Started on a new project, whuddya' think?

I weighed it (including decking) it will be 13 Lbs. ??? oz. without servos ETC. ETC. I was thinking of another chainsaw engine, but a Nitro wouldn't be out of the question. What size nitro though? what prop? I like the pusher type so I would be limited on prop sizes wouldn't I ? The last pic is what it should look like when it's finished. (still deciding on color)

DA gum ....

LOVE IT ! ! ! LOOKING GOOD ..... [8D]

What size nitro ? Well , figure if your planning on using a weedie engine , OR nitro , just convert the nitro engines size to match the output of the weedies prop .
Meaning - if the weedie you want to use , will push a 16X10 tri pusher , then the nitro should match it - like the one HAL , or myself done - around a 1.48 engine ( nitro )
Also aauming you are talking 2 strokers and not 4 stroker nitros .
Weedie's have the torque , whereas the nitro has has the HP . So , what you loose in HP , with the weedie , is where you gain the torque , which is why the same size prop is used

Anyway ... the smallest I would use for a hull that size would be a 90 and the largest - around a 1.48


Think of this also . Whatever size engine you would put in it if it were a water prop driven engine , that is about the same that you would use , for an airboat size hull . ( roughly of course )

<scratches chin, & thinks to himself that he's found a new friend>

I'm in the process of coming up with ideas for my build & saw your thread. How far along are you on this? I'm also currious to see how you plan on building the engine tower. Will it be constructed out of wood or go with aluminum?

My boat will utilize a G23 & like you, I'm currious about going with a pusher style v/s tractor.

Last question: You state that its 50" long but roughly how wide is it?

Not wanting to hijack your thread, but to compliment it.

PHCM wrote:

Thank you .

The engine mount is aluminum along with the cage. I've decided to use the engine and cage from my last build. (the hull had issues)

G23 ?? is that a weedy or chainsaw? a weedy spins the opposite way that a chainsaw engine does, The advantage to using a chainsaw is that you can use tractor props with pusher set-up (giving a larger selection) . If you want a pusher with a weedy, you need to get pusher props. I like the pusher only because .....um..... uhh... I don't know why. I think it looks more "true to life"

I think I might've gone a little wide on this build. The bottom is 20" the top is 28" which gives the sides a 35-40 (?) degree angle.

Didn't get very far today, I caught a bit of a nasty cold. You know, fever, cough... the whole bit.

Thank you for sharing.

My engine will be a bit more compact (weedy) but the aircraft version of it so a bit less reciprocating mass than the normal saw engines.

First thought that came to mind with the tower was to build out of aluminum also but to make two stringers running the length of the hull to mount it to. I'm really excited to get started but have a few more months to wait. I'll see if there's someone that can help me with CAD design or even start with the butcher board & start drawing out the plans myself.

Don't be surprised if this thread comes back to the top after a few months

Btw, heres the Zenoah I'll be using. Pretty small & compact.

Take a look at the boat I built last year . It is about the right size for your motor . There are some basic plans and build pictures and some videos . The build starts on the second page . http://www.rc-airboats.com/gallery/v...album12&page=1

here is more progress:

More progress:

Hey crispyspa ,
SUPER nice build there ! Definately something to be VERY proud of .[8D]
Food for thought though ....
On your rudders , I noticed that the pivot is NOT at the end/beginning of the rudder blade . This will cause too much pressure against your pivot point , so , I hope they are strong ( did this before and ended up with broken rudder . not at first , it took a little time - bout 4 days )
but again , BEAUTIFUL build ...

LOVE IT !

Man that is a beautiful build! I'm willing to bet that with this hull, you will not have any of the problems of prop walk. I will warn you that a boat of this size will run great, but beaware of the turns and head winds. I know that its hard to do, that is to slow down in the turns. Love your build great job.

Thank you Terbo and Gator. I really appreciate it. [8D]

Terbo, the rudders are 1/16 aluminum plate mounted on bearings. No worries there. I made her strong.

