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ADVICE ON A NEW BUILD PLS

Old 02-15-2006, 04:24 AM
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so54i88
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Default ADVICE ON A NEW BUILD PLS

hi everyone, it's great seeing there are some many people out there enjoying building from scratch. i think it's the way to go. thanks heaps to those people who helped me sourcing boat plans. i'm going to start building my 1st boat. as i'm a newbie, i'll need some advice on building. i've got different ideas and questions. i hope it's not a nuisance to anyone. any advice is very much appreciated. well, here they are:

when they say ply, do they mean any kind of plywood you get from a building supplies store or some (expensive? []) special stuff?

i'm still trying to figure out the best way to waterproof the inside and outside. i think making a mould and fibre glass the whole hull is bit too advanced for me (well, at this stage anyway) but i'm thinking to lay a thin sheet of fibreglass on both inside and outside. is it a way to go? i hope it also adds a bit more strength.

as i'm on a limited budget, i'm thinking to try and make most of the hardware possible. is it really necessary to have a flex drive (i think this is what it's called) coz it's REAAAAAAAALY expensive? [&o]

what would be the best stuff to use to glue the hull? epoxy or some other special glues?

as this is going to be my 1st boat, i'm going to keep it small, well maybe somewhere around 25-30" as i'm going to use a 2.5cc with a pull start. is it a realistic size for a 2.5cc coz i dont really want a "shopping basket"

sorry guys, have been brain storming as i write until i realised it's a bit long now. any advice/thoughts are very much appreciated. cheers
Old 02-15-2006, 05:24 AM
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Matty_c
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Default RE: ADVICE ON A NEW BUILD PLS

well for the waterproofing: on my crackerbox iam going to cover the hull inside out with polyurithane varnish.

for a flex drive from the hobby shop shouldent be to much the hobby shp neer my house they are like $20-$30 for the shaft then youl need a dog drive for it. for the dive on your boat it will be proably $80-$90 just my estimate but its not necesary to have a flex shaft.
someone else will probaly know more than me so its just my 2cents.


keep us posted.


Matty_C
Old 02-15-2006, 09:40 AM
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Default RE: ADVICE ON A NEW BUILD PLS

For construction purposes DO NOT USE ANYTHING BUT AIRCRAFT GRADE BIRCH PLYWOOD!!!!!!! Construction typically requires 1/16" for the skins and 1/8" for the bulkheads with the exception of the transom and engine mount rails which are 1/4". If you are weight conscious you can use 1/16" for the bulkheads but monos tend to have to few bulkheads to support that type of construction. 1/8" square spruce is used for reinforcing and supporting joints where required on the skin to skin and skin to bulkheads. Use fiber glass cloth to reinforce the engine mount rails to the bottom and the inner keel seam. Use only SLOOOOOOW set epoxy for construction and sealing both the interior and exterior. Do not use 5, 10 or 30 minute cure epoxy. You will not get penetration into the wood but you will get a weak joint. I'd recommend West Systems 105 with 206 catalyst or something similar from System 3. Check out Lone Star Balsa or National Balsa for plywood and spruce strips. You can try a Home Built Aircraft supplier also but I've found that they tend to be more expensive. The epoxy is usually available from a marine dealer.
Old 02-15-2006, 12:08 PM
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Default RE: ADVICE ON A NEW BUILD PLS

Well said John. I'd like to add, that glassing inside and out is a total waste of money and time. You are adding extra weight and expense for no reason. By glassing where John suggested, you will have a strong enough hull for most conditions. A THIN coat of epoxy on both the inside and outside is a good base for your paint job, as well as water proofing the ply, not to mention it's also fuel proof.
Old 02-15-2006, 02:36 PM
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so54i88
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Default RE: ADVICE ON A NEW BUILD PLS

that's great guys. thank you so much for the advice. i'm going to get the wood today (hopefully) i know a model shop in town who might have what i'm looking for.
Old 02-15-2006, 03:49 PM
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Default RE: ADVICE ON A NEW BUILD PLS

Although I fully agree with supporting the local hobby shop, I suggest you compare prices with the wood specialty places like Lone Star and National Balsa. You may find a substantial difference in price.

