wakehand

Hopefully i won't flunk basic... This is my first build - a Sig LT-40 Kadet which I picked up off ebay. It was sold as NIB and complete but after unpacking it and inventorying the contents, it appears to be missing the pack of (12) 1/8 x 3" x .600" SW-3 Shear Webs... I guess I'll just buy a sheet of balsa and cut some new ones out myself. Anyways, I'm looking forward to getting started. So far I've set up a workstation and taped down the plans. I had wanted to start gluing tonight but it seems my tightbond II has gone bad.

biam

Good luck on your build. Tite bond is my preference also. Check your plans for correct orientation of the grain of the balsa when cutting your new shear webs.

Hydro Junkie

One piece of advice I'm going to give is IF YOU COME ACROSS SOMETHING YOU DON'T UNDERSTAND OR CAN'T FIGURE OUT, ASK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

rgburrill

The local Hobbytown USA is less than a mile away and I pass it going both to and from work. Great place to stop when you run out of Tightbond.

wakehand

Thanks Biam, good tip on checking the grain orientation.

jwrich

My Feedback: (17)

Sig has great kits and the Kadet 40 is a great trainer. First, let me say, you should cover your plans with wax paper or plastic wrap before you start gluing anything.. CA glue, epoxy and tightbond are all needed. Also if you post picture of your progress and ask questions, we all can help you. Do you now know how to fly RC airplanes. IF NOT, Please contact a local club, they usually have someone who will teach you. Also they will point you to AMA. Building and flying RC airplanes is a great hobby, you will love it

Rich

wakehand

Hi Rich, good advice all around. My plans are covered with great planes plan protector, I've sent in application to a local club and i've joined MAAC, which is the Canadian equivalent of the AMA. I've had an interest in RC for the last 25 years, just never got around to building due to time/money/space constraints. I will take you up on asking a few questions... Do you know why there's a gap between the main spar and W2? That threw me for a loop but I'm sure i'll get to its purpose in the plans. Also I had a few 1-2-3 blocks kicking around and using a few magnets I made an ad-hoc jig to keep things square. The balsa for the missing shear webbing should arrive tomorrow so I'm hoping to make a lot of progress over the weekend.

jwrich

My Feedback: (17)

After looking at the picture, I think that space on both sides of the spar is for plywood to join both wing panels. The plywood is like the shear webs only on both side of the top & bottom spars. Do you have an instruction booklet? You should read all the steps to get an understanding how it all goes together. If not then you need to study the plans closely. The best thing to do is not glue a part in place until are sure that is how it goes. Keep posting pictures and ask questions. BTW, what is your first name? Talk to you soon.

Rich

wakehand

Hey Rich, sorry I was just being lazy. I scanned through but didn't read in detail. I'll kick things in gear when I start gaining a little more momentum.

Steve

jwrich

My Feedback: (17)

Steve no problem. Don't rush your build it can only lead to mistakes. From what I can see you are on the right track.

Rich

wakehand

Made a bit of progress this evening, wing ribs are now in along with the shear webbing. Everything was relatively straightforward but I do have a few questions. I've been primarily using Zap medium CA but have some reservations around its strength. I went over some of the joints with wood glue to create a fillet, in the hopes that this would add some structural reinforcement... Though i'm also a woodworker and I know this type of glue joint is very weak. What's the balsa building consensus here? Should I go over CA joints with wood glue? Or am I wasting my time? Also this little gem came in the mail today, a .72 saito 4 stroke, hopefully it's not too much power for this bird.

