dadkins

I hope you have a long skinny gas tank to mount on the strut - a little finish and then your going to need that >

1QwkSport2.5r

The fuel tank is going to be in the compartment below the engine. I've ran the engine on a stand with the fuel tank 2" lower than it will be in the boat and runs fine. The Jett pipe provides plenty of tank pressure at full rpm. I need to find a felt clunk that will fit a Hayes tank. Below 1/2 tank I get tiny bubbles at WOT. I'm using an 8oz Hayes slim tank currently.

Stain and first coat of sealer is on. I was going for a slight red color but the color of the adhesive between the plies of the plywood came through so it looks kinda brown instead. I'll have pictures later today.

1QwkSport2.5r

Got 2 coats on the hull parts and 3 coats on the wing parts.

1QwkSport2.5r

Rigging the hull for a float test in the bath tub. 7 coats of finish down so far.

Float test:

Gonna need a launch ramp to get it on plane, I think. I added batteries and servos, as well as some ballast for the fuel tank which isnt installed yet.

1QwkSport2.5r

So the boat is almost RTR, so I weighed it. With GPS, it's much heavier than I planned - 6.5lbs. I overbuilt it I guess. Anyway, is my TT .46 on a Jett pipe gonna be enough to get this pig going 45mph or better? I'm thinking a .61 size engine may be in order.

I've been getting 16,700 rpm on a APC 9x7 and 15,800rpm on a APC 10x5. Hull is 38" long, overall width is about 24".

crispyspa

While weight is a concern, I wouldn't start changing out engines until you've had a chance to test it the way it is.

dadkins

I am thinking you are going to need a launch ramp with a slingshot to get that thing up on top - then hopefully it will stay on top. I have a spare water baloon launcher if you need.

1QwkSport2.5r

I was going to run it as-is, but I'm doubtful it's going to do what I want it to. I was planning on putting a 56lx on it down the road anyway.

Think it'll plane out if I launch it at 1/4 throttle or maybe 1/2? It does sit pretty level in the bathtub so I don't think it's gonna need the onion to get on plane and stay there.

1QwkSport2.5r

I dont think I'll need a slingshot... But I will make a ramp at some point, though.

If this cruddy weather ever goes away, I'll get this baby out and test it out... She's RTR now. Still some slight tweaks and minor detail to do but its RTR as it sits.

1QwkSport2.5r

Still a few details to take care of before running it but here's a few more pictures of my creation. Still no name for it..









My camera kinda sucks, and the basement lighting in my house is cruddy.. Some of the pictures might look funny.. (crooked/lobsided/etc) Its just my less-than-ideal photography skills and old camera.

dadkins

She is looking GOOD - looks about ready to me. The good thing is... bad weather makes for good boat building...or sleeping.
As for a name how about Rigger-mortise, Blow Motion, for some reason the only names I can come up with are puns.?

1QwkSport2.5r

The weather here in Minnesota this winter was quite cold and we had some big snow storms so I had lots of time to build. The lakes in northern Minnesota haven't "iced out" yet but around me all of the lakes and ponds are open now. (I live in east-central Minnesota southeast of Minneapolis/St. Paul)

I started this build back in November, and I just finished it this week. I'm glad I scaled up the sponson size from the original idea I had. I carved styrofoam (as seen at the beginning of this thread I believe) to have a "rough draft" and after the build started I had to scale a few things up. I overbuilt it a tad as I wanted to make sure it didnt fly apart at WOT and possibly throw parts at possible on-lookers. I think it will hold together well, and with the right amount of power go like there's no tomorrow. I should be able to find out soon if the decent weather holds out until the weekend.

Thanks for the kind words - I know there's not many people that have an affinity for airboats like I do, but I built this boat to sort-of prove to the inboard guys that an Air-powered hydro can go fast. I doubt I'll ever race it, but Id love to see the thing go 60mph or better.

I posted these pictures in another thread in the Tach forum but I'll put them here too. Both of my boats side-by-side. The rule between the boats is 18" long to give an idea of the size of these things. If I were to put a "scale size" to either of them, I'd estimate them to be about 1/12th scale.

Dirk Jan

Very nice build!

I recommend you to change the sponson ride pads though. You designed the ride pads in such a way that they go up with an arc on the end. That's not a good solution. You don't want any radius or arc in this area. The sponsons will stick to the water like this, loosing overall speed.

Make the ride pads straight with sharp edges. It will definately improve performance!

But, again, beautiful build, I look forward to a video

1QwkSport2.5r

Unfortunately I can't change anything on these sponsons. I will eventually make new sponsons sized maybe a touch bigger. This was my first hydro so it was a learning experience from the start. You don't learn anything unless you don't make mistakes. Looks like rain for the next week so it might be awhile before I can test it.

Thanks for the tip.

dadkins

The TRUE test will be when you take it out on the water - If I didn't have such a CRAZY weekend I would love to drive over to CG and see that beast GO! Good luck on the Maiden voyage ! I don't recomend cracking a champagne bottle over the bow.
It needs a name. Blown away !, Hurricane ? Cyclonic ?

