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May 28, 2006, 12:17 AM
Where's the lift?
dgliderguy's Avatar
Thread OP
Build Log

Two guys building Thermics-- Reviving Nostalgia


My buddy Fred and I are going to be building two Jasco Thermics, from the TMRC laser-cut partial kit. Fred Guilfoyle (a balsa craftsman of the first order) is going to be building the smaller 50" Thermic 50X, and I am going to build the larger Thermic 72. Both of us have a passion for the old gliders of decades past, and we want to showcase these graceful free-flight vintage designs by converting them to R/C, and in so doing, take advantage of all the cool sub-micro radio gear that has come on the market lately. (Can you believe the tiny 4 gram servos and receivers that are so common now? We'da died for stuff like that back in the old 1/4A days.)

Tom Martin (www.tmrcsailplanes.com) has a line of fine laser-cut partial kits of many of the scale American-made sailplanes, such as the Schweizer gliders and the Hall Cherokee, and now he has added these two Nostalgia kits to his product line. The kits include all the laser-cut pieces, and even include laser-cut spars and trailing edges. My Thermic 72 has been modified to accommodate radio gear-- the original had a balsa block pod, and this one has formers and stringers (much like the smaller Thermic 50X), for a hollow pod that can contain the servos and receiver. The parts have been digitized off the plan, and the laser-cut pieces fit together with extreme precision, so you don't have to fudge and fill to get good glue joints. Just a drop of CA and its done. My wing (pictured) went together in just three hours of leisurely work, so you get the idea.

So anyway, here's my project, and I invite Fred to join in on this thread with his build progress, too. When we get them done, we want to launch them by towline, just like the old A2 Nordics of our youth. Ah, nostalgia!

Don Bailey
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May 28, 2006, 11:43 AM
My hangar is,... "almost" full
No Step's Avatar

Thermix-50X


Whoo-hoo! This is going to be fun. Holy-smokes! Don, it was just yesterday you talked of starting your Thermic-72. You have the wing done already! I'm jumping into this build.
I'm Fred Guilfoyle, the other half of this combo build thread. I've just started my Thermic 50X as well.

I chose to start with the stabilizer. Let me agree with Don here,.... the laser cut parts fit perfect. I put in all the main stab ribs, then went back and put the sub-ribs in place and they fit >perfect<, no sanding to fit needed. I do alot of scratch building, and to have the laser cut parts is pure joy for me. The laser notched T.E is a nice touch. I pondered omitting the sub-ribs, as the tail is rather robust, but decided to stick with a stock kit as much as possible. Since this is a free-flight design, I had to determine where the elev. hinge line went. I decided on 1 1/4" wide eleators. 3/16" balsa was used both sides of the hinge line for the LE and TE of elev. and stabilizer. Note,... the kit is supplied with material for the original model. Materials for any r/c mods. and electric power must be provided by the builder. Oh, and it is a 'short kit'. Strip wood must be provided by builder as well mostly just fuselage stringers. The numerous 1/16" ribs look like overkill for this small stab but that's the way they did it back in the "old days" I guess.

Edit: 75 minutes to build, 45 minutes to finish sand. 16 grams (1/2 oz.)

Fred
https://home.comcast.net/~guilfoyle72/
Last edited by No Step; May 28, 2006 at 02:00 PM.
May 28, 2006, 10:16 PM
AKA - The "Flywheel"
StevenatorLTFO's Avatar
What sort of target weights are you guys looking to get out of these two kits? Look like they should be real floaters!!

Steve
May 28, 2006, 11:34 PM
My hangar is,... "almost" full
No Step's Avatar

Thermix-50X


I'm thinking around 6+ ozs RTF for the T-50X. Box label says target weight is 4.75 ozs not including the radio, that's less than 5 ozs/sq ft. I plan on using 2 HS-55 servos and an old Gws 4 channel rx. and a 370 mah pack left over from another model. It's not the lightest hardware, but it's what I have laying around.
May 29, 2006, 01:55 AM
Where's the lift?
dgliderguy's Avatar
Thread OP

Thermic 72 pod and tail


More progress tonight. The fuselage pod is laid out on a solid sheet keel, with formers and stringers. The formers aren't labeled, so ya gotta trial fit 'em first to figure out which goes where. The stringers are 3/32 square stringer stock, which I stripped from sheet (as I do for all my stringer material). I wish I'da picked a harder wood-- they are a bit soft, so I may have problems with crushing if I'm not careful. A harder wood would have been more difficult to bend, though. Compromises...

