BUILD THREAD: Sig RISER-100 wing on Topmodel PRELUDE fuselage

[G-man]

There are modelers among us who are enamored with fat-profile, long-chord, lazy day super-floater gliders,
but who would be happy to have a prettier fuselage than those we build from the parts provided in the kit.

Here is a path to that end: build yourself a classic open-bay wing from balsa and plywood and mate it to a modern fiberglass fuselage.

Here are he major steps in my Sig RISER-100 wing on Topmodel PRELUDE fuselage, and the milestones in his thread:

1. INTRODUCTION
2. MATERIALS AND SOURCES
3. A WING MOUNT METHOD
4. A PUSH ROD INSTALLATION METHOD
5. MY HOMEMADE LARGE LETTERING METHOD
6. REINFORCING TWO HORIZONTAL STAB RIBS
7. INSTALLED EQUIPMENT, WEIGHT AND BALANCE
8. FLIGHT REPORT

 

[G-man]

2. MATERIALS AND SOURCES

Sig Manufacturing will supply a wing kit. If you build over the drawings and do not already have drawings from a previous build, order those also.
Sig provides a PDF of their very fine construction manual free online, or you may purchase a paper copy of it.

SIG RISER 100 KIT PARTS

Replacement Parts Riser 100 R/C SIGRC62 SELECT PARTS USING THE DROP DOWN MENU

sigmfg.com

I got my fuselage, canopy, bellcrank, and pre-built tailfeathers from Aloft Hobbies.

TopModel Prelude 2.5m Fuselage

Need a new fuselage for your TopModel Prelude? Well here's a fresh one. You may also want the canopy, elevator bellcrank and elevator and rudder assemblies. We also stock these parts.

alofthobbies.com

Topmodel 's website says they ship worldwide, and part numbers are listed in the PDF manual, available online.

Topmodel CZ - Prelude

TOPMODEL CZ, Production of airplane models first-class quality.

www.topmodelcz.cz

Here are my additional parts and components:

RECEIVER: FrSKY V8FR-II
MOTOR: Turnigy SK3 Gliderdrive 4.6 840 Kv
MOTOR MOUNT: ICARE/IKARUS electric motor mount, universal, 39.2mm diameter P/N 20109-1C

Electric motor mounts

icare-icarus.3dcartstores.com

ESC: Hobbywing Skywalker 60 Amp UBEC
SPINNER: Topmocel CZ P/N 02040058TZ 40mm spinner
PROPELLER: Aero=Naut CAM-Carbon Z 12x6
SERVOS: Power Up AS3513NG 23 gram analog mini servos 41 in/oz, 3.5 kg/cm
BATTERY PACK: EZ Flight Pro 3S 3000 mAh 3S
PUSHRODS: Sullivan Gold-n-Rod #505 BLUE/GOLD Semi Flexible

 

[G-man]

Oops, Sig Manufacturing is currently sold out of RISER-100 wing kits. (on 12/30/2023)
https://sigmfg.com/products/sig-riser-100-kit-parts?_pos=1&_sid=402123949&_ss=r&variant=46207936073

A builder might check with Sky Bench Aerotech to see if an Olympic II wing kit is available.
https://www.skybench.com/olympic-ii

Else, download drawings from Outerzone or order prints from Aerofred and build from balsa and plywood stock.
https://outerzone.co.uk/plan_details.asp?ID=10677
https://aerofred.com/search.php?search_keywords=Glider+wing&search_terms=all&submit=Search

Want a 2-meter size wood-wing-on-glass-fuselage project?
Wayne at Aloft was able to supply a lovely slip-on nose cone Blejzyk molded fiberglass fuselage for my beloved SENSOAR reenactment:

Curved lines are pleasing to the eye

Curved lines are pleasing to the eye

I think curved lines look great on airplanes, and it looks to me like Artur Blejzyk feels the same way. Here is a project that combines classic elliptical wing tips with a wonderfully round-shaped fuselage from Blejzyk Models. Back in the early 1990s friends and I flew the Hobby Horn SENSOAR...

forum.alofthobbies.com

Here’s more info in the Aloft Forums about wood-wing-on-glass fuselage projects.

