LukeZ's '69 U-7 - a bit late, but still fun

[LukeZ]

Hi all,

If you don't already know, I stumbled across this competition after it was already over. But I saw the plans were free, downloaded them, and have since gotten excited about building this boat.

There is a nice pond near the apartment where I recently moved to, and being into all things RC I decided I should get myself a boat to take advantage of the water. Having never done RC boats before I didn't even know where to start. Tower Hobbies was selling some plastic-y looking stuff, some of which was cool, I guess, but I hate to dump a load of money on a completed model. No, I prefer to dump a load of money on something I have to slave and sweat over. Eventually I came across a thread by Kmot over on RCGroups and from there I found my way here. I had not thought to imagine one could build a very fast and very nice looking boat out of balsa (my prefered medium), but once I discovered the possibility I knew that was the route for me.

After my first few posts here, somebody noticed that I live in the same general milieu of Garry Finlay and other notables and highnesses. I have been welcomed heartily by all of them and today I even got to see the Finlay shop first hand. There's probably not a lot of guys who, about one week into the hobby of RC boats, get to pester the big man himself with questions. Clearly I'm getting off to a good start...

Anyhow, that's it for background - here's my build thread. I know during the contest some threads were strictly for posts by the builder, but seeing that the contest is over, and that I'm a newbie, I'll welcome and appreciate anyone's comments or advice here.


Luke

[LukeZ]

First step in my build was to get the plans printed. I took them to a specialty printing shop and a few bucks later I'm good to go.

Although it's more work up front, I prefer to re-trace the plans onto posterboard which I can then cut into the individual pieces. This is because the posterboard is sturdier than paper and can be used as a template over balsa many times over. At the end of a build I can put all the posterboard pieces in an envelope, ready in case I ever want to build the same thing again. At any rate this has been my procedure for building airplanes from plans, which is where my experience has been heretofore.

So that's what I did - you can see all the necessary elements here: posterboard, carbon paper, pencil, french curve, straight edge, and sometimes masking tape to hold things still.


Luke

[LukeZ]

After the parts on the plan have been transferred to the posterboard, it's time to cut them out. In the past I used scissors for this but I have found them very difficult to work with. For one thing, it's impossible to cut a straight line for any distance with scissors. For another thing, it's impossible to cut a smooth curve with scissors. Therefore, scissors are best left for their intended purposes, such as trimming nose hairs and jabbing coconuts.

Instead of scissors I use an Exacto knife and cutting mat. For the straight lines I will use a straight-edge to keep the knife moving straight. The curved portions of a design I will cut out free hand. A french-curve is useful for tracing the parts, but a knife will track much more precisely than a pencil, so is not really needed for cutting them out. Also, most french curves I've seen are made out of plastic, and in my experience the Exacto knife inevitably knicks the edges, turning the beautiful french curve, in time, to something more like, say, a German or Scottish curve. In other words, it's no longer smooth and flowery.

With only a very small amount of patience and practice, posterboard templates can be rendered that are surprisingly accurate replicas of the parts on the plan - as you can see in the picture below (bulkheads A, B and C are the posterboard cut-outs, laid over the original plan).


Luke

[LukeZ]

After cutting out my templates I then cut out the actual balsa pieces. I had a bunch of balsa laying around from my airplane projects but come to find out, not much 3/32”, and not many sheets that were 6 inches wide. So I raided all the hobby stores in the nearby area, and as usual finding quality wood was very difficult. I am not sure what they expect us to build with the stuff they carry – abstract spaghetti art or something of the like. Probably they carry quality wood but no doubt it is snatched up very quickly (apparently 1/8” K&S tubing goes quick too).

At any rate I think I found enough passable balsa to get the job done and this afternoon I set to cutting out my parts. This went very quickly. There just aren’t many parts to this boat.

The model nearly falls together. I like how the front bulkheads interlock together with the stringers, it makes a very sturdy structure.

Framing up was going along real nice, and you can see how far I got before the dinner bell rang. And so I’m afraid that’s it for this weekend.