Hydro Junkie

The CA is more than capable of handling the load, adding more glue just adds unneeded weight. You have to remember, wood glue isn't a structural product. For epoxy to become a structural product, you need to add other things to it. A general rule to build by is that any weight that is added after the fact is your enemy. I probably would have cut lightening holes in all the ribs to make the structure lighter but, that said, you have to be careful to not take so much as to weaken it.
As for the engine, the plane is designed for a .40 to .54 four stroke. The issue here is going to be prop clearance. A four stroke can swing a larger prop than a two, but at less RPM. To keep it loaded properly, it will need around a 12X8 prop where an Evolution 46 would only need an 11X6. To use a smaller prop on your 72, you could go to a three blade and drop it down to a 10 to 11" prop

jwrich

My Feedback: (17)

The work on the looks very good. I primary use CA (medium& thin) and epoxy. I think the instruction will tell you where you need to use the epoxy. Many modelers use the tight bond, I don't because of the longer drying time. Junkie is spot on with his advice, again read the instructions. His advice about the engine very good, I never used a 4 stroke engine, long ago I did use 2 stroke glow. The past 25 year I fly giant scale with gas engines. I guess you could use larger wheels for prop clearance.

Keep up the good work and enjoy

Rich

wakehand

Good to know, I'll continue with just CA for now.

wakehand

I made modest progress tonight, all the spars are in, leading edge has been attached and wing rib 1 (which has the dihedral) is in place. I didn't like the die cut dihedral gauge sig provided, if you look at the attached picture you can see that there's some cupping when compared to the plan. I measured it out and it works out to about 93.5 degrees, which i transferred to my sliding bevel and then used to slant the rib.

jwrich

My Feedback: (17)

Very good catch, you are using your head, You are going to be alright. Continue to post the pictures, we all enjoy watching your build.

Rich.

vogelm1

My Feedback: (1)

The .72 4-stroke was a good choice in my opinion. That engine will run like a champ after being properly broken-in and fine-tuned. And the fuel economy and awesome sound you'll have...perfect. Others provided great advice like running larger wheels, or using a 3-blade prop - all this will allow you to run that .72 on your trainer no problem (if one or more of those options are even needed). The best part is once you become proficient at flying your trainer, that engine can be taken off and flown on a multitude of other .40-.60 sized sports planes in the future. I went the same route when starting out and it was a great choice of a motor. Good luck!

wakehand

Thanks Vogelm, my next plane will be a sig cub 1/5 so I wanted an engine that could be used with both airframes. I've read that people have converted their LT-40's to tail draggers, which should buy me a little clearance or I could go down the 3 blade prop route. What would you recommend? Also, any thoughts on 3 blade prop sizes?

vogelm1

My Feedback: (1)

Others will chime in too, but I'd stick with the tricycle gear set up for now - much easier to start out with. You can always convert the LT-40 to a tail dragger once you are proficient; which will be a good next step toward flying the Cub. Tail draggers take a bit more focus and coordination when learning, so the less you have to worry about on take off and landing at first, the better.

You could see how much clearance you have with a two-blade prop - might be OK. I had a Saito .72 with 2-blade on my Great Planes 60 trainer and it was fine. If you decide to go with a 3-blade, I generally keep the same pitch, but go down an inch in diameter. So if your benchmark prop on the .72 is say, a 13x6, then go with a 12x6 3-blade - that should get you pretty close in the ballpark to same thrust/power.

wakehand

I'm really enjoying the building process. I've made rapid progress over the last few days, the 2nd wing came together much quicker than the 1st (now that I kinda sorta know what I'm doing). My list of basic questions is still growing:

1) Are all kits typically the same in how they're built? Upper lower spars, leading and trailing edges, shear webs etc? Is it relatively easy to open up a short kit and put it together without a full instruction manual?

2) The shear webs appear to have shrunk along the grain, creating gaps between the spars. I've filled these in with wood glue and overall I believe the structure to be solid. I'm guessing most modellers check each part for fit and either sand or remake anything that doesn't fit?

3) Any suggestions for a good field tote and contents? A local hobby shop sells options from sig, hobbico and hanger 9, would like to get thoughts on what works best here.

Thanks for following along, happy to be part of this community.

