View Full Version : Converting Older Sailplanes

07-30-2005, 09:17 PM
Right now I am building two very old sailplanes. One is The AIRHOPPER from the very early 1940's and the other is the Super SINBAD.

The SS is almost done with the exception of fabricating the left side of the 72" wing.

The other started yesterday with the oblogitory cvutting out the ribs. All is cut with the exception of sanding them. I came across some VERY hard balsa (for a change) and the cutting really took its toll on the blades.

The AIRHOPPER is a 96" compound dihedral with the actual rudder section, an integral part of the fuselage. In its original plans, the ONLY adjustment(s) was a TRIM tab on the rudder. I am undertaking to make this a FULLY controlable system by actually making the rudder and the stab - functional.
The ailerons will be functional but I think the question I have is --- Will adding a spolier be too much?


Jason T
08-02-2005, 01:08 AM

Welcome to Wattflyer!

I would not think adding spoiler would be too much but I cannot say for sure.

Can you post some pics of this plane. It sounds very interesting.


08-08-2005, 12:23 AM
i think that you will find that with the older planes they glide forever... i would strongly reco spoilers on any glider that u build.......controlling ascent, precision landings and short field landings are impossible without spoilers.......i've been flying sialplanes for over 35 years and i wouldn't leave home without them...

hope this helps


William L Baker
08-08-2005, 04:04 AM
I agree, spoilers give better control of the landing process, and provide safe escape from lift. The dive out of lift invites flutter which will break wings !

William L Baker
08-09-2005, 01:09 PM
I have been flying electric sailplanes since 1976. My favorite is the Paragon. I wrote an article for Quiet Flyer (or whatever it was called then) on this conversion, it is out of print now . I used a Astro Flight geared FAI 15 with 11 to 13 inch props, 10 cells. Now flying them with Jeti 30/3, 10 1300 CP NiCds. Have flown many sailplanes, but the Paragon can climb out from low altitude in weak thermals better than any .No change in wing except addition of spoilers, no change in tail except separating stab from fin, stab in front and mounted with nylon screws. This allows adjusting stab incidence to fine tune the CG and incidence relationship. On fuselage eliminate all that lite ply (it is heavy and brittle) reduce fuselage cross section to whatever needed to contain on board gear, all balsa fuselage except for a 1/64 ply doubler inside from front to aft of Trailing edge, and put a layer of fiberglass on belly from nose to about mid chord protecting fuselage from landing abrasion. I use one servo in each wing to work the spoilers.

08-10-2005, 04:50 AM
I've an old V tail sailplane with a 96" wing span that I'd like to put a motor in. How many Watts per pound do you need for sailplanes (I know that it's 100 watts/lb for Sport flying and 150 for 3D)??

Also, given that spoilers sound necessary, should I add ailerons too?

How do you figure dimensions and placement for spoilers?

William L Baker
08-10-2005, 12:33 PM
I am a TLAR type designer (=that looks about right ), so I cant give you numbers.But I would say that how much power for your ship largely depends on how fast do you want to climb ? And balance that against cost and how much weight do you want to add ? And for some designs the limiting thing is room for batteries. However, that said, my 118"
span Paragons have all been powered with 10 NiCds, and either a Astroflight
FAI 15 G, or a Jeti 30/3 direct drive brushless, and this will give plenty of power for fun flying, but not a limited motor run competition type climb which would be an example of "all you can get" I have not measured the watts on these motors but I get about 90 to 120 seconds of climb power which I usually take in two or three "burns".If you use quick charge NiCds, which I like ,the Sanyo 1300CP and 1700CP cells give more power for less weight than any other I know of and can be recharged on the field at 3 to 4 times C. I am fond of taking two sailplanes to fly, and recharging one while I fly the other, and unless I have a real clinker of a flight, the charging model is ready to go when I land. Spoilers I generaly

make about 4 rib bays long, sometimes only 3. I make them from trailing edge stock 1 1/4 wide.They are very effective in droping the model with out allowing excess speed which will cause flutter like down elevator will.. An old trick , effective but difficult (needs practice) is to get inverted with a half loop and hold full down and try to keep the wings level. NOt easy but it can save a sailplane.Ailerons are not necessary , I dont use them on ships with enough diehedral to have good response to rudder. C ertainly for modern competition designs they are fine, but I would not retrofit them to old designs, as part of the charm for me is the simplicity. A major factor in current and therefore watts is the propellor. Add propellor diameter and you increase current , and you also increase heat in the motor and battery, and you need to keep runs shorter to avoid damage to these things, so like all things about airplanes, it is a trade off. For smaller sailplanes like two meter/six foot or so, 7 to 8 cells and a matching moror will generally be enough unless you are talking about the awful can motors they tend to put in kits.

