Question: Building a Whiplash Sport 40

[SeanKewley]

The sport 40 instructions actually call for the .40 sized rudder and strut, but they appear much too big and heavy. I sold the .40 size rudder and strut I bought for mine, and ordered a set of .21 sized hardware.

 

[RaceMechaniX]

Sean,

I could be wrong here in that it might be a 40 size rudder. I think the only difference is whether the rudder bracket is fitted in double shear (40 size) or in single shear (20 size) If the instructions say 40, go with the 40. I think the mounting pattern on the transom is identical either way. I have robbed the hardware off the sport 40 several times for my P-mono wich consisently bends 40 size rudders.

Tyler

 

[SeanKewley]

How much floatation foam should I put inside the hull? Is this over board?

 

[sport hydro]

You could probibly take out half of that foam. Remember that the hull is wood. It floats without the need for too much foam. Leave the foam in the sponson's and maybe a couple pieces on each side under the decking near the transom.

The boats looking good. You going to have it ready for the race season?

 

[SeanKewley]

You could probibly take out half of that foam. Remember that the hull is wood. It floats without the need for too much foam. Leave the foam in the sponson's and maybe a couple pieces on each side under the decking near the transom.

The boats looking good. You going to have it ready for the race season?

Thanks Ed!

It should be water ready by spring if all goes well.

 

[RaceMechaniX]

Sean,

I would leave the foam in around the sponson area, but leave the rear open. I say that becuase the front will be sealed by buklheads so water and more importantly fuel will not get up in there and fester. If you want to put some foam in the back, just make sure you are able to pull it out after a days running so it can dry out. Because there is so little weight on the tail of these boats, the rear end flats pretty good without foam.

Tyler

 

[SeanKewley]

That makes sense. I forgot about water/fuel drainage. Thanks!

 

[SeanKewley]

I have trimmed the canopy and finished the front cowl hold down, but I'm having a hard time trying to decide how to secure the rear section. I have some of the aeromarine E-Z locks and mounts, but I can't decide how to mount them in the hull. The rudder pushrod seems to be in the way.

Does anyone have some pics that they can share showing how they mounted the rear cowl hold down attachments?

thanks!

 

[SeanKewley]

Below is what I came up with for mounting the cowl lock/mounts. If anyone has a better suggestion please let me know as I haven't glued them in place yet.

 

[Bill Gibson]

Below is what I came up with for mounting the cowl lock/mounts. If anyone has a better suggestion please let me know as I haven't glued them in place yet.

Sean, your idea would probably work, but on my 20 whip, i just did the ol o-ring and ball end thing...just mount a Dubro landing gear strap on each side of the cockpit sides, close to the transom , then mount the balls on the top of the cowl,at the rear, but slightly behind of the strap so that the cowl is not only being held down, its also being pulled forward, so the tongue on the front of the cowl cant pop out...its cheap, super simple, and looks clean....i have had NO issues what so ever with this set up!

 

[SeanKewley]

Thanks Bill! I'll give that a try.

I made some more progress on my build. I got the header and pipe installed. The good news is that the header will allow me to keep the pipe under the cowl without cutting it, but I'm not sure what to do for a muffler. Will a silicone tube routed out through the transom provide enough noise reduction? If not, who makes a muffler that will fit in this limited space?

 

[Dasboatman]

"If not, who makes a muffler that will fit in this limited space?"

Hey Sean, Try one of Lenny Blake's from www.rumracingproducts.com. It will probably be too loud with just a stinger extension.It appears that your cowl latch blocks will be in the for your tip muffler and stinger extension tube. CHEERS !!! Bob

 

[SeanKewley]

"If not, who makes a muffler that will fit in this limited space?"

Hey Sean, Try one of Lenny Blake's from www.rumracingproducts.com. It will probably be too loud with just a stinger extension.It appears that your cowl latch blocks will be in the for your tip muffler and stinger extension tube. CHEERS !!! Bob

That looks perfect Bob! Thanks for the link.

Could you measure the diameter of the largest section and the length?... just to make sure it will fit under my cowling.

Also, is there any issue with running a silcone tube from the exit of the muffler out through the transom? i.e. water blocking the output etc.

 

[sport hydro]

Looks real good Sean.

You should be able to run a tube out the transom with no problems. The scale boats do it.

 

[SeanKewley]

Thanks Ed!

I went over to Mark Dauer's house today and he helped me fabricate a muffler that fits under the cowling. Gotta love club members with aluminum welders It looks like a car muffler, but it should work just fine.

I'll use some tubing to run it through the transom.

 

[larcor69]

Sean, Looking sweet! here's the way I had mine set up

 

[SeanKewley]

Sean, Looking sweet! here's the way I had mine set up

Thanks for the pic. I will exit my pipe there too. How did you do your cowl hold down in the rear?

 

[larcor69]

I used a 4-40 bolt threw the outside tub above the deck and an o ring on each side which sliped over a ballstud angled so it held the cowl towards the front to keep it tight heres a pic of who I mounted the O ring

 

[SeanKewley]

I've got the hull finished and I'm in the process of installing/bending the stuffing tube. What is a good starting point for the strut depth on the Whip 40? I will be using a 450 3 blade.

 

[larcor69]

3/4" to 7/8" gets you in the ball park, it's all test and tune