I think you're about right with the engine size. As far as the drive is concerned, I don't think you can get any cheaper than a flex drive mounted through the base of the transom (Surface Drive). All you will need is a length of brass tubing secured into the hull and extending out the back. Any other drive will require a strut that adds about $25 to the cost of the boat. You can't avoid a drive collett on the engine or the prop and drive dog. There are photos of my boat in a thread that discusses building a Wild Thing. Ross MacLeod started the topic. That boat has a surface drive. Search for "Wild Thing" Construction Pictures, then post #34.

Now, since you are in New Zealand. Where? I am also an airplane modeler and I'm building a 1/4 scale Tiger Moth. The color scheme will be patterned after ZK-BRC, the Mount Cook Lily. The airplane is still listed with the New Zealand CAA, registered to John Hargest at Gore on the South Island. Are you anywhere near there?
Old 02-15-2006, 06:52 PM
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Default RE: ADVICE ON A NEW BUILD PLS

If you order the wood be careful on how much shipping will cost you, where I live the shipping is more then I pay for the wood LOL. The local hobby shop may be cheaper they get it in balk and some times get a discount for being a biasness they will mark it up so they can make money but it may be the same price as the supplier would sell to you and you don’t have to pay for shipping do some looking around. Some of the local hobby guys may have some lying around to if you no any ask them about it or at lest where they get there wood from.

You can use other wood as well but its not as nice to work with, it will warp faster, its not as strong, probably heaver, and will lower the quality of your boat a bit but its farley available and cheep if you’re lucky free

If you do use other lower grad wood keep a look out for stuff you can some times find some nice wood just lying around. Some of the gas guys use old doors the ones with the card board in the middle (cheep interior door) they just rip them apart its not that good but if its all you have or can afford it will work but make sure you seal it riley well it will warp and soke up water more then the hire grad stuff.

There is no hobby shop here at all the closest is a 16hr drive, only thing I have is a Radio Shack off shoot. The owner supply’s some of the local air craft guys with stuff he is a hobby guy him self but I got some wood off him for $1.00 it was nice 1/16" 3 ply from over seas bout 2'x3' piece its not as hi grade but it will do for me he got it off of some packing from his store.
Old 02-15-2006, 10:46 PM
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so54i88
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Default RE: ADVICE ON A NEW BUILD PLS

thanks guys again for the advice. i have ordered some ply which will hopefully arrive tomorrow. for 2 sheets of 2mm ply it cost NZ$26 plus $6 shipping. not bad really. cheaper than me local store. but i'm going to support my local store and get the 6mm (or 1/4in) ply from there. i contacted a fiberglass place who stock heaps of fiberglassing materials and that phone call got me confused. apprarently there are epoxy glues as well as epoxy rasin. SILLY ME!!! i think John meant EPOXY RASIN. didn't you John? well, i'm in North Island. have also wanted to go to the South, it's absolutly beautiful down there. might try out this new boat in SI. emmm.....now that's a tought
Old 02-16-2006, 08:51 AM
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Default RE: ADVICE ON A NEW BUILD PLS

Take a look at the West Systems web site and get their information on Epoxy. Typically epoxy used in our boats is a resin and catalysist combination. That is the interpretation in this half of the world. There is a common term for an epoxy used to seal the surface of airplane wings and fuselages when the plane is covered with 1/2 to 3/4 ounce fiberglass cloth. That product is commonly called surfacing resin. It is an epoxy product but does not have the strength of the West Systems Epoxy. It is formulated to fill the surface prior to painting and it sands very easily. I would not use surfacing resin for construction but I have thinned construction epoxy for surface sealing. Using the terms your supplier has given you, I would lean towards the "Epoxy Glue". Have them explain to you the difference between their "glue" and "resin". It will likely be the same as I have explained.