ALOFT: Sig RISER-100 wing on Topmodel PRELUDE fuselage

ALOFT: Sig RISER-100 wing on Topmodel PRELUDE fuselage

The quality of my first Topmodel PRELUDE project fuselage, plus the service and support from Aloft impressed me so much that I ordered a complete PRELUDE kit; this time the PRELUDE REF (Rudder Elevator Flap) version...

forum.alofthobbies.com

Here’s the best news I could possibly present to you. Oh, Happy New Year.
This thread contains the development of a future Aloft product, a modern version of the classic 100-inch balsa wing for the PRELUDE fuselage:

ALOFT: Airtronics OLYMPIC-II wing on Topmodel PRELUDE fuselage

ALOFT: AH-100 Build (new title)

"The Wing is the Thing" I wish I could remember where I learned that. Perhaps it was an RC Soaring Digest article title. https://www.rcsoaringdigest.com I love that sailplane - so much that I built three of them for winch launch, and sold two of them to flying buddies. The third led to a...

forum.alofthobbies.com

 

[G-man]

3. A WING MOUNT METHOD

It’s hard for me to imagine that anyone interested in this project has not built five, ten, or more open bay wooden wings, so I will not cover wing construction details here.
For those less experienced in pushing sticks together to make a wing, the excellent Sig RISER-100 instruction booklet provides a bright shining path forward.

If there are people who somehow were absent from model glider flying in the 1980s and 1990s, and wonder why we cotton to the old-time designs, read the first three paragraphs of the Sig RISER-100 instructions, in message #2 above. Remember, those words were written in the 1980s. Consider also that the Boeing B-52 Stratofortress first flew in 1952 and is still in service. The Lockheed C-130 Hercules first flew in 1954 and is still in service. The fat airfoil, built-from-sticks model glider wing is one of those instances where old designs still have their charms.

So, construct your wing according to your own practice, or by following the steps in an instruction booklet or online video.
Presented here is a method to mount your wing to the Topmodel fiberglass fuselage.

The quick and easy method would be to insert dowels through the fuselage and fix the wing in place with rubber bands.
Some would discard this solution for poor aesthetics.

An alternative, the Sig RISER-100 instruction manual (steps 46-52) gives a bolt on wing mount method which would work here.

My method is wire pins in the front and nylon bolts in the rear. I like rapid glider assembly in the field, and prefer no tape or tape residue cleanup.

The key is to install the pins and hard points for the bolts after sheeting the bottom of the two innermost bays, and before applying the top sheeting.

I used 3/32 music wire for the pins and ¼ x 20 nylon bolts for the rear hold-downs.

Yes, the RISER-100’s 10.75 chord is longer that the 7.875 inch wing mount flat spot on the molded fuselage, so there is overhang at the rear. That may bother some people, but it didn’t bother me.

For fuselage preparation, drill holes in the front to receive the pins, and fit a ¼ inch plywood plate to receive the nylon bolts. The receiving threads can be simply tapped into the plywood, or you can use threaded inserts or T-nuts, according to your preference. This is my third wood wing conversion for the Topmodel fuselage and I used all three ways. They all work fine.

 

[G-man]

One correspondent wondered if we needed to fair in the slot between the wing LE and the fuselage vertical notch,
When we slide the PRELUDE canopy back to it's final resting place, it covers the slot pretty well.
My Olympic-II wing is shown here. The canopy did need a little grinding and sanding to fit the fat OLY airfoil.

 

[G-man]

MOTOR MOUNT THOUGHTS

My motor mount method needs two overnight epoxy cures, so it can be done while working on the wing.

I have made several motor mounts from G10 Fiberglass Plate, available from Aloft:

G10 Fiberglass Plate - 2mm x 350mm x 150mm (.078" x 13.77" x 5.9")

G10 fiberglass plate has many uses from control horns, servo trays, and many more.

alofthobbies.com

This method is useful if your motor has an odd bolt pattern, or you want larger or smaller cooling holes.
You will be refining your skill with a round file.

For this project I decided I'd had enough practice with the round file, and found a suitable G10 Fiberglass motor mount at ICARE/IKARUS:

Electric motor mounts

icare-icarus.3dcartstores.com

Since then I discovered that Aloft stocks some pretty impressive motor mounts:

Search: 84 results found for "motor mounts"

Aloft Hobbies offers top quality RC aircraft and radio gear with very reasonable pricing, fast shipping, and full service to backup our products. We are very loyal to our customers!

alofthobbies.com

Two overnight epoxy cures you say, Dave?
Yes, the first is to tack glue the mount in position with the motor bolted up and the spinner bolted on to set the position the mount plate.
- Apply a minimal amount of slow cure epoxy and hang the fuselage by the tail to cure overnight.
- Remove spinner and motor and apply more epoxy, and hang it by the tail to cure overnight.
- My practice is to add some milled fiberglass to the motor mount epoxy and the servo rail epoxy.

