Author Topic: Future "Overweight Pig" (Read 1955 times)

Tom Dugan · « **on:** July 06, 2006, 09:15:40 PM »

I am a novice builder and have just bought a Sig Magnum kit. So, I have been following the recent posts regarding building the Sig Magnum. Everything Ive read about the Magnum indicates that it generally builds on the heavy side. I know that extra effort needs to be taken to keep the weight down.

Greg Bahrman posted what he had done to keep the weight within reason:

"1. Hollowed all the top blocks
2. Bought 1/16 in. contest grade 4 lbs. balsa for sheeting the wings
3. Sheeted the fuse bottom with 1/8. The plans showed 1/4 in.
4. Sheeted the turtle deck with 3/32, not the recommended 1/8 and 1/4
5. lightening holes in the Stab and Rudder
6. Built up the elevators
7. The flaps are not even done yet.
8. Hollowed the wing tips
9. Hollowed the block between the stab and rudder fin.
10 lightening holes in the wing spar.
11. Triple cored foam wing
12. Hollowed the cowl block
13. Motor mounts are drilled with lightening holes behind the first former all the way back."

My question is...What could additionally be done to conserve more weight and still use the kit? The foam wings are triple cored...could lightening holes also be done to further save weight. What else could be done, or do you just do what Greg has done and keep your fingers crossed?.

Thanks...Thomas

Bill Little · « **Reply #1 on:** July 06, 2006, 10:21:23 PM »

Use the lighest wood you can substitute, and go with it. The kit built Magnum flys well, even if a touch heavy. We have one here, flew great with a ST 51. Don't have clue as to it's weight.

Give me a call anytime you feel like it. I should be flying before too long.

Bill <><

Tom Dugan · « **Reply #2 on:** July 07, 2006, 07:42:33 AM »

Bill,

What youre telling me is that there is nothing else to be done other than use the lightest wood and Greg Barhman's 1-13 list in the initial post?

The Magnum has been around a while and has been built by many. None of those that have built it can add to the list techniques to save weight?

Thomas

RC Storick · « **Reply #3 on:** July 07, 2006, 07:47:30 AM »

Building light is an art. You must consider every piece that goes on the plane. Like aluminum bolts for the landing gear and instead of 5 coats of paint try to get it done in 4. When the people get to see the Super Marine they will wounder how I got a plane so big so light finished so well. Sanding sanding sanding! Less wood and less paint = light light light!!!

Tom Dugan · « **Reply #4 on:** July 07, 2006, 09:58:48 AM »

Thanks Robert.

Even though Im a novice at building, I can build a pretty good looking plane. However, suggestions like this can only come the more experienced builder. It's ideas like aluminum bolts that Im looking for.

I would think this would be a hot topic and a chance for the far more experienced to share some of their tricks.

Thomas

Randy Powell · « **Reply #5 on:** July 07, 2006, 01:16:47 PM »

There will be an article by Pat Johnston in stunt news about building light planes. Most of it's pretty much common sense. Pat builds very light and has some good information

Bill Little · « **Reply #6 on:** July 07, 2006, 02:07:48 PM »

Quote from: TJDNC on July 07, 2006, 09:58:48 AM

Thanks Robert.

Even though Im a novice at building, I can build a pretty good looking plane. However, suggestions like this can only come the more experienced builder. It's ideas like aluminum bolts that Im looking for.

I would think this would be a hot topic and a chance for the far more experienced to share some of their tricks.

Thomas

Hi Thomas,

I didn't try to sound "funny" in my post. There are very few real TRICKS to building light. *Wood selection*, sanding, use as little glue as possible and the right types of glue, sanding, hollowing, sanding, use light accessories, sanding, and just being concious about weight. I don't mean to brag, but I do build as light and strong, when I really want to, as about anyone else. So, as Robert said, it is a process.

I can say that many of the designs of recent (and older designs) are somewhat "overbuilt".

I have spent hour upon hour talking with Bob Hunt and Billy Werwage about building and building light.

There just ain't that much "trick" to it.

Bill <><

Tom Dugan · « **Reply #7 on:** July 07, 2006, 07:34:57 PM »

Ty,

Lost Foam is an interesting idea. Bill little has shown me several lost foam wings that he has. When you build your wing, will you sheet balsa over the ribs so it looks like covered foam?

I wonder if it would be structurally sound and strong to take the triple cored foam wing and cut holes from top to bottom (like swiss cheese) to lighten it further. Has anyone tried this with any success?

Thomas

Bill Little · « **Reply #8 on:** July 07, 2006, 08:38:22 PM »

Hi Thomas,

Todd Lee had a P-51B that he built from a Sig Magnum. He sheeted the LE, TE, and put 1/4" cap strips where ribs "would be" (like Tom Dixon's "kept foam" system. The difference was that he sheeted the LE back to the 1st "foam spar", and the TE up to the back "foam spar", and removed the foam betwee the shetting even with the cap strips. So he in a sense "swiss chessed" the wing. It held up fine for several years, eventually started to sag in the "open areas".

Bill <><

Steve Helmick · « **Reply #9 on:** July 08, 2006, 02:12:00 PM »

Greg revealed one or two mistakes. He apparently didn't have a scale to weigh his balsa. Weigh every piece of balsa. It can vary from 4 lb/cu.ft. to 16 lb/cu.ft, so it can have a huge impact on the total weight. A real pretty piece of "C" grain will often be about 12 lb/cu.ft. Keep that off the tail end of your model!

