Sig Magnum

I picked up a new in box kit last week because I always wanted to build one. I have read the previous threads on this model and after studying the plans I can’t understand why this model is considered to build heavy. I fully intend to replace the wing sheeting with some good 4 to 6 pound stock because the stock sheeting is slightly heavy.

So what is it about the design that builds heavy, the fuse structure seems to be the same as any other control line design that I have seen. Actually the designs seems straight forward and easy to build. It’s a bunch of blocks that need to be hollowed just like the Brodak Legacy kit that I have so what’s the difference?

I intend to power the plane with a new Super Tigre 51.

Thanks for your help
John

I think you have hit the problem in your own post. SIG over the years has seemed to use randomly selected wood in their kits. Sometimes it is good. Sometimes it is not. I have three Mustang kits, for instance, and there was over a pound difference in the weight of these three, randomly selected kits. And that difference could be attributed solely to the weight of the wood inside.

If you check the wood in your kit and replace anything that is excessively heavy just as you would do if you were scratchbuilding your own design, it should come out just fine. If you have some marginally heavy wing sheeting, put the heavier on the outside wing. Same with the flaps. Use marginally heavy wood to your advantage. On built up kits we would often weigh the ribs and put the heavier ones on the outside for the same reason. Just remember, each gram you save accumulates, and it is leveraged at the tail.

Use an adjustable tip weight and leadout guide, make sure you use good controls and that the gear is strongly mounted, and have fun. Remember, this is the same design Todd Lee used to place highly at both the Nats and FAI trials in recent years.

The plane is fine. Build it and become its equal.

Unless you are a real expert in lightweight finishing, consider using Oracover (Ultracote) for the wing and rudders.
This is a real strong and easy to use material, and definately helps keeping weight down.
Norvald Olsvold

I suspect that a lot of the (over)weight can be traced to the adhesive (or excess use of) for sheeting the wings. Remember the difference in actual weight of a 3x36x1/16 piece of balsa from 4 lb stock to 8 lb stock is "only" 1/4 oz. Multiply this by the number of sheets for a wing (12-16??), and this would account for an extra 3-4 oz to the airframe.

Of course it doesn't hurt to fight down all the weight (especially when you consider the rest of the wood in the plane) , but being careful with the epoxy or whatever glue you use might be the best method. I know some guys actually lay on a coat or two of dope to seal the wood to keep it from absorbing the glue.

>I picked up a new in box kit last week because I always
>wanted to build one. I have read the previous threads on
>this model and after studying the plans I can’t understand
>why this model is considered to build heavy. I fully intend
>to replace the wing sheeting with some good 4 to 6 pound
>stock because the stock sheeting is slightly heavy.
>
>So what is it about the design that builds heavy, the fuse
>structure seems to be the same as any other control line
>design that I have seen. Actually the designs seems straight
>forward and easy to build. It’s a bunch of blocks that need
>to be hollowed just like the Brodak Legacy kit that I have
>so what’s the difference?
>
>I intend to power the plane with a new Super Tigre 51.
>
>Thanks for your help
>John

There are a number of reasons that the Magnum can get heavy but mostly it is from poor to sorry building techniques and or added changes. I have received many letters from satisfied modelers that have built and flown the Magnum.

Yes the wing sheeting can get heavy at times, but so does any other major kit manufacturer. Contest balsa wood is harder to come by than you think. We import more balsa than just about anyone and we always try to get as much contest wood as possible. But out of a shipment of balsa wood we expect to get only 15% that is actually contest wood. We order much more than that but by the time the wood is sorted and graded, that is about we get as true contest wood.

Another thing that increases weight is the use of contact cement to attach the wing skins. This stuff is really heavy and should not be used at all. Use (slow curing) epoxy and apply a thin coat to the inside of each of the wing skins, then squeegee off all the excess epoxy with an old credit card. Place the skins on the foam cores and place them back into the foam cradles. Place a piece of plywood on top of the stack slightly larger than the wing cradles. Weight down the cradles with at least 50 pounds of weights and allow the epoxy to cure for 24 hours.

Search in archives for other posts on building Magnums.

Later

Have to confess to building an overweight Magnum and also a Forerunner. Generous use of Core-Bond on the wing skins was the big sin. The Forerunner kits all had excellent wood selection but this one still came in over 60 oz. I later built another Forerunner at 48 oz using light coats of 3M 77 instead of the Core-Bond. Although weight savings from light wood substitution can only help, have to agree that construction & finishing techniques and glue selection are the bigger contributors to weight.

