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Old Sep 03, 2012, 05:08 PM
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I'm getting a kick out of this thread. It looks like Fickle Flier and I are on about the same build time-line. I've got all the sub-parts together, still working on the spoilers though. The fuselage is together and waiting on servo installation. Speaking of which....


Open question for any Riser pilots:

I'm planning on using standard servos and radio gear. The servos are shown in the plan mid-fuselage. I'm wondering if I'll need nose weight if I place the servos there. Should I place them forward of the wing?

NCSU
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Old Sep 04, 2012, 05:48 PM
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Based on what I've read while researching this build I will be placing all the gear as far forward as possible as from what I can tell you will almost always be forced to add nose weight. I have read that something like an HS-85 should be fine if you want to go a bit smaller on the servos (I am just using standard size myself).

I will do this with one exception. I am almost certain I will instal a ballast system of some sort under the wing so I will have to make changes accordingly for that to fit. This is one of the reasons I am sorta set on installing the servos in the wings for the spoilers (create a bit more room in the fuse for the ballast compartment.
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Old Sep 04, 2012, 11:24 PM
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I think it's a good idea to leave room for ballast in the middle. Standard servos are ok, but if you need smaller ones to make room, you could use HS-81's. HS-85's are more powerful than you need. I use them for rudder and elevator on 3 meter competition gliders. I'm guessing HS-55's would work for spoilers. You don't need anything expensive, and you don't have to go completely nuts saving weight. If you move the servos forward and you find out it's nose heavy that way, you can always go with a 4 cell AAA nimh pack or something. Should be good for 800 mah or so, which is plenty.

I don't know if anyone has mentioned it in this thread yet, but on many older gliders, speed range was increased by sanding the lower leading edge and first inch or two of the underside of the wing to get what is traditionally known as "phillips entry", though I suspect the pure aerodynamicists wouldn't like this term any more than "undercamber". You can get an idea of what I'm talking about by comparing the Clark Y and the Aquila airfoils. The Clark Y has a wider speed range.

http://www.aerospaceweb.org/question...ing/clarky.gif
http://www.ae.illinois.edu/m-selig/a...s/aquilasm.gif
This mod probably isn't worth it for beginners, as it gives you the capability of getting in trouble faster, but once you know how to fly, a bit of speed can be very handy in sink or when it's windy.
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Old Sep 08, 2012, 12:49 PM
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Spoilers and Ballast Bins and Servos and CG and.....

Hey, as usual, what Lincoln says is pretty much what I have observed.

Phillips Entry - As far as Phillips entry goes, my Spirit airfoil mod includes more Phillips Entry than the original and it has a pretty wide speed range, it's great when you get past the crash phase in the beginning of learning to fly and want more speed and/or penetration but it's not that desirable in the beginning.

Servo Placement- Yes, you are correct, you will almost certainly still need to add nose weight and you might as well use your radio gear to do as much of that balancing as you can before adding weight to the nose. Put the battery in front of the servos behind the noseblock, then put the servos in as far forward as you can. If they don't sit side-by-side, you can put them at angles one behind the other if that scoots them any farther forward.

Bulkhead Placement- You CAN move bulkheads to places other than where the plans show in order to have better servo/battery/etc placement. Just keep bulkheads near the leading and trailing edges of the wings. Any other bulkheads you can alter their size/shape, splice wood onto what you have or cut a new one, and you'll be glad you did. Just be sure that the wing/fusalage interface is well supported still and your wing-mount dowels are well integrated and not going to get torn loose.

Ballast and wing servos- In hindsight, I think you are completely on the right track to put your spoiler servos in the wings so that you will have a nicer cleaner more open space to put in a ballast bin or ballast mounting system and still have room to route wires, linkages,etc. I want to do a string-pull system someday just to do it and reduce weight, but I'm giving that up on my present Spirit. If you build this plane in a decent weight range, you'll be glad you have a ballast system for breezy days, it WILL fly much better in a breeze with ballast added. You can also have metal bars of different weights and use velcro to hold them in place rather than the bin-with-bearings that I made for my plane.

Ballast bin Vs Ballast with Velcro - The advantage of a ballast bin is that in a bad crash, the ballast comes loose and may bust up your ballast bin rather than driving the nose into further worse destruction and spliting open your forward fusalage as badly as "solidly" velcro'd metal bars might add to the damage. The disadvantage is that in a bad crash, your ballast bin will likely release ballast as it blows apart and you may have to rebuild it. When my Spirit augered into the ground, the ball-bearing ballast just blew through the forward balsa wall of the bin and went out and struck the bulkhead that the forward wing mount dowels are mounted in, however, I think that bulkhead came loose from the impact wedging the forward fusalage open more than any "shotgun" effect of ballast bearings striking it. But, overall, I did end up with an amazingly not-as-bad-as-I-expected total of damage that required much, much less repair than I would have thought as I watched that thing dive into the ground whistling it's way down. If I had gone with metal bars velcro'd to the sides of the fusalage, that weight may have stuck to the walls resulting in more moving inertia driving that balsa(with a fiberglass shell over the forward section) fusalage into the nonmoving ground and busting things up worse than it did. Hard to say without further experimenting with highspeed crashes that I'd rather not engage in any more than I have already.

