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Old Jun 24, 2014, 12:50 PM
Scratch Builder
tomclark's Avatar
United States, NM, Deming
Joined Apr 2014
45 Posts
Mini-HowTo
76" Tiger 90

I have been in the building mood lately. It is the hottest month of the year and the shop is cool and comfortable, so what the heck. I recently noticed that my stable of planes seemed to be getting old, and some were due to be retired and hung up on the shop ceiling. At first it seemed like they were just built a year or two ago, but then when the records were checked, two of the favorites were 10 and 12 years old - they earned their retirement.

Three weeks ago I drew up a slightly oversize Senior Kadet. I had been flying powered rockets and pattern planes for many years now, and it was time for a plane that would slow things down a bit - you know - something that would lower the blood pressure instead of raise it. On my blog there are more photos of the Kadet, along with a blog named "Blowing things up". I have been a scratch builder for as long as I can remember, and have never owned an ARF. Check out the 20-some photos on the blowing up blog and you will notice that I have liked scratching larger planes for most of the last 40 years. They simply fly better, and scratch building is far cheaper than kits and ARFs, but the real reason for building your own planes is that you can build them properly, so you will have a plane that will last for a thousand flights and not wear out in one season .

No one would expect beginners in our hobby to just start scratch building from their early days, but after anyone has built a few kits, you can't help but to start to learn some building techniques that you like better than others. Once you learn your own favorite building methods, it becomes easier to just start building from your pile of balsa wood. If you looked at the photos linked in my blog, you will notice that most of my planes are just sticks glued together. They don't use a lot of heavy plywood or sheet balsa. Sticks are cheap and strong…
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Last edited by tomclark; Jun 24, 2014 at 04:11 PM.
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Old Jun 24, 2014, 01:02 PM
Scratch Builder
tomclark's Avatar
United States, NM, Deming
Joined Apr 2014
45 Posts
page two

This how-to is just a photo essay to give you some ideas on basic easy construction. If you have any questions, just ask.

In a thread on the Goldberg Tigers you can't help but notice that many complained that their planes came out a bit tail heavy, so on this build the nose was lengthened about an 1.5" to help eliminate the problem. It's hard to do that when building a kit - since the parts are already cut, but when building your own, you can do anything you want.

My Tiger has a 76" wingspan and a 68" fuse, just in-between the Tiger 60 and the 120 Tiger. Why? I had a new 90 four stroke sitting in the drawer, and it is a fairly light engine. Expect finished weight will be 6-7 pounds.

I cut the stack of ribs out on my bandsaw. Just use a square to check the table before cutting, and it is amazing how fast and easy the ribs can be cut. I'll get into cutting tapered ribs in another thread.

The last photo shows the landing gear and servo mounts going in. A bit of lite-ply adds support
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Last edited by tomclark; Jun 25, 2014 at 08:00 AM.
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Old Jun 24, 2014, 01:07 PM
Scratch Builder
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United States, NM, Deming
Joined Apr 2014
45 Posts
page 3

The wing photos show basic construction. I really don't like wings without leading edge sheeting and or ribs without cap strips. It doesn't take a lot of sheeting to make a very strong wing.

These ailerons are 2.25 wide. Not huge but far bigger than standard for this plane. The rudder and elevator have also been enlarged a bit.

The wing is sheeted, then the ailerons are cut out, and strips of 3/8 balsa are cut and glued in place. They provide a good mounting for the hinges.
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Last edited by tomclark; Jun 29, 2014 at 07:35 AM.
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Old Jun 24, 2014, 01:20 PM
Scratch Builder
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United States, NM, Deming
Joined Apr 2014
45 Posts
page 4

It's beginning to look like the model being built. All the Tiger kits come with a canopy. Instead of trying to make one, it is easier to build a solid fuselage and then when covering make the canopy look like it is there.

These final photos show the wing tips going on, and the center fiberglassed. I used 1.75" dihedral under one tip. Any less and the wing would look like it was drooping.

My fuse is 4" wide, and the fiberglass cloth was 3.5" wide. This is before finish sanding. This is 7 ounce cloth. 5-Minute epoxy was used, and thinned with a bit of acetone. It is dumped on the cloth, and then spread using anything as a scraper.

I folded three wings in my first 5 years in this hobby, but have folded none in the last 35 years. Fiberglassing the center section works!