Mr. Cajun Gator, you are right about the prop walk, this one has no problems turning to the right.

[link=http://www.rc-airboats.com/gallery/albums/50-inch-quarter-scale-build/maiden_voyage.wmv]maiden voyage video[/link]

The only problem is glitching, and only on the throttle servo. I have no idea why. I did all the normal stuff like make sure no loose bolts etc...etc...but it's still there I cant maintain full thottle.

Again, Thank you for the compliments!

nice vid and very nice boat good work crispyspa.


Matty_C

About the glitching ,
Did you change out the servo and try another ? ( sounds like the servo might be bad )
If you don't have a spare , just remove the one for the rudder and put it into the throttle socket and try that .
Also , what kind of radio gear are you using ? Reason - AIRTRONICS ( and others ) do NOT like to be close . Try with the ( TX ) antenna down when close to the boat .

This is what is strange: The glitching didn't start until I re-positioned the engine when I was trying to cure the prop walk with the other hull . ( not turning right) The engine was mounted with the cylinder head on the port side of the boat, I moved it to it's present location, head down, and bam, glitching! I shielded the throttle cable with stripped down cable T.V. wire. It helped somewhat, but did not take the problem away.

I have a JR racing XR3i 75 MHz FM. radio, JR throttle servo and a Hi-tech 800bb 1/4 scale servo for steering.

A few more things you can try. remove the servo and take it apart, inspect close for any signs of moister. It would not hurt at this time time spray it down with some electrical cleaner. This will sound crazy but you can also submerge the servos in rubbing alcohal 75%. What will happen is the alcohal will absorb the moister, then evaporate. Do the same with the Rx. Also with the JR radio's I have had trouble with bad soilder joints, inspect where the crystal connects, make sure it free of corrosion and has a good fit. Then if the glitch is at WOT, inspect everything that may be loose, make sure that the throtle cable itself is not rubbing any thing. Check that you have the correct spark plug. Turbo would be better in telling you just what plug to use than I will. I have no experiance with the engine your running. I did not get to down load the vid yet but I will soon.

Evening again ,
the RX doesn't matter which servo you toss into it , but you need to find out if its the servo ( which is the first and easiest check to do )
Simply take the 1/4 scale and place it in the RX slot where the throttle goes ( usually number 2 ) and see if the 1/4 scale glitches , if not , then you know its not the RX or TX and something happened to the servo itself ( like maybe got a little wet ) . Then if this does not work , THEN you go on with the rest of the "process of elimination" steps to find it .

Good luck , cause sometimes glitches can be a PAIN[:@]

Oh , one more thing ... you say you shielded the throttle cable ... WHY ? what is it your using ? I use air line tubing from the auto parts store ( the stuff that you use for cars air shocks - it comes per foot and is around 12 cents per foot and is ONLY nylon/plastic mix and 1/32 stranded cable fits perfectly in it ( with no chance of glitching due to a metal liner )

The plug should be a resistor type plug with an R in the number .

GOOd point ! ( or you could also use a resistor boot cap and not worry about the plug being a resistor type and seeing how , sometimes the proper plug for the engine might not be available in resistor form , this is where the resistor plug boot comes in handy )

I got to watch the vid, it looks great. What size prop are you turning? Sounds like you will get better performance if you was to drop a size in the pitch, the diameter is fine. Great job, now that you have a race ready boat are you ready to race?

( didn't see that you posted a link to a vid untill after CAJUN said something )
Anyway ... ditto ... nice vid and same as Hal said . OR ... you COULD put a larger venturi carb on there ( bet it still has the small 7.2 venturi on it , huh ? , OR ... you could also open the canister muffler up and remove the guts and put two 1/2 inch holes in it for exhaust exits )

Terbo wrote:

HUH ? Are you getting vids/threads mixed up? *Referring to canister muffler* It has no muffler at all. Reason being that the exhaust comes out on the prop side of the head, and the prop swings about a 1/2 inch away from the exhaust port. No room for a muffler.