As for the type of wood issue, here is a good analogy. If you have good food available you eat good food. It there is no good food readily available, you are likely to eat garbage to stay alive.
Old 02-16-2006, 03:21 PM
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Default RE: ADVICE ON A NEW BUILD PLS

lol ya your analogy with the wood is vary true but its what you do with what you have that counts
Old 02-18-2006, 06:42 AM
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so54i88
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Default RE: ADVICE ON A NEW BUILD PLS

yea that's right. now a question. what do you do if your "trusty" local model shop sells you a piece of 8mm ply and told u is 6mm (just becasue it's precut to the size i wanted) AND SILLY ME angain [:@] that i didn't check the thickness until the bulkheads were all cut and went back to get more ply which i realised that the "new" 6mm ply is thinner. can't be angrier. just hope that the 8mm is better than 6mm but it surely adds bit more weight?
Old 02-18-2006, 07:48 AM
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Default RE: ADVICE ON A NEW BUILD PLS

You should be using only 6mm or in your case, 8mm ply for the transom and the engine mount rails. The other bulkheads can be 3mm. The skins are 1.5mm. If you cut all of the bulkheads from 8mm you'll have a boat that is heavier than it has to be. Just chalk it up to experience and continue your build. Now you have enough wood for your second boat.
Old 02-20-2006, 09:58 PM
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so54i88
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Default RE: ADVICE ON A NEW BUILD PLS

You are right John, I have plenty for my next boat. But just wish that the local model shop can be a bit more honest. [>:]Would you think it’s a good idea to cut some holes on the bulkhead? I have taken your advice on the Epoxy. I went and got some West System epoxy. I also got some filler as the guy at the shop told me it’s better to add a bit of filler as the epoxy alone might be a bit too thin.

Anyway, enough that. I have done all the cutting work (I know I’m bit slow on that). And it seems the radio box is quite small. I’m not too sure if you only keep the receiver in the box or servos go into the box as well. The more I look at it the more I think it’s toooooo small. Also I wonder if anyone can please help me with some measurements of the base of a typical 2.5cc engine coz again the more I look at the space between the engine rails the more I think the engine will not fit. [&o] I have not got my engine yet so I just wonder if someone has a 2.5cc engine. Thanks a lot.
Old 02-21-2006, 09:20 AM
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Default RE: ADVICE ON A NEW BUILD PLS

Lightening the bulkheads by putting "Lightening Holes" in them is commom practice. Especially with hydros. Just be sure you seal the interior well before you put the deck on and plan ahead for some floatation. Block expanded bead styrofoam has been my favorite. When you cut it, you and the immediate area get covered with little white beads. But it's water proof and easy to shape to fit into compartment. Do NOT use the expanding foam. I think you have heard that or read it elsewhere before from HJ and that is absolute gospel. As for the viscosity of West System epoxy, it does tend to run but I have never seen the need for filler where general construction is done. It's thick enough to stay in place when parts are fitted properly. I do use micro balloons to form filets on the exterior inside corners and to fill gaps that always seem to appear after the epoxy has cured.

As for the radio box, the servos should be inside with the receiver and battery pack. Considering the fact that todays servos are pretty compact for the torque output they deliver, you should be able to get everything into a reasonably small box. My latest Sport Gas Hydro radio box is about 130mm square and I have more than enough room for two servos, receiver and battery pack. I would suggest a HiTec HS 81 servo for the throttle and an HS 225 for the rudder. Contrary to common belief, the rudder on your size boat can be handled by a standard 40 oz. in. servo. The HS225 puts out about 50+ oz. in. You don't need high torque for a small boat.

The engine mount rail spacing is dictated by the engine mount, not the engine. I'm not familiar with engines below 3.5CC but you may be able to get the mount dimensions for the engine from the manufacturers web site. Look at the Rossi Sales web site (http://www.rossisales.com/ )for good quality mounts, rudders and struts.

Ron, please chime in here and give some advise about "Little Engines".
Old 02-21-2006, 09:28 AM
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Default RE: ADVICE ON A NEW BUILD PLS

you dont need to use birch ply any good outdoor grade ply will do the job dont need to get expensive birch ply although it is good any outdoor grade ply will do the job!!
Old 02-21-2006, 11:47 AM
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Square Nozzle
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Default RE: ADVICE ON A NEW BUILD PLS

I saw a sign in an auto parts store that fits this plywood discussion perfectly.

"Buying auto parts is like buying hay, you can buy good stuff or you can get the stuff that's been through the horse.

