wilga12

Hey everybody.......................How goes it??

I'm assuming that Pro27,with his SKdaddle,is the only person, (recently) to have taken a kit or plans boat,(Ski boat type) and adapt it to airpower..................If this is an incorrect assumption,please let me know,y'all.

I'd like to bounce this idea off of the troops,here to see what I can learn. Many years ago I sent to RCM Magazine for a set of plans for the 20 foot Schiada SK. (The hull length is 30 inches with an 11 inch beam and 3 inch sides, on the plans) I still have these. I dug them out the other day and decided that this boat, (Scaled up, 300%) would be the appropriate/most fun for me. Of course, after adapting it to airpower. I have 30,45,60 or 90 cc's of displacement to choose from, for power. All glow motors.

The main question,at this point is: Since the bottom is not flat,it's 15 degrees with 7 strakes, should I stay with the usual 30 to 35% ahead of transom, CG.?? I'll be utilizing a tractor engine configuration. AND a composite, Propellor

OK, I'm all ears guys....................Let me have it!! (Your thoughts, ideas and opinions)

As always Thanks................................Dave

asmithnc

Pro27 has not been on the forums in over a year +. You must have gone back quite a ways. How about a link so It will jog some memories.

biteme

I think the only problem you might have with the standard boat hull, would be the beam. Most airboats run with 1:2 or 1:1.5 ratio of beam to length. this is needed due to the higher COG on airboats. Most of us suggest 25 - 40% from transom for COG, so forward to back should be ok, just like I said, watch the balance on the beam. Another suggestion I have heard is to use a prop that is one inch less than the beam, using the appropriate engine to push said prop. This may however leave you underpowered for a boat so long, it may not matter. Something to consider, though. Sean

TERBObob

My Feedback: (21)

This is based on MY experiences only ....

When using a pusher prop .... the handling ( planing out ) comes a lot easier and the over-all handling is a slight bit better ( less porpoising and side bounce when turning )
When using a puller , and mounting the engine at the CG , the boat does not seem to perform as well , although with the proper thrust angle , and power , the boat will come on plane , but , with this style , it seems ( IMO ) that the boat is taking on more of an airplane attitude whereas , if the speeds where fast enugh , it would want to create a lifting effect ( also same was found when mounting the engine further forward . Found , the further forward from the transom area the engine was mounted , the more "airplane" effect the hull took at higher speeds , which , IMO , why a LOT of fellows tried utilizing "wings" to counter this effect . )
Overall , I also found that a hull designed more like a mono could handle rougher waters verses the flat , original styled hulls . The flat designs seemed to want to more bouncing, which , if the speeds were fast enough , would cause flip-overs .
As is also with flat bottom designs water prop driven boats , the glass-ier the water , the better handling .
I currently have 19 airboats , all of which are different in design ( hull ) and engine location . ( and thats not counting the ones I built and scrapped to the burn barrel - )
my best runners design is based on a cat hull with the engine being a pusher and twin rudders which are VERY small ( actually they were "left-over elevators" from a plane that sort of , went bye-bye and hit some trees )

The only other thing I would mention is that , unless you planned on running mostly straight and not having to make turns at a moderate , to fast speed , the width is a bit skinny ( if mounting the engine at utmost rear area ) . With the engine mounted ten inches or so above the hulls CG , would make for an easy side flip/dunk .
The hydro design is one that I have not yet tried and DO wish you the best of luck with configuring it . I do remember when it WAS tried ( here on the board ) , and also remember the MANY trials and errors he ran into to get it semi right .

wilga12

Mornin' Terbo,Asmith and Dogmoat...............................I just got up,and read my mail. Thanks for the come backs.

Asmithnc, You are right,about going back quite a ways. I did read the entire forum back to front,even the threads that a moderator, probably moved into the forum from a place that exsisted BEFORE the current Airboat forum. Evidently, the info on Pro27's Skdaddle, was way back,I guess that I got so caught up in the reading that I forgot to look at the dates.

Terbo, You mention that you felt that "It was a little skinny" You did remember to scale-up the beam figure,didn't you??...That would make the beam 33 inches now.

Dogmoat, I should be OK then, If I'm understanding you correctly,about the beam exceeding the prop dia. by an inch or so. The (Up-scale) beam will be 33 inches, and if memory serves the (largest dia.) that is suggested to be run on the 60cc motor, is 22 inches.

All good points to consider,Guys..........Thanks. Oh, I'm sure that you all are scratchin' your heads wondering WHY, I would elect to build such a long/big boat??..................Answer! As Terbo mentioned, The 15 degree bottom should have a much easier time dealing with not so glassy water, at speed. My lake of choice, is quite often (Blessed) with 4 to 8 inch wind chop,And that's during the winter when there are no water skiers and jet-ski's on the water. The measurement center to center on the swells is 12 to 16 inches. So, I figure the more "Tops" of waves/ripples that the hull can span the better................No??


Later......................................Dave

PS. Terbo, would you kinda' hit me with that "Air plane Effect" again please.. I think what you're saying is that a tractor engine set-up, translates to overall "hull lift" at speed?? After re-reading your response a few times I'm not sure of the hull type that you are thinking the Schiada is...............It's a mono with a 15 degree bottom i.e. a little closer to a flat bottom than the typical Deep-v offshore hull.

TERBObob

My Feedback: (21)

First ... yep , your right ... forgot to scale it up

And again , yep ... your absolutlely correct about your choice of bottoms . [&:] Good choice .
Now .... would be REAL nice , if you could keep us posted and hopefully post some pics as she progress's . ( then hopefully a vid after you'll all done )
Again , the only concern would be the vee bottom design . I scratched one and she was just TOO "tipsy" in the turns . ( and if I'm not mistaken , it , too , was aprox 15 degree vee - with no strakes - this one went to the burn barrel - )

wilga12

Ahh, Terbo

You say "She was a little TOO tipsy" just what was her beam and her prop dia.?? If I make use of my 60cc motor it's a "Boxer twin" configuration so, that should help considerably over the single cylinder "upright" set-up................No??

And, Oh yes, After all the reading that I've done,here in this forum You Bet, I knew that you were going to say that, about the videos/pictures. ....................Terbo the "AV" specialist...LOL

Currently I don't own a still camera, I do have a video-recorder,an old anolog unit,and just last night, I discovered that the analog pictures can be moved onto the PC, (for editing and viewing), with the right equipment/accessories.....................ARG!!............. ........Another learning process.


...............................Dave

TERBObob

My Feedback: (21)

LOL ... yes .. learning vid can be somewhat fun( especially when its analog - LOL )
but , hey .... the twins should help . ( I did a couple of single gassers upside down to help with the CG )

Selph-Inflicted

Wilga,

A slight V-hull works well all around. I have built several which run .46's
This is a very fun boat to run, although its a little hard to keep straight on dry ground do to the torque rolling on the V.

Here is a link to my latest one.
[link=http://rcairboats.net/v-web/bulletin/bb/viewtopic.php?t=865]Selph-Inflicted Slight V[/link]

Here is a video for you too.
[link=http://www.rc-airboats.com/gallery/albums/Chris-Selph/SI_Slight_V_Hull.wmv]Slight V Video[/link]

Good luck with your build! Keep us posted.

wilga12

S.I.............................You're right,It should be a little See-Saw like!...........LOL

I did forget to mention that this project was a water-only attempt.

.........................Dave