I have been flying Magnums (Magni in proper Latin) for over 10 years. One was 80 oz. Only a 14-6 would pull it. Rounds were great, but it stalled in the squares. My next Magnum was 63 oz. It still stalls in the triangles and hourglass on occasion. I think it's the thin wing. Magnum wing is about 2" at max thickness.
I think Todd flew modified (thicker) airfoils on his Magni. Maybe about 2 1/4".
My next plane will be a Time Machine derivative, which is about 2 1/2 or 2/5/8 " thick. I don't believe Time Machines are afflicted with stalls in squares.
From what I have seen, the full size Cardinal with 3" airfoil doesn't stall, but take lots of power to fly it, especially in the wind.

LAST EDITED ON May-14-04 AT 02:38 PM (CDT)
 
Thanks Mike Pratt!

I was shocked when I looked at the kit because it looks the same as the construction of the Legacy with the exception of the foam wing. There is no way the fuse and tail section builds heavy so that leaves the wing. With contest balsa on the wings and the use of good techniques for attaching the sheeting it should be fine. I think the main reason for the people saying the Magnum builds heavy is they use heavy sheeting and to much glue.It is one sharp looking plane and I look forward to building it.

What is the normal weight for this size stunt ship? I think the Legacy turns out to be 62 and above ounces when completed.

Mikey,
Is it true that you pay royalties to Jim Armour for the Epic styling?
Chris...

My Legacy came in at 64 ounces, with a RO-Jett 65. It flies just fine.

You can stall any wing at any time if you are not careful. My Time Machine weighed 60 ounces with a ST 51, and I felt it was under powered. It would wobble and mush if I wasn't careful. I have changed back to the RO-Jett 61 and the plane feels much better on the end of the lines. The engines are within a few grams of each other in the weight department, so it was an easy decision to make.

I'm sure my Time Machine would fly much better on either engine with a better pilot

I would definitely consider the Magnum for my ST 51 engines. Now all I have to do is find one.

Enjoy,

Ron King

>I have been flying Magnums (Magni in proper Latin) for over
>10 years. One was 80 oz. Only a 14-6 would pull it. Rounds
>were great, but it stalled in the squares. My next Magnum
>was 63 oz. It still stalls in the triangles and hourglass on
>occasion. I think it's the thin wing. Magnum wing is about
>2" at max thickness.
>I think Todd flew modified (thicker) airfoils on his Magni.
>Maybe about 2 1/4".
>My next plane will be a Time Machine derivative, which is
>about 2 1/2 or 2/5/8 " thick. I don't believe Time Machines
>are afflicted with stalls in squares.
>From what I have seen, the full size Cardinal with 3"
>airfoil doesn't stall, but take lots of power to fly it,
>especially in the wind.

Hi John,
Congratulations! 80 ounces is the heaviest Magnum I have heard of, LOL. At that weight I am sure that it would stall in a triangle or hourglass. If the Magnum is built at a reasonable weight (55 to 65 ounces) there is no way it would stall unless it is way too nose heavy. FYI, the wing thickness is 2-1/8" at the root and 1-7/8" at the tip. The photo model on the box was 60 ounces and I didn't use contest balsa wood and it had a front row dope finish.

As far as Todd's 1st & 2nd Opus Mustangs (AKA Magnum) both had a stock Magnum wing cores with cap strips instead of being fully sheeted. The weight savings were minimal and the wing caved in after a few years. I would not recommend the cap strips.

Chris,
That dog won't hunt but nice try LOL. The Magnum was designed in the late 70's and the Jim's Epic was in the early eighties but if they were side by side you would see that they are not even close. But they do share some of the same Classic lines.

Later Dudes,

Mikey,
Always loved the lines of both, I did not know the Magnum was that old.
Chris...

Possibly I got an above adverage kit from SIG, who knows. I built
per the instruction book, covered the whole plane in yellow tissue except for the wing which was done in med.silk span, then spayed cub
yellow, and trimed in monocote. w/an S.T. .46, tank, wheels, etc flying
wt. was 54oz, flew right well on 67ft solids center to center. My 2nd
one w/S.T. .60 all silkcovered came in at 60oz. It to flys very well.

Walter:+

My opinion is a couple of people built heavy ones and the plane got the "builds heavy tag".

Replacing the 30" wood in my kit with contest balsa resulted in a savings of around 7oz.