 

[Sandman]

Dave
Does it make sense to drill the holes at 90 degrees through the wing, then join the wings with the wing rod. and mount on fuselage and square everything up.
Then drill through the fuse and plywood mounting block in the fuselage at the slight angle caused my the dihederal angle.
You mentioned earlier that the distance from the LE to the holes is 7 15/16" ?
Is that a 1/16" plywood support under the hard point blocks.
The photo documentation looks great.

Don

 

[G-man]

Don,

> Does it make sense to drill the holes at 90 degrees through the wing, then join the wings with the wing rod. and mount on fuselage and square everything up.
> Then drill through the fuse and plywood mounting block in the fuselage at the slight angle caused my the dihederal angle.
Sure it does. Most mounting operations go better with the wing halves joined, with joiner rod and anti-rotation pin installed.
For final assembled appearance, I like my wing bolt holes 90 degrees to the top surface rather than the bottom surface.
This means they will enter the fuselage leaned back a little. This lets the bolt heads snug up flat against the upper side of the wing.

> You mentioned earlier that the distance from the LE to the holes is 7 15/16" ?
Yes, and that location was determined by the size and shape of the opening in the Topmodel fuselage.
I first located and installed the 1/4 inch plywood block to receive the wing mount bolts, and then
located everything else from that, including the position of the hard points in the wing halves.

I wanted it as far back as possible to allow servo bay access and to keep the wing squared up on the fuselage,
but there is a limit to how far back it can be because we run out of flat surface on the molded fuselage.

> Is that a 1/16" plywood support under the hard point blocks.
Yes, and its length was sized to reach both the first and second root ribs in each wing half.
On top of the 1/16 ply is hard balsa block.
Then double check the fit and strength of the front pins and close up the root ribs bay
- On the OLY-2 wing (yellow covering) the top surface is 1/16 balsa with a 1/16 ply strips added to bear bolt head pressure.
- On the RISER-100 wing (white covering) the top surface is 1/16 plywood.

// Dave

 

[G-man]

A WING MOUNT METHOD ADDENDUM

1. I forgot to add these photos of the framed up wing and the Topmodel tail parts installed.

2. I further forgot to mention that the Sig RISER-100 instruction manual (steps 46-52) gives
a bolt on wing mount method which could be used instead of the front pins method.
This method requires four bolts and thus more assembly/disassembly time in the field.

 

[G-man]

4. A PUSH ROD INSTALLATION METHOD

By this time the wing construction is complete, the wing mount parts in the fuselage have been done, and possibly the motor mount has been installed.

For servo installation, I used the common practice of plywood rails, attached to the fuselage sides with slow-set epoxy mixed with milled fiberglass.
I installed the servo rails and mounted the servos as the first step in the control linkage installation to fix the location of the front end of the pushrods.

Having purchased the uncovered Topmodel rudder, horizontal stabilizer, and bellcrank from Aloft, the next task is to connect the servos to the rudder and full-flying stabilizer.
I see three possible methods:

1. A PAIR OF BALSA STICK OR DOWEL PUSHRODS, like the Goldberg Gentle Lady and hundreds of other wooden model airplanes designed from the 1930’s to the present.
Our long PRELUDE fuselage would require long, and possibly bendy, sticks.

2. ONE CF TUBE PUSHROD AND ONE CONTROL SNAKE. This is the method used in the Topmodel PRELUDE design, as detailed in the instruction manual.
Myself, I am not in favor of the weight of the rigid pushrod hanging on the servo arm and on the molded plastic bellcrank at the rear.

3. A PAIR OF COMMERCIAL PUSHRODS. I used Sullivan #505 semiflexible Gold-N-Rods, mainly because I have used them probably 30 times in the past and they do the job for me.
From one of the suppliers: "Nylon push rods [are] made from a special compound to reduce thermal expansion, and prevent radio interference."