Enough said.
Old 02-21-2006, 12:12 PM
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Default RE: ADVICE ON A NEW BUILD PLS

martno1fan, I tried the door skin route ONCE. I'll never make that mistake again. It splintered and cracked to the point it wasn't usable. I found very quickly that it doesn't bend at all, making it useless for skinning a boat. Worst of all, it also soaks up water like a sponge, meaning that a scrape in the finish will destroy that piece of wood within minutes. Do yourself a favor and use birch ply. The time, money and boat you save will make the extra cost worth it

Just got to thinking. The plywood from the local home center is only 3 ply until you get to at least 1/2 inch(12mm) thick. It also has many voids and knots in it. The aircraft grade birch can be purchased with 5 plies starting at 1/8th inch(3mm) thick. This makes the birch stronger than the home center varieties. To take it one step further, unless you buy the outdoor type of plywood, the glues aren't water proof, so you have to spend more money anyway to get the water proof glue.
Old 02-22-2007, 06:37 PM
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Default RE: ADVICE ON A NEW BUILD PLS

hi, guys. i'm back. it's been a year since my last work on the boat. shame on me, really! [&o] i had a very very busy year with my job and all that. it's wonderful seeing those who have continued on more builds after the 1st. i'm now determined to get this boat finished. since the last post, i have received my engine and all gears apart from hardwares which i'm currently looking for on ebay. anyway, i'm back to it. will keep you guys posted.
Old 02-22-2007, 07:19 PM
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Default RE: ADVICE ON A NEW BUILD PLS

wow almost exactly 1 year and 1 day wow.
Old 02-23-2007, 10:06 PM
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Default RE: ADVICE ON A NEW BUILD PLS

got all parts ready to be glued and just realised that my servos are not going to fit in the servo box let alone receiver & batteries. maybe i downsize the plan to much. the transom is only 5.5cm high and 19.5cm wide. [:@] should have measure the servo before getting everyting cut!!! i'm thinking to increase the height of the boat say by 2cm will this affect the balance of the boat? does anyone have any suggestions please? thanks........................ HELP!!!!!!!!!!!!!!!!!
Old 02-24-2007, 12:01 AM
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Default RE: ADVICE ON A NEW BUILD PLS

I don't think 2cm is going to make that big of difference as far as balance goes. Just keep as much of the weight as low as you can.
Old 02-24-2007, 03:09 PM
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Default RE: ADVICE ON A NEW BUILD PLS

thanks for the advice. i actually found a way to mount the servos horizontally on the side of the radio box after trying different arrangements. i rekon it's going to fit so i'll keep the cut pieces and start gluing the hull. [>:]

i just want to check to see if i'm doing the right thing, since the size of the boat is reasonably small, it's going to be difficult to drill holes on stringers for engine mount, can i pre-drill for that? how do i tell where the best location is to secure engine mount on the stringer?
Old 02-26-2007, 02:55 PM
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Default RE: ADVICE ON A NEW BUILD PLS

i've never added pics to a forum so not sure if it works. but anyway, here they are. i have started to glue the hull together but realised that it warped a little. not sure if it's coz of the stringer being sitting in garage for a year or the joints of the stringer and bulkhead are too tight. but i came out alright after i glued it . it's curing slooooooowly.... hopely i did everything right, well too late anyway. here is a shot of the radio box and the servo i'm going to use so you guys can see what i was talking about that the box is too small. i'm going to mount the servos horizontally. any suggestions as to how far the engine should be mounted away from transom??

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Old 02-26-2007, 03:48 PM
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Default RE: ADVICE ON A NEW BUILD PLS

the Center of Gravity for boats should be around 30% of the length from the transom, so i would put the engine within a few inch's of that 30% mark, but you might need to move arounf the fuel tank to keep the CoG around that mark...
Old 02-27-2007, 06:55 PM
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Default RE: ADVICE ON A NEW BUILD PLS

update......transom and radio box are now glued to the hull, skills cut ready to be glued as soon as the transom is cured. i need to find a set of hardwares for the boat. any suggestions as to what i should be getting? i'll take John's advice on using a flex for the suface drive i'm going to have. i have found a rudder assembly on ebay for a quite reasonable price. but i wasn't sure about the sure. what size of the rudder shoould i be using? i'm going to try out some cheap plastic props first to see which ones are the best and maybe go from there. here is the engine i'm using it's ASP 15MX with pull start. it's brand new never ever been started yet....just hope it runs
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