When the Magnum came out in 1985 everyone (or at least the ones I flew with) considered a 64oz plane heavy. All I ever saw built from the kit weighed 64-72 oz so it was considered to build heavy.

Mikey, didn't the plane you built for the museuum weigh in the low 50's with a Tigre 46 in the nose?

>Replacing the 30" wood in my kit with contest balsa resulted
>in a savings of around 7oz.
>
>When the Magnum came out in 1985 everyone (or at least the
>ones I flew with) considered a 64oz plane heavy. All I ever
>saw built from the kit weighed 64-72 oz so it was considered
>to build heavy.
>
>Mikey, didn't the plane you built for the museuum weigh in
>the low 50's with a Tigre 46 in the nose?

Yes, 54 ounces without the tip weoght. FYI It also had 18 coats of clear dope and had a shine that looked three feet deep.

Just finished "kit bashing" a Magnum into an ME 109. Shortened the wings a little, to 640 squares, used lots of the kit wood. With an ST 46, this ship will be about 52 ounces. Magnum is certainly one of the best designs that's come along...just be careful with glue, use good wood, and finish lightly. Thanks, Mikey!

ST 46, ST 46, Did you say ST 46 ?

ST46?

The only 40 size engine that I would attempt to install in a Magnum may be one of Randy Smith's, new PA40RE. Power to spare and no weight at all.

I am trying to get around to building another Magnum. I have the wing put together and decked with slow cure epoxy and hardware, no flaps and no tips. This wing weights 15 ounces and this is heavy for a unfinished wing. Does this discourage me? not at all.

The last run of Sig Magnum kits had great wood included in the kits.
Any weight build up that I have experienced has come from not carving out the Tips, Top block and the Bottom block, leaving these solid will be a mistake. My advise is to sand, sand and sand again.

A quick word about the control surfaces and here is where I might catch some flack. I covered the elevators and flaps with contest grade balsa. The sheeting was sanded so thin, you could hold it up to a light and see right through the wood.

Be careful with your dope and watch the weight.

If you follow the instruction manual and becareful with the dope application. You should have a finished airframe, that should weigh between 45 to 50 ounces.

Hopefully you have a good engine to power this airplane, if not, it will be a quick flight.

May I suggest a ST51 or ST60. The ST60 is a older and still are readily available, while the ST51 is still in production.
Either engine will provide the performance that will be up to the task at hand. Either of these engines will fly this bird on 65 foot lines without any problems.

The ST51 weight, with tongue muffler is about 11.5 ounces, the ST 60 with tongue muffler is about 13 ounces. Which should bring you Magnum weight up to 58 ounces, if you know what you are doing or 63 ounces, if you fool around like I do. If your Magnum reaches 70 ounces, then you just like to paint!

By the way, my very first Magnum tipped the scales at 70 ounces and was powered bt a ST51 and a muffler that looked like a turd.

Good luck building.
Mike Clark

I've built two of them and flown them both for about 10 years. I lost one last year due to a line clip being flipped over. The plane went into the ground in inverted flight whe the clip decided to flip back where it belonged.
Anyway the 1st was monkoted wing and stab with K&B Epoxy painted fuselage. It weighed in at 58 ounces and after a repair, now weighs 61 ounces. The other weighed 59 ounces with a dope finish. I loved both planes and need to get the original one trimmed out again.
OS .46SF with a Graupner 12 x 5 (The old prop, the one they sell now is crap). I let the engine sing and the 5 pitch slows things down.
Bill

Hey Bill,

How's that "Chipmunk" replacement plane doing for the late lamented Magnum?

That defunct Magnum has had more press in Stunt News recently than it ever did when flying!

That "Chipmunk" is actually an Akrobat on steroids. Needs a Tigre .46 to pull that tank thru the sky. Hopefully my ARF Nobler will get finished in the next week or so. Then I can fly something newer than an 18 year old plane.

Hi John,
We accquired a set of Magnum wing cores and plans built one. It is pretty light, but it's been so long since we built it I can't remember the weight. I'm sure it was in the low 50s. It is a very good flyer. Right now it is undergoing a refinish, the original $cote finsh with Rustoleum trim didn't last. Especially the Rustoleum. hahaha
It has had a Royal 45, two different ST G51s, and a OS 46VF pipe.
Actually removed the pipe set up before we flew it with it. The G51s were more than adequate power, and when we had the Royal 45 running right, it flew great with that!
It's like what several others have said.... building/finishing techniques can determine a lot of the weight problems, or lack there of.
I think you will really like the Magnum!
Bill <><