1QwkSport2.5r

Thats cool. I think it should go okay. I'm still working the engine up to get better RPM's. I think it still needs a few more tanks of fuel on the cut-down 10x6 prop (now 7.5x6) to let it turn up good... sort-of training it for higher RPM's. I ran 3 tanks like this and its given me about 300rpm more on the top side than it did before I ran it this way. (This was a recommendation by Bob27s in the Jett forum in regards to the Jettstream tuned muffler) If I can get it to turn 17,000rpm on a 9x7, then it should be close to 16,000 on a 10x5 which would put the engine right in its powerband with this pipe. (Bob said 15,000-16,500rpm is the sweet spot for the muffler to be working the best)

I am working on the little odd-ball loose ends so its done-done and ready to run... First opportunity I have, I'll go down to the pond with my fishing pole and try it out. I'll probably have to set up my camera on a tripod since I don't have a cameraman. (Most of my buddies have zero interest in anything radio controlled, and doubt they'll come film for me..)

I think I might have to run it a few times before I can decide on a name. If its a turd and barely moves, a "fast" sounding name wont fit well... but who knows - it may surprise me.

dadkins

Maybe we can get together in the next few week and I'll be happy to film for ya. I have an HD movie camera too. Wait a minute. I have about a million things coming up in the near future, daughters graduating high school, grad party, her prom..- oh yeah...Mothers Day.
Have you ever been to Nichols Pond -Twin cities model boat club - I have never ran there, but have been there to watch - not many airboaters.

*delete M i k e u p delete*

That airboat looks great. You mention boat clubs; Edina had one , i think it was emyc or something like that. They helped me when Electro-Vee's were in there hay day. That club was mainly monos and they used to go to Wisconsin for races. This might be dumb inquiry, but would it be impossible to toss the airboat enough to get it on plane. There are some gas boat that require tossing to get them on plane. The old BOAT mag had some that showed being tossed.

1QwkSport2.5r

That'd be cool. I've been seeing more and more folks from the Twin Cities area doing the boat thing.. It'd be nice to run with someone else (or even hang out) since most of my bud's r/c's are always broken..

I haven't been to Nichols pond - I know where it is, but from the boat clubs website, they say you have to have some sort of insurance card to run there or something..? Not sure if thats just during races or all the time. I dont expect to be able to race this boat in any official race since I dont think this thing will be able to turn nearly as well as the wet-propped boats. Drag race, maybe... Drop me a PM or an Email sometime. [email protected]


I dont know that It would be worth me joining any clubs only because most if not all race classes are mono or hydro hulls running inboard/wet propped engines. If there were to be an airboat class, then I might consider it. I will go watch some of the races down at Nichols pond this summer and maybe meet a few people.

As far as launching the boat; I will probably have to chuck it or build a launch ramp to get it to jump on plane right away. During my mock-up/float test I found the water dipped just above the tips of the sponsons up front. I might be able to add some ballast weight to the radio/battery compartment in the rearmost hatch to maybe float the front higher. I originally had the sponsons to be 2" wide x 1 3/4" tall x 14" long but wanted some extra insurance it'd be able to plane on its own so I scaled them up to be 2 1/4"x2 1/4"x18". I figured a nice round 2:1 ratio would suffice for good floatation, stability, and easy planing. In the process I added some extra epoxy here and some aluminum there adding to the overall beef of the thing. My GPS weighs 12-14oz which adds a ton of weight to the front so I will go looking for a smaller lighter weight handheld GPS for getting speed numbers. My test pond is small and decently accessible around the perimter should I need to retrieve it. I have a small 1 person raft or a fishing pole..

I'm doing the finishing touches on the boat today and maybe do a little testing tomorrow if the weather is decent.

crispyspa

same for center tub at the transom.

dadkins

OK - The weather was NICE. Did you get a chance to try it?

1QwkSport2.5r

The center tub's bottom is all flat. I didn't radius the tub like I did the sponsons.

I think moving the engine back will cure the trouble I had with it. I'll make a launch ramp today.

1QwkSport2.5r

Wouldn't plane out. Need to move weight off the front and make a ramp. Engine ran really good though. I'm pushing the envelope on fuel draw though.

1QwkSport2.5r

Well, I am making some modifications to the engine mount, and I built a launch ramp. Between these changes, come he'll or high water I'm gonna get this beast to plane. I am hoping the wife will Let me go mess around for awhile this weekend. I'll post pics of the revised motor mount.

1QwkSport2.5r

Here's the mods I'm making to my engine mount. The legs on the original mount will be cut off and replaced with the horseshoe brackets. I slotted the back of the new brackets to have some adjustability with the engine's angle. I can then adjust it on the fly. I have it set so I can run the engine dead level as before, or add up to about 10°. I also have the engine set back 2" from original. Hoping the combination will allow me to get up on plane a bit easier..

I'll update when the new frankenmount is done.