Luke

[Garry Finlay]

"get to pester the big man himself with questions"

Guess I should hit the old L.A.-Weight-Loss program .

It was great talking with you Saturday. You have a good start on this project. My hull didn't look that clean and neat when it was framed up.

Garry

[eddieh]

Talk to the vendors that are listed, might be they'll extend you the discount if your doing the building....worth a shot bud... who knows guys that finish up late maybe not alls lost, never know what pops outta the surprise box

nice job so far , get er done

[raptor347]

That little guy is coming along nicely. I love to see clean building, even on the parts nobody ever sees.

You want to loan me those templates when you're done?

We could have a whole fleet of 30' Karlsons at the local pond.

[LukeZ]

Thanks for the encouragement guys. Brian, you're welcome to the templates if you want them. Not sure they'd be good for 30 cuts, but probably a few anyways. I for one would like to see 30 hulls cruising around a pond.

I've checked out the vendors and in fact have already ordered from at least one of them. Actually I think I'm pretty well stocked on all the things I need to finish this guy, except for two things: I still need a 5mm to 1/16th coupler, and if it's needed, one of those drive shaft bushings you were showing me, Garry. I've looked around for these online but haven't been able to find them. Do you know of a source? I've also been to Tammies and RC Modeler Northwest (out on 170th and TV Hwy), they don't have 'em either. Does that other shop downtown carry this stuff, do you recall?

The only other thing I need to decide at this point is a paint scheme. The Notre Dame colors look clean and neat, but seems like we already have a few of those around here. I was looking last night and the Miss Bardahl looks pretty nice. I'm also open to ideas...


Luke

[raptor347]

Luke,
Unfortunately the local shops don't carry much for boats, even less for FE. You'll need to order the coupler, pick a vendor. What bushings are you after? If you're looking for 1/8" shaft bushings, I've probably got some in a box somewhere.

I'll take you up on those templates. The design is actually a 30' Karlson. 30 boats on our little pond would probably be excessive

[Garry Finlay]

Hit Roger Newton’s site: www.newtonmarine.com – Plans - 101 for a list of Karelsen hulls.

And, when I am done with the work on the house, I will toss together a few items that will duplicate the drive tube, bushing, strut that I have on my little N.Dame. I think I have a spare 5mm – 1/8” coupler too. Between us Oregonians, we have you covered.

Garry

[LukeZ]

Garry - thanks for the link. There are some good photos there. The Timex also looks interesting. So many choices! I'm planning to use my Paasche airbrush to paint the boat. It's new and I've not used it before. I need to get some practice with it before I paint my Short Solent, so this will be a good project for it.

You're right, I guess I could also use a 5mm to 1/8th coupler, instead of down to 1/16th. Just slip a bit of that stainless steel tubing over my piano wire and file a notch in it, like I would for the prop end. Offshore does in fact have that size, so I could get one there. Twelve bucks seems a bit expensive for it, but I guess it would cost even more for a lathe. I think maybe the Offshore ones are that high because they're for flex shafts? ...but it seems like it should work the same.

Anyways, I don't want to get ahead of myself too much. I had a real bad case of the balsa allergies yesterday, but I'm hoping to get some work in this evening.


Luke

[Garry Finlay]

I have a spare 1/8 - 1/8 coupler and the tubing to reduce to 1/16. And I have the K&S .062 wire and brass to make the strut, stuffing tube and prop-end bushing. This weekend, if it is not too hot to work in the garage, I will start piecing things together. It will be a welcome change from caulking the tub, painting the walls and hanging towl racks.

[LukeZ]

Garry thanks for the help. Although, other than the coupler and bushing, I think I have all the tubing and brass sheet I need to put most of this together. Certainly I want you to get a break from caulking the tub, but don't make it too easy on me! At the very least I will still make up a drive shaft and compare it to yours.

The hull is coming along - I'll post some pictures in a minute.


