AJM SP21 coming along

[anthony_marquart]

Ill be running it here with people that are running different boats. i don't' know that there is anyone with a sp20 boat. but Ill get the boat on radar and in race conditions.. with video..

I'm not really trying to sell the kits.. I just want people to enjoy the design. I worked real hard to make it really easy to build and setup. just want people to use it.. I make no money off any of it,..

 

[anthony_marquart]

UPDATE!!!

2 POINTS TO MAKE..

1. It is running real well. I need time to test props and pipe to get more speed.. I'm thinking it's runing low 50's now.. not real fast.. but for a sp21 not too bad.. and it's ROCK SOLID NOT A HINT OF BLOWING OFF.. I need more prop for it..

2. The design can really take a hit. Crashed a nearly full speed in to rocks.. ,.. flew out and tumbled in the grass.. minimal damage.. nothing a bit of bondo won't fix..

Heres a vid,.. it's really ready to tune for speed now.,.. (after I fix it that is)

 

[RodneyPierce]

video is private

 

[anthony_marquart]

sorry updated

try now

 

[anthony_marquart]

any comments?

 

[DeanJohnson]

Do you have any pics of the finished interior? I like how the boat looked on flat water; have you run it on "race" water?

 

[anthony_marquart]

I've run it in ruff water with basically the same results. The hull has a large venting area beneath it. Maybe too much actually. For smooth water I would like to see it more free of water. When it gets rough the boat is more free. A bit like a seaducer on glass. Very wet. Add rough water and it's at home. Like think this design is turning out the same way.

After some though. The hull passed the durability test very well. I totally launched it off the rocks. The repair is almost done. Finish sand the bonds and paint. The amount of damage was so minimal I actually could have run it again if I needed points in a race.

Score for durability is a 10. Ease of build 10. We will see about high end performance soon.

On that topic. For a sport boat it seems that all speed is tied to getting free of water. This boat seems to actually need a bit of ripple at least to fee up. Looking for suggestions here guys. I'm new to sport boats. Is it all I the strut depth, rudder and turn fin set up? The motor is a very solid 5p with reduced head volume, carb mod and deck at .oo6. Running a 442 prop by mark.

 

[dschigoda]

Anthony,

On the sides of the center section - do you have something sandwiched between some birch ply? Like balsa, or bass wood or ?

Thanks.

Dave

 

[anthony_marquart]

yep,.. balsa

 

[dschigoda]

yep,.. balsa

1/4"?

 

[anthony_marquart]

yes,.. why?

 

[dschigoda]

yes,.. why?

Cool design, and build pics!

I'm just curious about 3 point hydro designs and structures in general. It has been years since I've built or raced a hydro. But I have been sketching out designs and structures as they have popped into my head over the years. I was thinking of doing something similar, in an 1/8 Scale design, but using blue styrofoam and ply (WOF) in the sides of the center section, but still have a large open center section, covered by a large hatch/cowl. But The balsa/ply/sandwich that you have here looks to be quicker to fabricate. On the other hand, styrofoam may be more water resistant if a crack ever develops? I'm interested. Please keep us posted on your progress. Best of luck to you!

 

[anthony_marquart]

IT's going very well.. unfortunately doing some traveling the next few weeks.. The 21 rigger is ready to run, the SP21 only needs a bit of work on the cowl attachment and its ready. There were questions about the strength of the design.. pretty much eliminated all those concerns already.. the sponsons have red tips now,..

still working on the sp40 and looking forward to a 40 rigger arriving..

 

[anthony_marquart]

Update.

Design is working very well. Running today yielded consistent 55 mph. No signs of blowing off at all. Anytime the hull got a bit nose high it would vent and settle right down. Not a record sp21 but rock solid in decent chop. Stock nr5p except reduced volume head button. Transom was dropping a touch in turns and slowing. May work with the rudder to add a touch of lift in turns and maybe a lifting prop. Very solid. Very stable platform.