I need to install the servos before I go much further, so I can think out the upper hatch portion of the pod. I want easy access to the radio components, should I ever have to get at them. I'm going with HS55 servos, and a Berg 4L receiver, plus a 4x220mah Nimh pack. I don't have any idea yet how much this thing will weigh, but I'll be willing to bet it won't be over 12 oz. Definitely a floater!

The tail is very simple. I decided to swap out the stock rudder for an enlarged one. May not be necessary, but the stock rudder just looked a little narrow to me. Better too much than too little. The stab is going to be a two-piecer with a joiner rod, for an all-flying stabilator arrangement, so no need for a hinged elevator. That's up next.
May 29, 2006, 11:31 AM
My hangar is,... "almost" full
No Step's Avatar

Thermic 50X


My wing assembly was ridiculously easy as well. I couldn’t resist one change however. The wing spars are laser cut out of the same stock as the fuselage keel, T.E.s, and fin parts,… medium/light weight balsa. I just couldn’t live with those as spars. So I replaced just the forward spars on the center panels with spruce of the same size. The tip panels and rear spars are still stock balsa and should be fine. Basic wing build-up took 2 hours, dihedral, sheeting and sanding took 1 1/2 hrs. The wing simply falls together. Everything lines up well, and fit is perfect.

1.4 ozs ready to cover.
Last edited by No Step; May 29, 2006 at 11:40 AM.
May 29, 2006, 06:10 PM
My hangar is,... "almost" full
No Step's Avatar

Thermic-50X


That fuselage pod looks good Don. The upper pod looks like it should be easy to make a hatch for access like you want to do. My Thermic 50X is football shaped, all stringers, so making a hatch would be hard without destroying the lines of the pod. I'll make my radio fully enclosed without any access hatch.
May 30, 2006, 08:19 AM
Registered User
claymeyer's Avatar
Exellent thread, guys! I've been eyeing the 72 for a while now... looks like I'm going to have to get one.

As far as the spar goes, are either of you going to beef it up with carbon tape so it could handle a winch launch? On the 72 would it be better to go with spruce spars?
May 30, 2006, 10:15 AM
Where's the lift?
dgliderguy's Avatar
Thread OP
Claymeyer,

I'm going stock with my spars, no hardwood, no carbon, nuthin. And I don't expect it to hold up to even a standard hi-start, gawdforbid a winch launch. The wing is pretty soft, but, that's how the old free-flight models were. My plan is to either hand-tow it with kite string, or use 1/4" flat rubber and monofilament fishing line, for a soft hi-start.

A builder could certainly swap out the hard balsa spars for spruce (like Fred did with his), and add carbon unidirectional tow, etc., to stiffen up the wing. I would still be reluctant to hook up such a fragile airplane to a 12v winch, though. It just isn't that kind of model.
May 30, 2006, 11:10 AM
auto-tune remix
slopemeno's Avatar
Go with the hand tow. Its so easy... trot 25 steps and the plane will be overhead at 100'. I used 25# monofilament and one of those plastic crosses (that you use when youre too cheap to buy an actual fishing pole) to wind the line around. A little flag of light nylon at the plane end of the line and a small ring, and youre good to go.
May 30, 2006, 11:14 AM
My hangar is,... "almost" full
No Step's Avatar
My fuselage is framed up, and I've mounted the radio as far fwd as possible. I think it's still going to be tail heavy. I'm glad I didn't use a lighter radio. I plan on using small Sullivan cables for pushrods. As soon as I get them on, I'll do one final control check before I add stringers.

