicing covering with the PVC this morning. It sure works great. I have to refine my technique a bit, but I will go as far as to say this stuff is revolutionary to what we do. I always hated that Seal lamin stuff, and it would get wrinkly and ugly in short order. I have heard that the PVC stays tight, and if so it will be a godsend. Not sure how many guys are seeing this thread, but this could be the most important topic that comes out of this.

Ray Richardson · « **Reply #27 on:** March 11, 2017, 10:27:47 AM »

Rich: You have got me interested in the PVC covering. How does the weight compare to our usual coverings, seal lamin, fascal, etc..

Paul Smith · « **Reply #28 on:** March 11, 2017, 11:42:20 AM »

Shutoffs:

The "moving bellcrank"system sold by Pat Willcox works OK.

It's inexpensive and reliable enough.

The only drawback is a bit of work to install it. Since FAST requires only a few models, the effort is reasonable. F2d goes through dozens of airframes in triple-elim contest, so it's easy to see why this device didn't take off in that event. But it would be OK for Fast.

Rich Perry · « **Reply #29 on:** March 12, 2017, 07:07:46 PM »

Ray, any weight difference would be negligible. I have no way to measure the difference as the stuff is so light. If anything the PVC would be lighter I would think, as it has no glue.

Envision this covering technique as putting your plane in a bag, and shrinking the film around it like they do a music CD case. Because that is essentially what you do. I am shopping now for one of the sealer trimmer machines Bobby is using in the video. I think that is the way to go.

Rich Perry · « **Reply #30 on:** March 17, 2017, 05:58:18 PM »

Well, I took one of my Old Nimbus fast designs that I use for Speed limit now. I shortened the boom and lightened the tail, making it smaller. It is 17 oz. ready to fly (but my purpose built .15 fast models will be lighter) with prop and engine, 480 sq. in. I got a couple of flights today, and all I can say is WoW! Best flying combat plane I have. Really excited to be involved with this class. I had no problem with the shutoff either, other than the couple of times I stalled her, then the bobble, lack of tension tripped the kill. But, at this point I am really happy.

Ken Burdick · « **Reply #31 on:** March 18, 2017, 08:09:40 AM »

what lines are you using?

Rich Perry · « **Reply #32 on:** March 19, 2017, 06:49:18 PM »

I am using .015" but the only set I had cut measured 55'. They are 52' eyelet to eyelet. I just got a new spool from MBS so I will start cutting new sets to 52' 2".

Rich Perry · « **Reply #33 on:** March 19, 2017, 06:54:17 PM »

learned a very hard and expensive lesson from those 2 flights I had. My new engine did not have tight rear cover bolts. I neglected to check them. So it seems if those bolts come loose, the back plate strikes the piston skirt and fries the piston and sleeve. So I now have these on order. Good thread lock is in order here it would seem. Or even wire tie the 3 together. Regardless, those bolts must be secured to not come loose it would seem, otherwise it gets expensive fast!

Ken Burdick · « **Reply #34 on:** March 19, 2017, 07:43:26 PM »

Sorry that happened.

I've only seen it once before, instant junk. Be sure you know the engine inch for inch. They run up so high you can't take it for granted. I'm guessing the engine was used before you bought it. Likely it was crashed and maybe cleaned out. I've never had to use loctite or anything like that, but I would check the bolts at the beginning of the season and on change overs.

k

Rich Perry · « **Reply #35 on:** March 20, 2017, 09:03:08 AM »

No Biggie, live and learn. I know now. I remember when I got my very first N36 fast engine, I accidentally put the lower portion of my glow plug clip in the exhaust port. Of course I hit the prop hard starting it. When that dented the heck out of the piston. So back to Henry it went! I never did that again though. Now I just need to make sure I get all the crap out of this one. Don't want any bits to jack up the new piston/liner.

Bob Mears · « **Reply #36 on:** March 21, 2017, 07:48:41 AM »

I always cut my glow clip so it couldnt get into the exhaust port. I do use locktite on my rear backplate bolts. Never the less, I have had some back out anyway. They must be a regular maintenance item.

Rich Perry · « **Reply #37 on:** March 21, 2017, 09:19:23 AM »

Yeah Bob, I have been told it is a common problem. Not sure I have ever had another engine design that destroys the piston, if the back plate comes loose. I cannot argue with the performance of the engine though. So they must have done it for a reason.

Ken Burdick · « **Reply #38 on:** March 21, 2017, 05:23:14 PM »

the design (s) are pretty innovative. Big hole in the crank, a very stuffed crankcase so that the backplate has to have a deep groove for the piston as it reached bdc. Most of the rest of the piston skirt is cut away for fuel flow. Most of mine have been Profi so the backplate hold down is different with a threaded ring holding a plug in place.