c.snook

hey guys im building a boat on a budget so i went to wally world the other day and bought a cheap 25cc weedy, so im goin to stick that in my 46in boat...anyways im wanting to build an exuast for it so that the exuast comes out the rear of the boat....is this a good idea, if i would of had one of those races engines i would have just bought one, so i guess my question is, i will need to make my own header and all that, do you guys think this is a good idea, im just wanting to open up this cheap motor so i can get some speed out of it!!

thanks for all of your guys help

TERBObob

My Feedback: (21)

From my own personal experience ....
finding the right tuned pipe ( whether you make one or buy one ) for a weedie is a HARD task .
There is a program that tells you ALL you need to know ( as long as you enter the correct numbers for that engine - exhaust timing , intake , etc , etc , etc ) and then , it STILL would be a major chore .

IMO ... run the engine with s gutted cannister muffler with TWO stacks coming out . ( make the pipes 1.5 times the size of the original opening and make TWO of them for the two tubes/pipes sticking out the top of the cannister muffler )
This would not only give you the cheapest best performance , but , also keep the inside of your hull , semi-clean

Most weedies only put out aprox .75 up to .9 hp with only 9k RPM's .
When compared to the Zenoah and Sikk ( CY ) engines , this is like running a VW beetle engine in an Indy car .

Don't get me wrong ... weedie's make GREAT fun runners ... but don't expect to break the sound barrier .

c.snook

ok so what you are sayin is too keep the stocker, and just run 2 pipes coming out of the stocker, out into the air so it is out of the hull???/

does that make any sense, ok basically make my own tube style exuast, using the stock header

TERBObob

My Feedback: (21)

Well ... kinda .
Heres a pic of what I am referring to :
[link=http://www.easycart.net/whobbies/images/EX1030_lg.jpg]WWH cannister exhaust[/link]

heres one mounted on an engine:
[link=http://martysrcboats.com/pix/bille.jpg]Pic from MARTYs site[/link]

Tidnab

My Feedback: (51)

What brand of weedie is it ?Some don't have a bolt on canister exhaust,but one held on by springs,which would require something like this http://slappy.org/~john/macexhaust.htm I had the original exhaust canister modified as TERBObob sugested on my modded Ryobi/Homelite engine,with two stacks coming out the top,but decided to change it to a muffler that would be inside the boat.I bought the header and manifold already made as I don't have brazing skills.The rest is made of 1 1/2" aluminum tubing with a 3/4"x1 1/2" reducer adapter on the one end and an aluminum cap I found on the other end.It has a 3/4" copper tube through it with 5 rows of 1/8' holes in it the length of the inside of the muffler.with a 3/4"x1/2" reducer on the inside to form the exit pipe which is attached to the exhaust tip on the transom by 1/2" id silicone liner heater hose.It also has a water exit tube on the end to dump excess water.I made mine 10" long to fit inside my crackerbox ,but it can be made any length to fit your hull.Haven't tried it on the water yet ,but sounds nice running on the stand.

TERBObob

My Feedback: (21)

Very good .... Nice cracker . Any more pics ?
You could also use a small mouse' can ( or small aerosol spray can of any kind ) and simply pull the part that sprays out , off the rest of the can and use some JB Weld to seal up around the hole when you put your tubing in it . And for the bottom , simlply drill a hole the size of your exiting tube out the back and also JB Weld it place .

Tidnab

My Feedback: (51)

I was going to use a WD-40 can but came across some 1 1/2" tubing that was a candle holder at Wal Mart's clearence isle.Here's more pics of the Dumas cracker and there's one in the boat stand post also .I have a Dunlap cracker also but it was to many pics to load on dialup.

c.snook

those drivers have huge booooobies...lol

DONS BOAT WORKS

My Feedback: (3)

I hope they have calm water. they could get a black eye.

coyv10

Hey I want them to come over to drive my boat..

Fredi28

Hey Tidnab, love the look of that crackerbox, you did a great job with it....How do you like running the crackers? I am just beginning my venture into the rcboat world and have plans for a dunlap cracker myself. ANy advice for a novice such as myself? i can only hope mine looks half as nice as yours.

Tidnab

My Feedback: (51)

Hi Fredi28,Thanks for the compliments.I started r/c boating with a big deep vee and it was a little boring,it did everything I wanted it to and I decided to get something give me a challenge.The crackerboxes are a challenge to get used to ,they bounce around,flip(barrel roll) in the turns if your not careful and sometimes do even if you are careful,but they are definatly not boring.The red crackerbox is a Dumas from a kit that I built and after that I built a Dunlap from the plans.The frames on the plans aren't equal from one side to the other.Redrawn frames are on http://groups.msn.com/OxfordCountyCrackerboxes/home.htm in the miscelanious section.Print them out and take them somewhere that has a large printer and tell them to increase them 170% and they'll be about right on.On the bottoms,sides and deck parts alow a little extra on the edges which can be taken off with a hand plane.Follow the pics on the OCC as the crackers are what they specilize in.Good info there and here on RCU.Here's some pics of my Dunlap.I don't have a prop or exhaust on it in the pics.

Fredi28

Thanks for all that info, I will definitely take your advice and go to that sight....I love the way your Dunlap model came out, looks very very nice. What type of wood did you use? I am going to use mostly balsa, with some plywood for the transom pieces, and then cover the balsa with fiberglass sheeting to strengthen it. Also, what type of electric motor and prop would you reccommend for me? Hope to hear back soon.



Mike

Tidnab

My Feedback: (51)

Mike,The use of balsa in a crackerbox wouldn't be very good as balsa isn't suited to wet conditions and wouldn't take the abuse that aircraft grade plywood can take even if you use fiberglass sheet.Use 1/8" thick plywood and you can use 1.5 oz fiberglass cloth if you want or do without it and coat with an epoxy finishing system such as West System,Pacer Z Poxy or Northeast hobby Products then sand with 600 grit wet sandpaper,prime and paint.You can get plywood from www.balsausa.com or www.aircraftspruce.com The epoxy from Tower Hobbies or Aircraft Spruce or your favorite hobby supplier.As for putting electric in that size boat,I wouldn't know about that as the only ones I 've heard of were gas powered,either a trimmer engine or a Zenoah or Sikk marine engine.You can get smaller crackerbox plans for electric power at http://www.rcstore.com/ME2/dirmod.as...s&ntier1=Plans or scale down the Dunlap plans to use electric.If you go gas power try a Prather 275 and then experiement with others.There's cheap McCulloch engines at http://www.staton-inc.com/Results1.asp?Category=13 Sorry c.snook for taking over your post.

Fredi28

ohh ok, thanks for the advice....i will let you know how everything turns out