No switch, just plug and unplug batt. connector.

I'm thinking of sheeting between the bottom stringers and keel, both sides, as a way of protecting the bottom from rips and punctures. If I just cover it per plans, any landings on dirt or rough ground might result in damage. I guess I could double cover in that area though. I'm thinking of covering it with Solite or Litespan. I've never used Litespan, but I think it was Don who said it's like a synthetic iron-on tissue but stronger. They have some at my LHS, so I may give it a try,... I dunno yet for sure.

Servos, batt., and rx. are glued in with black rubberized CA.

Fred
May 30, 2006, 11:47 AM
Registered User
claymeyer's Avatar
You don't hear much about hand-towing ... I don't want to get off subject, but do you attach the line to a tow-hook like you would a high start? Do you let the plane sit on the ground as you start running, or do you put it on a stand?

I was thinking about beefing up the spar of the 72 when I start building so I could high-start it, but hand-towing sounds more nostalgic and fun.
May 30, 2006, 12:42 PM
Where's the lift?
dgliderguy's Avatar
Thread OP
Quote:
Originally Posted by claymeyer
You don't hear much about hand-towing ... I don't want to get off subject, but do you attach the line to a tow-hook like you would a high start? Do you let the plane sit on the ground as you start running, or do you put it on a stand?

I was thinking about beefing up the spar of the 72 when I start building so I could high-start it, but hand-towing sounds more nostalgic and fun.
Yeah, hand towing is a lot of fun. Slopemeno is preaching the down-home religion with his post. You just hook up about a hundred feet of line to a regular belly hook, and get a buddy to hold the model, or set it on top of your car, then grab the other end of the line, and (depending on the breeze) you either walk backwards or trot forwards looking over your shoulder. Up goes the glider, like a kite on a string (which is exactly what it is!). The trick is to gage the amount of pull on the string, and not overload the structure. You can really feel it. If the breeze has some strength, you hardly have to walk backward at all.

I haven't tried hand-towing and operating a tranny at the same time. I expect to be able to tow hands-off, just like my old free-flight Nordics, and not have to input any rudder until I'm free of the line. We'll see.

Don.

P.S. Fred: I plan on doing some sheeting between stringers, too, for crush-resistance, and for belly protection. Your radio installation looks real good! How are you going to access the battery plug for on-off and for charging? BTW, I'm going with polyester mat and dope for my covering job, too; either Polyspan or Litespan, plus some colored tissue for graphics.
Last edited by dgliderguy; May 30, 2006 at 12:52 PM.
May 30, 2006, 01:56 PM
Registered User
Vince Herman's Avatar
Quote:
Originally Posted by No Step
I think it's still going to be tail heavy. I'm glad I didn't use a lighter radio. I plan on using small Sullivan cables for pushrods.
You might consider using CF rods inside teflon guides. tailboom.com has etched teflon tubing that can be CA'd. I used CF rod .024" running back to the tailfeathers on my discuss launch glider. Works well.
Quote:
No switch, just plug and unplug batt. connector.
I also used this method, but mostly because I have not ordered a switch jack yet. I wish I had a switchjack. A good discussion about switchjacks can be found here:
https://www.rcgroups.com/forums/showthread.php?t=504212

Quote:
Originally Posted by dgliderguy
The trick is to gage the amount of pull on the string, and not overload the structure. You can really feel it. If the breeze has some strength, you hardly have to walk backward at all.
I folded my first Thermic 50 this way. The wind was probably more that we should have been flying in, but try telling that to a 12 year old boy on a sunny day with his favorite glider in his hands. This thread is helping me re-live those 12 year old days... ;-)
May 30, 2006, 02:39 PM
Hot Dawg Glider Pilot
schrederman's Avatar
Hand tow, the way to go... I was looking at 4 trophies last night. They are all for Junior TLG (tow-line glider). All from the early '60s. They are the only trophies I have that really mean anything. Are you guys going to use 50 meter (164') lines as per the old Nordic days? hehehe... Have fun!

Jack Womack


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