An open letter

[WIDDOG]

Instead of half the wood being good and the other half being heavy. I would rather the wood be all heavy. Than lightening techniques could be used. I have to admit though that the wood that came with my Guillow's kit was all "Good". I also admit that even though I am building a Die Cut kit with "Good" wood it is extremely fun.

[David Lewis]

On the 300 series, the parts that can be omitted and still have plenty of strength left:

1/8" x 1/4" wing spar*
Side keels
Half the wing ribs*
Cabin side window pieces.

The cabin side window pieces are an awful lot of cubic millimetres of balsa, and they are not adding significant strength from what I can see. I usually recommend against lightening holes but this part would benefit if you are not going to get rid of it entirely. Also, the width of the tail outlines and formers can be reduced. This tends to work better than drilling lightening holes or scalloping, according to my experiments.

Except in the nose area, using as little glue as possible can be worth the extra care. Any glue joints with a lot of area, such as root rib to cabin side, or stabilizer to fuselage, only apply glue where it does some good, otherwise most of it will be wasted. Better yet, these joints can be re-designed to achieve a higher strength-to-weight, automatic alignment and use much less glue.

* The heavy wing spars might make sense on a cantilever wing, but strut braced it's overkill. The scale wing rib spacing follows Cleveland Model design format and, while it looks good, is unnecessary. There are opportunities to improve flight performance while at the same time reducing costs and build time.

[Bill Gaylord]

Instead of half the wood being good and the other half being heavy. I would rather the wood be all heavy. Than lightening techniques could be used. I have to admit though that the wood that came with my Guillow's kit was all "Good". I also admit that even though I am building a Die Cut kit with "Good" wood it is extremely fun.

You read my mind. I was going to mention my P47 build in my last post. One sheet of fuse formers was lighter and softer than most any Dumas wood I ever received. The other sheet of fuse formers was heavy. Being an rc build, the heavier formers were fine, but I had to laminate stringers across the formers, due to the sponge light side. That wouldn't have been an issue if all the formers had been air light, since the end result would have been light, with light weight, efficient reinforcement. That's something I often do. It wouldn't have been bad either if they had all been the heavier grade, since they wouldn't have required additional reinforcement, albeit a bit heavier than using reinforced lightweight formers.

[Bill Gaylord]

I usually recommend against lightening holes but this part would benefit if you are not going to get rid of it entirely.

Ditto on lightening holes. It's just as effective to trim wood or use lighter wood. Years ago when I used lightening holes in sheet balsa, I calculated the actual area and discovered that anything beyond 30% removal has the appearance of being shot at from close range, with a 12 gauge shotgun.

[David Lewis]

Bill, your Thunderbolt looks more like a display model than a flying model!

Now the problem with lightening holes in wood is that strength tends to decrease faster than weight because 1. the grain in between holes is going in the wrong direction and 2. stress is distributed unevenly. The exception may be balsa parts that are lightly loaded, such as wing ribs, or when you want to salvage kit parts that are unnecessarily strong without having to make them over again.

With a few exceptions I'm against lightening holes, scalloping, and sanding tail surfaces thinner because the strength goes down faster than the weight. I'm in favor of highly stressed structural members, with mass concentrated in the load paths, and no parts loafing or going along for the ride, and using contest balsa. However, this is from the designer's and scratch builder's point of view.

When you're building a kit, your philosophy changes a little because you have to make do with what you're given. Sometimes it's preferable to reduce weight inefficiently than not to reduce it at all.

[WIDDOG]

P 47 looks great!

I was so happy with the quality of the kit wood that came with my Bird Dog kit that I ordered a new Mustang kit from Guillow's. In the past I have cut the parts out of Contest Balsa wood. I like building with the kit wood better.

I noticed that the Mustang flies (rubber power) very well. I think it has a weak spot where the wings and the fuselage meet. If someone has some advice on this I would appreciate it.

[PsyberPhlier]

Bill, that P-47 is a showpiece.

WID, A guy on another forum (I think) told me about using bamboo skewers through the root rib, through the fuse and through the opposite root rib to act as a stiffener for a pretty weak glue joint.

Ted

[Johnny ace]

So, what does everyone think about laser cutting the 500 series?

[PsyberPhlier]

CUT 'EM ALL!

Ted

[kittyfritters]

Spoke to Mark this morning.

OK, Guys. Here's the skinny on the 500LC kits. The laser cutting layouts were done some time ago. You know this because some of you have built test kits. Based on the notes you sent back the laser cutting has been cleaned up. However, the the plans, 40 year old pen and ink drawings, had to be revised to go with the laser cut parts. So the plans are all being redrawn (in digital format)...a project that is nearly complete. The sales people wanted this done for the complete series before release so that they will all be released for sale at the same time. (Makes sense if you are selling to distributors.) Sorry, they did not go so far as to re-engineer them for removable cowls. Remember, 70% of the 500 series kits are built as static models, and those of us who fly know how to deal with the cowls. Of course, any new designs will be engineered for flyability as well like the more recent kits.

So, to sum it up, the 500LC kits are coming.

Keep 'Em Flying!

Howard

[PsyberPhlier]

Dang, now that's some good news.

[1778ppr]

That is great news! I'll buy the hole series.

[BillParker]

Thank you Howard! As always, YOU DA MAN!


bp

[Johnny ace]

Great news.thanks

[David Lewis]

CAD drawn plans have an advantage over offset lithograph plans; CAD drawings can be customized, corrected or revised in the middle of a production run quickly and inexpensively. Likewise for laser cut versus die cut. Unit manufacturing cost is higher but tooling cost is low -- just the CAD drafter or CNC programmer's labor. You don't have to engrave new litho plates or re-make steel rule dies.