Size of the venturi is unknown.

I tried the resistor plug, it didn't work.
To cure the glitch, I had to turn the engine back to the original position. (head to port) Any insight as to WHY the head down position would cause a glitch?

Cajun, I'm swinging an 18 x 10 Classic Series prop. I bought a Tachometer, Havn't used it yet so I dont Know what kind of RPM's I'm spinning. I'm guessing 6000.

Also I had said before that I had an 800BB servo, that was a typo, it's a 700BB.(not that it makes any difference)

I'll Edit the link to the video to make it easier to see.

Pic of new Engine stand:

Wow .. talk about screwy ( not you CRISPYSPA the mounting and the glitch )

Only thing I can think of , is that it had to have a loose connection and was doing metal to metal when inverted .

And sorry ... the older Homies had carb on one side , exhaust on the other ( must be one of the combo Homie/Ryobi engines )

Personal opinion - prop is too large of a diameter ... should drop to a 16 incher - pitch is ok ( I say drop in diameter cause not sure if you can find/buy one and 18 pusher with a lower pitch )

Just out of curiosity .. PLEASE let us know if you get that problem with the right turns again , now that you went back to engine sideways )

Only 2 things come to mind about rotatating the engine to stop a glitch, something loose on the engine that rubs when the engine is in the down position, or something binding in the throttle cable as its making a different bend. Only 2 guesses that I have.
If you drop the prop down to the MAS 18 x 8 classic, you will find that your boat has a much better take off, handles and responces to turns better and that it will have a faster top end speed, also it will get a better fuel mileage.
If you can at all possible I recomemend any type of muffler. To explain better check out, [link=http://cajungatorairboats.com/v-web/bulletin/bb/viewtopic.php?t=5]tune pipes how they work[/link]

Terbo,
Not a pusher. The engine is a chainsaw, which runs opposite of a weedy, allowing me to use a normal prop in a pusher configuration. bigger prop selection. It (the engine) was made in 1986.

Cajun,
The only way I can think of to be able to put a muffler on is to move prop away from the engine, which would require machining of a shaft. I think that would be out of the budget. The local machine shop starts a $65 an hour, not including materials. [&o]

18 x 8 ??? Faster top speed ?? Hmmm. but wouldn't that sacrifice low end torque ( for land running)?

Correct me if I'm wrong: Lower pitch prop depends on higher RPM for more speed? This engine has a max rated RPM of 8000.
At only 8000, would a smaller pitch be less efficient?

Also I've tried an APC 18 x 12 , it didn't perform as well as the MAS 18 x 10.(although there was no discernable change in RPM) I think tip width had something to do with that.

Machining of a shaft ? No ... contact Peter at WACKERENGINES and I'll be he either alreadys makes , or WILL make you a prop extension/adapter for it .


Peter F.

[email protected]

352 628 5810

( Florida )

EXCELLENT guy to deal with - VERY reasonable prices , AND excellent products .
( watch out though ... he LOVES to talk - )

( oh and without sounding smart***** - a chainsaw does not run backwards , its output shaft is simply on the other side
) and with certain chainsaws , you COULD even use choice of sides
Anyway ... is there any chance of showing some close-ups of how you mounted the pull start so it stays on there ?


Oh and about the prop ---- a lower pitch will allow the engine to come up to R's , whereas the higher pitch strains the engine and does not allow it to max out ( in addition to that it probably also is over heating a little - if you have a temp gun , test it ) Also , burning more fuel than needed which might cause fouling )

One more thing ... might want to contact your local lawnmower repair shop and see about possibly some new ring(s) for it if its that old ( would give you better HP ) and they're fairly cheap - usually around $6.00

And dontcha just LOVE it about the options of "pusher" props ? ( ) I thought about using a chainsaw from an old Husky I have , but never got around to it ... GREAT idea though ! Sounds more and more like you really put a lot of thought into this before you did anything . GREAT thoughts create great things . Hats off to ya .