Adios - Paul
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Old Sep 08, 2012, 02:40 PM
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Working on finishing up the outboard wings. last night I spent about 1/2 hour shaping the wingtips and gluing one on (I only had enough clamps for one). The outboard wings are about 1 gram different so fairly happy with that and I assume I will get it perfect in the end with a bit more sanding. I will be gluing the other tip tonight and doing the final sanding for the wing tomorrow. Then I think I will be joining the wing parts together.

The fuse still needs to be shaped, glassed (I think I might try to do the whole thing with Polycrilic and 1/2 ounce glass. Then I will paint it if I go this rout. I saw this on the Gambler website (probably my next build, but I also have a Bubble Dancer kit if I work up the nerve) Otherwise I could epoxy glass the front of the fuse and do covering. Not totally sure right now but I think I want it glassed somehow for the extra durability.
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Old Sep 08, 2012, 04:35 PM
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Fiberglass......

Hey, You could fiberglass the whole thing, but then you'd be adding rearward weight you'll have to counterbalance with more nose-weight in front. You'll very likely not gain much if any advantage from it either.

If you take that same total amount of glass and epoxy, and it use it all on the nose to
slightly behind the leading edge wing-mount, it will:
A) make the nose stronger- where it needs to be
B) Add more structural weight in front of the CG where you'll need it anyway.

What I do is I put probably 3 layers on from the tip of the nose to an inch or two behind the nose-block

Gotta go- back in a sec
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Old Sep 08, 2012, 04:37 PM
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You can save your self a step if you tint the polycryl with acrylic ink. I looks very much like ultra coat as far as color's go.You will still see the wood grain through the tinted varnish, and glass. Here is a couple of pics of my latest.
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Old Sep 08, 2012, 05:47 PM
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Now "That's" cool!

Doc993- I'll have to try that some time when I make something with a pod/boom or skinny tailed design.

Adios - Paul
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Old Sep 08, 2012, 06:10 PM
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Doc that looks really good!

I will admit I was a little concerned about the weight added to the tail area. Since you point it out as well maybe I will just stick to the front area as the Gambler is also a pod and boom set up. That must be why you never see that system used on full balsa fuse.

When covering the glassed fuse do you make it really smooth first, or does the covering pretty much take care of the cosmetic issues caused by the glass (I am not saying perfect just presentable)?

Thank you for all the help so far.
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Old Sep 08, 2012, 07:03 PM
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Oh yeah, fiberglass....

Hey, Fiberglass - What a mess! But sooooo worth doing while building rather than later during a repair(which it could well prevent)! I love it, and hate it, and love it, and hate it. But it's still totally worth every messy minute of it. A few elite people manage to do it quite well however.

As far as putting covering over fiberglass, it helps to have enough epoxy to fill the cloth, but not a thick layer over it. Then, sand it nice and smooth and you'll get a better adhesion of the covering, otherwise, if there's a textured surface of cloth (not filled with epoxy) or lumpy wavy surfaces, the covering will not stick quite as well and will look suboptimal but not be the end of the world. It will be more aethetically disagreeable to some than functionally limiting. In short, if I can get something smooth for flying reasons I will, but I don't go overboard on the perfect detail appearance since I make my planes to fly and land on the ground.

Oh yeah, so what I do is:

a) 2 or 3 layers on the nose block itself, then
b) add the next layer so it extends a 1-3 inches past the nose block, then
c) the last layer goes all the way to anywhere from 1/2-way through the forward compartment in front of the wing to as far back as 1" past the leading edge wing mount area.

That way you will have the most fiberglass where you need it the most, will do the most good, weigh the most farthest forward, and still do some good where it ends past the beginning of the wing.

It helps to cover the nose block with pre-cut triangles to overlap each other over the nose, use an old credit card or plastic sheet of something to squeegee the epoxy into and move excess around, use thread to wind around the nose if desired to hold it into place(If you see my pre-covered versions, they're not the most aesthically pleasing with the thread still in place, but white thread will be almost invisible).

Is "Polycrylic" an epoxy? If so, you can probably speed up it's curetime if desired with a heat gun, just be careful to not let it bubble. Heat will re-liquify epoxy while it's curing so you have to be careful. Again, I have something I blathered about it on my build log, just look for the picture of the fiberglassing of the nose.