Sullivan Semiflex Gold-N-Rod w/Gold-N-Clevises 36" (2) (SUL505)

This Package Contains Two 36" Nylon Gold-N-Rod Push Rod Systems from Sullivan. FEATURESUsed to connect servo arms in the model to the model's controlsurfaces.Made to tight tolerances to insure smooth operation with minimumfriction.Comes complete with Gold-N-Clevises and other installation...

hamilton-hobbies.myshopify.com

The nut to crack here is how to attach the pushrods to the inside of the long, narrow fuselage with no access through an open top, but from only the ends.
As you noodle through this problem, you may miss the balsa box fuselages of yore, where we installed the pushrods, and THEN closed up the top of the fuselage.

I know of three methods to secure the pushrod outer casings within the fuselage:

1. Glue the pushrod outer tubes to the inside of the fuselage.

2. Secure the pushrod outer tubes along the fuselage with plugs of foam.

3. Lay the pushrod outer tubes in place, secure and seal up their ends, and fill the fuselage with canned expanding insulating foam.
This method would have the additional benefits of stiffening and strengthening the fuselage, but would be difficult to modify or work on later if needed.

For this project I used the first method, employing Welder Adhesive. Back in the day some guys prepared the pushrod outer tubes for gluing by wrapping
masking tape around at 3-4 inch intervals and then dripping this CA glue down the outside of the tube. The tape adhesive is said to kick off the CA adhesive.

Both the CA and Welder Adhesive methods will require a technique to hold the pushrod outer tubes against the inside of the fuselage while the glue cures or dries.
One classic method is to remove the inner pushrod, insert music wire, and use magnets to hold the temporary assembly in place against the fuselage.
In the morning, pull the music wire and reinsert the inner pushrod.

I pre-tested the holding power of my magnets before gluing.
The front end of the pushrod is held in place by having the temporary music wire go through a Du-Bro EZ connector mounted on the servo arm.
To do the deed, I ran a bead of Welder Adhesive down one side of the tube, inserted the outer pushrod tube, applied the magnets,
gave the tube a quarter turn each way to spread the glue, and let it dry overnight.
Then repeated the steps the following day and night for the second pushrod.

 

[jure]

I like the magnetic holder trick for the gluing operation !

 

[Sandman]

Where does the rudder Gold-N-Rod outer tube exit the fuselage
Gotta love the magnet idea

 

[G-man]

> Where does the rudder Gold-N-Rod outer tube exit the fuselage

Photos added below.
Next time I'll make the slot 1/8 inch (2mm) higher for better match to ideal rudder control horn location.

Previously, after I got the rudder pushrod installed, and had the elevator pushrod working, I installed a vertical stab tail post.
Cut from 1/4 inch balsa sheet, it stiffens and holds the shape of the vertical, and receives the front half of the rudder hinges.

 

[G-man]

5. MY HOMEMADE LARGE LETTERING METHOD

1. Find a font online that you like and download it to your computer.

2. Print your selected text in a word processing or graphics editing program.

3. Tape heat shrink covering film to a tablet backing cardboard, and tape your printed letter(s) over the covering film.

4. Cut through the paper, the film, and the film backing with a sharp blade and firm pressure.
I use a metal ruler to assist with the straight lines, and cut the curves freehand, slowly and carefully.
Some cleanup can be done with scissors.

5. Lay out the letters on the wing and fix them on place with a covering iron. I draw top and bottom guide lines
with a permanent marked and remove them with alcohol on a paper towel after the letters are ironed in place.
I use tiny bits of masking tape to adjust the spacing between letters.

PRO TIP: Two copies of a letter or number can be cut at once. Use a fresh blade and press firmly.



How to find a font:

In your search engine, look up: Bold, Sans Serif Fonts
https://www.1001fonts.com/bold+sans-serif-fonts.html
https://www.dafont.com/theme.php?cat=501

Some websites (like dafont.com) will allow you to type in text and see how it looks in the selected font, and then download the font for personal use. Example:
https://www.1001freefonts.com/
https://www.1001freefonts.com/old-school-fonts.php

Here’s an attractive font which you can download free for personal use, then choose an amount you want to donate to the font designer
https://www.dafont.com/couture.font?text=WING+LETTERING&back=theme

Here’s the font I used for this project:
SUPR Tall – Extra Condensed & Bold Display Font

SUPR Tall – Extra Condensed & Bold Display Font - Design Cuts

SUPR TALL is an extra-condensed addition to the SUPR Font Family. By making this font even more condensed, it allows you to create larger type in smaller s

www.designcuts.com

 

[G-man]

6. REINFORCING TWO HORIZONTAL STAB RIBS

In my view, the Topmodel horizontal stabilizer is designed for light weight instead of brute strength. I approve of this design decision because it allows the very long fuselage model to be lighter overall, and to make it more able to float like a butterfly, dance like a ballerina in the air.

