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Building a Crackerbox step by step with lots of pics!

Old 08-01-2009, 12:20 AM
  #26  
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Default RE: Building a Crackerbox step by step with lots of pics!

I think mixing a little ammonia with water makes the balsa bend alot better. Not sure how it would work on this ply?
Old 08-01-2009, 02:25 AM
  #27  
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Default RE: Building a Crackerbox step by step with lots of pics!

Kenny thats a neat trickwhen i used to build full size boats some years ago we used a steam box to bend our wood when needed and its surprising how bendy wood becomes when its hot and damp.Your idea is very inventive im sure many will use that idea now me included cheers.Crackerboxsydney,sory i dont know your real name lol,if i were you id try this trick if you can get hold of a steam cleaner? if not you can use hot water.Just emerse the wood in it for a while then bend it clamp it in place and leave it till its cooled off and it should hold its shape somewhat.Let it dry out overnight before you start gluing and it should work fine.
Mart
Old 08-01-2009, 03:24 AM
  #28  
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Default RE: Building a Crackerbox step by step with lots of pics!

Agh bugger!i had a big old post all typed up and ready to go, and the session timed out or some nerdy error happened, and i lost it.
Anyway here's the gist: I'm Chris, from australia: G'day
Ican't justify buying a steamer so i'll do what i can with the various suggestions you've given me - thanks for all those.
Just finished all the non-bent stringers, here's some pics:
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Old 08-01-2009, 03:37 AM
  #29  
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Default RE: Building a Crackerbox step by step with lots of pics!

Chris we can get those small hand held steamers here for a few £ or $ to you or try the heat gun method.Either way im sure you will find a way, maybe hold it over the kettle just be sure to wear gloves or hold it in a rag .I still think get that thing in a jig now before you go any further and leave it in till you get the sheeting on.
Mart
Old 08-01-2009, 06:07 AM
  #30  
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Default RE: Building a Crackerbox step by step with lots of pics!

Hi Marty,
Over here the cheapest i've found is $20 on ebay, but its like $30 for shipping. Plus it'd set my build back a couple weeks waiting for it. Nice idea though, and i'd follow your advice honest if i built another one of these boats!
Regardless, i've come up with a just as good solution.
In the first photo, i've driven some wide+flat head nails into timber, in the shape that i want it bent.
Second photo shows how i hook the timber into the top nails, then i'll bend it down and lock it into a nail at the other end.
3rd and 4th photos show how i've blocked off a vacuum cleaner tube with a glove and filled it with boiling water, and left the timber in it for a coupe minutes.
Last photo shows the soggy timber locked into the nails.
In the morning, i'll remove the timber and see if it 'remembers' the bend.
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Old 08-01-2009, 07:22 AM
  #31  
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Default RE: Building a Crackerbox step by step with lots of pics!

Haha nice idea hope it works mate keep us informed.
Mart
Old 08-01-2009, 10:08 AM
  #32  
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Default RE: Building a Crackerbox step by step with lots of pics!

An easy way to do the chine stringer is to use 3-1/8"x1/4" pieces of whatever material you use for your stringers and lay them on top of each other and tack the one end together with some CA about 3/4" from the end.This is a trick used on the Dumas crackerbox instructions and works very well.You have to cut the notch for the chine stringer a little wider to accept the 3/8".It says on the instructions to start at the transom,but I started at the bow and angled the glued together tip to fit against the keel.As you get to the first frame you position the three piece stringer into the slot and while holding it firmly in the notch dribble some CA where the frame and inward stringer pieces meet.The pieces move against each other and bend as you position them.Keep going till you reach the transom and do the same at each frame.After thats all tacked in place go back and apply pressure with your fingers about every 3 " on the chine pieces and apply CA along the 3" section between each strip and continue along the whole chine till you have it all done.Make sure to apply CA to the frame/stringer joint.This method is only needed for the chine stringer because it is bending two directions at one time ,down and inward,toward the bow point.After you get you sheating on you'll reglue each joint and where the sheating joins the frames and stringers with epoxy glue or whatever you're using to assemble to add strength.
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Old 08-01-2009, 09:16 PM
  #33  
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Default RE: Building a Crackerbox step by step with lots of pics!

Sounds fascinating tidnab, i'm not 100%clear on what you're saying but i get the gist of it. And you've mentioned something i'm worried about - when the stringers bend in two dimensions. Oh well, i'm sure it'll be fine.
Anyway, took the bent stringers out of their confines this morning, and it worked pretty well!
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Old 08-01-2009, 11:45 PM
  #34  
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Default RE: Building a Crackerbox step by step with lots of pics!