Greg also wrote that he spread the epoxy on the foam core...not certain he really did that...but you spread the epoxy (or urethane glue) only on the balsa, not on the core. You'll never be able to scrape enough excess off the foam.

Steve

Tom Dugan · « **Reply #10 on:** July 08, 2006, 05:36:54 PM »

I hope I havent given the impression that I don't trust anything Im being told about building. Im just searching for ideas...trying to pick peoples minds. Ive met Bill and hope we have a long friendship. Ive seen his planes and know he is a great builder just like you have said. But, we are all different and pick up little tricks we perfect and use to build. These are what Im trying to find. Ive learned much from the few posts in tis thread, I hope there are more.

Thanks Ty and Bill for your knowledge.

Bill...Did you pay Ty to say all those nice things about you?

Greg L Bahrman · « **Reply #11 on:** July 08, 2006, 08:11:16 PM »

Quote from: Steve Helmick on July 08, 2006, 02:12:00 PM

Greg revealed one or two mistakes. He apparently didn't have a scale to weigh his balsa. Weigh every piece of balsa. It can vary from 4 lb/cu.ft. to 16 lb/cu.ft, so it can have a huge impact on the total weight. A real pretty piece of "C" grain will often be about 12 lb/cu.ft. Keep that off the tail end of your model!

Greg also wrote that he spread the epoxy on the foam core...not certain he really did that...but you spread the epoxy (or urethane glue) only on the balsa, not on the core. You'll never be able to scrape enough excess off the foam. Steve

Probably would of been a mistake if I knew better. But being the ignoramus I am I never suspected that I could buy a stunt ship that was really maybe a borderline stunt ship do to the quality of wood and or foam supplied. Had I of known I could of just got the plans and ordered my own wood. Of course I see using the 4 lbs. stuff on the wings along with the list of lightening work I did really didn't produce the desired results either. So I guess it's all really my fault Steve. Had I just went to Randy Smith this would all be a mute point. The kit I received had already been started by someone else so I just continued blindly on. Although I see there are builders much better than me admitting that a 70 oz. Magnum is not uncommon. So really you are starting with more than two strikes against you to start within the Magnum arena. Of course I could of NOT glassed the wing or stab and left the silkspan off the wings and left the carbon fiber veil off the fuse and maybe had a real nice stunt ship. OH well, It is what it is.

And we all have followed Sparkys latest Jet ship with interest and he used all good wood as Steve suggested and a foam wing and he ended up with more than he bargained for weight wise and he is obviously a better builder than most of us. I wonder what his mistakes were?

Greg L Bahrman · « **Reply #12 on:** July 10, 2006, 02:00:05 PM »

Quote from: Steve Helmick on July 08, 2006, 02:12:00 PM

Greg revealed one or two mistakes. He apparently didn't have a scale to weigh his balsa. Weigh every piece of balsa. It can vary from 4 lb/cu.ft. to 16 lb/cu.ft, so it can have a huge impact on the total weight. A real pretty piece of "C" grain will often be about 12 lb/cu.ft. Keep that off the tail end of your model!

Steve is right on this account also. Now that I have a scale I started weighing the parts that I can. Much is to be learned about wood weight and construction styles.
I weighed the kit suppplied foam stab and elevator assy covered and ready to be installed in the fuse and it weighs 4 ounces. This is about twice or more what it should weigh. I am considering redoing this.
New rudder and fin weighed 3/4 oz. Cowl weighed 5/8 oz. Both wheel pants together weighed only 3/4 oz. So you see that some things are light but some of the kit supplied parts are not. You can't tell by looking, but the scale is opening a whole new world to me. My next ship will be quite a bit better and lighter. I am finding out that you cannot build a light plane by updating this or that but you MUST make proper decisions on materials/weights throughout the build. At the completion you will see the totals come together in your favor..................... Right on Steve !!

Randy Powell · « **Reply #13 on:** July 10, 2006, 02:09:56 PM »

Greg,

Very good point. When I order wood, I weight every piece and mark it with both the weight and the type ("C" grain or whatever). When I'm actaully building I often just grab the lightest piiece I have and that's not always the be thing to do. For instance, I have 2 or 3 sheets of 1/8" "C" grain, 12lb stock stuff. Horrible for sheeting anything, but really nice when cut into strips and used for spars or area that need support compression strength.

Author Topic: Future "Overweight Pig" (Read 1955 times)

Tom Dugan

Future "Overweight Pig"

Bill Little

Re: Future "Overweight Pig"

Tom Dugan

Re: Future "Overweight Pig"

RC Storick

Re: Future "Overweight Pig"

Tom Dugan

Re: Future "Overweight Pig"

Randy Powell

Re: Future "Overweight Pig"

Bill Little

Re: Future "Overweight Pig"

Tom Dugan

Re: Future "Overweight Pig"

Bill Little

Re: Future "Overweight Pig"

Steve Helmick

Re: Future "Overweight Pig"

Tom Dugan

Re: Future "Overweight Pig"

Greg L Bahrman

Re: Future "Overweight Pig"

Greg L Bahrman

Re: Future "Overweight Pig"

Randy Powell

Re: Future "Overweight Pig"