William L Baker
08-10-2005, 12:47 PM
I do not know that sailplane design, but certainly it will need a full rudder, not just a trim tab. I would divide the vertical stabilizing surface into fin and rudder, about equal in area, up to about 40% fin and 60% rudder (the moveable part). You want a powerful rudder so it is effective even with small movements of the stick. I fly a lot with trim, or with just a little pressure on the stick, but there are times I need all I can get

10-07-2005, 01:35 AM
I have a Sophisticated Lady that has been converted to V-tail and has a S400 geared 3.8:1. I run 8-600AE's most of the time and she does just fine for a mild weather day. As the wind picks up I move to 1700AU or even 1250SCR or CP1700's.

It's no speed demon on the climb but I have caught thermals going up many times and just kill the motor and ride. I don't have spoilers onboard but there have been times I wish I had them. I have to plan ahead for the landing do I don't overshoot and restart or have to walk a ways.

The older planes are a blast to float with. I have a set of Aquila wings with spoilers and an AVA-E fuse that I may mate them to if I don't sell the stuff first.:rolleyes:

Go with spoilers if you have the room or even spoilerons. You won't regret it.

10-18-2005, 05:11 AM
Your estimates for power requirements are quite high. Fifty watts per pound is more realistic for sport planes. I've flown sailplanes with 35 watts per pound. No vertical performance to be sure but still flyable.


10-19-2005, 10:12 AM

How did your sailplanes come out? What motors did you use?

12-16-2005, 11:12 PM
Delta, I have several of the older model plans and noticed that the horizontal stabilizers (r&l) are of different sizes. This was to induce a set rate of turn in the free flight model to prevent flyaways and to keep them within the contest areas. So. check the drawings carefully. Good Luck !

12-19-2005, 01:16 AM
I'm going to be building a " Bird of Time" and electrifly it this nest Summer! And yes I'm going to add a spoiler to that sweet design!

02-16-2006, 06:02 PM
Hi to all in the thread,
Great topic, a few weeks back I posted a question over on R/C universe, in the electric sailplane heading, and drew a total blank.
I'm wondering if the NSP Kestel 100 is a good candidate for electrification, not many choices in a traditional wood kit, the Sig riser 100 is one other that I can think of, my concern with the Kestrel 100 is with the narrow fuse.
Any comments would be greatly appreciated.


02-17-2006, 03:31 AM
I'm not familiar with that plane but a few simple measurements would answer your questions. The big cocern is the motor. Get the inside measurement of the nose at the firewall. Search the manufacturers sites to see if you can locate a motor that will fit. Aveox had a few motors that might do if still available. If you can find a proper motor the rest should be easy especially now with the new LiPo batteries.


02-17-2006, 04:30 PM
Thanks for your response.
I already have the specs for the Riser 100, Sig was terrific, very helpful with their providing that info. I'll try pulling that info outta Sal at the WRAM show next Sat. :eek: I Googled everything I could find on the Kestel 100, no luck, one thing fo sure, you ain't gonna fit an outrunner in one of those rigs:D. I currently fly a NSP Diemos I 2M with a geared 4.4:1 Multiplex. I know that there are a ton of fiberglass standard class electrics out their, but I'm "old school" and like a built up wood kit, besides I'm CHEAP;),

Thanks again,

02-18-2006, 02:22 AM
Welcome to the world of cheap. I live there myself--at least I try to. I flew a converted Sig Riser 100 for a while. I still have the plane but I dont flyit these days. I wasn't happy with it but only because it was underpowered. I had a Speed 700 in it and while it flew it didn't fly well. I also have a kit for a Spectra 100. I've hrard a few horror stories about trying to convert it si it languishes in my kit collection. Maybe someday.