These stabs are not designed to withstand contest nose-dork, points-chasing arrivals like an Airtronics PRERGRINE or a Hans Meuler COMET, but with our electro-sailplanes we try not to land nose first anyway.

I had to remind myself to tread lightly when handling the parts, especially before they were covered. Four times the components themselves reminded me, with fractured ribs. I trust that every single reader works more carefully than I did, and is less ham-fisted than I am. Forewarned is forearmed.

The two stab halves are held onto the air frame by friction of the main fiberglass joiner rod and friction between special rubber grommets
and a steel locator rod. The friction produced by the rubber grommets against the steel locator rod is formidable.

It so happened that after covering the stab parts and when assembling the tail feathers the steel locator rod punched through a rib.
I removed some covering and stiffened the rib with 1/32 plywood on both sides, and installed a hard point of 1/16 plywood to resist
the steel rod punch-through. This repair added weight in the tail; hopefully not much.

PRO TIP: Strengthen the ribs before covering he stab halves.

 

[G-man]

7. INSTALLED EQUIPMENT, WEIGHT AND BALANCE

Sig RISER-100 CG spec: 90-98 mm from leading edge.

I used the 4.6 motor for this build, but I have flown the previous version with both motors, and either one works fine.

Bench testing indicated the 4.6 motor and 12x6 prop combination pulled no more than 21 amps,
so I downsized the ESC to a Turnigy 40 amp unit which had suitable connectors already installed.

Here are the results of balance tests with three battery packs.
1. EZ Flight Pro 3S – 221 grams : balance at 92 mm from LE
2. Admiral 2200 3S - 181 grams: balance at 95 mm from LE
3. Ovonic 2200 3S - 141 grams: balance at 98 mm from LE

All three packs allow at least an inch both in front and back of the pack for fine-tuning balance between flights.

My ready-to-fly weight: 870 grams; 29.5 ounces

 

[G-man]

8. FLIGHT REPORT

Awaiting suitable weather.

 

[Sandman]

That weight is just a little more than my 2M Gentle Lady, not bad for all that wing area.
What is the deal with the antenna's, where do they exit the fuse, and how did you fasten the blue antenna tubes to the fuselage.
Its 25 degrees today in Syracuse, that should be our winter mantra "Awaiting suitable weather''

 

[G-man]

Don,

>That weight is just a little more than my 2M Gentle Lady, not bad for all that wing area.

I was happy with the 870 grams overall weight result.
Much lighter than the 1.15 to 1.4 kg specification on the first page of the Elektro Sailplane PRELUDE instruction manual.

Maybe their prototype PRELUDE has four pretty hefty servos in the wing.
To my way of thinking flying without those four wing servos greatly increase our chances of
“float like a butterfly, dance like a ballerina” performance on each thermal seeking flight.

> What is the deal with the antenna's, where do they exit the fuse, and how did you fasten the blue antenna tubes to the fuselage.

The FrSKY 2.4 antennas are 5.5 inches long, and the blue tube antenna guides match that length. They do not exit the fuse.
The bare (outside the coax) ends of the antennas are 1.25 inches long, and the fuselage width there allows the two antennas to be at least that far apart.
The blue antenna tubes are glued to the LOWER fuselage sides with Welder Adhesive, to keep them 1.25 inches away from the carbon fiber reinforcements
molded into the entire length of the fuselage.


> Its 25 degrees today in Syracuse, that should be our winter mantra "Awaiting suitable weather''

Not all of our soaring brothers live in places which anticipate the joy of experiencing a “January Thaw."
But we do.
// Dave

"The January Thaw has origins rooted in New England folklore and describes a period of a few days in mid- to late-January in which unseasonably warm temperatures have a tendency to occur,"
said Art DeGaetano, climatologist at the center.

From folklore to science: The 'January Thaw' is real, as the Northeast and Middle Atlantic states are about to find out | Cornell Chronicle

After 10 days of digging out from the Blizzard of '96, temperatures across the northeastern and middle Atlantic regions of the United States have begun to rise in what folklore calls the "January Thaw."

news.cornell.edu

 

[G-man]

Still awaiting suitable weather.