OK now i've got those stringers glued into position. Ichose to use cable ties to hold them in place while drying, instead of string, because that way it was easier to hold them in place while i did some adjustments to get them just right. Also had to trim the front ends of the stringers with a stanley knife, so they come together to form a point.
Anyway, the front is beginning to take place which is awesome! My brother in law says mine is looking very 'boaty' now. Can't wait to finish it! Still got another weeks paternity leave to go, will i finish in time?
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Old 08-02-2009, 05:40 AM
  #35  
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Default RE: Building a Crackerbox step by step with lots of pics!

One thing you will need to do now before you get too much further ahead is to cut holes in your main frames so that you can get your internals (engine, pipe, radio box etc) into the hull. Once you have all the stringers done, dummy fit your internals to make sure you can get them all in there. Here's some pics from a build I did from sctrach a while ago.

ps, your stringer problem isn't as bad as what I had on that build, I had theb bandiung in 2 directions & twisting towards the rear. I used wet towels and an iron to steam them then quickly screwed them in place.

Here's my build thread if you're interested, it's a bit old now. I've changed the boat a bit since then (lots of testing & tweaking).

http://www.rcuniverse.com/forum/m_64...tm.htm#6406405
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Old 08-02-2009, 07:03 AM
  #36  
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Default RE: Building a Crackerbox step by step with lots of pics!

Dicko, i just read through your entire thread.Quite interesting! You've got me thinking now, i need to start thinking about mounting the engine. Maybe once i've sheeted the bottom i'll think more about that.
Glad to hear i'm not the only one stressing about bending the stringers!
Old 08-02-2009, 07:27 AM
  #37  
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Default RE: Building a Crackerbox step by step with lots of pics!

When you dummy mount the engine, make sure you have room to move it back & forward. Once the hull is finished, you'll need to mount all the hardware first, then adjust the engines position to get the COG right.
Old 08-03-2009, 02:50 AM
  #38  
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Default RE: Building a Crackerbox step by step with lots of pics!

Ok i've mounted the last of the stringers. This time, i simply heated them up in my boiling water +vacuum cleaner tube contraption, dried them a bit, zip tied / bent them in place, and epoxied them into place. Some of the other stringers that i only used PVA glue for have come loose, so i'm bringing out the big guns (epoxy). Ifigure if i don't use it in too many places, it'll be OK as far as encapsulating it in polyester resin goes.
Anyway, more pics. It's getting ridiculous, i've got 6 stringers meeting at the front now!
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Old 08-04-2009, 01:32 AM
  #39  
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Default RE: Building a Crackerbox step by step with lots of pics!

Spent today finishing off bits and pieces to get it ready for skinning. I removed the tabs, and shaved lots of bits here and there to get everything even(ish).
Pic 1: You can see how i drilled big holes in the bulkheads for aeration when its out of the water, and for fuel / electrical lines.
Pic 2: I am having a lot of problems with some new brand of epoxy that i bought, it won't cure after 2 days. You can see the epoxy to the right of this picture. So i've glued in another bit of ply using normal pva glue, that'll hold the stringer i think.
Pic 3: The offending rubbish epoxy.
Pic 4: I cracked this piece when shaving it down (same on the other side) so i've reinforced it with some pine.
Pic 5: Here's my engine! I finally managed to re-wind the recoil spring. It was a PAIN.

Question: How much (bulk) epoxy should i buy in order to give everything 3 coats of it? 1 litre?
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Old 08-04-2009, 02:16 AM
  #40  
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Default RE: Building a Crackerbox step by step with lots of pics!

1 Litre should be plenty. I stear clear of any epoxy like that. Go to a marine store & pick up a litre of good quality epoxy, you won't be sorry, you will end up using it on future builds or even around the house.
Old 08-04-2009, 02:46 AM
  #41  
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Default RE: Building a Crackerbox step by step with lots of pics!

I agree try any marine store for your epoxy or better still if theres a boatyard near try them they just might let you have a litre for a few cans of beer especially if you catch them at lunch time when the boss is out .Are yoiu still planning on covering the outside with glass cloth? i hope so or you might regret not epoxying more of the joints on the inside.Ive used wood glue on builds before but i allways epoxy the stress areas and use cloth tape on seams on the inside etc.
Mart
Old 08-04-2009, 09:58 PM
  #42  
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Default RE: Building a Crackerbox step by step with lots of pics!

I'm thinking of no glass on the outside just resin, and using glass tape over all the joins on the inside, and using poly resin not epoxy as it is 1/3rd the price. Will that work?

Okay i've called around and the best place is FMSin Seven hills (http://www.fibreglassmaterials.com.au/)
I"m going to visit them in an hour or so, what should i have on my shopping list?

I'm thinking 2L of poly resin (1L for me and 1L for my brother in law) &hardener, and some fibreglass tape. Anything else i've missed?
Old 08-06-2009, 02:43 AM
  #43  
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Default RE: Building a Crackerbox step by step with lots of pics!