02-18-2006, 04:16 PM
Thanks for the reply Bill,
If you put a speed 700 in the riser 100 you probably could go outrunner.
Sometimes going cheap doen't pay:mad:, a few years ago I spent 90 bucks on a Graupner geared can motor for my GP Spectra, big improvement over DD can motor, now the bad part, the origional motor lasted 4 flights, I then dropped another 30+ bucks on a better "can" motor, not much better. Ultimatly wound up breaking down and spending the "big bucks" for a geared brushless Multiplex , on sale at the time from NSP for "you guessed it" 90 bucks:o, OK, I did have to invest in a CC phoenix speed control, I'll never go back to a brushed motor.
By the way, I only fly electric in sailplanes, everything else is glow for now.


02-18-2006, 11:18 PM
When I flew the Riser 100 with the Speed 700 a brushless system cost $400 or more. Even Cobalt motors were very expensive. It was that long ago. I still fly brushed motors. I'm not about to toss out my perfectly good Cobalt or Neodym motors. They still do the job for sport flying. I still fly Speed 400 motors in some of my planes. Given the fact that my active hanger has about 22 flyable airplanes there is no way I could go completely brushless. I do have 9 brushless systems and as my walet allows I will most likely get a few more but as for now I'm happy.


02-18-2006, 11:43 PM
Hi Bill,

22 flyable birds:eek:, man o' man, this summer I plan to have 4 flyable, that's a record for me, and that max's out the memory in my old Airtronics Infinity 660.:rolleyes: I'll try to get a look at the Kestrel 100 at the NSP booth next sat. at the WRAM show.


02-19-2006, 12:06 AM
C'mon Pete
Gimme a break. I've only been in this hobby for 50 years or so. just wait till i get some experience;)


02-24-2006, 11:02 PM
While we are at it. I built a Lil Bird 11. Small version of the Bird of Time. Also built the large
Bird of Time. At 76 I'm tired of chasing the hi-start. Nose of the Lil Bird 11 is about one inch. Any one out there put an electric motor in one of these? Not a whole lot of room for a larger battery than the 4 cell 470 I used in it to run the recr and two mini servos.

01-30-2007, 06:35 AM
Hi My Son was 3months when this post was last Answered. I see you are still Alive. Howd it Go With

Will adding a spolier be too much?

I'd have said it would be a lot of work. and Doing it after the other mods would be you choice.

As for Flight Charicteristicly to Much.
I would have said. May be. Where they are Positioned can cause an Adverse effect. and if you can not counter it. you may have problems.
Remember . Spoilers Reduce lift. Airbreake systems just increase drag. If you reduce lift. you may need to get into a Higher attitude, and the tail elevator should be able to Accomadate this.

Welcome Back.

01-30-2007, 03:11 PM
Most of the spoiler designs for the BOT show on top of the wing, will that be
good enuff to create drag for shorter landings?

01-30-2007, 07:53 PM
The spoilers do more than create drag. By being on the top of the wing they actually "spoil" or hurt the lift character of the wing.

This loss of lift actually combines with the drag to help you settle the plane down in a shorter distance. Otherwise they want to float in ground effect forever.

01-31-2007, 04:55 AM
If you have the Spoilers . You may find as you land. you will need anything from a touch of Up elevator/Nose/Attitude to A Stomach full. This is where you think about where to Locate the Spoilers on the Wings Top surface. NB It could ba a CF strip that is Linked so it Pops up to SPOIL the Flow of air Over the top of the Wing. of cause. second thought after where to put them is How big the Spiler. you could have one servo. And being a trimer from way back. you may well just be able to Tune each Side so as to create an = amount of Drag and Spoil.

Spoilers tend to have a Greater effect on Lift than they Do drag. (Whatch them pop from the end of a Runway. (Particularly Airliners)

Air breaks can Come straight up (Like a sliding dore) and if located Properly, They will have a Greater Effect on Drag than their Direct Effect on Lift.

Spoilers can Fold up like the Alerons do. But not at the Trailing edge. Near CoP.

Flap systems have a Great Slowdown effect. (But can Require triming on the Elevator) so I would like to Know if you have got you Elevator and Rudders Working. Or at least a Plan on how to get one going.

Would love to See a Pic. :cool:

01-31-2007, 12:07 PM
On my RES planes I use my computer radio to mix in some up elevator when I deploy spoilers.

When doing this manually I suggest you deploy slowly so you can coordinate the spoilers and the elevator, otherwise you can dive pretty fast. My Sagitta 600 takes a fair amoung of up elevator. My Spirit needs less.