In the end, sanding, and more sanding will be your friend to make this kind of heavy fiberglass shell look nice and smooth prior to covering.

One tip I ran across that I have not tried yet is to lightly spray your plane where you're going to fiberglass it with something like 3M spray contact cement, press your pre-cut fiberglass on, then apply your epoxy and spread it in/on with your plastic spreader. This should keep things a lot tidy-ier.

By the way, smaller gliders can get by with wetted cotton cloth and yellow glue, but for 2M planes, I'll stick with good 'ol messy fiberglass-n-epoxy.

Adios - Paul
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Old Sep 08, 2012, 09:12 PM
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I block all the surfaces with 80, when the high spots and curves are close,Then I change to 150 grit.I do 80% of the sanding with 150.When the shape and contours are correct I lightly sand with 220 grit ,again lightly and not a lot,Then wipe with alcohol.It is best to plan on two coat s of class, on the 45 I do one at a time and the process goes smoothly., I also do the bottom first Tape a line mask with paper t.The glass can now be rapped over the bottom.Cut a piece of 45deg. glass and lay it on the fuse.Dab a little poly on the fabric.It will soak in and hold the fabric in place .Now you can brush it out to a smooth coat .Next morning trim along the paper and do one more cote with the 45 going the other way ..You can also use a heavy-er glass on the bottom and do one cote..Then I spray the color.spray can ,tint ,what ever, light cotes,Then two to three coats of poly.Sand dust nibs with 600 between coats.It sounds like a lot but if you do light coats it does: not add much weight.Also I have found that H2O based products need to cure for a week or so then it is really a tough,durable finish. It also looks good when repaired.The part I like the best is you can still see the wood grain,I have also added water based pearl to the clear for even more effect.This stuff works for me and I learned it here on RC groups.Thank you all.
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Old Sep 17, 2012, 06:37 PM
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Servo Instal Question

How do you instal Servos?

The directions in my kit say on a hardwood rail. Could I use Oak? Could I just epoxy them in? Could I use balsa?

How do you install the Rail Just glue in place?

I was thinking of doing a couple things. I was thinking about just epoxying them to the bottom plywood sheeting, or making a set of oak rails from leftover scrap. How do you usually install servos in this sort of glider.

Thank you
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Old Sep 17, 2012, 10:12 PM
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A sturdy way to attach servos is to make a piece of aircraft ply (1/8" thick would be good) that fits nicely in the fuselage in the servo area. Make two holes just big enough for the servos, and glue it in. This helps to reinforce that big open area where the hatch is. If the fit into the fuselage is precise, you can use wood glue. otherwise use epoxy. You can screw the servos into the plywood.

Cross rails are ok, but they often come loose in a crash. Don't use balsa, it's too soft. Oak is probably overkill, but ok. Ditto for maple. Usually when they say hardwood in kit instructions, they really mean "not balsa", even though balsa is technically a deciduous tree, and therefore a "hardwood". You could use a bit of the nearest 2X4 and it would be ok. Plywood is nice because it's harder to split with the screws.

However, you can glue the servos in place if you like. I think I would use Goop, but epoxy would be ok. Goop is probably a bit more shock resistant. Particularly if you put in little spacers to make the glue line slightly thicker. Maybe 1/32" thick?? Some people wrap the servos in tape first, which makes them easier to remove.
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Old Sep 17, 2012, 10:19 PM
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If you use 3/4 fiberglass with epoxy, and blot it with tissue, it will not add much weight at all. There are 1.5 meter DLG's that have 350 square inches* of fiberglass covered wing and weigh maybe 9 ounces ready to fly. You can sand it a tiny bit after it gets set up really hard. (Several days). Then you could mist on a very light coat of paint. I like glass because it doesn't get all ratty the way covering material on a fuselage sometimes can. However, one layer of 3/4 ounce cloth isn't going to add a lot of strength. It will make things more dent resistant, however.

I suspect epoxy is much stronger than Polycrilic, but I don''t know that for sure.

*That's really more like 700 squares (i.e. top and bottom) plus some more square inches in the tail. Typically a wing weighs, as I recall, 125 to 150 grams. That includes servos (I think), foam core, spar, etc. in addition to the glass, and it includes extra glass in the middle.
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Old Sep 17, 2012, 10:25 PM
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P.S. A rule of thumb I've heard is that you allow for the same weight in epoxy as the cloth itself. So 3/4 ounce per yard glass might be 1.5 ounce per yard with the epoxy in it. A SWAG for the surface area of an Oly 650 fuse might be 200 square inches. That would be maybe a quarter ounce or less than seven grams. Maybe a bit more epoxy would soak into the wood a bit. Or a very similar weight to Monokote. Calculating with figures from the source below, opaque Monokote with no overlaps would be around ten grams.


http://www.homefly.com/reference/Covering%20Weights.htm
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