Okay now i've painted half of the boat before running out of time. Tomorrow hopefully will finish painting the rest with the resin. Seems to be OK to work with, although it does harden up a bit too quickly for my liking.
Also Ifound the fuel tank for the engine finally, i knew it was hiding somewhere! So i gave it some fuel and spent 10 minutes tuning the carby, and now it idles nicely.
Questiono you think i'll be able to mount the fuel tank under the engine like it's supposed to go, or will that mean my engine will need to be mounted too high in the hull?


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Old 08-06-2009, 03:39 AM
  #44  
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Default RE: Building a Crackerbox step by step with lots of pics!

From the looks of it, it may be too high to fit inside. Would have to test fit yourself. Ditch the weedwacker tank and buy one designed for r/c use. Lots of people are going for the IV bags, may want to look into those.
Old 08-06-2009, 05:09 AM
  #45  
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Default RE: Building a Crackerbox step by step with lots of pics!

Having built a few weedy powered boats yes you will need to remove the tank,you half answered your own question yes it will be too high.The tank is fine to use,in fact theyre very good tanks and usually fit snug between the rails,least mine do.Just be sure the tank vent isnt blocked,i sometimes drill a small hole through the vent in the lid.I cant seem to find a pic of mine in the boat so ive attached a pic of someone elses in a sprintcat,they fit well and work pretty much the same as any other tank plus they hold more than enough fuel .Usually the clunk is fixed into the tank at the far end so i sometimes pull this so it disconnects so when at speed your fuel feed line isnt left in an air pocket which can happen.If you remove the filler cap you will be able to see what i mean asuming yours is the same.
Mart
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Old 08-06-2009, 10:54 PM
  #46  
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Default RE: Building a Crackerbox step by step with lots of pics!

Sounds like fair advice on the fuel tank, as i suspected. Ok now i'll need longer fuel lines. Do i really need expensive tygon stuff? Or can i just get clear plastic tube from the hardware store?

Okay i've finished encapsulating it in resin, what next? Do i work on mounting the motor and driveline now? Or do i get stuck into skinning the bottom and sides?
Cheers
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Old 08-07-2009, 12:50 AM
  #47  
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Default RE: Building a Crackerbox step by step with lots of pics!

With as little fuel line as you will need I would buy the better type. But heck...if you think its easy to get at it shouldn't be a proble. I know my zippkit cracker has a pretty accessable fuel system. Its looking good, you will like running it...

Australia sure seems to have a strong presence in the boating community here on rcu !
Old 08-07-2009, 12:55 AM
  #48  
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Default RE: Building a Crackerbox step by step with lots of pics!

You will need tygon, cheap stuff will disolve in the fuel. I get my tygon line from the mower store, it's cheaper than the hobby shops & exactly the same stuff, they also have a range of diameters to choose from.

The boat is coming along nicely.

One other thing you may need is Q-cells to mix with the resin to make a bog/filler to use as a glue or filler to make the edges rounder which makes it easier to form the glass into, glass tape doesn't like conforming to sharp corners.
Old 08-08-2009, 02:35 AM
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Default RE: Building a Crackerbox step by step with lots of pics!

Good point foodstick, if its easy to get at then who cares if it breaks down. I'll stick with the cheap fuel line for now.
Dicko, i plan on using a lot of bodyfiller / bog / bondo on the outside to round it off nicely. My woodwork is far from perfect!
As for filleting the inside edges, i'll have to think about that q-cell stuff, sounds good.
Anyway, i've been working on my engine mount, and stringering my brother's boat, see the attached photos. For the engine mount, i've bought a $1 piece of metal from bunnings and attacked it with the angle grinder!
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Old 08-08-2009, 02:43 AM
  #50  
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Default RE: Building a Crackerbox step by step with lots of pics!


ORIGINAL: CrackerboxSydney

Good point foodstick, if its easy to get at then who cares if it breaks down. I'll stick with the cheap fuel line for now.
Dicko, i plan on using a lot of bodyfiller / bog / bondo on the outside to round it off nicely. My woodwork is far from perfect!
As for filleting the inside edges, i'll have to think about that q-cell stuff, sounds good.
Anyway, i've been working on my engine mount, and stringering my brother's boat, see the attached photos. For the engine mount, i've bought a $1 piece of metal from bunnings and attacked it with the angle grinder!
All your outside edges should be sharp. You don't want any rounded edges on the hull, otherwise it won't handle well. On the left hand side of the boat you can chamfer the chine from the stern tapering to no chamfer about 8" from the stern. You want the stern to be chamfered about 1/4". This will help stop the boat barrel rolling in turns.

Using cheap fuel line may also damage your carb needles as when it degrades particles will shed off & block the jets causing headaches trying to start & keep your engine running. I strongly recommend tygon line.

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