The two small holes in the last photo will be cut out for the aileron wires to come through. A string was super-glued in place so the servo wires can be pulled through in the next step.

Will add more photos after the plane is covered, and some flight photos soon.
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Last edited by tomclark; Jun 24, 2014 at 08:58 PM.
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Old Jul 05, 2014, 10:50 PM
Scratch Builder
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United States, NM, Deming
Joined Apr 2014
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Making a little progress. Just finished covering and about to finish the installation of the rest of the hardware, then on to test flying. The Tiger has such great lines that I'm really looking forward to flying it.
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Old Jul 09, 2014, 10:21 PM
Scratch Builder
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United States, NM, Deming
Joined Apr 2014
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All finished and ready for the first test flight. I expect that the Tiger will be a smooth flying plane. Finished weight 6.5 lbs. Span 76". Cord 13.5". Wing loading 14.6 oz/sq ft. Fuse length 73".
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Old Jul 13, 2014, 11:58 AM
Scratch Builder
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United States, NM, Deming
Joined Apr 2014
45 Posts
First flight report

There is nothing like taking off with a new airplane, especially one that you designed and built yourself. I had the first flight with this new plane this morning. What a great flier!

Of course I did not design the original Goldberg Tigers, but when you scratch build your own version, you can change anything you like: Build it any size you like, and use all your favorite construction techniques. I used my favorite 16% airfoil as it provides a compromise between speed and flyability, used simple stick construction as it is strong and cheap, enlarged the flight surfaces to provide more control input, and changed a gentle flier into a plane suitable for a more experienced pilot.

Hope you guys give scratch building a try one of these days. The rewards are gratifying.
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Last edited by tomclark; Jul 14, 2014 at 07:53 AM.
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Old Jul 14, 2014, 07:02 AM
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Joined Jan 2014
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Great work, thanks for posting.
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Old Jul 14, 2014, 07:52 AM
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USA, FL, Pensacola
Joined Jul 2009
322 Posts
Great job Tom, I love scratch'n them out myself.

What airfoil did you use on this plane? I have a Tiger 60 kit I acquired many years ago but I'd rather build a 90 size one as my eyes aren't getting any younger.

That 1 3/4" dihedral doesn't look like much when it's in the air.

Rick
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Old Jul 14, 2014, 09:42 AM
Scratch Builder
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United States, NM, Deming
Joined Apr 2014
45 Posts
Rick,

I used a 16% semi-symetrical. It has a slight flat on the bottom of the wing so it can be simply built directly on the workbench, instead of using jigs or pain-in-the-rear tabs. I really think no one could ever tell that it is not full symmetrical when they are flying the plane.

Imagine how the wing would look if less dihedral was used. Actually, the plane would fly just fine with no dihedral, but it would look as if the wings are drooping. The pattern planes use a 16% root and a 12% tip. Makes for good slow speed flying, yet keeps the power requirements lower.

If you check out all the photos on my blog, most of those planes used similar airfoils. The 102" stick used a 12% because the wing is so big, yet it is powered with just a 120.

Tom
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Old Jul 16, 2014, 01:49 PM
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Mexico, CHIS, Tuxtla Gutiérrez
Joined Nov 2013
42 Posts
Beautiful work, I like so much scratch build, I made Britten Normal Islander, Stik 40, many trainers, rcm trainer, and right now I'm worrking in a Miss Scarlett.
I have 2 questions.
1. the Miss Scarlett was an airplane designed for 45-60 2 stroke, but I saw that Modeltech made it for 52 4 stroke (bluemax), Do you think this airplane can flown with a 52 4 Stroke?
2. I have in mind to scrathbuild a 72" stik, Do I need to use high torque servos, if I plan to use a 120 4 stroke engine?
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Old Jul 16, 2014, 05:14 PM
Scratch Builder
tomclark's Avatar
United States, NM, Deming
Joined Apr 2014
45 Posts
Did you check out my blogs. (just click on my name) There are lots of photos of my builds, including my Islander.

I always use standard servos, because I have so many of them. Of course some planes use 4 on ailerons and 2 on elevator.

I flew a 72" stick with a 52 FS. It was very quiet and flew great. Of course the plane only weighed 5.5 lbs.

Tom
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