Luke

[LukeZ]

The next step after leaving off the other day was to glue on the rear non-trip stringers or walls or whatever they're called. Why are they refered to as non-trip? There's a lot of boating terminology here that I'm not familiar with....

[LukeZ]

Next came the sponson bottoms. These were the only parts so far that I had a bit of trouble with. And trouble really isn't even the word for it, it was so slight.

So far as I could tell from the plans, the sponson bottoms are to be glued on the bottoms of the front stringer and bulkheads. However, on my assembly, the front stringers extended down below bulkheads A, B and C by about 3/32nds. In other words, they weren't flush. I checked them against the plans and I think I cut them out pretty close, but perhaps I didn't assemble the stringer and bulkheads tightly enough.

At any rate, for me to get a flush surface for the sponson bottoms, I would have to sand a strip off the bottom of the front stringers. I figured I would probably break something with all that vigorous sanding, not to mention alter the angle of the front stringer in the process. So instead I decided to strip a 3/32nds piece off the side of the sponson bottoms, making them a bit narrower. Then they could be glued to the bottom of the bulkheads, but instead of being underneath the front stringers, they would abut them.

Unfortunately I didn't take too many pictures of this. But here's one of me removing the strip from the sponson bottoms, and then a rough diagram of what I'm trying to describe...

[LukeZ]

Anyways, no big deal there, and after the sponson runner/doublers are attached, you won't even be able to tell.

Here's a few more pics of finishing up the hull. The deck comes next but before I attach it I'm going to seal the wood in some of the cavities that will be hidden by the decking.

This thing goes together pretty fast. If the parts were laser or die-cut I think a person could easily complete the basic hull in a single day.


Luke

[LukeZ]

Don't mean to give anyone vertigo on that last picture... it will let me upload 800x600, but not 600x800. Gotta love technology.

Luke

[LukeZ]

Haven't had a chance to work on the boat the last couple days, but if I can keep my mind from frying in this heat, I will try to seal the inside and finish up the decking this weekend.

I have several options - currently I have some water-based polyurethane (by Varathane), some oil-based polyurethane (Minwax Spar Poly), and I also have some Z-Poxy resin that I hear a lot of people use thinned with denatured alcohol. I think I've ruled out the water-based poly because some have said it can warp wood, in addition to which glue supposedly do not adhere well to wood treated this way.

Is there any advantage of the oil-based poly or the thinned resin methods? I know people have used both so I can only assume the wood will still accept glue after these treatments - specifially I'm thinking of the underside of my decking, which will have to be glued after sealing, unless I'm missing something...


Luke

[Garry Finlay]

I’ve use Z-Poxy. But here is a tip that some do not buy into. I just seal the interior that is exposed (inside the “inside-stringers” only). This will save a little time and work – and a half ounce of weight. The theory is; the area between the bulkheads will not see moisture, hopefully. It has not been a problem on any of my hulls.

I have a spare 1/8” – 1/16” coupler. And I have some K&S brass for bushings for either 1/8” or 3/16” stub shaft. I’ve used both sizes for 1/8” prop shafts for this type boat.

It was too hot to do anything serious, other than study boat plans.

Garry

[Darin Jordan]

I used the Water Based "Spar Urethane" by Varathane on the entire inside of mine, prior to putting the deck on... Just a normal coat... When it dries, it weighs next to nothing but definately seemed to add some water resistance... If you are going to race this, then at some point, you are likely to take on some damage to the exterior which WILL let in water... If you are just sport running, you shouldn't have a problem...

On the interior that is exposed through the hatch cover, I used a thin coat of finishing epoxy... Helps the velcro stick better and I think it adds a measure of strength and eases cleanup... Basically makes it shiney and smooth inside so it can be wiped down easily, and you WILL get water in here to some degree, as well as shaft lube, motor lube, etc...

I haven't weighed mine since it's completely painted, so I'll do that and we'll see where it is... It feels light enough for a race rig... I'll post some numbers when I have them...

GOOD LUCK!