Ellis Grumer "Grandpa" - RC Groups
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Mar 01, 2017, 06:57 PM
AndyKunz's Avatar
Build Log

Ellis Grumer "Grandpa"


The "Grandpa" is a half-size version of Ellis Grumer's "Grandson 40", FM plan number CF921.

I'm not much of a biplane person, but this plane still has special meaning for me. Ellis was my "building buddy" for the last few years of his life. He built three of these planes, giving them numbers based on his age when finished. He built one as a gift for Keith Shaw, one as a raffle prize for the LVRCS Electric Fly which now bears his name, and one which was given to a friend at his decease. This one will be for the raffle at the event this June.

So, without further ado, I'd like to get started.

Andy
Last edited by AndyKunz; Mar 01, 2017 at 07:08 PM.
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Mar 01, 2017, 07:55 PM
AndyKunz's Avatar
I went digging through my plans archive looking for a set of original Grandpa plans (I inherited his plans and templates). Frustrated for not finding them (I know I had them - I printed them for him!) I did find a reference to the plane having a 31" span.

Thayer Syme was kind enough to print my plans order at 50%, which rather closely matched the 31". Well, after I got the plans I realized I had missed one place I store drawings - and there they were, right on top! And even better - they perfectly matched the drawings from Thayer.

As I reviewed the original plans with Ellis' notes on them, I want to clear up a little confusion that has come up a few times over the years when we talk about this model. The Grandpa design is Ellis' name for his Grandson when reduced to 50% with a few construction changes to accommodate the smaller size.

The next step was to dig through photographs (over 15000 of them, fortunately organized nicely) to find some of Ellis' construction photos. I'll be adding some of them to remind me of what I want to do as I get there, and of course to bring back some cherished memories.

Andy
Mar 02, 2017, 07:26 AM
Registered User
Nice tribute to a really nice guy, Andy!

CD
Mar 02, 2017, 09:14 AM
Gravity sucks.
mrittinger's Avatar
How bout an indoor job too?
Mar 02, 2017, 10:04 AM
AndyKunz's Avatar
I have an indoor job - I sit at my desk and make code for Spektrum transmitters!

I'm building this as a tribute to a dear friend, and to help out my "home club" in PA. And maybe it will sell a few plans for Thayer. For indoor biplanes I'd go with the E-Flite UMX PT-17 or the new UMX Waco.

Andy
Mar 02, 2017, 10:28 AM
Obviously I'm a "Minus Member"
buzzltyr's Avatar
I remember you telling me about Ellis well over a decade ago, Andy (when I was building the Jitterbug I bought from you). This will be a wonderful tribute to him, I'm sure. Would you contemplate a laser cut short kit for this one? Also, where is Thayer selling plans from? I know he is trying to restart FM, but did not know he had a plans service as well.
Mark
Mar 02, 2017, 10:55 AM
AndyKunz's Avatar
Mark,

It's really good to hear from you! Hopefully all is well. The Jitterbug is the only kit Ellis ever built - everything else was from plans, either his own or from a magazine. Dave Szuter did a beautiful model.

I may make a laser kit, and this thread is going to document the many changes that it will entail vs. the full-size Astro-powered version. We'll see as we go along.

Thayer launched the FM Plans last summer. They are available at http://store.flying-models.com/ There are a few missing from the list, so if you're looking for something and don't see it, just ask Thayer.

Andy
Mar 02, 2017, 11:43 AM
Wanted for breaking Ohm's Law
Dennis Sumner's Avatar
Andy,

I get to see "Ellis" fly every year when Keith Shaw brings out the Buker Jungmeister that Ellis built years ago. Keith recovered it and has a miniature "Ellis" in the cockpit. Very cool! Keith has shared stories of Ellis and the great KRC electric flyin's from many years ago......
Last edited by Dennis Sumner; Mar 02, 2017 at 05:14 PM.
Mar 02, 2017, 02:21 PM
Gravity sucks.
mrittinger's Avatar
I think he had it at Toledo a few years back...
Mar 02, 2017, 10:36 PM
Obviously I'm a "Minus Member"
buzzltyr's Avatar
Quote:
Originally Posted by AndyKunz
Mark,

It's really good to hear from you! Hopefully all is well. The Jitterbug is the only kit Ellis ever built - everything else was from plans, either his own or from a magazine. Dave Szuter did a beautiful model.

I may make a laser kit, and this thread is going to document the many changes that it will entail vs. the full-size Astro-powered version. We'll see as we go along.

Thayer launched the FM Plans last summer. They are available at http://store.flying-models.com/ There are a few missing from the list, so if you're looking for something and don't see it, just ask Thayer.

Andy
Thanks for the link to Thayer's plans, Andy. I look forward to following along with this build. I really do think it is terrific that you would honor Ellis in this manner.
Mark
Mar 04, 2017, 12:24 PM
AndyKunz's Avatar
My goal for today is to build the top wing. That means a little CAD for getting the airfoil into the laser cutter - probably the most time-consuming part.

I took a few measurements so we know where this is going.

Top wing: 145 sq in.
Lower wing: 135 sq in.
Span: 31 7/8"
Length: 24 1/4"

Andy
Mar 04, 2017, 03:30 PM
AndyKunz's Avatar
Goal achieved - top wing is framed up.

I am using the multiple LE spars that are a characteristic of Ellis' later designs. This was a technique he learned in Keith Shaw's design article which you can probably find on Ken Myers' site. Who says you can't teach an old dog new tricks? Ellis was over 80 when he learned that one!

Back to construction - there's a spar on the lower front side of the airfoil between the 1/4" sq LE and the 1/8" lower main spar. This was not installed yet because it is elevated above the work table. It will be much easier to put all the others in place, then remove the wing and flip it over for the last one.

Before pulling it off, though, I need to add webs and some spar bracing.

Andy
Mar 04, 2017, 09:33 PM
AndyKunz's Avatar
Tail surfaces were built in the mean time. The tips on the horizontal will be trimmed to final outline later. I did cut the center section portion because I wanted to have an accurate centerline and cuts for the vertical fin tabs.

The fin and rudder had much more roundness about them, so I drew up some parts in CAD and laser cut them. The tabs on the fin base were lined up with the slots in the stab so they should fit nicely together.

These were all made using hard 1/8" balsa.

Andy
Mar 06, 2017, 08:04 PM
AndyKunz's Avatar
The rounded edges of the stab and elevator were created by poking holes from the bottom side of the plans through to the wood. The dots were connected, and then trimmed with an X-acto. Later on they'll be sanded to final shape.

The same technique was used for the center of the top wing.

The shear webs are installed on both spars for the top wing using medium 1/32" balsa. While gluing to the front or rear face is far less effective than making a true I-beam with the in the middle between the spars, it's quite sufficient at this small scale.

Andy
Mar 06, 2017, 10:12 PM
AndyKunz's Avatar
I had a little time left over tonight, so I drew up the ribs, cut them, and started the framing for the lower wing.

I'm doing something a little different than Ellis did here. Instead of having the rear 1/8" sq spars plus a thick balsa shaped for the gapless aileron hinge, I'm making the rear spar from 1/16 x 1/4 and moving it back a little bit to make it the hinge for the ailerons. The ailerons will be top-hinged instead - a lot easier and quicker to build, less weight, and just as strong.

Andy


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