Hydro Junkie

1) Are all kits typically the same in how they're built? Upper lower spars, leading and trailing edges, shear webs etc? Is it relatively easy to open up a short kit and put it together without a full instruction manual? For the most part, yes. When you start adding built up ailerons and flaps or retracting landing gear, things start to get more complex. On top of that, each designer has their own way of doing things so there will be variances. As far as building without an instruction book, you might want to get a few more full kit builds under your belt before trying it. I would also mix the manufacturer of the kits as well since GP, Sig and Hobbico may not all do things the same way. In my case, I build scale boats from plans without having instructions and, from time to time, there are things that do require a bit of knowledge in design and building that someone doing their first build wouldn't be able to do without experienced help. This is where the manual is invaluable to a new builder such as yourself.

2) The shear webs appear to have shrunk along the grain, creating gaps between the spars. I've filled these in with wood glue and overall I believe the structure to be solid. I'm guessing most modelers check each part for fit and either sand or remake anything that doesn't fit? As I said in an earlier post, WOOD GLUE IS NOT A STRUCTURAL PRODUCT, IT'S JUST ADDED WEIGHT!!!!!!!!!!!! When making parts, be it a plans build or replacing missing or damaged parts, ALWAYS cut over sized and sand to fit. You can never be sure the wood is the same size and shape as when it was cut due to drying or absorbing moisture. You also have to remember, a die cut kit may have been cut with worn dies so the parts may not be accurate to begin with. One other thing that many experienced woodworkers will tell you is that it's actually best to store your wood in the area you are going to build in for a couple of weeks before starting your build so that the wood can stabilize to that environment.

3) Any suggestions for a good field tote and contents? A local hobby shop sells options from sig, hobbico and hanger 9, would like to get thoughts on what works best here. This is where it's actually best to go to a flying field and see what everyone is using. Some like a two piece tote where the battery box can be separated and taken to the start up area while others want a tote that they can take everything they may need. This is really a matter of what works best for the person using the tote.

jwrich

My Feedback: (17)

Steve, a lot of the questions you have are common. Most of them will be answered when you meet guys at the club meetings and at the flying field. Sooner you get with a local RC Club the better. You will meet some very friendly people who will welcome you into the hobby. Keep asking question here, Hydro is excellent in answering you questions. This is a wonderful hobby and I have met some great guys & Gals and had a lot of fun.

Rich

Hydro Junkie

Rich, I appreciate the vote of confidence.
When I answer a question, such as the sheer web one three posts back, I actually look at the situation from multiple backgrounds. Since I do build planes, I have had to deal with balsa that's dried out or swollen. By letting it sit for a period of time, it's normally possible to use this material. By the same line of thinking, PAPER expands and contracts with moisture and age as well, meaning that a plan sheet might change size by as much as a quarter inch over night if humidity increases. I found this to be the case when building a boat years ago. I had traced out some parts and, when transferring it to the wood, found the paper had expanded due to an increase in humidity. Needless to say, the parts didn't match when they were cut out so I had to scrap everything

wakehand

Ah a boat builder, which design did you build? I'm going to tackle an ilur dinghy one day Ilur ?Clinker-kit? | François Vivier, naval architect, once the shop's set up and I've acquired enough clamps.

On the topic of shear webs... I've noticed that other LT-40 builds show laser cut shear webbing, whereas mine were pre-cut and bundled together with a bit of plastic wrap. Perhaps I have an older version of the kit or maybe the person who owned it before me messed with it (it was an ebay purchase). I'm reasonably confident that I don't have a structural issue but I might make a small modification. I have some thin maple veneers (slightly thinner than a business card) which i may tack to the sides of the spars. The weight penalty would be relatively small in relation to the added stiffness...

Hydro Junkie

Nothing as big as that. I build and race sport 20, sport 40 and scale unlimited hydroplanes. Here's a picture of one of my sport 20 boat builds. It's based on the 1973 Pay'N Pak and built from a Dumas kit, using the kit parts for templates and then highly modified:

And this is the boat I've been racing the past several years, not one I built but it does run fairly well:

I'm presently building a replacement of the Elam above, a 1985 Executone, a 2015 Oberto/Miss Madison and a pair of Paks, one 1/8 scale and one gas scale as the 1978 Miss Madison